Daftar Publikasi

Efficient algorithms are being developed to search for strong gravitational lens systems owing to increasing large imaging surveys. Neural networks have been successfully used to discover galaxy-scale lens systems in imaging surveys such as the Kilo Degree Survey, Hyper-Suprime Cam (HSC) Survey, and Dark Energy Survey over the last few years. Thus, it has become imperative to understand how some of these networks compare, their strengths and the role of the training data sets which are essential in supervised learning algorithms used commonly in neural networks. In this work, we present the first-of-its-kind systematic comparison and benchmarking of networks from four teams that have analysed the HSC Survey data. Each team has designed their training samples and developed neural networks independently but coordinated a priori in reserving specific data sets strictly for test purposes. The test sample consists of mock lenses, real (candidate) lenses, and real non-lenses gathered from various sources to benchmark and characterize the performance of each of the network. While each team’s network performed much better on their own constructed test samples compared to those from others, all networks performed comparable on the test sample with real (candidate) lenses and non-lenses. We also investigate the impact of swapping the training samples among the teams while retaining the same network architecture. We find that this resulted in improved performance for some networks. These results have direct implications on measures to be taken for lens searches with upcoming imaging surveys such as the Rubin-Legacy Survey of Space and Time, Roman, and Euclid.

We present a short report on the Astronomy training activities targeting junior and high school science teachers in Banjar City and its neighboring districts. The training is aimed to introduce the use of Astronomy as a means of delivering and exercising science since Astronomy rarely fails to attract people’s interest. More than 30 teachers, comprising mostly science teachers in the area, joined our 3-day training program, which consists of short talks, hands-on experiments, as well as presentation and discussion. The program covers the following topics: Solar System, Motion of Celestial Bodies, Telescopes and Observation, Stars, and Galaxy-Cosmology; focusing mainly on pedagogical content knowledge using experience-based learning. By the end of the training, the participants considered Solar System and Stars as the topics with the most and the least impact/comprehension improvement for them, respectively. Nevertheless, there are only slight differences on the impact scale among the topics, all of which show a mean impact scale textgreater 3.75 out of 5. Additionally, 75% of the participants stated the materials were helpful and beneficial for them as a teacher. This indicates that, according to the participants, the training in general was fruitful and increased their understanding on the topics delivered.

The arrival of the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST), Euclid-Wide and Roman wide-area sensitive surveys will herald a new era in strong lens science in which the number of strong lenses known is expected to rise from $mathcal O(10textasciicircum3)$ to $mathcal O(10textasciicircum5)$. However, current lens-finding methods still require time-consuming follow-up visual inspection by strong lens experts to remove false positives which is only set to increase with these surveys. In this work, we demonstrate a range of methods to produce calibrated probabilities to help determine the veracity of any given lens candidate. To do this we use the classifications from citizen science and multiple neural networks for galaxies selected from the Hyper Suprime-Cam survey. Our methodology is not restricted to particular classifier types and could be applied to any strong lens classifier which produces quantitative scores. Using these calibrated probabilities, we generate an ensemble classifier, combining citizen science, and neural network lens finders. We find such an ensemble can provide improved classification over the individual classifiers. We find a false-positive rate of 10−3 can be achieved with a completeness of 46 per cent, compared to 34 per cent for the best individual classifier. Given the large number of galaxy–galaxy strong lenses anticipated in LSST, such improvement would still produce significant numbers of false positives, in which case using calibrated probabilities will be essential for population analysis of large populations of lenses and to help prioritize candidates for follow-up.

We report the discovery of new lensed quasar candidates in the imaging data of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) Data Release 4, covering $1, 310deg textasciicircum2$ of the sky with median seeing in the i band of ≈0.6 arcsec. In addition to two catalogues of Million Quasars Catalog v7.2 and AllWISE Catalog of Mid-Infra Red Active Galactic Nuclei, containing confirmed and candidate quasars, we preselect quasar sources using colour cuts from the HSC (grizy) and unWISE (W1 + W2) photometric data based on SDSS spectroscopic catalogues. We search for the presence of multiple point sources with similar colour through the convolution of the Laplacian of the preselected quasar image cutouts with the Laplacian of the point spread function, resulting in a reduction of lens candidates from 1 652 329 to 121 511 (7.4 per cent). After visual binary classification, we grade 6 199 (0.4 per cent) potential lenses on a scale of 0 to 3, with 3 indicating a lens and 0 indicating a non-lens. Finally we obtain 162 lens candidates with an average grade of ≥2, and among them, we successfully recover 18 known lenses. By fitting the light distribution and removing the known contaminants, we discover that 57 new systems contain at least two point sources and a galaxy in between, including 10 possible quadruply lensed quasars. This new sample exhibits a median separation of 1.26 arcsec and a magnitude limit of i ≈ 22. Spectroscopic or high-resolution imaging follow up on these newly discovered lensed quasar candidates will further allow their natures to be confirmed.

We apply a novel model based on convolutional neural networks (CNNs) to identify gravitationally-lensed galaxies in multi-band imaging of the Hyper Suprime Cam Subaru Strategic Program (HSC-SSP) Survey. The trained model is applied to a parent sample of 2 350 061 galaxies selected from the $sim$ 800 deg$textasciicircum2$ Wide area of the HSC-SSP Public Data Release 2. The galaxies in HSC Wide are selected based on stringent pre-selection criteria, such as multiband magnitudes, stellar mass, star formation rate, extendedness limit, photometric redshift range, etc. Initially, the CNNs provide a total of 20 241 cutouts with a score greater than 0.9, but this number is subsequently reduced to 1 522 cutouts by removing definite non-lenses for further inspection by human eyes. We discover 43 definite and 269 probable lenses, of which 97 are completely new. In addition, out of 880 potential lenses, we recovered 289 known systems in the literature. We identify 143 candidates from the known systems that had higher confidence in previous searches. Our model can also recover 285 candidate galaxy-scale lenses from the Survey of Gravitationally lensed Objects in HSC Imaging (SuGOHI), where a single foreground galaxy acts as the deflector. Even though group-scale and cluster-scale lens systems were not included in the training, a sample of 32 SuGOHI-c (i.e., group/cluster-scale systems) lens candidates was retrieved. Our discoveries will be useful for ongoing and planned spectroscopic surveys, such as the Subaru Prime Focus Spectrograph project, to measure lens and source redshifts in order to enable detailed lens modelling.

Astronomical observatory construction plays an essential role in astronomy research, education, and tourism development worldwide. This study develops siting distribution scenarios for astronomical observatory locations in Indonesia using a suitability analysis by integrating the physical and atmospheric observatory suitability indexes, machine learning models, and long-term climate models. Subsequently, potential sites are equalized based on longitude and latitude zonal divisions considering air pollution disturbance risks. The study novelty comes from the integrated model development of physical and socio-economic factors, dynamic spatiotemporal analysis of atmospheric factors, and the consideration of equitable low air-pollution-disturbance-risk distribution in optimal country-level observatory construction scenarios. Generally, Indonesia comprises high suitability index and low multi-source air pollution risk areas, although some area has high astronomical suitability and high–medium air pollution risk. Most of Java, the east coast of Sumatra, and the west and south coasts of Kalimantan demonstrate \"low astronomical suitability–high air pollution risk.” A total of eighteen locations are recommended for new observatories, of which five, one, three, four, two, and three are on Sumatra, Java, Kalimantan, Nusa Tenggara, Sulawesi, and Papua, respectively. This study provides a comprehensive approach to determine the optimal observatory construction site to optimize the potential of astronomical activities.

Quasars experiencing strong lensing offer unique viewpoints on subjects related to the cosmic expansion rate, the dark matter profile within the foreground deflectors, and the quasar host galaxies. Unfortunately, identifying them in astronomical images is challenging since they are overwhelmed by the abundance of non-lenses. To address this, we have developed a novel approach by ensembling cutting-edge convolutional networks (CNNs) - for instance, ResNet, Inception, NASNet, MobileNet, EfficientNet, and RegNet – along with vision transformers (ViTs) trained on realistic galaxy-quasar lens simulations based on the Hyper Suprime-Cam (HSC) multiband images. While the individual model exhibits remarkable performance when evaluated against the test dataset, achieving an area under the receiver operating characteristic curve of textgreater97.3% and a median false positive rate of 3.6%, it struggles to generalize in real data, indicated by numerous spurious sources picked by each classifier. A significant improvement is achieved by averaging these CNNs and ViTs, resulting in the impurities being downsized by factors up to 50. Subsequently, combining the HSC images with the UKIRT, VISTA, and unWISE data, we retrieve approximately 60 million sources as parent samples and reduce this to 892 609 after employing a photometry preselection to discover textlessitextgreaterztextlessi/textgreater textgreater 1.5 lensed quasars with Einstein radii of textlessitextgreaterθtextlessi/textgreatertextlesssubtextgreaterEtextlesssub/textgreater textlessitextgreatertextlesstextlessi/textgreater 5″. Afterward, the ensemble classifier indicates 3080 sources with a high probability of being lenses, for which we visually inspect, yielding 210 prevailing candidates awaiting spectroscopic confirmation. These outcomes suggest that automated deep learning pipelines hold great potential in effectively detecting strong lenses in vast datasets with minimal manual visual inspection involved.

While supervised neural networks have become state of the art for identifying the rare strong gravitational lenses from large imaging data sets, their selection remains significantly affected by the large number and diversity of nonlens contaminants. This work evaluates and compares systematically the performance of neural networks in order to move towards a rapid selection of galaxy-scale strong lenses with minimal human input in the era of deep, wide-scale surveys. We used multiband images from PDR2 of the HSC Wide survey to build test sets mimicking an actual classification experiment, with 189 strong lenses previously found over the HSC footprint and 70,910 nonlens galaxies in COSMOS. Multiple networks were trained on different sets of realistic strong-lens simulations and nonlens galaxies, with various architectures and data pre-processing. The overall performances strongly depend on the construction of the ground-truth training data and they typically, but not systematically, improve using our baseline residual network architecture. Improvements are found when applying random shifts to the image centroids and square root stretches to the pixel values, adding z band, or using random viewpoints of the original images, but not when adding difference images to subtract emission from the central galaxy. The most significant gain is obtained with committees of networks trained on different data sets, and showing a moderate overlap between populations of false positives. Nearly-perfect invariance to image quality can be achieved by training networks either with large number of bands, or jointly with the PSF and science frames. Overall, we show the possibility to reach a TPR0 as high as 60% for the test sets under consideration, which opens promising perspectives for pure selection of strong lenses without human input using the Rubin Observatory and other forthcoming ground-based surveys.

Over the last two decades, around 300 quasars have been discovered at z ≳ 6, yet only one has been identified as being strongly gravitationally lensed. We explore a new approach—enlarging the permitted spectral parameter space, while introducing a new spatial geometry veto criterion—which is implemented via image-based deep learning. We first apply this approach to a systematic search for reionization-era lensed quasars, using data from the Dark Energy Survey, the Visible and Infrared Survey Telescope for Astronomy Hemisphere Survey, and the Wide-field Infrared Survey Explorer. Our search method consists of two main parts: (i) the preselection of the candidates, based on their spectral energy distributions (SEDs), using catalog-level photometry; and (ii) relative probability calculations of the candidates being a lens or some contaminant, utilizing a convolutional neural network (CNN) classification. The training data sets are constructed by painting deflected point-source lights over actual galaxy images, to generate realistic galaxy–quasar lens models, optimized to find systems with small image separations, i.e., Einstein radii of θ E ≤ 1″. Visual inspection is then performed for sources with CNN scores of P lens textgreater 0.1, which leads us to obtain 36 newly selected lens candidates, which are awaiting spectroscopic confirmation. These findings show that automated SED modeling and deep learning pipelines, supported by modest human input, are a promising route for detecting strong lenses from large catalogs, which can overcome the veto limitations of primarily dropout-based SED selection approaches.

We conduct a search for galaxy-scale strong gravitational lens systems in Data Release 4 of the Hyper Suprime-Cam Subaru Strategic Program (HSC SSP), consisting of data taken up to the S21A semester. We select 103191 luminous red galaxies from the Baryon Oscillation Spectroscopic Survey (BOSS) sample that have deep multiband imaging from the HSC SSP and use the YattaLens algorithm to automatically identify lens candidates with blue arc-like features. The candidates are visually inspected and graded based on their likelihood of being a lens. We find 8 definite lenses, 28 probable lenses, and 138 possible lenses. The new lens candidates generally have lens redshifts in the range $0.3 \lesssim z_\mathrm{L} \lesssim 0.9$, a key intermediate redshift range to study the evolution of galaxy structure. Follow-up spectroscopy will confirm these new lenses and measure source redshifts to enable detailed lens modeling.

Astronomi merupakan salah satu cabang ilmu yang telah dan sedang menghadapi guyuran Big Data dari hasil pengamatan survei-survei besar di dunia. Data yang dihasilkan memiliki orde terabytes per malam dengan kedalaman dan kualitas data pengamatan yang semakin baik. Salah satu kegiatan penelitian yang lazim dilakukan setelah proses akusisi data adalah klasifikasi yang tidak jarang berujung pada penemuan objek atau fenomena baru di langit. Kegiatan tersebut dilakukan dengan menggunakan berbagai metode mulai dari metode tradisional menggunakan mata manusia, semi-otomatis, dan yang berbasis kecerdasan buatan seperti deep learning. Tidak jarang objek atau fenomena yang gagal dianalisis oleh metode-metode tersebut kemudian ditemukan secara tidak sengaja (serendipity) oleh peneliti maupun publik dalam berbagai kesempatan. Pekerjaan ini akan mengulas beberapa contoh kasus dari literatur dengan pendekatan kualitatif tentang penemuan tidak sengaja yang tidak jarang memberikan sains baru dalam astrofisika. Selain itu juga akan dibahas peluang menemukan objek baru eksotis khususnya bagi pengguna data sekunder astronomi.

We carry out a dedicated search for strong-lens systems with high-redshift lens galaxies with the goal of extending strong lensing-assisted galaxy evolutionary studies to earlier cosmic time. Two strong-lens classifiers are constructed from a deep residual network and trained with datasets of different lens redshift and brightness distributions. We classify a sample of 5,356,628 pre-selected objects from the Wide layer fields in the second public data release of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) by applying the two classifiers to their HSC $gri$-filter cutouts. Cutting off at thresholds that correspond to a false-positive rate of $10^{-3}$ on our test set, the two classifiers identify 5,468 and 6,119 strong-lens candidates. Visually inspecting the cutouts of those candidates results in 735 grade-A/B strong-lens candidates in total, of which 277 candidates are discovered for the first time. This is the single largest set of galaxy-scale strong-lens candidates discovered with HSC data to date, and nearly half of it (331/735) contains lens galaxies with photometric redshifts above 0.6. Our discoveries will serve as a valuable target list for ongoing and scheduled spectroscopic surveys such as the Dark Energy Spectroscopic Instrument, the Subaru Prime Focus Spectrograph project, and the Maunakea Spectroscopic Explorer.

We have carried out a systematic search for galaxy-scale strong lenses in multiband imaging from the Hyper Suprime-Cam (HSC) survey. Our automated pipeline, based on realistic strong-lens simulations, deep neural network classification, and visual inspection, is aimed at efficiently selecting systems with wide image separations (Einstein radii $\sim 1.0--3.0$"), intermediate redshift lenses (z $\sim 0.4-0.7$), and bright arcs for galaxy evolution and cosmology. We classified gri images of all 62.5 million galaxies in HSC Wide with i-band Kron radius $\gt 0.8$" to avoid strict pre-selections and to prepare for the upcoming era of deep, wide-scale imaging surveys with Euclid and Rubin Observatory. We obtained 206 newly-discovered candidates classified as definite or probable lenses with either spatially-resolved multiple images or extended, distorted arcs. In addition, we found 88 high-quality candidates that were assigned lower confidence in previous HSC searches, and we recovered 173 known systems in the literature. These results demonstrate that, aided by limited human input, deep learning pipelines with false positive rates as low as $\sim 0.01$% can be very powerful tools for identifying the rare strong lenses from large catalogs, and can also largely extend the samples found by traditional algorithms. We provide a ranked list of candidates for future spectroscopic confirmation.

We present a lensed quasar search based on the variability of lens systems in the HSC transient survey. Starting from 101,353 variable objects with i-band photometry in the HSC transient survey, we used a variability-based lens search method measuring the spatial extent in difference images to select potential lensed quasar candidates. We adopted conservative constraints in this variability selection and obtained 83,657 variable objects as possible lens candidates. We then ran CHITAH, a lens search algorithm based on the image configuration, on those 83,657 variable objects, and 2,130 variable objects were identified as potential lensed objects. We visually inspected the 2,130 variable objects, and seven of them are our final lensed quasar candidates. Additionally, we found one lensed galaxy candidate as a serendipitous discovery. Among the eight final lensed candidates, one is the only known quadruply lensed quasar in the survey field, HSCJ095921+020638. None of the other seven lensed candidates have been previously classified as a lens nor a lensed candidate. Three of the five final candidates with available HST images, including HSCJ095921+020638, show clues of a lensed feature in the HST images. A tightening of variability selection criteria might result in the loss of possible lensed quasar candidates, especially the lensed quasars with faint brightness or narrow separation, without efficiently eliminating the non-lensed objects; CHITAH is therefore important as an advanced examination to improve the lens search efficiency through the object configuration. The recovery of HSCJ095921+020638 proves the effectiveness of the variability-based lens search method, and this lens search method can be used in other cadenced imaging surveys, such as the upcoming Rubin Observatory Legacy Survey of Space and Time.

We report the results of combined analyses of X-ray and optical data of two galaxy clusters, CL 0024$+$1654 and RX J0152.7$-$1357 at redshift $z = 0.395$ and $z = 0.830$, respectively, which offer a holistic physical description of the two clusters. Our X-ray analysis yields temperature and density profile of the gas in the intra-cluster medium (ICM). Using optical photometric and spectroscopic data, complemented with mass distribution from gravitational lensing study, we investigate any possible correlation between the physical properties of the galaxy members, i.e., their color, morphology, and star formation rate (SFR) with their environments. We quantify the properties of the environment of each galaxy by galaxy number density, ICM temperature, and mass density. Although our result shows that the two clusters exhibit a weaker correlation compared to relaxed clusters, it still confirms the significant effect of the ICM on the SFRs in the galaxies. Various physical mechanisms are suggested to explain the relation between the properties of galaxies and their environment.

We present a new catalog of $9318$ Ly$\alpha$ emitter (LAE) candidates at $z = 2.2$, $3.3$, $4.9$, $5.7$, $6.6$, and $7.0$ that are photometrically selected by the SILVERRUSH program with a machine learning technique from large area (up to $25.0$ deg$^2$) imaging data with six narrowband filters taken by the Subaru Strategic Program with Hyper Suprime-Cam (HSC SSP) and a Subaru intensive program, Cosmic HydrOgen Reionization Unveiled with Subaru (CHORUS). We construct a convolutional neural network that distinguishes between real LAEs and contaminants with a completeness of $94$% and a contamination rate of $1$%, enabling us to efficiently remove contaminants from the photometrically selected LAE candidates. We confirm that our LAE catalogs include $177$ LAEs that have been spectroscopically identified in our SILVERRUSH programs and previous studies, ensuring the validity of our machine learning selection. In addition, we find that the object-matching rates between our LAE catalogs and our previous results are $\simeq 80$-$100$% at bright NB magnitudes of $\lesssim 24$ mag. We also confirm that the surface number densities of our LAE candidates are consistent with previous results. Our LAE catalogs will be made public on our project webpage.

We present a catalog of 4195 optically confirmed Sunyaev-Zel'dovich (SZ) selected galaxy clusters detected with signal-to-noise textgreater 4 in 13,211 deg$^2$ of sky surveyed by the Atacama Cosmology Telescope (ACT). Cluster candidates were selected by applying a multi-frequency matched filter to 98 and 150 GHz maps constructed from ACT observations obtained from 2008-2018, and confirmed using deep, wide-area optical surveys. The clusters span the redshift range $0.04 \lt z \lt 1.91$ (median z = 0.52). The catalog contains 222 $z \gt 1$ clusters, and a total of 868 systems are new discoveries. Assuming an SZ-signal vs. mass scaling relation calibrated from X-ray observations, the sample has a 90% completeness mass limit of $\textrm{M500c} \gt 3.8 \times 10^{14}$ M$_\odot$, evaluated at z = 0.5, for clusters detected at signal-to-noise ratio textgreater 5 in maps filtered at an angular scale of 2.4'. The survey has a large overlap with deep optical weak-lensing surveys that are being used to calibrate the SZ-signal mass-scaling relation, such as the Dark Energy Survey (4566 deg$^2$), the Hyper Suprime-Cam Subaru Strategic Program (469 deg$^2$), and the Kilo Degree Survey (825 deg$^2$). We highlight some noteworthy objects in the sample, including potentially projected systems; clusters with strong lensing features; clusters with active central galaxies or star formation; and systems of multiple clusters that may be physically associated. The cluster catalog will be a useful resource for future cosmological analyses, and studying the evolution of the intracluster medium and galaxies in massive clusters over the past 10 Gyr.

We present spectroscopic confirmation of three new two-image gravitationally lensed quasars, compiled from existing strong lens and X-ray catalogues. Images of HSC J091843.27–022007.5 show a red galaxy with two blue point sources at either side, separated by 2.26 arcsec. This system has a source and a lens redshifts $z_s = 0.804$ and $z_ℓ = 0.459$, respectively, as obtained by our follow-up spectroscopic data. CXCO J100201.50+020330.0 shows two point sources separated by 0.85 arcsec on either side of an early-type galaxy. The follow-up spectroscopic data confirm the fainter quasar has the same redshift with the brighter quasar from the Sloan Digital Sky Survey (SDSS) fiber spectrum at $z_s = 2.016$. The deflecting foreground galaxy is a typical early-type galaxy at a redshift of $z_ℓ = 0.439$. SDSS J135944.21+012809.8 has two point sources with quasar spectra at the same redshift $z_s = 1.096$, separated by 1.05 arcsec, and fits to the HSC images confirm the presence of a galaxy between these. These discoveries demonstrate the power of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP)’s deep imaging and wide sky coverage. Combined with existing X-ray source catalogues and follow-up spectroscopy, the HSC-SSP provides us unique opportunities to find multiple-image quasars lensed by a foreground galaxy.

Gravitationally lensed quasars are useful for studying astrophysics and cosmology, and enlarging the sample size of lensed quasars is important for multiple studies. In this work, we develop a lens search algorithm for four-image (quad) lensed quasars based on their time variability. In the development of the lens search algorithm, we constructed a pipeline simulating multi-epoch images of lensed quasars in cadenced surveys, accounting for quasar variabilities, quasar hosts, lens galaxies, and the PSF variation. Applying the simulation pipeline to the Hyper Suprime-Cam (HSC) transient survey, we generated HSC-like difference images of the mock lensed quasars from Oguri & Marshall's lens catalog. We further developed a lens search algorithm that picks out variable objects as lensed quasar candidates based on their spatial extent in the difference images. We tested our lens search algorithm with the mock lensed quasars and variable objects from the HSC transient survey. Using difference images from multiple epochs, our lens search algorithm achieves a high true-positive rate (TPR) of 90.1% and a low false-positive rate (FPR) of 2.3% for the bright quads with wide separation. With a preselection of the number of blobs in the difference image, we obtain a TPR of 97.6% and a FPR of 2.6% for the bright quads with wide separation. Even when difference images are only available in one single epoch, our lens search algorithm can still detect the bright quads with wide separation at high TPR of 97.6% and low FPR of 2.4% in the optimal seeing scenario, and at TPR of $\sim94%$ and FPR of $\sim5%$ in typical scenarios. Therefore, our lens search algorithm is promising and is applicable to ongoing and upcoming cadenced surveys, particularly the HSC transient survey and the Rubin Observatory Legacy Survey of Space and Time, for finding new lensed quasar systems. [abridged]

We present spectroscopic confirmation of three new two-image gravitationally lensed quasars, compiled from existing strong lens and X-ray catalogs. Images of HSC J091843.27-022007.5 show a red galaxy with two blue point sources at either side, separated by 2.26 arcsec. This system has a source and a lens redshifts $z\_s = 0.804$ and $z\_l = 0.459$, respectively, as obtained by our follow-up spectroscopic data. CXCO J100201.50+020330.0 shows two point sources separated by 0.85 arcsec on either side of an early-type galaxy. The follow-up spectroscopic data confirm the fainter quasar has the same redshift with the brighter quasar from the SDSS fiber spectrum at $z\_s = 2.016$. The deflecting foreground galaxy is a typical early-type galaxy at a redshift of $z\_l = 0.439$. SDSS J135944.21+012809.8 has two point sources with quasar spectra at the same redshift $z\_s = 1.096$, separated by 1.05 arcsec, and fits to the HSC images confirm the presence of a galaxy between these. These discoveries demonstrate the power of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP)'s deep imaging and wide sky coverage. Combined with existing X-ray source catalogues and follow-up spectroscopy, the HSC-SSP provides us unique opportunities to find multiple-image quasars lensed by a foreground galaxy.

Strong lenses are extremely useful probes of the distribution of matter on galaxy and cluster scales at cosmological distances, but are rare and difficult to find. The number of currently known lenses is on the order of 1,000. We wish to use crowdsourcing to carry out a lens search targeting massive galaxies selected from over 442 square degrees of photometric data from the Hyper Suprime-Cam (HSC) survey. We selected a sample of $\sim300,000$ galaxies with photometric redshifts in the range $0.2\lt z_{phot} \lt 1.2$ and photometrically inferred stellar masses $\log M_* \gt 11.2$. We crowdsourced lens finding on this sample of galaxies on the Zooniverse platform, as part of the Space Warps project. The sample was complemented by a large set of simulated lenses and visually selected non-lenses, for training purposes. Nearly 6,000 citizen volunteers participated in the experiment. In parallel, we used YattaLens, an automated lens finding algorithm, to look for lenses in the same sample of galaxies. Based on a statistical analysis of classification data from the volunteers, we selected a sample of the most promising $\sim1,500$ candidates which we then visually inspected: half of them turned out to be possible (grade C) lenses or better. Including lenses found by YattaLens or serendipitously noticed in the discussion section of the Space Warps website, we were able to find 14 definite lenses, 129 probable lenses and 581 possible lenses. YattaLens found half the number of lenses discovered via crowdsourcing. Crowdsourcing is able to produce samples of lens candidates with high completeness and purity, compared to currently available automated algorithms. A hybrid approach, in which the visual inspection of samples of lens candidates pre-selected by discovery algorithms and/or coupled to machine learning is crowdsourced, will be a viable option for lens finding in the 2020s.

We report the serendipitous discovery of HSC J0904$-$0102, a quadruply-lensed Lyman break galaxy (LBG) in the Survey of Gravitationally-lensed Objects in Hyper Suprime-Cam Imaging (SuGOHI). Owing to its point-like appearance, the source was thought to be a lensed active galactic nucleus. We obtained follow-up spectroscopic data with the Gemini Multi-Object Spectrographs on the Gemini South Telescope, which confirmed this to be a lens system. The deflecting foreground galaxy is a typical early-type galaxy at a high redshift of $z_ {\ell} = 0.957$ with stellar velocity dispersion $\sigma_v = 259 \pm 56$ km s$^{-1}$. The lensed source is identified as an LBG at $z_\mathrm{s} = 3.403$, based on the sharp drop bluewards of Ly$\alpha$ and other absorption features. A simple lens mass model for the system, assuming a singular isothermal ellipsoid, yields an Einstein radius of $\theta_ \mathrm{Ein} = 1. 23^{\prime\prime}$ and a total mass within the Einstein radius of $M_ \mathrm{Ein} = (5.55 \pm 0.24) \times 10^{11}\mskip3mu M_ \odot$ corresponding to a velocity dispersion of $\sigma_ \mathrm{SIE}= 283 \pm 3$ km s$^{-1}$, which is in good agreement with the value derived spectroscopically. The most isolated lensed LBG image has a magnification of $\sim 6.5$. In comparison with other lensed LBGs and typical $z \sim 4$ LBG populations, HSC J0904$-$0102 is unusually compact, an outlier at $\gt 2\sigma$ confidence. Together with a previously discovered SuGOHI lens, HSC J1152$+$0047, that is similarly compact, we believe that the HSC Survey is extending LBG studies down to smaller galaxy sizes.

We report the largest sample of candidate strong gravitational lenses belonging to the Survey of Gravitationally-lensed Objects in HSC Imaging for group-to-cluster scale (SuGOHI-c) systems. These candidates are compiled from the S18A data release of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) Survey. We visually inspect $\sim39,500$ galaxy clusters, selected from several catalogs, overlapping with the Wide, Deep, and UltraDeep fields, spanning the cluster redshift range $0.05 < z_{cl} < 1.38$. We discover 641 candidate lens systems, of which 537 are new. From the full sample, 47 are almost certainly bonafide lenses, 181 of them are highly probable lenses and 413 are possible lens systems. Additionally, we present 131 lens candidates at galaxy-scale serendipitously discovered during the inspection. We obtained spectroscopic follow-up of 10 candidates using the X-shooter. With this follow-up, we confirm 8 systems as strong gravitational lenses. Out of the remaining two, the lensed sources of one of them was too faint to detect any emission, and the source in the second system has redshift close to the lens but other additional arcs in this system are yet to be tested spectroscopically. Since the HSC-SSP is an ongoing survey, we expect to find $\sim600$ definite or probable lenses using this procedure and more if combined with other lens finding methods.

Strong gravitationally lensed quasars provide powerful means to study galaxy evolution and cosmology. We use Chitah to hunt for new lens systems in the Hyper Suprime$-$Cam Subaru Strategic Program (HSC SSP) S16A. We present 46 lens candidates, of which 3 are previously known. Including 2 additional lenses found by YattaLens, we obtain X-shooter spectra of 6 promising candidates for lens confirmation and redshift measurements. We report new spectroscopic redshift measurements for both the lens and source galaxies in 4 lens systems. We apply the lens modeling software Glee to model our 6 X-shooter lenses uniformly. Through our analysis of the HSC images, we find that HSCJ022622$-$042522, HSCJ115252$+$004733, and HSCJ141136$-$010216 have point-like lensed images, and that the lens light distribution is well aligned with mass distribution within 6 deg. Thanks to the X-shooter spectra, we estimate fluxes on the Baldwin- Phillips-Terlevich (BPT) diagram, and find that HSCJ022622$-$042522 has a probable quasar source, based on the upper limit of the Nii flux intensity. We also measure the FWHM of Ly$\alpha$ emission of HSCJ141136$-$010216 to be $\sim$254 km/s, showing that it is a probable Lyman-$\alpha$ emitter.

We report optical spectroscopic observations in 2017 at Bosscha Observatory on an interesting nova, ASASSN-17hx (Nova Sct 2017). The nova ASASSN-17hx was observed on July 26th, July 29th, July 31st, and August 14th. Based on the light curve, we propose that our spectroscopic observation of ASASSN-17hx was conducted during iron curtain phase. The observed spectra showed a strong H$\alpha$ emission line and multiple emission lines of Fe II multiplets, which is typical for a Fe II type nova. However, since ASASSN-17hx was classified as a He/N type only few days after its outburst, it is suggested that the nova is actually a hybrid type nova. We will discuss the characteristic of ASASSN-17hx by analysing its expansion velocity, electron density, and evolution of the emission lines.

We present the spectroscopic observation of $\beta$ Lyrae, an interacting eclipsing binary, with orbital rotation period of 12.9 days, with one component known as the B-emission (Be) star. The primary star is a B6-B8II of 3 M$\odot$ and the secondary is a 13 M$\odot$ B0.5V star. The secondary star is embedded in the accretion disk produced by the infalling matter from the primary star, and this disk is estimated as the source of the emission lines. The observations were conducted at Bosscha Observatory, Lembang, Indonesia from May to August 2018, using 10-inch Meade LX-200R Telescope (D = 254 f/D = 9.84), equipped with a Littrow High Resolution Spectrograph (LHIRES) III, grating of 1200 grooves/mm yielding in the resolution of R$\sim$5900, and CCD SBIG ST-402 XME camera with backfocus at 17.5 mm. Seeing during observation was estimated to be 2 arc seconds. During this period, we have obtained 15 spectra in various wavelength coverage, 4 spectra covering around $\lambda\lambda$ = 5779 – 6046 AA (typical S/N = 0.02), 1 spectrum covering around $\lambda\lambda$ = 6430.257 – 6694.434 AA (typical S/N = 0.06), and 10 spectra covering around $\lambda\lambda$ = 6487 – 6752 AA (typical S/N = 0.06). The observed spectra show Halpha-emission profiles with V/R variation, He I 6678 AA with P-Cygni profiles, and He I 5876 AA with P-Cygni profiles. These variations are due to the fact that $\beta$ Lyrae is a binary star system, and also it is suspected that another possible mechanism might be involved.

We performed an investigation of the possibility of constraining the dark energy models such as w-cold dark matter, holographic dark energy, and Ricci dark energy, using a special type of Einstein ring system, called as double-source plane (DSP) lensing system. We found that DSP lensing system only gives a good constraint of the model parameters. We also found that the method highly complimentary to cosmic microwave background measurement for each model.

Bosscha Observatory is the largest and oldest observatory in Indonesia that has been actively doing astronomical research since 1928. Bosscha Observatory was originally very suitable for observing astronomical objects because of its ideal night sky conditions and covered most of the northern and southern sky areas. However, starting at the end of 1980, the quality of the night sky at Bosscha Observatory has decreased along with the development of cities around the observatory. Therefore, the construction of a new observatory in Indonesia is currently underway, i.e. the Timau National Observatory. One of the main causes of the decreasing quality of the night sky at Bosscha Observatory is light pollution. Light pollution is one form of pollution caused by excessive light outside the room released into the sky, causing an increase in brightness of the night sky. The brightness increasing of the night sky causes relatively faint astronomical object, e.g. Milky Way Galaxy that is difficult to observe. Based on the analysis of the dynamics of light pollution in a radius of 20 km from Bosscha Observatory and at a radius of 90 km from the Timau National Observatory in 2013-2017 using VIIRS-DNB satellite imagery, it is known that there is a wide change in light pollution for the very low, low, medium, high, and very high. The average area of light pollution at a radius of 20 km from Bosscha Observatory for the category of very low, low, medium, high, and very high categories experienced a rate of -41.3 $\pm$ 135.2 km$^2$ / year, 5.9 $\pm$ 97.2 km$^2$ / year, 15.1 $\pm$ 14.6 km$^2$ / year, 18.0 $\pm$ 42.6 km$^2$ / year, and 2.1 $\pm$ 10.2 km$^2$ / year. The rate of increase in the extent of light pollution for the medium, high, and very high categories occurs south of the Bosscha Observatory, which is towards the city of Bandung. The average area of light pollution in a 90 km radius from the Timau National Observatory for the very low, low, medium, and high categories experienced a rate of 20.8 $\pm$ 43.4 km$^2$ / year, -22.1 $\pm$ 40.9 km$^2$ / year, 3.0 $\pm$ 7.3 km$^2$ / year, and -1.7 $\pm$ 7.3 km$^2$ / year. Therefore, the night sky in the 128-268 degrees azimuth direction at Bosscha Observatory is relatively not ideal as a location for observing astronomical objects, and the Timau National Observatory is still relatively ideal as a location for observing astronomical objects, but it is necessary to monitor the dynamics of light pollution in the direction of 207-215 degrees azimuth which leads to Kupang City.

We introduce the second generation of the Bosscha Robotic Telescope (BRT), a remotely and automatically operated 0.35-meter telescope. This paper will describe the BRT technical properties, system, and the data from early observations. We have been working on the robotic automation of the telescope system in order to be ready for the national observatory along with international telescope networks. The use of the telescope includes monitoring observation of variable stars, exoplanet, near earth asteroid; and observational for education.

Bosscha Observatory, Institut Teknologi Bandung, has been experimenting to observe crescent moon using small telescope equipped with digital cameras since 2007. The initial motivation was to provide evidence, i.e. digital image, of the first crescent moon visible after new moon (hilal) for moslem community in determining the first day of Ramadan and Shawwal. Initially, observation was done after sunset, following common believe that crescent moon can be detected only after glare from the Sun disappear. In early 2000's it was shown that crescent moon can be detected using CCD camera before sunset (in daylight) with special setup. We catched up the idea in 2013. In this paper we summarize what we have learned so far. Now, detection of crescent moon with elongation e > 4° is not a problem. Detailed report will be written somewhere else.

We present the preliminary result of exoplanet survey observation of NGC 6494 and NGC 6633 at Bosscha Observatory. This research is part of a long-term program of exoplanet survey observations in the open star cluster near the celestial equator. Transit method is used to detect planets orbiting stars in the open star clusters. We are using the 11 inch diameter telescope and targeting transit depth up to 0.01 magnitudes. So far, we still do not detect transiting exoplanets. However, we detect several stars showing variability in its flux resembling the characteristic of variable star. Follow up observation would be needed to identify the type of variable stars.

Using the data taken from our 0.36 m f/7.2 robotic telescope, we performed a very first light curve (LC) analyses of eclipsing binary ASAS 172533-1221.4, one of target stars which is part of program stars in our variable star survey project. The LC of this star was constructed by using $\texttt{LEMON}$, a semi-automatic photometric pipeline written in Python. We refined a Time of Minima (ToM, $T_ 0$) and variability period of this system, $P$ and updated its ephemerides as min I (HJD) = 2457200.255578 + 0.678861 $\times$ E. The LC modeling of the system was conducted with the $\texttt{PHOEBE}$ (PHysics Of Eclipsing BinariEs) software built on top of the widely used WD program . The assorted LC modeling solutions are shown as follows: mass ratio $q = 0.811 \pm 0.009$, inclination $i = 70.62 \pm 0.01^\circ$, temperature of primary and secondary component $T_ 1 = 5559.23 \pm 83.51$ K and $T_ 2 = 3871.64 \pm 43.66$ K, respectively, and modified Kopal potentials which are a function of primary's and secondary's radii $\Omega_ 1 = 3.436 \pm 0.018$ and $\Omega_ 2 = \Omega_ \mathrm{cr} = 2.980$, respectively. It is concluded that ASAS 1725533-1221.4 is found to be near-contact system with almost similar size between primary and secondary components, with its secondary component is already filling its Roche lobe.

WASP-74b is an exoplanet in one of the brighter systems accessible to Southern telescope. We report the analysis of light curve from the transit event of WASP-74b observed at Bosscha Observatory. This report is focused on deriving physical parameters from a single transit lightcurve of WASP-74b at around JD 2457597.14 using Markov Chain Monte Carlo sampler (MCMC) and simple trends model. Physical parameters of the system are successfully derived, in agreement with the discovery paper which uses data from longer monitoring and more thorough observation.

To know the level of light pollution due to human activities, we performed sky brightness measurements at Bosscha Observatory, Indonesia (107$^\circ$36' E; 6$^\circ$49' S, 1300 m above the sea level) during years 2011-2012 by using a portable photometer at zenith direction. From 400 records of night, we obtained that average and maximum sky brightness were 17.75 $\pm$ 0.86 mag/arcsec sq. and 19.14 $\pm$ 0.79 mag/arcsec sq., respectively. Cities around the Observatory, that are Bandung and Lembang, clearly give a strong contribution to light pollution. The patches of Milky Way galaxy are disappearing from the sky. Higher maximum sky brightness occurred after midnight. Brightness values before midnight were 17.83 $\pm$ 0.83 mag/arcsec sq. on average and 18.98 $\pm$ 0.78 mag/arcsec sq. at maximum, with average temperature of 18.8 $\pm$ 1.3 $^\circ$C. The average and maximum magnitudes after midnight were 17.67 $\pm$ 0.88 mag/arcsec sq. and 19.41 $\pm$ 1.24 mag/arcsec sq. with average temperature of 17.1 $\pm$ 1.6 $^\circ$C. Sky brightness depends on Moon age and monthly seasonal variations, but it has no relation with Earth eccentricity.

We present the spectroscopic variations of 14 program Be stars observed within 2008 – 2009 at the Bosscha Observatory, Lembang, Indonesia, using Zeiss Double Refractor equipped with Bosscha Compact Spectrograph. The Be stars show spectroscopic profiles as Be and Be shell, and sometimes as B-normal. These profiles originate from the disk-like envelope or rings surrounded the star's equatorial plane. Our program stars are: 5 as Be single-peaked, 2 as Be double-peak, and 7 as B-normal stars. We also measure the Ip/Ic ratio from the line profiles.

A longstanding challenge in astronomical spectroscopy is to uncover the carriers of diffuse interstellar bands (DIBs). They are broad absorption features due to the interstellar matter (ISM). They are seen in stellar spectra of background stars or other astronomical objects. Although we do not know utterly the carriers of the DIBs, they can be a promising tracer of the ISM. One of the interesting properties is their correlations with the interstellar (IS) extinction. For each band, the correlation has considerable dispersion and differences that possibly due to the IS physical conditions. Some DIBs are sensitive to the stellar radiation field, and some are not. To study the effect, we measured the DIB observed in Be/B stars spectra. The stars were observed by using Bosscha Compact Spectrograph at the Bosscha Observatory, Lembang, Indonesia. We performed an automated fitting of a combination of a smooth stellar continuum, the DIB profile, and a synthetic telluric transmission to the spectrum. The DIB measurements were compared to the general DIBs-extinction relationship. The correlation is found to be in good agreement with previous determinations.

In this paper I identify a number of research topoics relating to Indonesian astronomical history that I feel are of international importance. Through these studies, Indonesia can make a valuable contribution to international history of astronomy. I also will discuss the role of SEAAN's new Working Group on Astronomical History and Heritage, and the values of the Journal of Astronomical History and Heritage and proceedings of the ICOA conferences as outlets for papers about Indonesian astronomical history. Finally, I mention chapters about Indonesia that will appear in a forthcoming book on the early development of astrophysics in Asia.

The spectral evolution of the Nova V5668 Sgr has been observed on 12 June, 23 June, and 15 August 2015 using NEO-R1000 spectrograph attached to the C-11 telescope at Bosscha Observatory, Lembang, Indonesia. The observed spectra indicate that the nova has been entering the nebular phase. The spectra during this phase showed strong forbidden lines of [O I] $\lambda$6300, 6364, [O II] $\lambda$7320, and [O III] $\lambda$5007, [N II] $\lambda$5755. The spectra also showed emission line of Fe II $\lambda$4924, 5169, 5317, 6149. We classify Nova V5668 Sgr into the Fe II type. We present and discuss the variation of nebular abundance N(X)/N(H) of the Nova V5668 Sgr in the light of its evolutionary stages.

Since 1950s, several authors have reported the so-called anomalous gravity during the total solar eclipses through various experiments. To address this issue, in the moment of the total solar eclipse of 9 March 2016 passing most regions in Indonesia, we undertook microgravity measurements using two precise gravimeters. The measurements were made at two locations: (1) Poso (central Sulawesi), a location close to the centre passage of the total eclipse and (2) Lembang (West Java), the site of Bosscha Observatory, where the partial solar eclipse occurred. The two sites are selected to measure the possible different influence of the eclipse on aligning the three objects. The measurements were recorded three days before and one day after the eclipse at various intervals from 30 seconds to a short time at 5 seconds. The finer recording was performed several hours before and after the total eclipse. This measurement allowed detailed analysis, not only in time but also in frequency range. A detailed analysis is presented in this paper. We consider all possible geophysical as well as atmospheric effects. The residual data show that the shielding effect, usually thought as responsible factor on anomalous gravity, is not significant.

On March 9th 2016, some regions in Indonesia witnessed the Total Solar Eclipse (TSE). At that time, Indonesia was the only mainland in the world that could observe TSE. This moment is extraordinary because its probability of being observed at the same point happens every 350 years. On a purpose of raising public awareness and engaging more participations, UNAWE Indonesia developed a handy material and sent the so called educational packages which provided essential information about eclipse, especially TSE. Each package contains of modul of TSE study and materials for simple TSE activity so people who received the package could observe TSE safely. In the delivery of this program, we established a collaboration partner, whom are teachers, as an 'eclipse ambassador'. The local partners were responsible for socializing the information for school or their community. We encouraged them to conduct an observation activity and ask them to fill an evaluation report. As a result, 48 out of 59 partners or equal to 81.3% of all partners has sent the evaluation of the package and documentation of the activity during TSE. They responded positively as it was easy to understand, functional, and convenient.

Based on more than 50 partial nights of CCD monitoring, we derive 118 new times of maximum light of the SX Phoenicis star CY Aquarii. These times support a linear ephemeris for 2013-2015.

Optical observation through sub-meter telescope equipped with CCD camera becomes alternative method for increasing orbital debris detection and surveillance. This observational mode is expected to eye medium-sized objects in higher orbits (e.g. MEO, GTO, GSO & GEO), beyond the reach of usual radar system. However, such observation of fast moving objects demands special treatment and analysis technique. In this study, we performed photometric analysis of the satellite track images photographed using rehabilitated Schmidt Bima Sakti telescope in Bosscha Observatory. The Hough transformation was implemented to automatically detect linear streak from the images. From this analysis and comparison to USSPACECOM catalog, two satellites were identified and associated with inactive Thuraya-3 satellite and Satcom-3 debris which are located at geostationary orbit. Further aperture photometry analysis revealed the periodicity of tumbling Satcom-3 debris. In the near future, it is not impossible to apply similar scheme to establish an analysis pipeline for optical space surveillance system hosted in Indonesia.

We present the results of visual double stars speckle observations from 2013 using a Zeiss Double Refractor 60 cm with visual focal length f = 1,078 cm, and CCD SBIG ST-402 MEA. A Bessel V filter with $\lambda = 550$ nm was placed in front of the CCD camera to reduce the chromatic aberration of the objective lens. The objects selected for this observation were calibration candidates and program stars with separations ranging from 0.9-6 arc second, and were located in both the northern and southern hemispheres. Seeing at Bosscha Observatory is generally 1-2 arc second, imposing a limit on visual double star separation below which the system cannot be resolved by long exposure imaging (longer than ~50 ms). Speckle interferometry methods are used to resolve double stars with separations below the typical size of seeing effects. A series of images were captured in fast short-time exposures ($\sim$50 ms) using a CCD camera. The result of our experiment shows that our system can be used to measure separations of 0.9 arc second (for systems with small $\Delta m$) and $\Delta m \approx 3.7$ (for wide systems).

We present the results of exoplanet observations at Bosscha observatory. Photometric method used to detect reduction on star flux during planet transit in front of the star. Defocus techniques are used to reduce the effects of measurement error on transit lightcurves. We chose targets that have been confirmed to have planets. Stars brighter than 10 magnitudes were selected to achieve good signal to ratio. This observation is part of initial phase of exoplanet observation program in Bosscha Observatory. The results will be used to assess the ability of Bosscha Observatory telescopes in exoplanet transit detection.

Not Available

The Eclipsing Binaries' Minima Monitoring Project (BIMA) is a joint project between Institut Teknologi Bandung (ITB) and National Astronomical Research Institute of Thailand (NARIT). This project is dedicated to observe minim of eclipsing binaries light curves to derived their time of minimum. Since its commissioning in 2012, this project has secured 71 minima of more than 30 eclipising binaries until September 2014. In the first year, BIMA project has established the observational technique, data handling system, calculation for determination time of minimum, and automatization for image reduction and analysis. In the second year, BIMA project began to combine its time of minimum data with other previous observations to analyze O-C (Observed-Calculated) Diagram of all observed systems. The O-C diagram is one of indispensable tools to study evolution in eclipsing binaries in which it indicates period change or correction for periode prediction. Period changes closely related to evolutionary phase of the systems can be detected. In this paper, we present and discuss preliminary analysis of O-C diagram from one particular eclipsing binary system, V566 Oph.

Mr. K. A. R Bosscha, a Dutch tea planter and successful businessman, has become a legendary figure in Indonesia for his various concerns to society. Through his generous support, he helped to found the observatory in 1920. The site of the observatory is in Lembang, West Java, and a suitable place for southern hemisphere observation. The library of Bosscha Observatory was built to support and facilitate research activities of Indonesian astronomers. The core of the library's collection consisted of a donation from Professor H.G. van de Sande Bakhuiyzen, the retired director of Leiden Observatory. Various national and international institutions have contributed to the development of the library. Today, information technology is a major influence on Bosscha Observatory and its librarian.

UU Aqr is a nova-like cataclysmic variable whose variability was found spectroscopically by Volkov et al. (1985). Since its discovery, UU Aqr shows various activities yet cannot be explained. In this paper we present an overview of the system's uniqueness and recent results of its photometric observations carried out at Bosscha Observatory (Lembang, Indonesia).

We present the result of visual double stars speckle observation in 2012, using 24 inch (60 cm) refractor at the Bosscha Observatory. The objects selected for this observation are calibration candidates, their separations range from 1-7 arc second, and they are located in both northern and southern hemisphere. Seeing effect due to the Earth atmospheric turbulence limits the resolution of ground-based telescopes. Seeing over Bosscha Observatory is generally 1-2 arc second, imposing a limit on visual double star separation below which the system cannot be resolved by long exposure imaging (longer than ̃$\sim$50 ms). Speckle interferometry method is used to resolve double stars with separation below typical size of seeing effect. Series of images are captured in fast short-time exposures (̃$\sim$50 ms) using CCD camera. The result of our first experiment shows that our system can be used to measure separation of 1.8 arc second, with $\Delta m \simeq 1$.

Lunar Occultation (LO) is an event where limb of the Moon passing over a particular heavenly bodies such as stars, asteroids, or planets. In other words, during the event, stars, asteroids and planets are occulted by the Moon. When occulted objects contact the lunar limb, there will be a diffraction fringe(s) which can be measured photometrically, until the signal vanishes into noise. This event will give us a valuable information about binarities (of stars) and/or angular diameters estimation (of stars, planets, asteroids) in milliarcsecond resolution, by fitting with theoretical LO pattern. CCDs are common for LO observation because of its fast read out, and recently are developed for sub-meter class telescope. In this paper, our LO observation attempt of μ Sgr and its progress report are presented. The observation was conducted on July 30th, 2012 at Bosscha Observatory, Indonesia, using 45cm f/12 GOTO telescope combined with ST-9 XE CCD camera and Bessel B filter. We used drift-scan method to obtain light curve of the star as it was disappearing behind Moon's dark limb. Our goal is to detect binarity (or multiplicity) of this particular object.

Eclipsing Binaries' Minima (BIMA) Monitoring Project is an observational program host by Bosscha Observatory - Lembang, Indonesia. The main purpose of the program is to build an open-database based on observations conducted at Bosscha Observatory. Differential photometry method will be used and the objects that will be studied are those considered suitable for astronomical CCD observations with small telescopes (diameter of 8 inches or more). The program has officially started in June 2012, and here we present the details of the program.

We present a study of the morphology of quiescent filament observed by H-alpha Solar Telescope at Bosscha Observatory in association with coronal hole observed by Atmospheric Imaging Assembly (AIA) instrument in 193 $\mathring{\mathrm{A}}$ from Solar Dynamics Observatory. H-alpha images were processed by imaging softwares, namely Iris 5.59 and ImageJ, to enhance the signal to noise ratio and to identify the filament features associated with coronal hole. For images observed on October 12, 2011, November 14, 2011 and January 2, 2012, we identified distinct features of coronal holes above the quiescent filaments. This associated coronal holes have filament-like morphology with a thick long thread as it's 'spine', defined as Deep Coronal Hole. Because of strong magnetic field of sunspot, these filaments and coronal holes emerged far from active region and lasted for several days. It is interesting as for segmented filament, deep coronal holes above the filaments lasted for a quite long period of time and merged. This association between filament and deep coronal hole can be explained by filament magnetic loop.

We report the first measurements of radio frequency spectrum occupancy performed at sites aimed to host the future radio astronomy observatory in Indonesia. The survey is intended to obtain the radio frequency interference (RFI) environment in a spectral range from low frequency 10 MHz up to 8 GHz. The measurements permit the identification of the spectral occupancy over those selected sites in reference to the allocated radio spectrum in Indonesia. The sites are in close proximity to Australia, the future host of Square Kilometre Array (SKA) at low frequency. Therefore, the survey was deliberately made to approximately adhere the SKA protocol for RFI measurements, but with lower sensitivity. The RFI environment at Bosscha Observatory in Lembang was also measured for comparison. Within the sensitivity limit of the measurement equipment, it is found that a location called Fatumonas in the surrounding of Mount Timau in West Timor has very low level of RFI, with a total spectrum occupancy in this measured frequency range being about 1 %, mostly found at low frequency below 20 MHz. More detailed measurements as well as a strategy for a radio quiet zone must be implemented in the near future.

Indonesia is a very big country with over 238 million people. And we only have one higher learning institution on astronomy, so how do we reach and convey astronomical information effectively to the whole country? The answer lies in Astronomy Clubs who play an increasingly important role to communicate and educate the public. As part of South East Asia, Indonesia is actively involved in the region to develop astronomy.

We present new CCD photometric observation of V899 Herculis system which obtained in May-June 2010 at Bosscha Observatory ITB, Lembang Indonesia, using the 20.3 cm(f/10.0) Schmidt-Cassegrain GAO-ITB RTS telescope equipped with ST8 CCD camera. We secure 1 time of primary minimum. We employed Cubic Fit method tep{bre1973} to make minimum timing and define the primary minima. Discussion on the nature of V899 Her based on new O-C diagram analysis will be presented.

F. M. Walter, Stony Brook University, reports that photometric and spectroscopic observations were obtained using the SMARTS/Cerro Tololo facilities, starting on Aug. 9 UT. Photometry with the 1.3-m telescope (+ ANDICAM dual-channel photometer) shows maximum light (V = 9.1, K = 6.2) within a day or two of Aug. 13.0 UT; by Aug. 23.0, the nova had faded to V = 11.2 and K = 8.1. Optical spectroscopy with the 1.5-m telescope (+ RC specrograph) between Aug. 9.0 and 22.0 shows the spectrum of a classical 'Fe II'-type nova near maximum light. A similar assessment was determined by H. L. Malasan, J. Suherli, and E. Wiyando, Bosscha Observatory, Institut Teknologi Bandung, Indonesia; and A. Arai and H. Kawakita, Koyama Astronomical Observatory, Kyoto Sangyo University, Japan, from optical spectroscopy obtained on Aug. 16.6 UT at Bosscha Observatory. The spectroscopic details are given on CBET 2796.

With over 80 years of existence, Bosscha Observatory in Lembang, West Java, Indonesia, still stands as one of the largest observatories that is registered by International Astronomical Union in the South East Asia region. Since first commissioned by the NISV (Netherlands Indische Sterrenkundige Vereeniging), Bosscha Observatory had played a major role in astronomy, particularly in research and observational activities in the southern hemisphere. But the current development has produced a serious impact on Bosscha Observatory, both tangible and intangible. With the challenges Bosscha Observatory faced the past decades, what can be done in the future to conserve not only the tangible value but most importantly the intangible value it embraces for the scientific development? This paper emphasizes its values, and opens some perspectives and ideas for conserving a (candidate to) Astronomy and World Heritage site. This important issue of how to best preserve the scientific value of this scientific heritage it embodied is discussed in some detail.

In this paper we present the prediction of the first lunar crescent visibility using contrast based on Schaefer's model and best time proposed by [12] for the beginning of Ramadhan and Syawal 1431 H at observing place in Bosscha Observatory, [E 107° 36.96', S 6° 49.55', with elevation of 1310 meters above sea level]. The geocentric altitude of the Moon at the sunset time on August 10 is 1° 58.98' and illuminated fraction of crescent (FI) = 0.20%. On August 11, 2010 the altitude of the Moon at the sunset time is 15° 42.71' and FI = 2.57%. The calculated contrast on August 10, 2010 is less than zero. It means that the brightness of the moon is smaller than brightness of the sky. Based on the contrast value, it is impossible to observe the lunar crescent by the naked eye at that time, even equipped by special design telescope for the crescent observation at Bosscha Observatory. Sultan [11] proposed a predicted model it is still possible to observe the very young lunar crescent even under circumstance before the time of sunset, if the contrast of sky is perfect. On August 11, 2010 contrast has its maximum at 50 minutes after sunset. The result of observation of the lunar crescent at Bosscha Observatory, the crescent could be seen before sunset at 17:15 local time (UT+7 hours) using special design telescope with additional nose of 1 meter length [6]. The model used here is tend to predict the brightness for naked eye observation, which less contrast compare to observation with the well design telescope.

This paper presents a Monte Carlo simulation, using Planetary System Generator, which has been built based on a simple accretion model by Dole (1970) and by considering the present structure of the Solar System. Data of known extrasolar planets have also been taken into account.   It was then applied to generate 47 Ursae Majoris (47 UMa)-like planetary systems. The results are subsequently compared to the observed data of 47 UMa. The dynamical evolution as well as the stability of the system have been evaluated by using a n-body formalism accounted for in our simulation. The generated system reproduced approximately the observational data and suggests that some other accompanying planets may exist. The orbital evolution is also found to be stable within the current age of the system.

Most methods of orbit determination are often difficult for numerical implementations since they are developed before the computer era. The recently developed mathematical technique of semi-definite programming (SDP) has been implemented for many problems in scientific fields including astrometry. This is a good opportunity to resolve orbits of binary systems located in the southern hemisphere since more than seventy years Bosscha Observatory had been continuously conducting observations of binary systems. Here we describe prospects of application of SDP for deriving orbital parameters of binary systems using data supplied by Bosscha Observatory that has been published in the Centre de Donnees astronomiques de Strasbourg. This study will support observers at Bosscha Observatory to appropriately select target stars belong to binary systems for their ongoing researches. Since SDP is a powerful scheme, free trial-and-error and human-independent judgment, we suggest that SDP may become a standard method for determining orbital parameters of binary systems.

Since its first discovery, most extrasolar planets were detected using radial velocity (RV) method. However, the RV method does not provide all parameters required to characterize a planetary system. Recently, Charbonneau et al.(2000) and Brown et al(2001)have shown that the RV planet orbiting HD 209458 can be observed using transit method yielding some additional information. As pointed out by Castellano (2004), this method can be undertaken using small aperture telescopes and inexpensive CCDs. We report here new observations of planetary transit in HD 102195 and HD 209458 performed at the Bosscha Observatory since March 2006. Some preliminary results will be presented

WDS 01158-6853 I-27CD=SA0 248342 has the proper motion +404. in right ascension and 105. in declination. Magnitude of each star is 7.84 for primary and 8.44 for secondary, separated by 320. from the quadruple system Kappa Tuc=LDS 42 = HJ 3423 AB. The visual binary star of WDS 01158-6853 I-27CD is historically one of the most important double star in constellation Tucana. We have collected the observational data consisting of separation angular ($\rho$) and position angle ($\theta$) from the observations of 1897 up to 2001 taken at the Bosscha Observatory and other Observatories in the world. This study presents the recent status of orbit binary system WDS 01158-6853 I-27CD. By using Thiele Van den Bos method and empirical formula of Strand's Mass-Luminosity relation we have determined the orbit and mass of WDS 01158-6853 I-27CD. The results are; $P=85.288$ years, $e=0.053$, $T =1911.23$, $i=27.93$, $\Omega=52.83$, $\omega=10.73$, $M_1=0.7\; M\odot$, $M_2=0.5\; M\odot$, $p=0".0589$

Since the Bosscha Observatory was established in 1923 researches on visual binary stars played an important role in astronomical studies in Indonesia. The visual binary of WDS 17190-3459 = MLO 4AB = HD156384 = HIP84709 was extensively observed at our observatory and other observatories. This system has already passed periastron three times since observed in the end of year 1876. The observation data is more than enough to construct an orbit. By using Thiele-Innes method we computed the orbit, and physical parameters are determined by using mass-luminosity relation. The result is presented in the table. Orbital Parameters: $e = 0.578$, $P = 42.3$ years, $T = 1974.9$, $i = 132.7^\circ$,$\omega = 247.5^\circ$, $\Omega = 318.1^\circ$, $a = 1".713$, $\mu = 8.51$ /years Physical Parameters: $p = 0".134$, $M_ \mathrm{bol,1}=6.7$, $M_ \mathrm{bol,2}=7.4$, $M_ 1 = 0.6\; M\odot$, $M_ 2 = 0.5\; M\odot$, $q = 0.863$. At time being there are several new methods for determining the orbit; for example the method of Gauss done by Söderhjelm (1999) for calculating the orbit of the same stars WDS 17190-3459. Our results are relatively same.

Habitable zone in a planetary system is defined as the region around a star where life-supporting planets can exist. Typically it requires the presence of liquid water on the planetary surface. Considering the formation of planetary systems, we investigate how stellar mass affects the probability of terrestrial planets formed within habitable zone. We use our Planetary System Generator code (Yamani, 2007) to generate planetary systems by investigating its sensitivity through several parameters, such as stellar mass, stellar luminosity, and effective temperature. The probability of finding terrestrial planets within the habitable zone of extrasolar planetary system has been then calculated. We selected the exoplanet systems: Gl 581, HD 128311, 55 Cnc, 47 UMa, and Ups And-like to evaluate the presence of planets within their habitable zone.

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System

A new determination of the relative orbit of Sirius has been conducted, in support of an ongoing sequence of Hubble Space Telescope observations. The last major determination of the relative Sirius A/B orbit was that of van den Bos (1960). The van den Bos investigation included all visual observations up to 1960. The present analysis incorporates all post-1960 visual observations as well as a substantial set of published photographic observations, from the Bosscha Observatory and the US Naval Observatory, covering three decades prior to 1986. Additionally, the observations of the apparent orbit of Sirius A about the system barycenter (Gatewood &amp; Gatewood 1978) are reevaluated with respect the new relative orbit. A combination of these data sets is used to establish an improved and updated orbit for Sirius as well as the astrometric masses of the two components. This work was supported in part by STScI grant GO-9334.

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System

The photographic observations on the components of Sirius were made at the Bosscha Observatory (1955 - 1986) after the invention of the Sirius grating by van Albada (1956). This special grating enables to photograph the two components that differ by 10 magnitudes. An overview on the technique of the photographic observations on this pair is presented, as well as the method of measurements and reductions.

B. Hidayat, M. Ikbal Arifyanto, J. Aria Utama, and S. Athiya, Bosscha Observatory, Lembang, write: "Spectroscopic observations of N Vel 1999 were obtained at the Bosscha Schmidt telescope (+ objective prism; dispersion 31.5 nm/mm at H-gamma) on June 1.50 and 2.50 UT, with unfiltered IIa-O plates exposed for 12 and 6 min, respectively. Although the 12-min exposure yielded an overexposed spectrum, emission lines of H, He, and [O III] are clearly distinguishable. Based on the three spectra collected on June 2, the following lines are seen (positions and widths of the lines are based on a standard spectrum of a B9 star, secured with the same telescope): [O III] 500.7-nm (half the strength of H-beta), 495.9- nm (half the strength of H-beta), 436.3-nm (certainly observable); [Fe II] 492.4-nm (rather faint but traceable), 423.3-nm (faint); S II(?) 406.8-nm (rather broad, confuse, barely visible); [Ne III] 386.9-nm (half the strength of H-beta). All of the H lines down to H_7 appear on our plates; their estimated width is about 20.0 nm, decreasing rather slowly toward H_7. Shallow depression on the blue side of H-beta is noticable. He II 468.6-nm is rather wide."

A series of photographic observations on the components of Sirius was carried out in the years 1976-1986 at the Bosscha Observatory. We present the analysis and the results of the measurements. Tables are also available in electronic form at the CDS via anonymous ftp 130.79.128.5 or http://cdsweb.u-strasbg.fr/Abstract.html

The photographic observations of 72 visual double stars are presented. The observations were made in the years 1992-1997 with the 60-cm double refractor of the Bosscha Observatory at Lembang. Table 1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html

The photographic observations on the components of Sirius have been made at the Bosscha Observatory after the invention of the Sirius grating by van Albada (1956). This special grating enables us to photograph the two components that differ 10 magnitude Combination of our results with the measurements carried out at the US Naval Observatory (1965-1972) on this pair have covered almost all the observable part of a revolution. An orbit of this system calculated by van den Bos (1960), which mostly based

The photographic observations of 72 visual double stars are presented. The observations were made in the years 1992-1997 with the 60-cm double refractor of the Bosscha Observatory at Lembang. (1 data file).

A series of photographic observations on the components of Sirius was carried out in the years 1976-1986 at the Bosscha Observatory. We present the analysis and the results of the measurements. (2 data files).

This catalog contains the results of photographic observations of 248 double stars, obtained at the Bosscha Observatory at Lembang, Indonesia 1981-1983. (1 data file).

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System

We present the results of photographic observations of 399 visual double stars of the Hipparcos Input Catalogue (HIC), observed in the years 1980 and 1990-1991 with the 60-cm double-refractor of the Bosscha Observatory at Lembang, Java.

We present the results of photographic observations of 399 visual double stars of the Hipparcos Input Catalogue (HIC), observed in the years 1980 and 1990-1991 with the 60-cm double-refractor of the Bosscha Observatory at Lembang, Java. (1 data file).

For over 20 years, the seasonal regression of the martian polar caps has been regularly observed from the Hida and Kwasan Observatories in Japan and the Bosscha Observatory in Indonesia (e.g., Iwasaki et al., J. Geophys. Res., 95, 14751, 1990). Some of the interesting features which have been observed include a temporary halt observed in the regression of the north polar cap; observed variations in the regression of both polar caps with longitude; and isolated outliers of ice such as the Mountains of Mitchell. Simulations of the regression of the martian polar caps obtained via a complex energy balance computer model (e.g., Lindner, J. Geophys. Res., 98, 3339, 1993) have been compared to the dataset. We find that variations in terrain and surface roughness can easily account for these interesting features in the data. This material is based on work supported by the National Science Foundation under Grant No. INT-9402136. Any opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect those of the National Science Foundation.

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System

We present the analysis result of photographic observations of 221 visual double stars, observed in the years 1987-1989 with the 60cm double-refractor at the Bosscha Observatory at Lembang, Java.

Results are presented of photographic observations of 186 pairs of visual double stars, carried out with the 60-cm visual refractor of the Bosscha Observatory at Lembang (Java) between 1984 and 1986. The procedures used in observations, measurements, and reducing were identical to those described by van Albada-van Dien (1983).

A synthesis method is used to analyze B and V observations of Delta Cap obtained at the Bosscha Observatory in 1984 and 1985. Both components of the binary are found to be well inside their critical Roche lobes. The data are consistent with a model using a mass radio $q = 0.365$ which yields a main-sequence mass for the primary star. A distance of 8-11 pc is implied.

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System

The regression of the Martian south polar cap for the 1986 apparition is examined with the measurements of the photographs of Mars obtained at the Bosscha Observatory and at the Hida Observatory. In the period Ls=240°-250°, the size of the south polar cap in 1986 seems to be bigger than that in 1971, but similar to that in 1939, which is bigger than those of other years. The case of the regression seems to be one of the biggest type in the period Ls=240°-250°. Like the case of the north polar cap, the behavior of the south polar cap is different from year to year.

We present the results of photographic observations of 248 double stars, obtained at the Bosscha Observatory at Lembang, Indonesia, in the years 1981-1983.

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System

Photographic observations of 238 pairs of visual binaries obtained on 770 plates using the 60-cm visual refractor of Bosscha Observatory (Lembang, Java) during 1976-1979 are reported, continuing the catalog of van Albada-van Dien (1983). The data-reduction procedures are briefly described, and the data are presented in a table.

All the southern globules in the catalog of Bok and Cordwell (1973) but one have been surveyed for candidates for T Tau stars using the `51/71`- cm Bosscha Schmidt telescope with an objective prism. A total of six $H_\alpha$- emission objects, three of which are new, and fifteen suspected ones have been found in the survey area of altogether 3.28 square degrees in and around 24 globules. However, some circumstantial evidence suggests a low possibility of their T Tau nature collectively. The celestial coordinates and rough estimates of the magnitude and color of the stars are derived from the Palomar Sky Survey prints.

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System

One of the prime astrophysical interests of the Observatorium Bosscha is, and has always been, double star research: visual double star research with the double-60 cm Zeiss telescope (dedicated in 1928), and theoretical research of evolved massive spectroscopic binaries (since 1972). For one thing, this is the very reason that this IAU Colloquium No. 80, celebrating the 60th anniversary of the Observatorium Bosscha in Lembang, is devoted to binary astrophysics. Up to now, visual, photographic, and photometric tools have been used for binary research at the Observatorium Bosscha. An important, essential additional tool for binary research is spectrographic equipment, in order to measure radial velocities of binary components. Therefore, we suggest to make a plan for a new modern telescope, a reflector with a primary mirror of about 2 m in diameter and with a modern spectrograph/detector combination for radial velocity measurements. At a number of major astronomical observatories scientists have been considerating to erect new telescopes devoted primarily to radial velocity measurements. The reason for this is that at the end of this decade the parallax and proper motion measurements to be made by the ESA astrometric satellite Hipparcos will become available of more than 100 000 single stars and double stars. At that time there will be a compelling need for radial velocity measurements of all these stars to complement the parallax and proper motion measurements. With the combination of this data enormous progress will be made in double star research, and in the study of galactic dynamics, another topic of interest of the Observatorium Bosscha. If it could be realized to build such a dedicated radial velocity telescope in Indonesia, Indonesian astronomers could take a leading role in this field of research. Without going into technical details, we would like to emphasize here that such a new instrument should be a trueNew Generation Telescope, and that the Institut Teknologi Bandung should participate from the very beginning in its design, construction and assembling, and the subsequent servicing; ITB could participate in the field of optics, mechanics, and electronics. Modern astronomy offers tremendous challenges to technology, which are of great interest to technological institutes. The new telescope should be computer controlled, and the spectrograph should have a modern digital read-out (Reticon, IPCS, or CCD). The telescope should have one of those recently becoming availablethin mirrors, allowing more mechanical freedom. It could be a telescope with a siderostat which feeds the light into a fixed telescope, thus improving both the stability of the telescope and that of the spectrograph. In this way the staff and students of ITB, as well as the technical staff of the Observatorium Bosscha will be drawn into modern techniques of many varieties. And for ITB such an enterprise may even have a spin-off into other fields than astronomy. One aspect which is of great importance for the new telescope is the selection of its site. The present site of the Observatorium Bosscha in Lembang is a good one, but for a new modern telescope one wants to make sure that it is going to be located at the most ideal site. Therefore an Indonesian site-survey should be initiated promptly. Site survey equipment is available at many big observatories and could be borrowed. The site survey should extend over at least 4 5 years to monitor the meteorological and environmental situation at many sites. In the meantime the design and fund rainsing can be considered. Modern day astronomy depends on financial support from governments and inter-governmental organizations. Therefore it is urged that a proposal for a new telescope as indicated above clearly describes the advantages of such a new telescope both for astrophysical research in Indonesia, and for the introduction of new technologies in Indonesian technological institutes. The recently formed Steering Committee for Indonesian-Netherlands Astrophysics (INA) is willing to explore the possibilities for this plan. We hope that after investigating the interest of ITB in this matter, a proposal could be made before the end of this year.

A powerful, streamlined new Astrophysics Data System

The purpose of this note is to present the result of tests of the new sub-beam prism, recently acquired and used in conjunction with the Bosscha Schmidt telescope (The, 1961).

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System

In this paper the results of photographic measurements and the determinations of the mean positions of 168 mostly southern double stars are reported. The plates used for the measurements were taken with the refractor of the Bosscha Observatory at Lembang, Indonesia.

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System

A powerful, streamlined new Astrophysics Data System