Upcoming next-generation sky surveys will detect large number of faint objects with magnitudes larger than 25. When objects are crowded within a limited a field of view, blending becomes unavoidable. Blending leads to the omission of many sources during photometry in these fields, which cause an underestimates of tens of percent in crowded fields, and remains a major challenge for existing source-extraction techniques. Although artificial neural networks had shown promising results in the detection and classification in wide-field surveys, they often fail with severely blended stars. We developed a robust deep learning model, Astro-RetinaNet, based on the Retinanet algorithm to detect and classify blended sources in single-band astronomical images. After training and evaluating the performance of our network on simulated images, we find precision of 0.96, 0.89,0.70, 0.50,0.75 for single star, 2-star, 3-star, 4-star and 5-or-more star blending cases, respectively, with star number density $\sim$22000 stars per $\rm arcmin^2$. We compare our method's detection capability and completeness both on CSST simulated NGC 2298 images and HST observed M31 images. In crowded and non-crowded stellar fields of simulated NGC 2298, our results show that the model can recover $82\%$ and $95\%$ sources respectively at magnitude ($i$ band) of 25, while for SExtractor and Photutils the completeness reduces to $20\%, 59\%$ and $60\%, 88\%$ respectively. In the M31 case, as faint as 27 magnitude ($F814W$) in a crowded field, Astro-RetinaNet detects 2,224 sources, significantly outperforming Photutils and SExtractor by factors of 3.4 and 7.1, respectively.
Martina Cádiz-Leyton, Guillermo Cabrera-Vives, Pavlos Protopapas
et al.
Multiband astronomical time series exhibit heterogeneous variability patterns, sampling cadences, and signal characteristics across bands. Standard transformers apply shared parameters to all bands, potentially limiting their ability to model this rich structure. In this work, we introduce Astro-MoE, a foundational transformer architecture that enables dynamic processing via a Mixture of Experts module. We validate our model on both simulated (ELAsTiCC-1) and real-world datasets (Pan-STARRS1).
Fabian Schüssler, M. de Bony de Lavergne, A. Kaan Alkan
et al.
In recent decades, astronomy and astrophysics have experienced several fundamental changes. On one hand, there has been a significant increase in the observation of transient phenomena, which are short-lived events such as supernova explosions, fast radio bursts, and gamma-ray bursts. In addition, the detection of a growing number of different cosmic messengers provides researchers with crucial information about these objects. For example, the detection of high-energy neutrinos and gravitational waves regularly complements traditional astronomical observations in the electromagnetic spectrum. This trend is expected to intensify in the coming years with the commissioning of a wide variety of next-generation observatories, which will enable more in-depth studies of the transient sky. To enhance our understanding and optimize the observations of these phenomena, we have developed the Astro-COLIBRI platform. It is freely available to amateur and professional astronomers in the form of a smartphone application (iOS and Android), a web interface, an API, and a chatbot 'Astro-COLIBRI GPT', among many other features. Astro-COLIBRI serves as a central access point for information on astrophysical sources and transient events, allowing a wide network of observers to track and receive real-time alerts. Here we highlight the key features of Astro-COLIBRI, with a particular emphasis on recent innovations. These include a discussion forum that facilitates user interactions and our strengthened collaboration with various networks of amateur astronomers.
Mathieu de Bony de Lavergne, Halim Ashkar, Atilla Kaan Alkan
et al.
Follow-up of gravitational wave alerts has proven to be challenging in the past due to the large uncertainty on the localisation, much larger than the field of view of most instruments. A smart pointing strategy helps to increase the chance of observing the true position of the underlying compact binary merger event and so to detect an electromagnetic counterpart. To tackle this, a software called tilepy has been developed and was successfully used by the H.E.S.S. collaboration to search for very-high energy gamma-ray emission from GWs during the O2 and O3 runs. The optimised tiling strategies implemented in tilepy allowed H.E.S.S. to be the first ground facility to point toward the true position of GW 170817. Here we present the main strategy used by the software to compute an optimal observation schedule. The Astro-COLIBRI platform helps to plan follow-up of a large range of transient phenomena including GW alerts. The integration of tilepy in this tool allow for an easy planning and visualisation of of follow-up of gravitational wave alert helping the astronomer to maximise the chance of detecting a counterpart. The platform also provides an overview of the multi-wavelength context by grouping and visualising information coming from different observatories alongside GW alerts.
Leah M. Fulmer, Stephanie Juneau, Catherine Merrill
et al.
The Astro Data Lab is preparing to host large spectroscopic datasets such as a copy of the Dark Energy Spectroscopic Instrument (DESI) survey, which is projected to include approximately 40 million spectra of galaxies and quasars as well as over 10 million spectra of stars by 2026. Currently, we serve DR16 spectra from the Sloan Digital Sky Survey (SDSS), including Baryon Oscillation Spectroscopic Survey (BOSS), and Extended BOSS (eBOSS) spectra. A spectral viewer tool allows users to visually and interactively inspect spectra. Given the large size of these spectroscopic datasets, a typical use case might consist of a selection or query for a subset of objects of interest (e.g., a subsample of stars or galaxies or quasars), followed by visual inspection of the selected spectra. It is anticipated that in some cases, users will want to go through a long list of spectra (e.g., thousands) quickly while looking for specific features. This document contains a description of the requirements for such a spectral viewer tool to be incorporated within the Astro Data Lab environment at NSF's NOIRLab. For each object, the spectral viewer will display the observed spectrum and, if available, the noise spectrum, sky spectrum, and best-fit template spectrum. Users will be able to control the display interactively after they launch the tool as part of their Data Lab workflow. The primary objective will be to support the visualization of spectroscopic datasets hosted at the Astro Data Lab but this requirements document could be a useful reference or inspiration for other applications and/or other datasets in the astronomy community.
A compact green astro-comb with 43-GHz repetition rate is developed based on a Ti:Sapphire optical frequency comb (OFC) and a mode-selecting cavity. The OFC's large repetition rate of 1.6 GHz eases the requirements for the mode-selecting cavity. Unnecessary frequency-modes of the OFC are suppressed down to $5 \times 10^{-4}$ at 535 nm - 550 nm using a single mode-selecting cavity with 70-MHz linewidth. The radial velocity precision $σ\sim 1.4$ m/s is achieved at the High Dispersion Echelle Spectrosraph for the Okayama 188-cm telescope of the National Astronomical Observatory of Japan using our astro-comb. With further improvements of the mode-selecting cavity and removal of fiber modal noises, our system will provide a simple, compact, and precise astro-comb setup in visible wavelength region.
Luigi C. Gallo, Alexander Koujelev, Stephane Gagnon
et al.
The Canadian Astro-H Metrology System (CAMS) on the Hitomi X-ray satellite is a laser alignment system that measures the lateral displacement (X/Y) of the extensible optical bench (EOB) along the optical axis of the hard X-ray telescopes (HXTs). The CAMS consists of two identical units that together can be used to discern translation and rotation of the deployable element along the axis. This paper presents the results of in-flight usage of the CAMS during deployment of the EOB and during two observations (Crab and G21.5-0.9) with the HXTs. The CAMS was extremely important during the deployment operation by providing real-time positioning information of the EOB with micrometer scale resolution. In this work, we show how the CAMS improves data quality coming from the hard X-ray imagers. Moreover, we demonstrate that a metrology system is even more important as the angular resolution of the telescope increases. Such a metrology system will be an indispensable tool for future high resolution X-ray imaging missions.
Why do we write this note? It is erroneous to pretend to extract physical information from the experimental light curves (time series) of astrophysical systems by means of linear stochastic differential equations (LSDE). In general, the time evolution of these systems is governed by a set of nonlinear differential equations. Hence, the LSDEs are not suitable to model their dynamics. In spite of this, recently the LSDEs have been proposed as tools for the analysis of AGN light curves. Their use in this context seems to be dictated by their simplicity rather than by a real physical argument. We stress in this note that the correct approach to the analysis of signals coming from systems with nonlinear dynamics is to tackle the problem using methodologies in well defined physical contexts.
Uta Grothkopf, Dominic Bordelon, Silvia Meakins
et al.
Using the ESO Telescope Bibliography database telbib, we have investigated the percentage of ESO data papers that were submitted to the arXiv/astro-ph e-print server and that are therefore free to read. Our study revealed an availability of up to 96% of telbib papers on arXiv over the years 2010 to 2017. We also compared the citation counts of arXiv vs. non-arXiv papers and found that on average, papers submitted to arXiv are cited 2.8 times more often than those not on arXiv. While simulations suggest that these findings are statistically significant, we cannot yet draw firm conclusions as to the main cause of these differences.
Hitomi (ASTRO-H) carries two Hard X-ray Telescopes (HXTs) that can focus X-rays up to 80 keV. Combined with the Hard X-ray Imagers (HXIs) that detect the focused X-rays, imaging spectroscopy in the high-energy band from 5 keV to 80 keV is made possible. We studied characteristics of HXTs after the launch such as the encircled energy function (EEF) and the effective area using the data of a Crab observation. The half power diameters (HPDs) in the 5--80 keV band evaluated from the EEFs are 1.59 arcmin for HXT-1 and 1.65 arcmin for HXT-2. Those are consistent with the HPDs measured with ground experiments when uncertainties are taken into account. We can conclude that there is no significant change in the characteristics of the HXTs before and after the launch. The off-axis angle of the aim point from the optical axis is evaluated to be less than 0.5 arcmin for both HXT-1 and HXT-2. The best-fit parameters for the Crab spectrum obtained with the HXT-HXI system are consistent with the canonical values.
We demonstrate a compact 29.3 GHz visible astro-comb covering the spectrum from 560nm to 700nm. A 837 MHz Yb:fiber laser frequency comb phase locked to a Rb clock served as the seed comb to ensure the frequency stability and high side mode suppression ratio. After the visible super-continuum generation, a cavity-length-fixed Fabry-Perot cavity made by ultra-low expansion glass was utilized to filter the comb teeth for eliminating the rapid active dithering. The mirrors were home-made complementary chirped mirrors pair with zero dispersion and high reflection to guarantee no mode skipping. These filtered comb teeth were clearly resolved in an astronomical spectrograph of 49,000 resolution, exhibiting sharp linetype, zero noise floor, and uniform exposure amplitude.
We have constructed the most-comprehensive catalog of photometry and proper motions ever assembled for a globular cluster (GC). The core of $ω$Cen has been imaged over 650 times through WFC3's UVIS and IR channels for the purpose of detector calibration. There exist from 4 to over 60 exposures through each of 26 filters, stretching continuously from F225W in the UV to F160W in the infrared. Furthermore, the 11-year baseline between these data and a 2002 ACS survey has allowed us to more than double the proper-motion accuracy and triple the number of well-measured stars compared to our previous groundbreaking effort. This totally unprecedented complete spectral coverage for over 470,000 stars within the cluster's core, from the tip of the red-giant branch down to the white dwarfs, provides the best astro-photometric observational data base yet to understand the multiple-population phenomenon in any GC. In this first paper of the series we describe in detail the data-reduction processes and deliver the astro-photometric catalog to the astronomical community.
Aakash Ravi, David F. Phillips, Matthias Beck
et al.
Using a turn-key Ti:sapphire femtosecond laser frequency comb, an off-the-shelf supercontinuum device, and Fabry-Perot mode filters, we report the generation of a 16 GHz frequency comb spanning a 90 nm band about a center wavelength of 566 nm. The light from this astro-comb is used to calibrate the HARPS-N astrophysical spectrograph for precision radial velocity measurements. The comb-calibrated spectrograph achieves a stability of $\sim$ 1 cm/s within half an hour of averaging time. We also use the astro-comb as a reference for measurements of solar spectra obtained with a compact telescope, and as a tool to study intrapixel sensitivity variations on the CCD of the spectrograph.
Debian Astro is a Debian Pure Blend that aims to distribute the available astronomy software within the Debian operating system. Using Debian as the foundation has unique advantages for end-users and developers such as an easy installation and upgrading of packages, an open distribution and development model, or the reproducibility due to the standardized build system.
After its first implementation in 2003 the Astro-WISE technology has been rolled out in several European countries and is used for the production of the KiDS survey data. In the multi-disciplinary Target initiative this technology, nicknamed WISE technology, has been further applied to a large number of projects. Here, we highlight the data handling of other astronomical applications, such as VLT-MUSE and LOFAR, together with some non-astronomical applications such as the medical projects Lifelines and GLIMPS, the MONK handwritten text recognition system, and business applications, by amongst others, the Target Holding. We describe some of the most important lessons learned and describe the application of the data-centric WISE type of approach to the Science Ground Segment of the Euclid satellite.
Tadayuki Takahashi, Kazuhisa Mitsuda, Richard Kelley
et al.
The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions developed by the Institute of Space and Astronautical Science (ISAS), with a planned launch in 2015. The ASTRO-H mission is equipped with a suite of sensitive instruments with the highest energy resolution ever achieved at E > 3 keV and a wide energy range spanning four decades in energy from soft X-rays to gamma-rays. The simultaneous broad band pass, coupled with the high spectral resolution of Delta E < 7 eV of the micro-calorimeter, will enable a wide variety of important science themes to be pursued. ASTRO-H is expected to provide breakthrough results in scientific areas as diverse as the large-scale structure of the Universe and its evolution, the behavior of matter in the gravitational strong field regime, the physical conditions in sites of cosmic-ray acceleration, and the distribution of dark matter in galaxy clusters at different redshifts.