arXiv subjects

Hugo Tranin

Publications and source records attributed to Hugo Tranin.

10 recordsLinked to original sources

arXiv2026

A Faint Progenitor System for the Faint Supernova 2024vjm

Type Ia Supernovae (SNe Ia) are well known for their role as standardizable cosmological candles. Their uniformity is credited to their single origin as thermonuclear explosions of White dwarf (WD) stars. Nevertheless, some SNe Ia break this regularity. Prominently, the Iax subclass are less energetic and remarkably diverse, raising questions about their progenitor systems. While no progenitor system of a normal SN Ia has ever been detected, a luminous blue star was identified in pre-explosion images of the site of the bright SN Iax SN 2012Z, suggested to be a helium giant companion star acting as a mass donor to a WD SN progenitor. This is in line with models of weak mass accretion of a WD from a binary companion, producing an explosion that does not fully disrupt the star. However, these models fail to explain the properties of the faintest Type Iax explosions, suggesting either they originate from other WD binary systems, or even from massive progenitor stars. Here, we present the faint SN Iax SN 2024vjm - possibly the faintest supernova observed to date. Using a deep pre-explosion image taken by the recently launched Euclid space mission, we show that its progenitor system must be fainter than the helium giant SN Iax progenitor candidate of SN 2012Z, as well as that of the luminous red companion or remnant of the faint SN 2008ha, and may require a subdwarf helium star as a mass donor. The deep image also provides strong arguments against a massive star origin for this faint supernova. Our observations argue that SN 2024vjm is a WD explosion, but we find that remarkably faint SNe Iax fade more slowly than bright ones, i.e., they evolve in an opposite manner from the famous Phillips relation that makes regular SNe Ia cosmological candles.

astro-ph.HE↗

arXiv2025

A catalog to unite them all: REGALADE, a revised galaxy compilation for the advanced detector era

Many applications in transient science, gravitational wave follow-up, and galaxy population studies require all-sky galaxy catalogs with reliable distances, extents, and stellar masses. However, existing catalogs often lack completeness beyond $\sim 100$ Mpc, suffer from stellar contamination, or do not provide homogeneous stellar mass estimates and size information. Our goal is to build a high-purity, high-completeness, all-sky galaxy catalog out to 2,000 Mpc, specifically designed to support time-domain and multi-messenger astrophysics. We combined major galaxy catalogs and deep imaging surveys -- including the Legacy Surveys, Pan-STARRS, DELVE, and SDSS -- and added spectroscopic, photometric, and redshift-independent distances. We cleaned the sample using the Gaia catalog to remove stars and visually inspected all ambiguous cases below 100 Mpc through a classification platform that gathered 27,000 expert votes. Stellar masses were estimated using optical and mid-infrared profile-fit photometry, and we improved the accuracy of photometric distances by combining multiple independent estimates. The resulting catalog, REGALADE, includes nearly 80 million galaxies with distances under 2,000 Mpc. It provides stellar masses for 88% of the sample and ellipse fits for 80%. REGALADE is more than 90% complete for galaxies contributing 50% of the total $r$-band luminosity out to 360 Mpc. In science tests, it recovers 60% more known supernova hosts, doubles the number of low-luminosity transient hosts, and identifies more reliable hosts for ultraluminous and hyper-luminous X-ray sources. REGALADE is one of the most complete and reliable all-sky galaxy catalog to date for the nearby Universe, built for real-world applications in transient and multi-messenger astrophysics. The full dataset, visual classifications, and code will be released to support broad community use.

astro-ph.GA↗

arXiv2025

Hot springs and dust reservoirs: JWST reveals the dusty, molecular aftermath of extragalactic stellar mergers

We present James Webb Space Telescope (JWST) observations of four Luminous Red Novae (LRNe): dusty, extragalactic transients from stellar mergers following common-envelope evolution (CEE) in massive binary stars. Our targets - AT2021blu, AT2021biy, AT2018bwo, and M31-LRN-2015 - span a broad range in progenitor primary masses ($\approx$3-24M$_{\odot}$) and post-merger ages ($\approx$1100-3700 days). All four were observed with the Mid-Infrared Instrument (MIRI) from 5-25$\mu$m; AT2021blu and AT2021biy additionally have 5-12$\mu$m spectra from the Low-Resolution Spectrometer. These spectra show strong features of oxygen-rich molecules, including water vapor, supporting the recent association of water fountain sources with CEE. Radiative transfer modeling of the spectral energy distributions yields dust masses of $\approx$4.2$\times10^{-5}$, 3$\times10^{-4}$, 7.5$\times10^{-5}$, and 7.7$\times10^{-4}$M$_{\odot}$ respectively - corresponding to $\approx10$%, 60%, 6% and 12% of median dust masses in core-collapse supernovae (CCSNe) at similar phases. Accounting for their occurrence rates, we estimate that LRNe can contribute $\sim$25% as much dust as CCSNe to the cosmic dust budget. Furthermore, the lower expansion velocities of LRNe may reduce dust destruction by reverse shocks compared to CCSNe, potentially increasing this contribution. In addition to dust masses, we use our \emph{JWST} observations to measure late-time properties such as the luminosities, temperatures, radii, and dust-to-gas ratios of the merger remnants. Our results highlight the need for broader infrared studies of LRNe to quantify their contribution to the cosmic dust budget, study the evolution of oxygen-rich molecules, and probe the final fates of CEE.

astro-ph.SR↗

arXiv2025

The population of hyperluminous X-ray sources as seen by XMM-Newton

Ultraluminous and hyperluminous X-ray sources (ULXs and HLXs) are among the brightest astrophysical objects in the X-ray sky. While ULXs most likely host stellar-mass compact objects accreting at super-Eddington rates, HLXs are compelling candidates for accreting intermediate-mass black holes. Our goal is to produce a clean sample of HLXs by removing possible contaminants and characterise the spectral properties of the remaining population. Starting with a set of 115 HLXs detected by XMM-Newton, we identified and removed contaminants (AGNs, X-ray diffuse emission detected as point-like, and tidal disruption event candidates) and retrieved 40 sources for which XMM-Newton spectra are available. We fitted them with an absorbed power law model and determined their unabsorbed luminosities and hardness ratios. We constructed the hardness-luminosity diagram, compared the results with the spectral properties of the HLX prototype, ESO 243-49 HLX-1, and conducted a deeper analysis on a few promising candidates. The resulting HLX population spans a luminosity range from $1\times10^{41}$ erg s$^{-1}$ to nearly $10^{43}$ erg s$^{-1}$ and is homogeneously spread in hardness between 0.5 and 5. Half of the population has hardness ratios higher than a typical AGN, and could be considered the extension of the ULX population at higher energies. We found four very soft outliers, which are characterised by steep power law spectra and no X-ray emission above 1$-$2 keV, similarly to ESO 243-49 HLX-1. Those with multi-epoch archival data show changes in luminosity up to almost two orders of magnitudes. We show that sources currently identified as HLXs can be more diverse than ULXs and disentangling between different types of objects is not trivial with currently available data. New observations would be beneficial to expand the current sample and uncover the true nature of many objects of this class.

astro-ph.HE↗

arXiv2024

Isolated neutron stars as Science Validation for XMM2ATHENA: Ensuring robust data for future X-ray Astronomy

The discovery of radio-quiet, X-ray thermally emitting isolated neutron stars (XINSs) in the ROSAT All-Sky Survey revealed a previously overlooked component of the neutron star population. Advancements in X-ray instrumentation and the availability of deep, wide-area optical surveys now enable us to explore XINSs at fainter X-ray fluxes and greater distances. In this study, we investigated candidates selected from the 4XMM-DR9 catalogue using XMM-Newton, focusing on long-term flux stability, spectral characterisation, and astrometry. By leveraging resources from the XMM2ATHENA project -- including updated catalogues, multiwavelength characterisation and machine learning classification -- we refined our understanding of this sample of soft X-ray emitters. Our findings enhance the characterisation of XINS candidates, laying the groundwork for more targeted investigations and future catalogue searches.

astro-ph.HE↗

arXiv2024

Hertzsprung gap stars in nearby galaxies and the Quest for Luminous Red Novae Progenitors

After the main sequence phase, stars more massive than 2.5 M$_\odot$ rapidly evolve through the Hertzsprung gap as yellow giants and supergiants (YSG), before settling into the red giant branch. Identifying YSG in nearby galaxies is crucial for pinpointing progenitors of luminous red novae (LRNe) - astrophysical transients attributed to stellar mergers. In the era of extensive transient surveys like the Vera Rubin Observatory's LSST, this approach offers a new way to predict and select common envelope transients. This study investigates potential progenitors and precursors of LRNe by analysing Hubble Space Telescope (HST) photometry of stellar populations in galaxies within 20 Mpc to identify YSG candidates. Additionally, we use ZTF and MeerLICHT/BlackGEM to identify possible precursors, preparing for future observations by the LSST. We compiled a sample of 369 galaxies with HST exposures in the F475W, F555W, F606W, and F814W filters. We identified YSG candidates using MESA stellar evolution tracks and statistical analysis of color-magnitude diagrams (CMDs). Our sample includes 154,494 YSG candidates with masses between 3 and 20 $M_\odot$ and is affected by various contaminants, such as foreground stars and extinguished main-sequence stars. After excluding foreground stars using Gaia proper motions, contamination is estimated at 1\% from foreground stars and 20\% from extinction affecting main-sequence stars. Combining our YSG candidates with time-domain catalogs yielded several interesting candidates. Notably, we identified 12 LRN precursor candidates for which followup is encouraged. We highlight the importance of monitoring future transients that match YSG candidates to avoid missing potential LRNe and other rare transients. LSST will be a game changer in the search for LRN progenitors and precursors, discovering over 300,000 new YSG and 100 precursors within 20 Mpc.

astro-ph.SR↗

arXiv2023

Statistical study of a large and cleaned sample of ultraluminous and hyperluminous X-ray sources

Ultra-/hyper-luminous X-ray sources (ULX/HLX) could be interesting laboratories to improve our understanding of the supermassive black hole growth through super-Eddington accretion episodes and successive mergers of lighter holes. ULXs are thought to be powered by super-Eddington accretion on stellar-mass compact objects, while HLXs may be explained by accretion on intermediate-mass black holes (IMBHs). However, a significant portion of ULX/HLX derived from catalog searches are background AGN. Here we build samples of ULX/HLX from recent XMM-Newton, Swift-XRT and Chandra catalogs and the GLADE catalog of galaxies. We aim to characterize the frequency, environment and X-ray properties of ULXs and HLXs to better assess their differences and understand their populations. After a thorough classification of these X-ray sources, we remove 42% of S/N>3 sources, shown to be contaminants, to obtain the cleanest sample of ULX/HLX to date. From a sample of 1342 ULXs and 191 HLXs, we study their frequency, hardness, variability, radial distribution, and preferred environment. We build their Malmquist-corrected X-ray luminosity functions (XLF) and compare them with previous studies. The large sample size allows us to statistically compare ULXs and HLXs and assess differences in their nature. The interpretation of HLXs as IMBHs is investigated. A significant break is seen in the XLF at ~$10^{40}$erg/s. Our ULX sample, containing ~2% of contaminants, confirms that ULXs are located preferentially in spiral or star-forming galaxies. Some HLXs are significantly softer that ULXs and XRBs. Unlike ULXs, HLXs seem to reside equally in spiral as well as lenticular and elliptical galaxies and 35% of them have an optical counterpart. We estimate their mass and find 120 of them in the range of $2000-10^5 M_\odot$. Most HLXs seem consistent with an accreting massive black hole in a dwarf galaxy satellite.

astro-ph.HE↗

arXiv2023

Tidal disruption events and quasi periodic eruptions

Tidal disruption events (TDEs) occur when a star passes close to a massive black hole, so that the tidal forces of the black hole exceed the binding energy of a star and cause it to be ripped apart. Part of the matter will fall onto the black hole, causing a strong increase in the luminosity. Such events are often seen in the optical or the X-ray (or both) or even at other wavelengths such as in the radio, where the diversity of observed emission is still poorly understood. The XMM-Newton catalogue of approximately a million X-ray detections covering 1283$^2$ degrees of sky contains a number of these events. Here I will show the diverse nature of a number of TDEs discovered in the catalogue and discuss their relationship with quasi periodic eruptions.

astro-ph.HE↗

arXiv2023

XMM2ATHENA, the H2020 project to improve XMM-Newton analysis software and prepare for Athena

XMM-Newton, a European Space Agency observatory, has been observing the X-ray, ultra-violet and optical sky for 23 years. During this time, astronomy has evolved from mainly studying single sources to populations and from a single wavelength, to multi-wavelength or messenger data. We are also moving into an era of time domain astronomy. New software and methods are required to accompany evolving astronomy and prepare for the next generation X-ray observatory, Athena. Here we present XMM2ATHENA, a programme funded by the European Union's Horizon 2020 research and innovation programme. XMM2ATHENA builds on foundations laid by the XMM-Newton Survey Science Centre (XMM-SSC), including key members of this consortium and the Athena Science ground segment, along with members of the X-ray community. The project is developing and testing new methods and software to allow the community to follow the X-ray transient sky in quasi-real time, identify multi-wavelength or messenger counterparts of XMM-Newton sources and determine their nature using machine learning. We detail here the first milestone delivery of the project, a new online, sensitivity estimator. We also outline other products, including the forthcoming innovative stacking procedure and detection algorithms to detect the faintest sources. These tools will then be adapted for Athena and the newly detected or identified sources will enhance preparation for observing the Athena X-ray sky.

astro-ph.IM↗

arXiv2021

Probabilistic classification of X-ray sources applied to Swift-XRT and XMM-Newton catalogs

Context. Serendipitous X-ray surveys have proven to be an efficient way to find rare objects, for example tidal disruption events, changing-look active galactic nuclei (AGN), binary quasars, ultraluminous X-ray sources (ULXs), and intermediate mass black holes. With the advent of very large X-ray surveys, an automated classification of X-ray sources becomes increasingly valuable.Aims. This work proposes a revisited naive Bayes classification of the X-ray sources in the Swift-XRT and XMM-Newton catalogs into four classes -- AGN, stars, X-ray binaries (XRBs) and cataclysmic variables (CVs) -- based on their spatial, spectral and timing properties and their multiwavelength counterparts. An outlier measure is used to identify objects of other natures. The classifier is optimized to maximize the classification performance of a chosen class (here XRBs) and it is adapted to data mining purposes.Methods. We augmented the X-ray catalogs with multiwavelength data, source class, and variability properties. We then built a reference sample of about 25000 X-ray sources of known nature. From this sample the distribution of each property was carefully estimated and taken as reference to assign probabilities of belonging to each class. The classification was then performed on the whole catalog, combining the information from each property.Results. Using the algorithm on the Swift reference sample we retrieved 99%, 98%, 92% and 34% of AGN, stars, XRBs, and CVs, respectively, and the false positive rates are 3%, 1%, 9% and 15%. Similar results are obtained on XMM sources. When applied to a carefully selected test sample, representing 55% of the X-ray catalog, the classification gives consistent results in terms of distributions of source properties. A substantial fraction of sources not belonging to any class is efficiently retrieved using the outlier measure, as well as AGN and stars with properties deviating from the bulk of their class. Our algorithm is then compared to a random forest method; the two showed similar performances but the algorithm presented in this paper improved insight into the grounds of each classification.Conclusions. This robust classification method can be tailored to include additional or different source classes and can be applied to other X-ray catalogs. The transparency of the classification compared to other methods makes it a useful tool in the search for homogeneous populations or rare source types, including multi-messenger events. Such a tool will be increasingly valuable with the development of surveys of unprecedented size, such as LSST, SKA and Athena, and the search for counterparts of multi-messenger events.

astro-ph.HE↗