arXiv subjects

D. Muñoz-Giraldo

Publications and source records attributed to D. Muñoz-Giraldo.

4 recordsLinked to original sources

arXiv2026

Unveiling the period-bounce population of cataclysmic variables: Spectroscopic and time-domain follow-up of eROSITA-selected candidates

During their secular evolution, cataclysmic variable stars (CVs) evolve toward shorter orbital periods ($P_{\rm orb}$) until reaching a minimum near $P_{\rm orb}\sim80$ min, after which they evolve back toward longer periods. CVs that have evolved past this evolutionary turning point are known as period-bouncers (PBs). Despite predictions that 40-80% of all CVs should be PBs, only 3-25% of the observed CV population is composed of PBs, a discrepancy likely due to their intrinsic low luminosities. We aim to investigate the evolutionary status of 213 SRG/eROSITA-selected PB candidates. The sample also includes 19 previously confirmed PBs, which serve as benchmarks for evaluating the candidates. We confirmed 24 new CVs through the identification of Balmer emission lines in optical spectra from the Sloan Digital Sky Survey V (SDSS-V) and of dwarf-nova outbursts in archival photometric surveys. By fitting hydrogen-rich atmosphere models to the SDSS-V spectra, we estimated the effective temperature and secular mass accretion rate of the WDs. We also measured the Balmer decrements, used as diagnostics of the physical conditions of the accretion disc, to assess whether they are consistent with known PBs. In addition, we analysed archival light curves from the Transiting Exoplanet Survey Satellite (TESS) to determine $P_{\rm orb}$ for a subset of systems, and compiled multi-wavelength photometry to construct and model spectral energy distributions (SEDs), from which we inferred approximate donor spectral types. Our analysis of the new CVs indicates that they are consistent with being PBs, potentially increasing the population of confirmed PBs by $\sim 50\%$. Our results suggest that a substantial fraction of the PB population may remain hidden in WD catalogues.

astro-ph.SR↗

arXiv2026

The SRG/eROSITA All-Sky Survey DR2: Cumulative X-ray catalogues from the first three surveys and multi-wavelength counterparts in the western Galactic hemisphere

The eROSITA telescope array on board the Spektrum-Roentgen-Gamma (SRG) mission began its all-sky survey program in December 2019, scanning the sky at an approximately six-month cadence. Here, we present new catalogues of point-like and extended X-ray sources derived from the first three completed eROSITA all-sky surveys (eRASS:3), covering the western Galactic hemisphere, which Germany's eROSITA consortium holds proprietary rights for. We describe the observational strategy, data processing, and analysis pipelines. We also characterise the resulting X-ray source populations. The eRASS:3 main catalogue contains nearly two million sources, including 1,911,744 point-like and 63,796 extended sources, detected in the 0.2-2.3 keV energy band, eROSITA's most sensitive energy window. This volume has doubled the X-ray source content of eRASS1 and provides a comprehensive census of X-ray-emitting objects across diverse astrophysical classes. We also released a secondary hard catalogue of nearly 15,000 sources detected in the harder 2.3-5.0 keV energy band. In addition, we released six catalogues, three for the main sample and three for the hard sample, in which we identify and classify the optical and infrared counterparts of eRASS:3 point-like sources. This approach delivers a homogeneous, high-quality identification of mostly extragalactic X-ray emitters; for example, we estimate that approximately 88% of the 1.4 million counterparts identified within the footprints of the Legacy Survey Imaging for DESI are extragalactic sources. This work has enabled the generation of samples optimised for completeness and purity, while expanding the discovery space for rare populations. The second data release (DR2) of the SRG/eROSITA all-sky survey is a catalogue-only release, comprising the catalogues presented in this work together with an updated version of the eROSITA upper flux limit server.

astro-ph.HE↗

arXiv2026

SRG/eROSITA X-ray selected cataclysmic variable candidates observed in SDSS-V DR20

We report on the spectroscopic observations obtained during SDSS-V DR20 of accreting compact binaries (ACB), specifically the cataclysmic variables (CVs), that were identified as likely compact binary candidates from the SRG (Spectrum Roentgen Gamma) eROSITA eRASS1 and eRASS:3 observations. Our primary aim is to obtain a complete inventory of all CVs that were detected in eRASS1 and eRASS:3, with the goal to help better understand close-binary evolution, the population density, and demographics of these systems in the Galaxy. Previous population studies had their respective limitations, with volume-limited samples suffering from low-number statistics, while magnitude-limited observations were biased to only the brighter systems. All CVs are X-ray emitters, eROSITA, therefore, presents a unique opportunity to identify CVs based on their X-ray emission. Given eROSITA's sensitivity, we expect to find most X-ray active CVs within 500 pc, and magnetic CVs to several kpc. Using X-ray data from the eROSITA together with optical data from Gaia, three different approaches were explored to identify the Gaia optical counterpart to the eROSITA X-ray source of the likely ACB. From this, unique candidates were identified and were submitted in three different cartons to SDSS-V for optical spectroscopic observations as part of the Milky Way Mapper survey. From our submitted candidates, we found 538 likely CVs. We also identified CVs that were observed in other eROSITA based cartons, in which we identified an additional 49 systems that are likely CVs and which were not in our selection. We therefore identified 587 systems as CVs from the eROSITA based SDSS-V observations. We also attempted to sub classify the CVs as dwarf-novae, novalikes, or magnetic systems based on the eROSITA X-ray data, the emission line properties in the optical SDSS-V spectra, and other data in the public domain, if available.

astro-ph.SR↗

arXiv2024

The SRG/eROSITA all-sky survey: First X-ray catalogues and data release of the western Galactic hemisphere

The eROSITA telescope array aboard the Spektrum Roentgen Gamma (SRG) satellite began surveying the sky in December 2019, with the aim of producing all-sky X-ray source lists and sky maps of an unprecedented depth. Here we present catalogues of both point-like and extended sources using the data acquired in the first six months of survey operations (eRASS1; completed June 2020) over the half sky whose proprietary data rights lie with the German eROSITA Consortium. We describe the observation process, the data analysis pipelines, and the characteristics of the X-ray sources. With nearly 930000 entries detected in the most sensitive 0.2-2.3 keV energy range, the eRASS1 main catalogue presented here increases the number of known X-ray sources in the published literature by more than 60%, and provides a comprehensive inventory of all classes of X-ray celestial objects, covering a wide range of physical processes. A smaller catalogue of 5466 sources detected in the less sensitive but harder 2.3-5 keV band is the result of the first true imaging survey of the entire sky above 2 keV. We show that the number counts of X-ray sources in eRASS1 are consistent with those derived over narrower fields by past X-ray surveys of a similar depth, and we explore the number counts variation as a function of the location in the sky. Adopting a uniform all-sky flux limit (at 50% completeness) of F_{0.5-2 keV} > 5 \times 10^{-14}$ erg\,s$^{-1}$\,cm$^{-2}$, we estimate that the eROSITA all-sky survey resolves into individual sources about 20% of the cosmic X-ray background in the 1-2 keV range. The catalogues presented here form part of the first data release (DR1) of the SRG/eROSITA all-sky survey. Beyond the X-ray catalogues, DR1 contains all detected and calibrated event files, source products (light curves and spectra), and all-sky maps. Illustrative examples of these are provided.

astro-ph.HE↗