The very faint X-ray transient Swift J174610-290018 at the Galactic center

Abstract

Very Faint X-ray Transients (VFXTs) are a class of X-ray binary systems that exhibit occasional outbursts with peak X-ray luminosities (L_X< 1e36 erg s^-1) much lower than typical X-ray transients. On 22nd February 2024, during its daily Galactic center monitoring, Swift-XRT detected a VFXT, 7 arcmin from Sgr A* dubbing it Swift J174610--290018. We aim to characterize the outburst that occurred in 2024, and a second, distinct outburst in 2025, to understand the nature and accretion flow properties of this new VFXT. Swift-XRT light curves are used to constrain the duration of the two events. We carried out X-ray spectral analysis exploiting XMM and NuSTAR data. We used Chandra and XMM observations of the last 25 years to constrain the quiescent luminosity of the source. During the 2024 outburst, which lasted about 50 days, the source reached a luminosity in the 2-10 keV band of L_X = 1.2e35 erg s^-1 (assuming it is located at the Galactic center). The 2025 outburst is shorter (about 5 days), and reached L_X = 9e34 erg s^-1. The spectral features of the source include an excess at 6.5-7 keV, which can be associated either with a single reflection line or with the ionized Fe XXV and XXVI lines. The same source was identified in both the XMM and Chandra catalogs of point sources (known as 4XMM J174610.7--290020). During previous detections, the source displayed luminosity levels ranging from L_X= 2e32 to L_X = 3e34 erg s^-1 between 2000 and 2010. Moreover, it exhibited a potential type I X-ray burst in 2004. The analysis of the outbursts and the potential type I burst strongly suggests the neutron star low mass X-ray binary (NS-LMXB) nature of the VFXT. The source can be described by an accretion disk corona (as has been recently proposed by the XRISM/Xtend analysis). This scenario explains the overall low luminosity of this transient and the peculiar iron lines in the spectrum.

arXiv commentAccepted for publication in A&A. Minor revisions. Title changed

References in corpus (45)

• On the Absorption of X-rays in the Interstellar Medium
• The European Photon Imaging Camera on XMM-Newton: The MOS Cameras
• The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission
• Atomic Data for Astrophysics. II. New Analytic Fits for Photoionization Cross Sections of Atoms and Ions
• X-ray spectral modelling of the AGN obscuring region in the CDFS: Bayesian model selection and catalogue
• A geometric distance measurement to the Galactic Center black hole with 0.3% uncertainty
• Chandra X-ray Spectroscopic Imaging of Sgr A* and the Central Parsec of the Galaxy
• Thermonuclear (type-I) X-ray bursts observed by the Rossi X-ray Timing Explorer
• Studies in Astronomical Time Series Analysis. VI. Bayesian Block Representations
• Photospheric radius expansion X-ray bursts as standard candles
• The XMM-Newton serendipitous survey IX. The fourth XMM-Newton serendipitous source catalogue
• X-ray Emissions from Accreting White Dwarfs: a Review
• Magnetars: Properties, Origin and Evolution
• A Catalog of X-ray Point Sources from Two Megaseconds of Chandra Observations of the Galactic Center
• A Deep Chandra Catalog of X-ray Point Sources toward the Galactic Center
• An Overabundance of Transient X-ray Binaries within 1 pc of the Galactic Center
• Systematic study of magnetar outbursts
• ASCA X-ray source catalogue in the Galactic Center region
• The XMM-Newton/Chandra monitoring campaign of the Galactic center region: Description of the program and preliminary results
• The XMM-Newton view of the central degrees of the Milky Way
• Low-level accretion in neutron-star X-ray binaries
• Accretion disks and coronae in the X-ray flashlight
• Population of persistent high mass X-ray binaries in the Milky Way
• The behavior of subluminous X-ray transients near the Galactic center as observed using the X-ray telescope aboard Swift
• The INTEGRAL Galactic bulge monitoring program: the first 1.5 years
• The Zoo of X-ray sources in the Galactic Center Region: Observations with BeppoSAX
• The faintest accretors
• Self-Consistent Thermal Accretion Disk Corona Models for Compact Objects: I. Properties of the Corona and the Spectrum of Escaping Radiation
• A four-year XMM-Newton/Chandra monitoring campaign of the Galactic Centre: analysing the X-ray transients
• An in-depth study of a neutron star accreting at low Eddington rate: On the possibility of a truncated disk and an outflow
• The nature of very faint X-ray binaries; hints from light curves
• An Ultra-deep Chandra Catalog of X-ray Point Sources in the Galactic Center Star Cluster
• XMMU J174716.1-281048: a "quasi-persistent" very faint X-ray transient?
• GALACTICNUCLEUS: A high-angular-resolution $JH{K}_s$ imaging survey of the Galactic centre. IV. Extinction maps and de-reddened photometry
• A catalogue of soft X-ray sources in the galactic center region
• Probing the Interstellar Dust towards the Galactic Centre: Dust Scattering Halo around AX J1745.6-2901
• The X-ray binary population in the Galactic Center revealed through multi-decade observations
• The peculiar Galactic center neutron star X-ray binary XMM J174457-2850.3
• X-ray spectroscopy of the ADC source X1822-371 with Chandra and XMM-Newton
• A catalogue of unusually long thermonuclear bursts on neutron stars
• The EXOD search for faint transients in XMM-Newton observations: Method and discovery of four extragalactic Type I X-ray Bursters
• Outbursts in ultracompact X-ray binaries
• The Fe Line Flux Ratio as a diagnostic of the maximum temperature and the white dwarf mass of Cataclysmic Variables
• 25 years of XMM-Newton observations of the Sgr A complex: 3D distribution and internal structure of the clouds
• New transient Galactic bulge intermediate polar candidate XMMU J175035.2-293557

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