The complex spectral behavior of the newly discovered neutron star X-ray binary Swift J1858.6-0814

Abstract

We report on the \nustar{} observation of the newly discovered neutron star X-ray binary Swift~J1858.6-0814 taken on 23rd March 2019. The light curve of the source exhibits several large flares during some time intervals of this observation. The source is softer in the high-intensity interval where the large flaring activity mainly occurs. We perform time-resolved spectroscopy on the source by extracting spectra for two different intensity intervals. The source was observed with a $3-79 \kev{}$ luminosity of $\sim 9.68\times 10^{36}$ ergs/s and $\sim 4.78\times 10^{36}$ ergs/s for high and low-intensity interval, respectively assuming a distance of $15$ kpc. We find a large value of the absorbing column density (${\mathrm{N}}_{\mathrm{H}}\sim 1.1\times 10^{23}$ cm${}^{-2}$), and it appears to be uncorrelated with the observed flux of the source. Each spectrum shows evidence of Fe K$\alpha$ emission in the $5-7$\kev{} energy band, an absorption edge around $\sim 7-8$\kev{}, and a broad Compton hump above $15$\kev{}, indicating the presence of a reflection spectrum. The observed features are well explained by the contribution of a relativistic reflection model and a partially covering absorption model. From the best-fit spectral model, we found an inner disc radius to be $4.87_{-0.96}^{+1.63}{R}_{ISCO}$ (for the high-intensity interval) and $5.68_{-2.78}^{+9.54}{R}_{ISCO}$ (for the low-intensity interval), indicating a significant disc truncation. The disk inclination is found to be relatively low, $i<33^0$. We further place an upper limit on this source's magnetic field strength considering the disc is truncated at the magnetospheric radius.

arXiv comment13 pages, 14 figures, 3 Tables, Accepted for publication in MNRAS

References in corpus (50)

• On the Absorption of X-rays in the Interstellar Medium
• The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission
• Atomic Data for Astrophysics. II. New Analytic Fits for Photoionization Cross Sections of Atoms and Ions
• Advection-Dominated Accretion and the Spectral States of Black Hole X-Ray Binaries: Application to Nova Muscae 1991
• Broad-band gamma-ray and X-ray spectra of NGC 4151 and their implications for physical processes and geometry
• Thermonuclear (type-I) X-ray bursts observed by the Rossi X-ray Timing Explorer
• Improved Reflection Models of Black-Hole Accretion Disks: Treating the Angular Distribution of X-rays
• The May 1989 outburst of the Soft X-ray Transient GS 2023+338 (V404 Cyg)
• X-ray reflected spectra from accretion disk models. I. Constant density atmospheres
• Accretion Disk Boundary Layers Around Neutron Stars: X-ray Production in Low-Mass X-ray Binaries
• Relativistic iron emission lines in neutron star low-mass X-ray binaries as probes of neutron star radii
• On the Misalignment of Jets in Microquasars
• Near-Infrared Spectroscopy of Low Mass X-ray Binaries : Accretion Disk Contamination and Compact Object Mass Determination in V404 Cyg and Cen X-4
• Broad relativistic iron emission line observed in SAX J1808.4-3658
• Light Curves of Rapidly Rotating Neutron Stars
• A rapidly-changing jet orientation in the stellar-mass black hole V404 Cygni
• Accreting millisecond pulsar SAX J1808.4-3658 during its 2002 outburst: evidence for a receding disc
• MAXI J1820+070 with NuSTAR I. An increase in variability frequency but a stable reflection spectrum: coronal properties and implications for the inner disc in black hole binaries
• XMM-Newton detects a relativistically broadened iron line in the spectrum of the ms X-ray pulsar SAX J1808.4-3658
• Dynamical confirmation of a black hole in MAXI J1820+070
• A Fast X-ray Disk Wind in the Transient Pulsar IGR J17480-2446 in Terzan 5
• A Hard Look at the Neutron Stars and Accretion Disks in 4U 1636-53, GX 17+2, and 4U 1705-44 with $\text{NuSTAR}$
• Exploring The Effects Of Disk Thickness On The Black Hole Reflection Spectrum
• The Black Hole Binary V4641 Sagitarii: Activity in Quiescence & Improved Mass Determinations
• Furiously Fast and Red: Sub-second Optical Flaring in V404 Cyg during the 2015 Outburst Peak
• A four-year baseline Swift study of enigmatic X-ray transients located near the Galactic center
• The Soft State of the Black Hole Transient Source MAXI J1820+070: Emission from the Edge of the Plunge Region?
• NuSTAR Observations of the Accreting Atolls GX 3+1, 4U 1702-429, 4U 0614+091, and 4U 1746-371
• Effects of Rapid Stellar Rotation on Equation of State Constraints Derived from Quasi-Periodic Brightness Oscillations
• Energy Release During Disk Accretion onto a Rapidly Rotating Neutron Star
• Testing reflection features in 4U 1705-44 with XMM-Newton, BeppoSAX and RXTE in the hard and soft state
• On the Fe K absorption - accretion state connection in the Galactic center neutron star X-ray binary AX J1745.6-2901
• A persistent ultraviolet outflow from an accreting neutron star binary transient
• NuSTAR and XMM-Newton broad-band spectrum of SAX J1808.4-3658 during its latest outburst in 2015
• The rapid X-ray variability of V4641 Sagittarii (SAX J1819.3-2525 = XTE J1819-254)
• Truncation of the Accretion Disk at One Third of the Eddington Limit in the Neutron Star Low-Mass X-ray Binary Aquila X-1
• V4641Sgr - Super-Eddington source enshrouded by an extended envelope
• Discovery of thermonuclear (Type I) X-ray bursts in the X-ray binary Swift J1858.6-0814 observed with NICER and NuSTAR
• The Changing-look Optical Wind of the Flaring X-ray Transient Swift J1858.6-0814
• Relativistic X-Ray Reflection and Photoionised Absorption in the Neutron-Star Low-Mass X-ray Binary GX 13+1
• NuSTAR observations of the Transient Galactic Black Hole Binary Candidate Swift J1858.6-0814: A New Sibling of V404 Cyg and V4641 Sgr?
• Dips and eclipses in the X-ray binary Swift J1858.6-0814 observed with NICER
• The variable radio counterpart of Swift J1858.6-0814
• Conflicting disk inclination estimates for the black hole X-ray binary XTE J1550-564
• Outflows and spectral evolution in the eclipsing AMXP SWIFT J1749.4-2807 with NICER, XMM-Newton and NuSTAR
• Reflection component in the Bright Atoll Source GX 9+9
• Soft X-ray emission lines in the X-ray binary Swift J1858.6-0814 observed with XMM-Newton-RGS: disc atmosphere or wind?
• Broadband X-ray emission and the reality of the broad iron line from the Neutron Star - White Dwarf X-ray binary 4U 1820-30
• A rapid optical and X-ray timing study of the neutron star X-ray binary Swift J1858.6-0814
• X-ray flashes from the low-mass X-ray binary IGR J17407-2808