Spectral Analysis of New Black Hole Candidate AT2019wey Observed by NuSTAR

Abstract

AT2019wey is a new galactic X-ray binary that was first discovered as an optical transient by the Australia Telescope Large Area Survey (ATLAS) on December 7, 2019. AT2019wey consists of a black hole candidate as well as a low-mass companion star ($M_{\text{star }}\lesssim 0.8M_{\odot }$) and is likely to have a short orbital period ($P_{\text{orb }}\lesssim 8$ h). Although AT2019wey began activation in the X-ray band during almost the entire outburst on March 8, 2020, it did not enter the soft state during the entire outburst. In this study, we present a detailed spectral analysis of AT2019wey in the low/hard state during its X-ray outburst on the basis of Nuclear Spectroscopic Telescope Array \emph observations. We obtain tight constraints on several of its important physical parameters by applying the State-of-art \texttt{relxill} relativistic reflection model family. In particular, we determine that the measured inner radius of the accretion disk is most likely to have extended to the innermost stable circular orbit (ISCO) radius, i.e., $R_{\text{in}}=1.38_{-0.16}^{+0.23}{R}_{\text{ISCO}}$. Hence, assuming $R_{\text{in}}$=$R_{\text{ISCO}}$, we find the spin of AT2019wey to be $a_{\ast }\sim$ $0.97$, which is close to the extreme and an inner disk inclination angle of ~$i\sim$ $22^{\circ }$. Additionally, according to our adopted models, AT2019wey tends to have a relatively high iron abundance of $A_{\mathrm{Fe}}\sim$ 5 $A_{\mathrm{Fe},\odot }$ and a high disk ionization state of $\log \xi \sim$ 3.4.

14 pages, 4 figures; Accepted for publication in SCPMA

References in corpus (14)

• The Zwicky Transient Facility: Data Processing, Products, and Archive
• The role of the reflection fraction in constraining black hole spin
• The Origin of Black Hole Spin in Galactic Low-Mass X-ray Binaries
• The synchrotron boiler and the spectral states of black hole binaries
• On the origin of spectral states in accreting black holes
• Insight-HXMT observations of jet-like corona in a black hole X-ray binary MAXI J1820+070
• Reflection Spectra of the Black Hole Binary Candidate MAXI J1535-571 in the Hard State Observed by NuSTAR
• Self-Consistent Black Hole Accretion Spectral Models and the Forgotten Role of Coronal Comptonization of Reflection Emission
• A New Spin on an Old Black Hole: NuSTAR Spectroscopy of EXO 1846-031
• NuSTAR Observations of the Black Hole GS 1354-645: Evidence of Rapid Black Hole Spin
• The Case for Hypercritical Accretion in M33 X-7
• Stronger Reflection from Black Hole Accretion Disks in Soft X-ray States
• A detailed study on the reflection component for the Black Hole Candidate MAXI J1836-194
• VLBA discovery of a resolved source in the candidate black hole X-ray binary AT2019wey