AstroSat detects XTE J1701-462 near the 2022 outburst peak
ATel #15726; Unnati Kashyap (IIT Indore), Manoneeta Chakraborty (IIT Indore)
on 28 Oct 2022; 09:32 UT
Credential Certification: Manoneeta Chakraborty (mono.phy@gmail.com)
Subjects: X-ray, Binary, Neutron Star, Transient
The neutron star Low Mass X-ray Binary (LMXB) source XTE J1701-462 is currently in outburst as detected by MAXI/GSC (ATel #15592) on 2022 September 06 and further confirmed by follow-up observations (ATels #15594, #15602, ATel #15605, ATel #15616, #15627). On September 20, 2022, the first detection of a radio counterpart was reported (ATel #15621). More recently, AstroSat observed XTE 1701-462 in the horizontal branch of Z track (Atel #15654).
We report the AstroSat ToO observation of XTE J1701-462 between 2022 October 01 03:26:52.0 UTC and October 03 13:52:43.0 UTC for a total on-source exposure time of 30 ks. Our AstroSat observations of XTE J1701-462 were conducted near the outburst peak, as confirmed by the comparison with the long-term MAXI light curve. The hardness intensity diagram exhibits a distinct Horizontal Branch (HB) and a Normal Branch (NB) of its Cyg-like Z track during the AstroSat observations.
The simultaneous broadband spectrum using LAXPC and SXT in the 0.7-25.0 keV energy range is fitted by two thermal (absorbed disk blackbody and blackbody radiation) models. We find an absorption column density of (2.92 +/- 0.01)x10^22 atoms/cm^2, blackbody temperature of 3.35 +/- 0.05 keV, and inner disk temperature of 1.82 +/- 0.01 keV. The total unabsorbed flux in the 0.7 to 25.0 keV range is estimated as (9.70 +/- 0.01)x10^(-9) erg/s/cm^2. The AstroSat light curve of XTE J1701-462 shows large scale variability, and the power spectrum is observed to consist of low frequency red noise and a broadband noise. We detect a quasi-periodic oscillation (QPO) at 35.25 +/- 1.19 Hz. A possible second harmonic signature of the QPO was also observed. Further multi-wavelength monitoring of XTE J1701-462 is recommended.
We would like to thank the AstroSat operations team for prompt scheduling of this ToO observation and for providing access to the data.
