AstroSat observation of AT2019wey

ATel #13976; Yash Bhargava (IUCAA), Varun Bhalerao (IIT Bombay) & Dipankar Bhattacharya (IUCAA)
on 28 Aug 2020; 13:15 UT
Credential Certification: Varun Bhalerao (varunb@iitb.ac.in)

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AT2019wey is a transient source of unknown nature, discovered in the optical band in December 2019 (ATLAS19bcxp, Tonry et al, TNS report 54098). The source was also detected by SGR (Mereminskiy et al. Atel #13571), leading to broadband studies including radio (Yao et al. Atel #13921) and X-ray bands (Yao et al. Atel #13932, #13957). Based on the recent X-ray brightening of the source (Negoro et al Atel #13948, #13949), we proposed for a Target of opportunity (ToO) observation using AstroSat, and 18 ks of SXT exposure time were conducted starting on 2020-08-26 04:34:08 UT. Preliminary analysis of the spectrum in 0.7-7.0 keV energy range indicates that the spectrum can be well described by a thermal component along with a non-thermal high energy tail. We found two models give a reasonable fit to data (a) absorbed disk with a inner temperature of 0.3 keV and a power law of index 1.9 (n_H of 2.74e22 cm^-2) (b) absorbed blackbody of temperature 0.24 keV and power law of an index of 1.93 (n_H of 2.07e22 cm^-2). Similar power law index is also reported in Yao et al (Atel #13932) based on the NICER observations earlier in the month. We measure a 0.7-7.0 keV flux of 8.27e-10 ergs/cm^2/s, corresponding to an unabsorbed flux of 1.2e-9 ergs/cm^2/s. Further analysis is under way. We thank the AstroSat Time Allocation team and operations team for the quick response to the ToO proposal.