Large Flares from GRS 1915+105 in its Unusual Low State as Observed by Astrosat
ATel #12805; V. Jithesh, Bari Maqbool, Gulab C Dewangan and Ranjeev Misra (IUCAA)
on 25 May 2019; 07:14 UT
Credential Certification: V. Jithesh (jitheshthejus@gmail.com)
Subjects: X-ray, Black Hole, Variables
We observed the Galactic microquasar GRS 1915+105 in its unusual low state using SXT and LAXPC instruments onboard {\it Astrosat}. The source was observed for an effective exposure of 22.6 ks with SXT as the primary instrument starting on 2019 May 15T02:04:22 till 2019 May 16T07:14:37.
The source exhibited the flaring activities in the 3-80 keV band light curve of LAXPC20, where the intensity changed by a factor $\sim 5$ (light curve is provided in the link below). Each flare typically lasts for a few hundred seconds (280--640 s). This activity was observed in the first 60 ks time of the light curve with eight distinct flares. Then the flaring activity becomes weak and disappears completely. Similar variability behaviour has been observed in the 0.3-8 keV light curve of SXT. Interestingly, the source was reported in the re-brightening phase starting from 2019-05-14 (ATEL #12761). Thus, the observed flaring activity may be related to the re-brightening of GRS 1915+105. We have also investigated the timing properties of the source in this state. The extracted power density spectrum in the 3-15 keV band is mainly dominated by the broad noise with no quasi-periodic oscillation. The average unabsorbed flux in the 0.8-30 keV band is 4.34 (+0.11, -0.10) E-9 erg/cm^2/s. Detailed spectral analysis is in progress.
We thank all the Astrosat operations team members for scheduling this ToO observation and for delivering the data quickly.
Astrosat LAXPC Light Curve