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Detection of beta-class variability in Black Hole source GRS 1915+105 by Astrosat Scanning Sky Monitor

ATel #8185; M. C. Ramadevi (ISAC), B. T. Ravishankar (ISAC), Anuj Nandi (ISAC), V. Girish (ISAC), Brajpal Singh (ISAC), Anand Jain (ISAC), Vivek Kumar Agrawal (ISAC), Anil Agarwal (ISAC), Dipankar Bhattacharya (IUCAA), S. Seetha (ISRO), M. Ramakrishna Sharma (ISAC), Vaishali Sharan (ISAC), V. C. Babu (ISAC), Reena Yadav (ISAC), G. Meena (ISAC) , N. Sitarama Murthy (ISAC), Kumar (ISAC), B. N. Ashoka (ISAC), Ravi Kulkarni (ISAC), Nirmal Iyer (ISAC), D. Radhika (ISAC), Ankur Kushwaha (ISAC), K. Balaji (ISAC), G. Nagesh (ISAC), Manoj Kumar (ISAC), Dhruti Ranjan Gaan (ISAC), Prashanth Kulshresta (ISAC), Pankaj Agarwal (VSSC), Matthew Sebastin (VSSC), A. Rajarajan (VSSC), S. V. S. Subba Rao (ISAC), Pandiyan, R. (ISAC), K. Subba Rao (ISAC), Chaitra Rao (ISAC), K. Suryanarayana Sarma (ISAC)
on 18 Oct 2015; 06:14 UT
Credential Certification: Dipankar Bhattacharya (dipankar@iucaa.in)

Subjects: X-ray, Binary, Black Hole

The Scanning Sky Monitor (SSM) on board ASTROSAT was made operational on October 12th, 2015, the 15th day after launch (September 28th, 2015). After initial observations of the Crab Nebula, on October 14th 2015, the SSM was maneuvered for a stare at the galactic Black Hole source GRS 1915+105. Among several bright sources in the SSM field of view (including Cyg X-1, Cyg X-2, Ser X-1), GRS 1915+105 is the brightest with an X-ray intensity of ~2 Crab (http://maxi.riken.jp). GRS 1915+105 is well known for showing very peculiar, but structured X-ray variability of different 'classes' (Belloni et al 2000 Astronomy and Astrophysics 355, 271). During the period of SSM observations (Oct 14, 2015 UT 08:47 to UT 21:45; ASTROSAT Orbit No. 00240 to Orbit 00247), we found the source to exhibit variability of so-called class β. Both soft and hard dips are clearly seen in the light curve of the source. The light curve obtained from Orbit 00242 is available at ISRO web page http://www.isro.gov.in/sites/default/files/galleries/Gallery/grs1915astrosatssmorb242.png

Further analysis is underway to reconstruct the image of the SSM Field of View in order to quantify the X-ray flux of the source. β class variability of GRS 1915+105 is associated with the ejection of material in the form of jets from the Black Hole system, accompanied by radio emission. Follow-up observations in the radio and infrared bands are encouraged.