Unprecedented brightening of blazar S5 716+714 and a brighter CGRaBS J0510+1800

ATel #6962; Sunil Chandra (TIFR, Mumbai), Pankaj Kushwah(TIFR, Mumbai), S. Ganesh(PRL, Ahmedabad), Navpreet Kaur(PRL, Ahmedabad), Kiran Baliyan(PRL, Ahmedabad, India)
on 20 Jan 2015; 11:35 UT
Credential Certification: Kiran S Baliyan (baliyan@prl.res.in)

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Mt Abu InfraRed Observatory (MIRO), operated by the Physical Research Laboratory, Ahmedabad, India, equipped with 1.2m and 0.5m optical telescopes monitors AGNs, particularly when these are in flaring mode. Here we report on the optical brightness of two flaring blazars: S5 716+714 and CGRaBS J0510+1800 employing 0.5m CDK-20 Telescope mounted with optical EMCCD. S5 0716+714 is reported to be in continued brightening phase (Atel #6942, #6944, # 6953, #6957) in NIR and optical windows. We monitored in R (more than 45 mins), V, B & I bands and found it in unprecedented bright phase. From the earlier reports, it appears to be brightening continuously and therefore needs to monitored in all possible e-m windows. On the night of January 18, we present the following brightness values for the source: MJD 57040.88301 V= 12.066+/-0.01 MJD 57040.89259 B= 12.543+/-0.005 MJD 57040.90259 I= 11.166+/-0.03 MJD 57040.90208 R= 11.677+/-0.005 These are the brightest ever values for S5 0716+714. The long-term behaviour of the source shows that it has gone several cycles of brightness and fading with a period of roughly 12- 15 years. At the same time, the viewing angle appears to change in such a way that it increases as source gets dimmer. We had looked at the data upto December 2012 and based on that felt that it should start brightening by late 2014 or early 2015 while viewing angle decreases. The present status of the source appears to justify that. However, more observations at all energy regimes, including estimation of viewing angle, are required to understand this enigmatic source. Blazar CGRaBS J0510+1800 which was also reported to be in flaring state (Atel #6935, NIR H(band)=14.82 on January 16, 2015), shows the following brightness value: R= 15.917 +/-0.01 We will continue monitoring these with 1.2m and 0.5 m telescopes of MIRO.