Swift confirms flare in BL Lacertae  in the Optical/UV
Dirk Grupe and Aaron Lackey-Stewart (Morehead State University)
We analyzed the most recent Swift observation of BL Lacertae (BL Lac) and confirm the flare seen in the NIR as reported by Carrasco et al. (ATEL 8311). The flare already started around 2015-October-13 (MJD 57308; target ID 30720, segment 189). Swift detected a jump in all 6 UVOT filters by about 1 mag compared with the previous observation of BL Lac on October 06. The observed magnitudes on October 13 were 13.72+/-0.04, 14.49+/-0.05, 14.09+/-0.05, 14.73+/-0.06, 15.45+/-0.08, 15.50+/-0.06 in V, B, U, W1, M2, and W2, respectively. Swift showed a peak in the UV/Optical light curve on October 31st (MJD 57326, segment 195; similar to the peak found in the NIR by Carrasco et al., ATEL #8311) with the following observed magnitudes: 13.40+/-0.04, 14.21+/-0.05, 13.77+/-0.05, 14.53+/-0.06, 15.12+/-0.07, 15.20+/-0.06. These values are slightly fainter than during the all-time high seen in November 2013 (Grupe et al., ATEL #5598). In the last Swift observation on November 20 (MJD 57346, segment 200) it remained in a relatively bright state in the UV/Optical and is currently at 14.00+/-0.04, 14.80+/-0.05, 14.34+/-0.05, 15.02+/-0.07, 15.63+/-0.11, 15.76+/-0.07. Although BL Lac showed an increase of its UV flux by a factor of more than 3.3 during the peak compared with the October 06 observation, we do not detect a significant increase in the X-ray emission (see also http://www.swift.psu.edu/monitoring/source.php?source=BLLacertae ;Stroh & Falcone, 2013, ApJS, 207, 28).
optical,ultra-violet,x-ray,agn,blazar