[ Previous | Next | ADS ]

Gamma-Ray Blazar BL Lacertae at historic high brightness in millimeter, X-ray and far-infrared bands

ATel #4557; Ann E. Wehrle (Space Science Institute), Dirk Grupe (Penn State), Mark Gurwell (CfA), Svetlana Jorstad (Boston University), Alan Marscher (Boston University)
on 8 Nov 2012; 19:32 UT
Credential Certification: Ann E Wehrle (awehrle@spacescience.org)

Subjects: Millimeter, Sub-Millimeter, Far-Infra-Red, X-ray, AGN, Blazar

Referred to by ATel #: 4565, 4568, 4600, 4973

We report on the current unprecedented brightness of BL Lacertae (2200+420) as observed by the Submillimeter Array (SMA), Swift, and the Herschel Space Observatory. Prompted by the reports of historic flaring at centimeter and millimeter bands by the F-GAMMA program (ATEL 4349.), we began Target of Opportunity monitoring in late October 2012 with the Submillimeter Array, Swift, and the Herschel Observatory. At the SMA, we measured 11.9 +/- 0.6 Jy at 225 GHz (1.3mm) and 11.0 +/- 0.6 Jy at 342 GHz (870 microns) on 29 Oct 2012. On 4 November 2012, the 225 GHz flux had risen to 13.7 +/- 0.7 Jy, the highest measured since SMA observations began in 2002, see http://sma1.sma.hawaii.edu/callist/callist.html?plot=2202%2B422 . The preliminary Herschel flux densities from Oct 29-30th are 2.1 +/- 0.06, 2.7+/-0.08, 3.7 +/- 0.18, 5.6 +/-0.4, 6.6 +/-0.5 and 8.1 +/-0.6 Jy at 70, 100, 160, 250, 350 and 500 microns, respectively. The 70, 100 and 160 micron observations were made with PACS; the 250, 350 and 500 micron observations were made with SPIRE. The brightness is approximately 2.2-2.6 times higher than it was in May 2011. With Swift, we measured an X-ray count rate of 0.9 +/- 0.1 counts/second on 29 Oct 2012 which corresponds to 5.3 (+/- 0.5) x 10^-11 ergs/s/cm^2 in the 0.3-10 keV band. For comparison to the multiyear RXTE light curve, the flux in the 2.4-10 keV band was 4.1 (+/-0.5) x 10^-11 ergs/s/cm^2. The Swift XRT flux levels are the highest in 7 years of observing and represent a six fold increase over levels earlier in October. Comparison to the long term RXTE light curve between 2004 and 2011 displayed in Marscher et al. (2008, Nature, 452, 966) and Marscher (2012 in the 2011 Fermi Symposium, eConf C110509, arXiv:1201.5402) shows that the highest brightness previously was 3.6E-11 erg/s/cm^2, in early 2006 and in a major X-ray outburst in late 2011. Daily observations with Swift and the SMA will continue through 23 November 2012. Additional observations with Herschel are scheduled for 8, 13, 14, 15, 16, 19 and 20 November. We note that the public Fermi LAT light curves at http://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/ show that the source began increased gamma-ray activity about 500 days ago, and has been detected weekly at estimated levels ranging up to 1 x 10^-6 ph/s/cm^2 with a few recent nondetections. Recent observations reporting increased brightness include ATELs #4031 , #4028 , and #4271 . Additional multiwavelength observations are encouraged during this period of unprecedented activity in BL Lac. The Herschel Space Observatory is described in Pilbratt, G.L., Riedinger, J.R., Passvogel, T. et al. 2010, A&A, 518, L1; the PACS instrument in Poglitsch, A., Waelkens, C., Geis, N. et al. 2010, A&A, 518, L2; and the SPIRE instrument in Griffin, M.J., Abergel, A., Abreu, A. et al. 2010, A&A, 518, L3. The Submillimeter Array is a joint project between the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics, and is funded by the Smithsonian Institution (USA) and the Academia Sinica (Taiwan). Swift is a NASA MIDEX mission whose instruments were developed by an international team from the United States, the United Kingdom, and Italy, with additional scientific involvement in France, Japan, Germany, Denmark, Spain, and South Africa. The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. We thank the Swift PI Neil Gehrels, the Observation Duty Scientists and the science planners. We thank the Herschel Project Scientist Goran Pilbratt, the science schedulers and mission controllers. We thank A. Falcone and M. Stroh (Penn State) for use of their Swift monitoring program at http://www.swift.psu.edu/monitoring/.