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FACT and MAGIC measure an increased gamma-ray flux from the HBL 1ES 1959+650

ATel #9203; A. Biland (ETH Zurich), R. Mirzoyan (Max-Planck-Institute for Physics) on behalf of the FACT and MAGIC Collaborations
on 1 Jul 2016; 18:08 UT
Credential Certification: Daniela Dorner (dorner@astro.uni-wuerzburg.de)

Subjects: Gamma Ray, VHE, AGN, Blazar

Referred to by ATel #: 9239

The FACT and MAGIC collaborations report the measurement of an enhanced gamma-ray flux at about 1 TeV from a position consistent with the HBL 1ES 1959+650 (z=0.047, Schachter et al. 1993, ApJ, 412, 541).

Recent activities from this source were reported in gamma rays (ATel #9010, #9139, #9148, #9168), IR (ATel #9070) and X-rays (ATel #9121), and since Summer 2015 several periods of enhanced activity have been observed. After the bright flare of MJD 57552 (ATel #9148), the flux decayed within 1-2 nights to a level of 0.5-1 Crab units and stayed around or below that level for about 15 days.

From MJD 57570.04 till 57570.18, FACT measures an increased average flux corresponding to at least 2 Crab units. The source is detected with about 13 standard deviations in 3.3 hours of observation. The results of a preliminary, automatic quick look analysis are publicly available.
http://fact-project.org/monitoring/index.php?y=2016&m=06&d=30&source=7&timebin=3&plot=night shows the 20-minute-binned background subtracted light curve. These values are corrected neither for the effect of large zenith distance under which the source is observable nor for the amount of night-sky-background light, with both effects decreasing the measured gamma rate. The measurement might be affected the meteorologic phenomenon calima possibly causing an apparent lower flux.

FACT is regularly monitoring 1ES 1959+650. Currently, it is observing the source each night from 1:00 to 04:30 UTC, if weather conditions permit. The FACT contact person for this source is D. Dorner (dorner@astro.uni-wuerzburg.de)

The preliminary analysis of the MAGIC data taken from MJD 57570.00 to 57570.21 indicates a flux of about 2.6 that of the flux from the Crab Nebula above 300 GeV. MAGIC observations on 1ES 1959+650 will continue during the next days, and multi-wavelength observations are encouraged. The MAGIC contact person for these observations is R. Mirzoyan (Razmik.Mirzoyan@mpp.mpg.de)

MAGIC is a system of two 17m-diameter Imaging Atmospheric Cherenkov Telescopes located at the Canary island of La Palma, Spain, and designed to perform gamma-ray astronomy in the energy range from 50 GeV to greater than 50 TeV.

The First G-APD Cherenkov Telescope (FACT) is an Imaging Atmospheric Cherenkov Telescope with 9.5 sqm mirror area, located next to the two MAGIC telescopes. It is pioneering the usage of silicon photosensors and monitoring bright, variable sources at energies above 750 GeV. The Collaboration includes ETH Zurich and the Universities of Dortmund, Geneva and Wuerzburg.