FACT measures increased gamma-ray flux from the high-energy peaked BL Lac object 1ES 1959+650 since five nights
ATel #9139; A. Biland for the FACT Collaboration
on 10 Jun 2016; 22:04 UT
Credential Certification: Adrian Biland (email@example.com)
Subjects: TeV, VHE, AGN, Transient
The FACT collaboration reports the measurement of 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 at gamma rays (ATel #9010), IR (ATel #9070) and X-rays (ATel #9121), and the since Summer 2015 several periods of enhanced gamma-ray activity have been observed.
Since five nights, FACT measures an increased average flux corresponding to more than 0.5 Crab units
with indication for intranight variability exceeding 1 Crab unit around MJD 57546.1-57546.2 and
57549.1-57549.2. For each of these five nights, the source is measured with a significance
exceeding 5 standard deviations.
The results of a preliminary automatic quick look analysis are publicly
shows the evolution of a nightly binned background corrected 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
FACT is regularly monitoring 1ES 1959+650. Currently it is observing the source each night from 02:30
to 05:00 UTC if weather conditions permit. Contact person for this source is D. Dorner
The First G-APD Cherenkov Telescope (FACT) is an imaging air Cherenkov
telescope with 9.5 sqm mirror area located in the Observatorio del
Roque de los Muchachos on the Canary Island La Palma. 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.