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Discovery of Very High Energy gamma-ray emission from 1FGL J2001.1+4351 by MAGIC

ATEL # 2753; Mose Mariotti (University od Padova) on behalf of the MAGIC collaboration
on 22 Jul 2010; 17:10 UT
Password Certification: MosŤ Mariotti (

Subjects: Gamma Ray, >GeV, AGN

The MAGIC Collaboration reports the discovery of Very High Energy (VHE; >100 GeV) gamma-ray emission from the source MAGIC J2001+435, which is positionally consistent with the Fermi-LAT gamma-ray source 1FGL J2001.1+4351 (RA 20 01 13.5, dec 43 53 02.8, J2000), and the radio source MG4 J200112+4352 (RA 20 01 12.9, dec 43 52 52.8, J2000), which was recently identified with a BL Lac object (see Bassani et al., MNRAS 397 (2009) L55). The redshift of this source is still unknown. This source was flagged as a promising VHE source candidate by the Fermi-LAT collaboration, information which was shared with the MAGIC collaboration (as well as other IACTs) back in October 2009. The VHE detection is based on a 1.5 hour-long observation performed on July 16th in stereoscopic mode with the two 17m diameter imaging Cherenkov telescopes on La Palma, Canary Islands, Spain. The preliminary analysis of the MAGIC data using the standard cuts optimized for soft energy spectra sources yields a detection of ~120 gamma-rays, corresponding to a pre-trail statistical significance of ~7 standard deviations. The observed flux is estimated to be ~20% of the Crab nebula flux above 100 GeV. Earlier MAGIC observations indicated a substantially lower flux; hence indicating that the source is variable on a few days timescale. Observations with Swift have also been performed on this source location. A preliminary analysis of the Swift/XRT data shows that the X-ray flux from July 16th 2010 is ~3 times larger than the X-ray flux measured during previous Swift observations in July 2010, hence indicating that the source is variable (on few days timescale) and that it was X-ray active during the MAGIC observations on July 16th, indicating a correlation between VHE and X-ray activity at that time. Observations at other wavelengths and efforts to determine the redshift of this object are encouraged. Questions regarding the MAGIC observations should be directed to Mose Mariotti ( Questions regarding multifrequency observations of this object should be directed to David Paneque (

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