The MAGIC collaboration reports the discovery of very high energy (VHE;
E>100 GeV) gamma-ray emission from MS1221.8+2452 (12h24m24.2s
+24d36m24s, J2000.0). MS1221.8+2452 is a blazar located at a redshift of
0.218 (Sbarufatti et al., 2005, ApJ 635, 173) and classified as a high
synchrotron peaked (HSP) BL Lac. It is one of the very few BL Lacs that
has been imaged with the Hubble Space Telescope (Jannuzzi et al., 1997,
ApJ 491, 146). It has been included in the ROSAT Bright Source Catalog
(Voges et al., 1999, A&A 349, 389) and identified as XBL
(X-Ray-Selected BL Lac) by the Einstein Extended Medium Sensitivity
Survey (Rector et al. 2000, AJ 120, 1626).
The object was observed with the MAGIC telescopes for 4 hours from
2013/04/30 to 2013/05/01. The preliminary analysis of these data
resulted in the detection of MS1221.8+2452 with a statistical
significance of more than 5 standard deviations. The VHE flux of this
detection was estimated to be about 4% of the Crab nebula flux above 200
GeV.
MS1221.8+2452 was observed with Swift during March and April 2013,
showing flux variability ranging from 3e-12 erg/cm2/s to 13e-12
erg/cm2/s in the 0.3-10 keV energy range. This source was flagged as a
promising VHE source candidate by the Fermi-LAT collaboration,
information that was shared with the MAGIC collaboration (as well as
other ground-based gamma-ray instruments).
MAGIC observations on MS1221.8+2452 will continue during the next days
until 2013/05/12 and multiwavelength observations are encouraged.
The MAGIC contact persons for these observations are J. Cortina (cortina@ifae.es) and F. Borracci (frabor@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 20 TeV.