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MAGIC observes very high energy gamma ray emission from PKS 1424 +240

ATEL # 2098; Masahiro Teshima, Spokesperson for the MAGIC collaboration
on 24 Jun 2009; 15:15 UT
Distributed as an Instant Email Notice (Request for Observations)
Password Certification: Masahiro Teshima (mteshima@mppmu.mpg.de)

Subjects: Gamma Ray, >GeV, Request for Observations, AGN

The MAGIC collaboration reports the observation of very high energy gamma ray emission above 100GeV from PKS 1424 +240, categorized as an Intermediate BL Lac object. The distance of this source is unknown. The discoveries of high-energy and very high energy gamma ray emissions from this source were reported earlier this year by Fermi (Abdo et al., arXiv:0902.1340; Abdo et al., arXiv:0902.1559) and 9 days ago by VERITAS (ATEL #2084), respectively. MAGIC observed PKS 1424 +240 intermittently from May 2006 to June 2009 using the 17m diameter telescope on La Palma, Canary Islands, Spain. Observations in 2006 and 2007 with a total observation time of 20 hrs show a marginal excess of events, but no clear evidence of gamma ray emission. Recent observations in 2009 from April to June, with a total observation time of 10 hrs in overlap with the VERITAS observation, show a possible state of high flux of the source. They result in an excess of 365 events corresponding to a statistical significance above 5 sigma, confirming the VERITAS signal (ATEL #2084). The integral flux of high energy gamma rays from PKS1424 +240 is estimated to be (1.1 +- 0.4) x 10^-10 cm^-2 s^-1 (>100GeV) for the period April-June 2009. The observed signal is concentrated mainly in the energy range below 300GeV, and the spectrum seems to be very soft. The differential spectral index is estimated as 4.6 +- 1.6. The light curve of PKS 1424 +240 in the optical R-band was obtained using the 1.03 m telescope at Tuorla Observatory, Finland, and the 35cm telescope at the KVA observatory on La Palma, Canary islands, Spain. The PKS 1424 +240 appeared in a relatively high state with Mag(R) = 14.0 in February to June 2009. The light curve peaks at Mag(R) = 13.9 around 26 May 2009. The optical data are available at the web site http://users.utu.fi/kani/1m/PG_1424+240.html MAGIC will continue the observation of PKS 1424 +240. Multi-frequency observations are strongly encouraged.


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