MAGIC detection of an increased activity from PG 1553+113 in very-high-energy gamma rays
ATel #14520; Oscar Blanch (IFAE-BIST), on behalf of the MAGIC collaboration
on 7 Apr 2021; 11:41 UT
Credential Certification: Oscar Blanch (blanch@ifae.es)
Subjects: Gamma Ray, TeV, VHE, Blazar
The MAGIC telescopes have observed an increase in the very-high-energy (VHE; >100 GeV) gamma-ray flux from PG 1553+113 (RA=15:55:43, DEC=11:11:23, J2000.0). The preliminary analysis of the MAGIC data taken on 2021/04/06 (MJD 59310.1), during a regular monitoring of the source, indicates an integral flux of ~0.25% of the flux from the Crab nebula above 150 GeV, which is a factor of ~4 higher with respect to the low-state VHE flux from this source.
PG 1553+113 is a bright VHE blazar with uncertain redshift (z>0.4; Danforth et al. 2010, ApJ 720, 976). It is one of the few blazars with a convincing quasi-periodic emission in the gamma-ray band, as observed by the Fermi-LAT satellite (Ackermann et al. 2015, ApJL 813, L41). In the next months the source is expected to approach a gamma-ray maximum according to the ~2 years periodic modulation.
The MAGIC observations were performed within the framework of a multi-year, multiwavelength campaign started in 2015. In optical, the source is currently monitored with the Telescopi Joan Oró (Montsec Observatory) as part of the Tuorla Blazar Monitoring Program (https://users.utu.fi/kani/1m/PG_1553+113.html). The long-term lightcurve shows an enhanced optical activity that started already in March, at the beginning of the 2021 monitoring campaign.
MAGIC observations on PG 1553+113 will continue during the next months and multiwavelength observations are encouraged. The MAGIC contact persons for these observations are Oscar Blanch (blanch@ifae.es), Elisa Prandini (elisa.prandini@unipd.it), and Serena Loporchio (serena.loporchio@ba.infn.it).
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.
