Fermi LAT Detection of a Gamma-ray Flare from the BL Lac Object ON 246
ATel #7596; Josefa Becerra (NASA GSFC/UMD), on behalf of the Fermi Large Area Telescope Collaboration.
on 6 Jun 2015; 03:27 UT
Credential Certification: Josefa Becerra Gonzalez (josefa.becerra@nasa.gov)
Subjects: Gamma Ray, >GeV, VHE, Request for Observations, AGN, Blazar, Transient
The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope has observed increasing gamma-ray flux from a source positionally consistent with the BL Lac object ON 246 (RA=187.55871 deg, Dec=25.30198 deg, J2000, Beasley et al. 2002, ApJS, 141, 13; with redshift z=0.135, Nass et al. 1996, A&A, 309, 419), also known as S3 1227+25 and 3FGL J1230.3+2519 (3FGL; Acero et al. 2015, arXiv:1501.02003).
The source has been detected on 4 June 2015 with a daily averaged flux (E> 100 MeV) of (0.9+/-0.2)x10^-6 ph cm^-2 s^-1 with a hard photon spectral index of 1.64+/-0.11 (errors are statistical only). This corresponds to a flux increase of a factor around 83 compared with the average flux reported in the 3FGL. Please note that most of the emission is coming from the second half of the day, from 12 to 24 h UTC. The first GeV flare of the source occurred on 22 January 2015 (ATel #6982), reaching a flux about 31 times the one reported on the 3FGL. It was recently detected in the VHE band by VERITAS (ATel #7516) and showed activity in NIR (ATel #7365), optical-UV and X-rays (ATel #7523, ATel #7526).
Since Fermi operates in all-sky survey mode, gamma-ray monitoring of this source will continue. In consideration of the activity of this source we strongly encourage multi-wavelength observations. The Fermi LAT contact persons for this source are D. Gasparrini (dario.gasparrini@asdc.asi.it), S. Cutini (sara.cutini@asdc.asi.it) and J. Becerra (josefa.becerra@nasa.gov).
The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.
