Fermi LAT detection of long-duration enhanced GeV gamma-ray emission of PKS 1830-211 and a flare of TXS 0646-176
ATel #12252; Stefano Ciprini (1. INFN Tor Vergata; 2. ASI Space Science Data Center; Rome, Italy), on behalf of the Fermi Large Area Telescope Collaboration
on 30 Nov 2018; 10:56 UT
Credential Certification: Stefano Ciprini (stefano.ciprini@ssdc.asi.it)
Subjects: Gamma Ray, >GeV, Request for Observations, AGN, Black Hole, Blazar, Quasar, Gravitational Lensing
Referred to by ATel #: 12293, 12327, 12541, 12594, 12601, 12603, 12622, 12659, 12667, 12685, 12739, 13030, 13065, 15649
The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed increasing gamma-ray flux from a source positionally consistent with PKS 1830-211, also known as 3FGL J1833.6-2103 (Acero et al. 2015, ApJS, 218, 23) with radio coordinates (J2000) R.A.: 278.416201 deg, Dec.: -21.061048 deg (van Ommen et al., 1995, ApJ, 444, 561).
PKS 1830-211 is a flat spectrum radio quasar (FSRQ) placed at redshift z=2.507 (Lovell et al. 1998, ApJ, 508, L51), having intervening absorption systems and being subject to gravitational lensing by a galaxy at z=0.886 (Wiklind & Combes 1996, Nature, 379, 11). In the past PKS 1830-211 showed major GeV gamma-ray outburst activity in 2010 (Abdo et al. 2015, ApJ, 799, 143).
PKS 1830-211 has been recently bright in GeV gamma rays for several months, and was reported last October in ATel#12136 by the Fermi LAT Collaboration. Preliminary analysis indicates that on 2018 November 29, the prolonged outburst of this source further increased, reaching a daily averaged gamma-ray flux (E>100 MeV) of (4.2+/-0.6)X10^-6 photons cm^-2 s^-1 (statistical uncertainty only), with corresponding photon spectral index (E>100 MeV) of 2.3+/-0.2. The gamma-ray flux was above the 3.0X10^-6 photons cm^-2 s^-1 level the previous three days (Nov. 26, 27 and 28) as well. GeV gamma-ray activity of PKS 1830-211 has been announced four times since 2009 by the Fermi LAT Collaboration (ATel#12136, ATel#6361, ATel#4158, ATel#2943) and two times by the AGILE Collaboration (ATel#2242, ATel#2950).
Also on 2018 November 29 the LAT observed increasing gamma-ray flux from a source positionally consistent with TXS 0646-176, also known as 3FGL J0648.8-1740, with radio coordinates (J2000) R.A.: 102.118744 deg, Dec.:-17.734844 deg (Petrov et al. 2006, AJ, 131, 1872), and redshift z=1.232 (Hewitt & Burbidge 1993, ApJS, 87, 451).
Preliminary analysis indicates that TXS 0646-176 on November 29 reached a daily averaged gamma-ray flux (E>100 MeV) of (1.5+/-0.1)X10^-6 photons cm^-2 s^-1, with corresponding photon spectral index (E>100 MeV) of 2.4+/-0.1. GeV gamma-ray activity of TXS 0646-176 has been announced on two previous occasions by the Fermi LAT Collaboration.
Both the sources are included in the list of publicly monitored sources, with their preliminary light curves that can be found at FSSC
Because Fermi normally operates in an all-sky scanning mode, regular monitoring of these sources will continue. In consideration of their ongoing activity we strongly encourage multiwavelength observations. For both the sources the Fermi LAT contact person is S. Ciprini (stefano.ciprini@ssdc.asi.it).
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.