Fermi LAT observations of PSR J1119-6127 before and after its recent bursts
ATel #9365; P. H. Thomas Tam (Sun Yat-Sen University), on behalf of the Fermi Asian Network
on 11 Aug 2016; 08:25 UT
Credential Certification: P.H.Thomas Tam (grbtom@gmail.com)
Subjects: Gamma Ray, Pulsar
Referred to by ATel #: 9378
We report on the Fermi LAT observations of PSR J1119-6127, a rotation-powered pulsar with high magnetic field that showed two magnetar-like bursts on 2016-07-27 13:02:07.91 UT and 2016-07-28 01:27:51 UT, recorded by the Fermi GBM and Swift BAT instruments, respectively (Kennea et al., GCN Circ. 19735/ATel #9274; Younes et al., GCN Circ. 19736).
The spin-down luminosity of PSR J1119-6127 is E_dot=2.3x10^36 erg/s, and the pulsar emits pulsed gamma-rays (Parent et al., 2011, ApJ, 743, 170).
To look for any change in gamma-ray flux around recent bursts on July 27 and 28, we carried out a series of likelihood analyses of the region around the pulsar. Given that it is a gamma-ray pulsar, we fixed the spectral shape to the one specified in Parent et al. (2011), which also gives a photon flux of (9.3+-1.2)E-8 ph/cm2/s (all photon flux in this message refers to the flux above 100 MeV). We obtained a ~19-month light curve binned every three weeks, from 2015-01-01 to 2016-08-08. Three weeks were chosen to ensure a TS>10 detection for most bins. We found that the gamma-ray flux has decreased around mid-April, i.e., from its average value of (7.8+-0.5)E-8 ph/cm2/s (obtained using the data taken from between 2015-01-01 and 2016-04-15, which is consistent with that reported in Parent et al., 2011), to an average of (4.1+-1.0)E-8 ph/cm2/s between 2016-04-16 and 2016-08-08.
The Fermi LAT began Target of Opportunity (ToO) observations (PI: G. A. Younes) of PSR J1119-6127 between 2016-08-01 02:12:00 and 2016-08-08 UT 22:56:00, which essentially boost the LAT exposure on PSR J1119-6127 by about a factor of 2.4 during this period as compared to the survey mode.
We thank the Fermi LAT team for rapidly scheduling the ToO observation and providing data products. 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.
We encourage continuous monitoring of the pulsar across the electromagnetic spectrum.