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Observation of Gamma-Ray Emission from PSR J2022+3842

ATel #3466; M. Pilia, A. Treves (Universita' dell'Insubria), A. Pellizzoni, A. Trois (INAF-OACagliari), S. Motta (Insubria, INAF_OABrera)
on 1 Jul 2011; 14:40 UT
Credential Certification: Sara Elisa Motta (sara.motta@brera.inaf.it)

Subjects: Gamma Ray, Pulsar

We report a tentative detection of pulsed gamma-ray emission from the recently discovered radio and X-ray pulsar J2022+3842 (Arzoumanian et al. 2011, arXiv 1105.3185).

The pulsed gamma-ray emission is observed in Fermi data using a solution based on the X-ray ephemeris provided by RXTE in an 8-days time interval (2010 Jan 27- Feb 4 UT), and compatible with it. Gamma-ray observations were folded in the interval 2010 Jan 17 - Feb 14 UT. Taking into account the number of trials in F0 (40) and F1 (10), pulsations are detected at a 5 sigma confidence level at energies above 200 MeV and at 3.6 sigma above 100 MeV. At E>100MeV, a total of 660+/-130 pulsed counts (event extraction radius ROI=2 deg) is observed, at frequency F0=41.1730092(4) Hz, and frequency derivative F1=-7.30(4)e-11, referred to epoch 2010 Jan 31.0 UT, within the RXTE ephemeris error. The corresponding pulsed flux above 100 MeV is 2.7(5)e-7 ph/cm^2/s and the luminosity is 3.6(6)e35 erg/s (=0.03*E'_rot) assuming a distance d=10 kpc and a beaming factor f=1 corresponding to emission over 4pi sr.

Extending the interval, the significance of the detection decreases. No pulsation is found using the radio ephemeris valid on a wider 512 days time interval (2009 May 06 - 2010 Sep 30 UT) with respect to the RXTE ephemeris. This can be explained by the fact that the pulsar timing behavior is irregular during the radio observations, with glitch like activity, scattering and timing noise which cannot be accounted for by sparse long time ephemeris (Arzoumanian et al. 2011).

Multiwavelength observation campaigns are encouraged to confirm the detection on longer time spans.