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.