GeV Gamma-ray Emission from the Binary PSR B1259-63/SS2883 During the 2010 Periastron Passage

arXiv:1111.0367v1 [astro-ph.HE] 2 Nov 2011 2011 Fermi Symposium, Roma., May. 9-12 1 GeV Gamma-ray Emission from the Binary PSR B1259-63/SS2883 During the 2010 Periastron Passage Masaki Mori Department of Physical Sciences, Ritsumeikan University, Kusatsu, 525-8577 Shiga, Japan Akiko Kawachi Department of Physics, Tokai University, Hiratsuka, Kanagawa 259-1292, Japan Shigehiro Nagataki Yukawa Institute for Theoretical Physics, Oiwake-cho, Kitashirakawa, Sakyo-ku, Kyoto 606-8502, Japan Jumpei Takata Department of Physics, University of Hong Kong, Pokfulam Road, Hong Kong, China PSR B1259-63/SS2883 is a binary system which consists of a 48-ms radio pulsar and a massive star in a highly eccentric orbit with a period of about 3.4 years. Non-pulsed and non-thermal emissions from this binary have been reported in the radio, X-ray and TeV gamma-ray energy ranges. Light curves in the radio and X-ray bands showed characteristic double-peaked features which can be attibuted to the interactions of the pulsar wind and the Be disk during the crossings by the pulsar. The TeV light curves around periastron differ between 2004 and 2007 observations, and the feature is not conclusive. We report a detection of GeV gamma-ray emission around the periastron passage in December 2010 with Fermi-LAT. I. INTRODUCTION The PSR B1259-63/SS2883 system is one of a few binary systems detected in TeV gamma-ray energies. Gamma-rays should be emitted via interaction of high-speed wind from the 48-ms pulsar with the Be star wind and disk. The elliptic orbit with long (3.4- yr) period offers a unique experimental field of wind interaction with varying distance between the pulsar and the Be star [1, 2]. In 2004 and 2007, H.E.S.S. de- tected TeV gamma-rays as a marginal pre-periastron peak and a clear post-periastron peak [4, 5]. We stud- ied the 2010 periastron (December 14) passage in GeV gamma-rays using the Fermi-LAT data and compared the result with SPH simulation [2]. II. FERMI-LAT OBSERVATION Fermi-LAT data were obtained via Fermi Science Support Center and analyzed using the Fermi Science Tools (v9r17p0) with P6 V3 DIFFUSE instrument re- sponse function by the standard pipeline [3]. Exam- ples of countmaps are shown in Figures 1 to 3. For the whole observation period (August 4, 2008 – Febru- ary 9, 2011) the gamma-ray signal from PSR 1259- 63/SS2883 is not signifincant (Figure 1). Howerver, in the month after the periastron passage (December 22, 2010 – January 21, 2011) there is a hint of signal (Figure 2) with a TS (test statistic) value of 5 (which means it is significant at 2σ level) and in the follow- ing month (January 21, 2011 – February 9, 2011) the gamma-ray signal is highly significant (Figure 3) with a TS value of 58 (7σ level). III. LIGHT CURVES Light curves in 30-day bins and 5-day bins (assum- ing E−2 spectrum) are calculated with the help of Tools as shown in Figures 4 (30-day bin) and 5 (5-day bin). We detected gamma-ray signal between 30 days and 65 days after the periastron, although there is a hint of emission 20 days and 5 days before the perias- tron. We can compare the light curve with a predicted curve shown in red lines in Figure 5 (arbitrary scaled) which is calculated by SPH simulation of interaction FIG. 1: Fermi-LAT countmap (200 MeV–10 GeV, Aug. 4, 2008 – Feb. 9, 2011). Gamma-ray signal from PSR 1259-63/SS2883 is not significant. eConf C110509 2 2011 Fermi Symposium, Roma., May. 9-12 FIG. 2: Fermi-LAT countmap (200 MeV–10 GeV, Dec. 22, 2010 – Jan. 21, 2011). There is a hint of gamma-ray signal from PSR 1259-63/SS2883 with TS=5. FIG. 3: Fermi-LAT countmap (200 MeV–10 GeV, Jan. 21, 2011 – Feb. 9, 2011). Gamma-ray signal from PSR 1259-63/SS2883 is significant with TS=58. between the pulsar and the Be star [6]. The general tendency of the observed light curve is not inconsitent with prediction. IV. DISCUSSION We found a significant GeV gamma-ray signal from this system between 30 days and 65 days after the periastron. Emission in this epoch should be related to the time-varying geometry of this system. We will compare the gamma-ray light curves and spectra with simulation [6] to understand the emission from this binary system. After the analysis presented here has been com- pleted, we found similar results from Fermi-LAT data have been reported [7, 8]. FIG. 4: 30-day-bin light curve. Positive detection is ob- served only after the periastron. Open circles are fluxes with marginal significance (∼3σ). FIG. 5: Close-up of light curve in 5-day bins around pe- riastron. Points are plotted including marginal detections (9

📄 Read Full PDF on ArXiv

📸 Image Gallery

Reference

This content is AI-processed based on open access ArXiv data.