Possible Detection of a Cyclotron Resonance Scattering Feature in the X-Ray Pulsar 4U 1909+07
Abstract
We present timing and broad band spectral studies of the high-mass X-ray binary pulsar 4U 1909+07 using data from Suzaku observations during 2010 November 2-3. The pulse period of the pulsar is estimated to be 604.11 ± 0.14 s. Pulsations are seen in the X-ray light curve up to ~70 keV. The pulse profile is found to be strongly energy-dependent: a complex, multi-peaked structure at low energy becomes a simple single peak at higher energy. We found that the 1-70 keV pulse-averaged continuum can be fit by the sum of a blackbody and a partial covering Negative and Positive power law with Exponential cutoff model. A weak iron fluorescence emission line at 6.4 keV was detected in the spectrum. An absorption-like feature at ~44 keV was clearly seen in the residuals of the spectral fitting, independent of the continuum model adopted. To check the possible presence of a cyclotron resonance scattering feature (CRSF) in the spectrum, we normalized the pulsar spectrum with the spectrum of the Crab Nebula. The resulting Crab ratio also showed a clear dip centered at ~44 keV. We performed statistical tests on the residuals of the spectral fitting and also on the Crab spectral ratio to determine the significance of the absorption-like feature and identified it as a CRSF of the pulsar. We estimated the corresponding surface magnetic field of the pulsar to be 3.8 × 1012 G.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 2013
- DOI:
- 10.1088/0004-637X/779/1/54
- arXiv:
- arXiv:1310.0948
- Bibcode:
- 2013ApJ...779...54J
- Keywords:
-
- pulsars: general;
- stars: individual: 4U 1909+07;
- stars: neutron;
- X-rays: stars;
- Astrophysics - High Energy Astrophysical Phenomena;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 7 Pages, 7 Figures, Accepted for publication in The Astrophysical Journal