Abstract

Optical Spectroscopy of the Be Star in the gamma-ray Binary PSR B1259-63

Erika Grundstrom (Vanderbilt University / Fisk University)

Observations of the rare Be star/pulsar system PSR B1259-63 have been made in energy bands from gamma rays to radio waves since its discovery in 1991. It consists of a 48 ms pulsar and a Be star with an outflowing equatorial circumstellar disk. The eccentric orbit (e=0.87) takes 3.4 years and the most recent periastron took place in December 2010. During the periastron, the pulsar actual plunges through the disk as the disk plane and the orbital plane are misaligned. As part of a multi-wavelength campaign to observe as many wavelengths as possible during this latest periastron passage (likely the only one during the Fermi Gamma-ray Telescope operations), we embarked on an H-alpha optical spectroscopy campaign. The H-alpha regime gives a great deal of information about the Be star disk which should provide constraints on the physical models of the system and the generation of the high energy gamma rays. We used the SMARTS 1.5m telescope at CTIO to obtain spectra from December 2010 to May 2011 approximately once every 3 days during December and about once per week during the rest of the observational time period. Here, we report on the behavior of the Be star disk and discuss implications for the models of the binary system.

Mode of presentation: poster