Recent Outbursts of the High-mass X-Ray Binary CI Camelopardalis

Abstract

Abstract CI Camelopardalis (CI Cam) is a High Mass X-Ray Binary (HMXB) that was discovered by the All Sky Monitor on board the Rossi X-Ray Timing Explorer when it underwent an outburst in 1998. CI Cam, also known as XTE J0421+560, peaked first in X-rays followed by optical and radio wavelengths (2.25, 8.3, 15 GHz). Several soft X-ray flares were observed after the initial flare. The optical flux was observed to quickly return to quiescent levels, while the radio flare was of much longer duration. The outburst was also detected by the X-ray satellite BeppoSax and the Burst and Transient Source Experiment on board the Compton Gamma Ray Observatory. The optical counterpart, CI Cam, is a B0-2 blue supergiant Be star and, assuming a compact object as an accretion companion (black hole, neutron star, white dwarf), the system can be designated an HMXB. Additionally, there is a pulsating third companion with periods of 0.41521 and 0.26647 days. While the initial outburst occurred in 1998, there is photometric evidence that there have been several later outbursts of similar magnitude to the original 1998 event. This paper will discuss these later outburst events as well as the identified pulsation modes.