“X-RAY SPECTROSCOPY OF THE HIGH-MASS X-RAY BINARY PULSAR

CENTAURUS X-3 OVER ITS BINARY ORBIT”-Sachindra Naik, Biswajit Paul, and

Zulfikar Ali

Introduction: Interest: Extended dips in the light curve Cen-X: Eclipsing HMXRB pulsar

Orbital period ~2.1 days, pulse period ~4.8 s Composed of two stars:

Neutron star: mass of 1.21 ± 0.21 O 6-8 III Supergiant (V779 Cen): mass of 20.5 ±

0.7 & radius of 12 Distance = 5.7 ± 1.5 kpc Luminosity ~5.0 x 1037 erg s-1

B-field strength = (2.4-3.0) x 1012 G Spectra: 6.4 keV, 6.7 keV, & 6.97 keV iron

emission lines

Light curves & other infoThe XIS detectors cover the 0.2-12 keV range and the HXD/PIN detectors cover 10-70 keV.

The end of one eclipse is seen at about 0-50 ks; the beginning of another comes at about 150 ks.

These eclipses and other features are present in the data up to about 40 keV; at higher energies, on the other hand, the graph becomes essentially featureless.The graph obviously has many features other than the eclipses at the ends; besides these two, it contains three dips, four egresses, five ingresses, six high-count regions, and two bumps that have different exposure times and count rates.

Discussion:

The X-ray light curve of the system shows a lot of variation presence of dips.

The dips are due to the presence of dense matter that absorbs the X-ray photons. Partial covering absorption model

Problem: Iron emission lines

Bibliography:

Naik, S., Paul, B., & Ali, Z. (2011). X-RAY SPECTROSCOPY OF THE HIGH-MASS X-RAY BINARY PULSAR CENTAURUS X-3 OVER ITS BINARY ORBIT. The Astrophysical Journal,737(79), 1-8.