AN EXAMINATION OF THE X-RAY SOURCES IN THE GLOBULAR CLUSTER NGC 6652
- University of Alberta Physics Department, CCIS 4-183, Edmonton, AB T6G 2E1 (Canada)
We observed the globular cluster NGC 6652 with Chandra for 47.5 ks, detecting six known X-ray sources, as well as five previously undetected X-ray sources. Source A (XB 1832-330) is a well-known bright low-mass X-ray binary (LXMB). The second brightest source, B, has a spectrum that fits well to either a power-law model ({Gamma} {approx} 1.3) or an absorbed hot gas emission model (kT {approx} 34 keV). Its unabsorbed 0.5-10 keV luminosity (L{sub X} = 1.6{sup +0.1}{sub -0.1} Multiplication-Sign 10{sup 34} erg s{sup -1}) is suggestive of a neutron star primary; however, Source B exhibits unusual variability for an LMXB, varying by over an order of magnitude on timescales of {approx}100 s. Source C's spectrum contains a strong low-energy component below {approx}1 keV. Its spectrum is well fit to a simplified magnetic cataclysmic variable (CV) model, thus the soft component may be explained by a hot polar cap of a magnetic CV. Source D has an average L{sub X} (0.5-10 keV) {approx}9 Multiplication-Sign 10{sup 32} erg s{sup -1} and its spectrum is well fit to a neutron star atmosphere model. This is indicative of a quiescent neutron star LXMB, suggesting Source D may be the third known LMXB in NGC 6652. Source E has L{sub X} (0.5-10 keV) {approx}3 Multiplication-Sign 10{sup 32} erg s{sup -1}, while Source F has L{sub X} (0.5-10 keV) {approx}1 Multiplication-Sign 10{sup 32} erg s{sup -1}. Their relatively hard X-ray spectra are well-fit by power-law or plasma emission models. Five newly detected fainter sources have luminosities between 1 and 5 Multiplication-Sign 10{sup 31} erg s{sup -1}. NGC 6652 has an unusually flat X-ray luminosity function compared to other globular clusters, which may be connected to its extremely high central density.
- OSTI ID:
- 22037236
- Journal Information:
- Astrophysical Journal, Vol. 751, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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