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Rotational Broadening Measurement for the Neutron Star X-Ray Transient XTE J2123-058 | | John A. Tomsick
; William A. Heindl
; Deepto Chakrabarty
; Philip Kaaret
; | | Date: |
9 Aug 2002 | | Journal: | Astrophys.J. 581 (2002) 570-576 | | Subject: | astro-ph | | Affiliation: | CASS/UCSD), Deepto Chakrabarty (MIT), Philip Kaaret (Harvard-Smithsonian CfA | | Abstract: | We used optical spectroscopy of the neutron star X-ray transient XTE J2123-058 to measure the rotational broadening of the binary companion’s stellar absorption lines and determined that the companion’s projected rotational velocity is vsini = 121 (+21)(-29) km/s. This value is considerably larger than the measurements of vsini obtained previously for three other neutron star systems where the values are between 34 and 65 km/s. The larger value is likely due to the combination of high binary inclination and short (6 hr) orbital period for XTE J2123-058. Along with previously measured parameters, the rotational broadening measurement allowed us to determine the binary parameters, including the ratio of the neutron star mass to the companion mass, q = M_1/M_2 = 2.7 (+1.3)(-0.9), the neutron star mass, M_1 = 1.46 (+0.30)(-0.39) solar masses, and the companion mass, M_2 = 0.53 (+0.28)(-0.39) solar masses, assuming a Roche lobe filling companion synchronously rotating with the binary orbit. These values are consistent with a previous measurement where the H alpha emission line was used to determine the semiamplitude of the neutron star’s radial velocity curve (K_1). It is a significant result that the two methods give consistent values. We also report the first measurement of the XTE J2123-058 companion’s radius. Assuming synchronous rotation, we obtain R_2 = 0.62 (+0.11)(-0.15) solar radii, which is in-line with that expected for a late K-type star on or close to the main sequence. Finally, we report the first precise spectroscopic determination of the binary orbital period (P_orb = 21442.3 +/- 1.8 seconds). | | Source: | arXiv, astro-ph/0208205 | | Services: | Forum | Review | PDF | Favorites | |
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