نویسندگان
پژوهشگاه دانشهای بنیادی
کلیدواژهها
عنوان مقاله English
نویسندگان English
One of the effective methods for identifying high-mass neutron stars is to study binary systems containing millisecond pulsars. In such systems, the companion star is affected by intense pulsar irradiation, which alters its apparent brightness and allows for the estimation of the neutron star’s mass. This irradiation also displaces the optical center of the companion relative to its center of mass, which in turn increases the uncertainty in precisely determining the orbital parameters and the neutron star mass. In this study, we investigated the binary system PSR J2215+5135 using Eclipsing Light Curve (ELC) modeling along with combined photometric and spectroscopic data, and estimated the mass of the neutron star through comprehensive modeling of the system’s irradiation. The binary system lies at an estimated distance of ~ 3 kpc from Earth. Its neutron star is a rapidly rotating millisecond pulsar with a spin period of 2.61 ms, while the binary orbit has a period of 4.14 hr. To achieve this, we employed a physical model of the irradiated companion star and simultaneously fitted light curves in three different bands as well as radial velocity curves from two distinct spectral groups. Our results yield a center-of-mass velocity for the companion star of K1 = 414.6−2.6 +4.6 km/s and an orbital inclination angle of i = 64.1°. The neutron star’s mass was determined to be M2 = 2.28−0.11 +0.12 M☉, and the companion star’s mass was estimated at M1 = 0.32±0.10 M☉. In part of this work, the effect of hot spots on the companion's surface was examined and compared to models excluding such features. To avoid exclusivity in analyzing data from compact-object binaries, the use of accessible and general-purpose modeling tools is essential, as it enables independent reproduction and validation of results by various research groups. The significance of this study lies in the fact that, unlike many proprietary tools, the ELC model is publicly available to the scientific community. Achieving results with over 99% consistency compared to specialized codes underscores the credibility and reliability of this model for future studies—including projects related to the Iranian National Observatory. Moreover, the identification of a neutron star with such a high mass places stringent constraints on the equation of state of dense matter and may prompt revisions of existing theoretical models.
کلیدواژهها English
