Clark C J, Kerr M, Barr E D, Bhattacharyya B, Breton R P, Bruel P, Camilo F, Chen W, Cognard I, Cromartie H T, Deneva J, Dhillon V S, Guillemot L, Kennedy M R, Kramer M, Lyne A G, Sánchez D Mata, Nieder L, Phillips C, Ransom S M, Ray P S, Roberts M S E, Roy J, Smith D A, Spiewak R, Stappers B W, Tabassum S, Theureau G, Voisin G
Max Planck Institute for Gravitational Physics (Albert Einstein Institute), Hannover, Germany.
Leibniz Universität Hannover, Hannover, Germany.
Nat Astron. 2023;7(4):451-462. doi: 10.1038/s41550-022-01874-x. Epub 2023 Jan 26.
Reliable neutron star mass measurements are key to determining the equation of state of cold nuclear matter, but such measurements are rare. Black widows and redbacks are compact binaries consisting of millisecond pulsars and semi-degenerate companion stars. Spectroscopy of the optically bright companions can determine their radial velocities, providing inclination-dependent pulsar mass estimates. Although inclinations can be inferred from subtle features in optical light curves, such estimates may be systematically biased due to incomplete heating models and poorly understood variability. Using data from the Fermi Large Area Telescope, we have searched for gamma-ray eclipses from 49 spider systems, discovering significant eclipses in 7 systems, including the prototypical black widow PSR B1957+20. Gamma-ray eclipses require direct occultation of the pulsar by the companion, and so the detection, or significant exclusion, of a gamma-ray eclipse strictly limits the binary inclination angle, providing new robust, model-independent pulsar mass constraints. For PSR B1957+20, the eclipse implies a much lighter pulsar (1.81 ± 0.07 solar masses) than inferred from optical light curve modelling.
可靠的中子星质量测量是确定冷核物质状态方程的关键，但此类测量很少见。黑寡妇和红背蜘蛛是由毫秒脉冲星和半简并伴星组成的致密双星系统。对光学明亮伴星的光谱分析可以确定它们的径向速度，从而提供与倾角相关的脉冲星质量估计。尽管可以从光学光变曲线的细微特征推断倾角，但由于加热模型不完整以及对变异性了解不足，此类估计可能会存在系统偏差。利用费米大面积望远镜的数据，我们对49个蜘蛛系统进行了伽马射线食搜索，在7个系统中发现了显著的食，其中包括典型的黑寡妇PSR B1957+20。伽马射线食要求伴星直接遮挡脉冲星，因此伽马射线食的探测或显著排除严格限制了双星倾角，提供了新的、可靠的、与模型无关的脉冲星质量约束。对于PSR B1957+20，该食意味着脉冲星质量比根据光学光变曲线建模推断的要轻得多（1.81±0.07太阳质量）。
