标题： 一个新的红背脉冲星候选体 4FGL J2054.2+6904 显示英文标题

标题： A new redback pulsar candidate 4FGL J2054.2+6904

摘要： 费米 catalogs 包含大约 2000 个未关联的 $\gamma$光源。 其中一些最近被识别为脉冲星，包括所谓的红背和黑寡妇，它们是毫秒脉冲星，处于与非退化或部分退化的低质量恒星伴星紧密双星系统中，并受到脉冲星风的辐射。 我们研究了之前提出的作为脉冲星候选者的费米源 4FGL J2054.2+6904 的可能光学和 X 射线对应体。 我们使用档案光学数据以及 Swift/XRT 和 SRG/eROSITA X 射线数据来澄清其性质。 利用跨越 4.7 年的 $g$ 和 $r$波段的 Zwicky 变化设施数据，我们发现了一个周期为 $\approx$7.5 小时的信号。折叠后的光变曲线呈现出平滑的正弦形状，峰峰值幅度为 $\approx$0.4 星等。 对候选对应体的光学能谱分布的光谱拟合得到半径为 0.5$\pm$0.1$R_\odot$，温度为 5500$\pm$300 K，表明是一颗 G2–G9 型恒星。 它的 X 射线能谱可以用吸收幂律很好地拟合，光子指数为 1.0$\pm$0.3，未被吸收的流量为$\approx 2\times10^{-13}$erg s$^{-1}$cm$^{-2}$。 所有关于 4FGL J2054.2$+$6904 的属性及其假定的对应体表明它属于红背家族的一员。 显示英文摘要

摘要： The Fermi catalogue contains about 2000 unassociated $\gamma$-ray sources. Some of them were recently identified as pulsars, including so called redbacks and black widows, which are millisecond pulsars in tight binary systems with non- and partially-degenerate low-mass stellar companions irradiated by the pulsar wind. We study a likely optical and X-ray counterpart of the Fermi source 4FGL J2054.2+6904 proposed earlier as a pulsar candidate. We use archival optical data as well as Swift/XRT and SRG/eROSITA X-ray data to clarify its nature. Using Zwicky Transient Facility data in $g$ and $r$ bands spanning over 4.7 years, we find a period of $\approx$7.5 h. The folded light curve has a smooth sinusoidal shape with the peak-to-peak amplitude of $\approx$0.4 mag. The spectral fit to the optical spectral energy distribution of the counterpart candidate gives the star radius of 0.5$\pm$0.1$R_\odot$ and temperature of 5500$\pm$300 K implying a G2--G9-type star. Its X-ray spectrum is well fitted by an absorbed power law with the photon index of 1.0$\pm$0.3 and unabsorbed flux of $\approx 2\times10^{-13}$ erg s$^{-1}$ cm$^{-2}$. All the properties of 4FGL J2054.2$+$6904 and its presumed counterpart suggest that it is a member of the redback family.