AI 中文总结
研究球状星团中双毫秒脉冲星M92A的光学性质，利用哈勃空间望远镜多时期多波长数据，通过构建图表、研究自行、建模光变曲线等方法，确定其光学伴星，推断伴星物理性质，为脉冲星伴星性质研究增添内容。
AI 中文摘要
球状星团中的双毫秒脉冲星是极端条件下双星和恒星演化研究的关键。识别其光学伴星有助于表征这些系统并限制可能的再循环机制。为此，我们利用哈勃空间望远镜获得的多时期、多波长数据集，在球状星团M92中寻找PSR J1717 + 4308A（以下简称M92A）的光学对应体。我们构建了颜色 - 星等图，研究自行以评估星团成员身份，并对观测到的光变曲线进行建模。我们确定了一个距离标称射电位置仅0.02弧秒的物体为M92A可能的光学伴星。这颗恒星在相同光度水平下比主序星明显更蓝，并表现出明显的光度变化，其周期与双星的轨道运动一致。光变曲线显示两个最大值和两个最小值，表明强烈的潮汐扭曲和轻微的辐照。这种轻微的辐照与脉冲星的自旋-down与伴星通量的比率（$f_\mathrm{sd}$）一致，对于M92A，该比率接近椭球主导和辐照主导区域之间的边界（$f_\mathrm{sd} \approx 2.71$）。通过光变曲线建模，我们推断出伴星的主要物理性质。最佳拟合模型表明这是一个高倾角系统，伴星质量相对较低，中子星质量较大。伴星的基础温度约为7200 K，是迄今为止已知最热的红背之一。因此，这个物体为毫秒脉冲星伴星性质的拼图增添了更多内容，并有助于勾勒出不同类别的红背特征。
英文摘要
Binary millisecond pulsars (MSPs) in globular clusters (GCs) are key for binary and stellar evolution studies under extreme conditions. The identification of their optical companion stars is instrumental in order to characterise these systems and to constrain the possible recycling mechanisms. For this work, we searched for the optical counterpart to PSR J1717+4308A (hereafter M92A) in the GC M92. To this end, we exploited a multi-epoch, multi-wavelength dataset obtained with the Hubble Space Telescope. We constructed colour--magnitude diagrams, investigated proper motions to assess cluster membership, and modelled the observed light curves. We identified an object located at only 0.02 arcsec from the nominal radio position as the likely optical companion to M92A. The star is significantly bluer than the main sequence at the same luminosity level and exhibits clear photometric variability with a periodicity in agreement with the orbital motion of the binary. The light curve displays two maxima and two minima, indicative of strong tidal distortion and only mild irradiation. Such mild irradiation is consistent with the ratio of the pulsar spin-down to the companion flux ($f_\mathrm{sd}$), which for M92A lies close to the boundary between ellipsoidal- and irradiation-dominated regimes ($f_\mathrm{sd} \approx 2.71$). From the light curve modelling we inferred the main physical properties of the companion star. The best-fit model indicates a high-inclination system with a relatively low-mass companion and a massive neutron star. With a base temperature of $\sim7200$ K, the companion ranks among the hottest redbacks known to date. This object therefore adds additional pieces to the puzzle of MSP companion properties and contributes to outlining the characteristics of redbacks across the different classes.
Comments9 pages, 6 figures, accepted for publication in Astronomy & Astrophysics
