A systematic search of Zwicky Transient Facility data for ultracompact binary LISA-detectable gravitational-wave sources

He-star donor AM CVn stars and their progenitors as LISA sources

Ultracompact cataclysmic variables (CVs) of the AM CVn type are deemed to be important verification sources for the future space gravitational wave detectors such as the Laser Interferometer Space Antenna (LISA). We model the present-day Galactic population of AM CVn stars with He-star donors. Such a population has long expected to exist, though only a couple of candidates are known. We applied the hybrid method of binary population synthesis (BPS) which combines a simulation of the population of immediate precursors of AM CVn stars by a fast BPS code with subsequent tracking of their evolutio…

利用 Gaia DR3 天体测量数据研究 LISA 银河系双星

LISA Galactic binaries with astrometry from Gaia DR3

本文基于 Gaia DR3 天体测量更新55个 LISA 候选银河系双星的距离，并用贝叶斯方法预测不同观测时长的可探测性，识别出18个验证双星和22个可探测源。

利用兹威基瞬变设施（Zwicky Transient Facility）的强剥离富钙IIb型超新星样本探究核心坍缩超新星的低质量端

Probing the low-mass end of core-collapse supernovae using a sample of strongly-stripped Calcium-rich Type IIb Supernovae from the Zwicky Transient Facility

本研究利用Zwicky Transient Facility的9个富钙IIb型超新星样本，通过光谱与测光分析确认其前身星为8-12倍太阳质量的低质量恒星，填补了低质量核心坍缩超新星观测样本的空缺，并揭示了强剥离超新星的过渡性质及相关双星系统的演化意义。

The first ultracompact Roche lobe-filling hot subdwarf binary

We report the discovery of the first short period binary in which a hot subdwarf star (sdOB) fills its Roche lobe and started mass transfer to its companion. The object was discovered as part of a dedicated high-cadence survey of the Galactic Plane named the Zwicky Transient Facility and exhibits a period of $P_{\rm orb}=39.3401(1)$ min, making it the most compact hot subdwarf binary currently known. Spectroscopic observations are consistent with an intermediate He-sdOB star with an effective temperature of $T_{\rm eff}=42,400\pm300$ K and a surface gravity of $\log(g)=5.77\pm0.05$. A high-sig…

Gaia19bxc: possible polar below the period minimum

Gaia19bxc is a transient detected on 2019 May 9 by the Gaia Photometric Science Alerts Team. I analyzed the past public Zwicky Transient Facility (ZTF) data and found that Gaia19bxc has a period of 0.04473647(3) d and two different maxima in one cycle. This object also showed high and low states in the ZTF data. Based on the high amplitude (2.0 mag) of the short-term variations, short period, almost zero color indices between the different ZTF bands and the absence of a longer period, I classified it to be a likely polar. There has been no established polar below the period minimum of cataclys…

二元演化的最终阶段：多信使研究

The final stages of binary evolution using multi-messenger studies

LISA探测到的最紧凑双星需要高精度光谱观测以研究多信使研究中的轨道演化和潮汐加热。

多信使光谱学

Multimessenger Spectroscopy

本文提出一种多信使方法，利用LISA引力波数据预测双白矮星双星的轨道相位，以调度光学光谱观测，从而无偏地测量质量并预测相位精度。

巨蟹座HM 5.4分钟轨道周期的光谱学证据

Spectroscopic Evidence for a 5.4-Minute Orbital Period in HM Cancri

巨蟹座HM是一颗候选的超紧凑双星白矮星，其视轨道周期只有5.4分钟，这是由X射线和光学光变曲线对该周期的调制以及缺乏更长周期的变化所证明的。在这封信中，我们提出了一种新的光谱仪，它显示了氦发射线在径向速度和振幅上的5.4分钟的周期上的明显调制，而不是其他的。这些数据强烈地表明，该双星从较冷、质量较小的恒星的辐射面发射He I 4471，从质量较大的恒星周围的环发射He II 4686。从它们的相对径向速度，我们测量到质量比q=0.50+/-0.13。我们的结论是，所观察到的5.4分钟的周期几乎可以肯定代表了相互作用的双白矮星的轨道周期。因此，我们确认HM Cnc是已知的最短周期的双星：恒星演化理论的独特测试，以及激光干涉仪空间天线（LISA）的最强引力波的已知来源之一。

A 15.7-Minute AM CVn Binary Discovered in K2

We present the discovery of SDSS J135154.46-064309.0, a short-period variable observed using 30-minute cadence photometry in K2 Campaign 6. Follow-up spectroscopy and high-speed photometry support a classification as a new member of the rare class of ultracompact accreting binaries known as AM CVn stars. The spectroscopic orbital period of $15.65 \pm 0.12$\,minutes makes this system the fourth-shortest period AM CVn known, and the second system of this type to be discovered by the Kepler spacecraft. The K2 data show photometric periods at $15.7306 \pm 0.0003$\,minutes, $16.1121 \pm 0.0004$\,mi…

Year 1 of the ZTF high-cadence Galactic Plane Survey: Strategy, goals, and early results on new single-mode hot subdwarf B-star pulsators

We present the goals, strategy and first results of the high-cadence Galactic plane survey using the Zwicky Transient Facility (ZTF). The goal of the survey is to unveil the Galactic population of short-period variable stars, including short period binaries and stellar pulsators with periods less than a few hours. Between June 2018 and January 2019, we observed 64 ZTF fields resulting in 2990 deg$^2$ of high stellar density in ZTF-$r$ band along the Galactic Plane. Each field was observed continuously for 1.5 to 6 hrs with a cadence of 40 sec. Most fields have between 200 and 400 observations …