arXiv subjects

Linjia Li

Publications and source records attributed to Linjia Li.

6 recordsLinked to original sources

arXiv2026

CW Cas: A solar-type contact binary system with an unseen third companion in a hierarchical quadruple system

We present a comprehensive multiband photometric and spectroscopic study of the G-type binary CW Cas whose parameters have not been well determined. Our double-lined spectroscopic radial velocity curve of this system yields a reliable mass ratio of $q = 1.88(9)$. By combining $BVR_{c}I_{c}$ bands, TESS light curves and radial velocity curves, we found that CW Cas is a W-subtype shallow contact binary with a fill-out factor of 15\%. The components have masses of $0.98(6)M_{\odot}$ and $0.52(4)M_{\odot}$, separated by $2.25(5)R_{\odot}$. A notable asymmetry in the maxima of the light curves was detected and explained by a dark spot located on the surface of at least one component. Comparison of light curves from different years revealed that these dark spot activities exhibit cyclic variations with an approximate period of 1250 days. Orbital period analysis via O-C diagram spanning 125 years shows a long-term decrease superimposed with periodic oscillation caused by the light-travel-time effect (LTTE) due to a third body. This tertiary component has an orbital period of $P_{3} = 99.4(6)$ years and a minimal mass of $M_{3}=0.91(1)M_{\odot}$. The absence of detectable signatures for this massive object in either spectroscopic or photometric datasets implies it must be a compact object such as a white dwarf or neutron star. Furthermore, a visual companion was identified based on Gaia DR3 astrometric data, suggesting that CW Cas is part of a hierarchical quadruple system. As such, CW Cas represents a valuable laboratory for probing 2+1+1 hierarchical multiple system hosting compact object.

astro-ph.SR↗

arXiv2026

IY Lyr: A Thick-Disk first-overtone RR Lyrae Star with a Possible Neutron Star Companion

IY Lyr, historically misclassified as an eclipsing binary, has been previously identified as a first-overtone RR Lyrae star (RRc star). Using multiband photometry (All-Sky Automated Survey for Supernovae, Zwicky Transient Facility, TESS, and our BVRI data), Large Sky Area Multi-Object Fiber Spectroscopic Telescope spectroscopy, and Gaia astrometry, we investigate its pulsation, binarity, and Galactic population. From O-C analysis, we detect a long-term period decrease and a light-travel time effect with an orbital period of 3.94 $\pm$ 0.09 years, eccentricity of 0.46 $\pm$ 0.15, and a mass function of 0.65 $\pm$ 0.14 M$_{\odot}$. The companion is independently supported by radial velocity residuals and Gaia proper motions. Combined constraints yield an orbital inclination of 94.2$^{\circ}$ $\pm$ 1.1$^{\circ}$ and a companion mass of 1.37 $\pm$ 0.19 M$_{\odot}$. Chemical abundances ([Fe/H] $\simeq$ -1.0 $\pm$ 0.1, [$\alpha$/Fe] $\simeq$ +0.27 $\pm$ 0.03, Xiang et al. 2019) and dynamics ($L_{\rm z}$ $\simeq$ 1287 $\pm$ 35 kpc km s$^{-1}$, $Z_{\rm max}$ $\simeq$ 1.17 $\pm$ 0.10 kpc) identify IY Lyr as likely an old, high-$\alpha$, thick-disk star. The companion mass lies at the peak of the neutron star mass distribution, and the system's age excludes a main-sequence star; we conclude the companion is most likely a typical neutron star, although a massive white dwarf near the Chandrasekhar limit cannot be ruled out. IY Lyr is among the few RRc binaries with a compact companion supported by multiple methods, and it has important implications for thick-disk binary evolution and neutron star formation.

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arXiv2024

KM UMa: An active short-period detached eclipsing binary in a hierarchical quadruple system

The first detailed photometric and spectroscopic analysis of the G-type eclipsing binary KM UMa is presented, which indicates that the system is a short-period detached eclipsing binary. The radial velocity curves were calculated using the cross-correlation function method based on Large Sky Area Multi-Object Fiber Spectroscopic Telescope, Sloan Digital Sky Survey, and our observations, which determined the mass ratio as $q=0.45\ (\pm0.04)$. Based on the light curves from the Transiting Exoplanet Survey Satellite, other survey data, and our multiband observations, the positive and negative O'Connell effects have been detected evolving gradually and alternately over the last 20 yr, which can be explained by the presence of spots on the primary component. A superflare event was detected in the SuperWASP data on 2007 February 28, further indicating that KM UMa is a very active system. We calculated its energy to be $5\times10^{34}$ erg by assuming it occurred on the primary star. Utilizing hundreds of medium-resolution spectra and one low-resolution spectrum, the equivalent width variations of the $H_{\alpha}$ line were calculated, indicating the presence of a 5.21 ($\pm0.67$) yr magnetic activity cycle. The orbital period variations were analyzed using the O-C method, detecting a long-term decrease superimposed with a periodic variation. The amplitude of the cyclic variation is $0.01124\ (\pm0.00004)$ day, with a period of $33.66\ (\pm 0.0012)$ yr, which exceeds the 5.21 yr activity cycle, suggesting that this is more likely attributable to the light travel time effect of a third body. Simultaneously, a visual companion has been detected based on the Gaia astrometric data, indicating that KM UMa is actually in a 2+1+1 hierarchical quadruple system.

astro-ph.SR↗

arXiv2024

Deep and low mass-ratio contact binaries and their third bodies

Deep and low mass-ratio contact binaries (DLMCBs) are believed to be in the final stage of their contact phase, potentially leading to the formation of fast-rotating single stars such as FK Com-type stars and blue stragglers, as well as luminous red novae. These systems serve as an excellent laboratory for studying stellar coalescence and merging processes. Our search for DLMCBs began in 2004 and has since identified a group of such systems. Together with that collected from the literature, more than 100 DLMCBs have been detected so far. Half of them have had their periods investigated based on O-C curves. Some have shown period increases, while others have exhibited period decreases. Among them, more than half DLMCBs have cyclic variations, suggesting the possibility of the existence of a third body orbiting around the DLMCBs. Furthermore, with more data obtained extending the span of the O-C curve, more cyclic variations could be detected. The high proportion of signs of the presence of third bodies makes them an essential factor to consider when studying the merger of contact binaries.

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arXiv2020

The contact binary V344 Lacertae: is it a triple system?

The VRI passbands light curves of V344 Lac were presented and analyzed by using the latest version of the W-D code. The observed spectrum reveals that V344 Lac is not an A3 type but would be a later F type star according to the yielded temperature. The results of solution show that V344 Lac is an A-subtype contact binary, with a mediate photometric mass ratio of 0.387(0.003) and a mediate contact factor of 44.6(3.0)%. Based on the parallax given by Gaia, the parameters of the components are estimated as: M1 = 1.16 Ms, M2 = 0.45 Ms, R1 = 1.31 Rs, R2 = 0.88 Rs, L1 = 2.512 Ls, L2 = 1.057 Ls. The period investigation indicates that V344 Lac may have an eccentric orbital oscillation, with P3 = 12.4(0.5) yr, A3 = 0.0020(0.0002) d, and e = 0.38(0.16). Analysis shows such oscillation would be caused by a magnetic activity which can be explained by the Applegate mechanism. Meanwhile, according to the value of l3 and the estimated physical parameters of V344 Lac, the mass of the third companion may be 0.79 Ms. This third body could be a wide company.

astro-ph.SR↗

arXiv2013

Updated photometry and orbital period analysis for the polar \objectname{am herculis} on the upper edge of the period gap

Twenty-one new optical light curves, including five curves obtained in 2009 and sixteen curves detected from the AAVSO International Database spanning from 1977 to 2011, demonstrate 16 new primary minimum light times in the high state. Furthermore, seven newly found low-state transient events from 2006 to 2009 were discovered, consisting of five Gaussian-shaped events and two events with an exponential form with decay timescales of $<$0.005 days; these timescales are one order of magnitude shorter than those of previous X-ray flare events. In the state transition, two special events were detected: a "disrupted event" with an amplitude of $\sim$ 2 mag and a duration of $\sim$ 72 minutes and continuing R-band twin events larger than all known R-band flares detected in M-type red dwarfs. All 45 available high-state data points spanning over 35 yr were used to construct an updated O-C diagram of \objectname{AM Herculis}, which clearly shows a significant sine-like variation with a period of 12-15 yr and an amplitude of 6-9 minutes. Using the inspected physical parameters of the donor star, the secular variation in the O-C diagram cannot be interpreted by any decided angular momentum loss mechanism, but can satisfy the condition $τ_{\dot{\rm M}_{2}}\simeqτ_{\rm KH}>>τ_{\dot{\rm R}_{\rm 2}}$, which is required by numerical calculations of the secular evolution of cataclysmic variables. In order to explain the prominent periodic modulation, three plausible mechanisms - spot motion, the light travel-time effect, and magnetic active cycles - are discussed in detail.

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