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arXiv 2024年

作者： Zha, Shuai Müller, Bernhard Powell, Jade Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China School of Physics and Astronomy Monash University ClaytonVIC3800 Australia Centre for Astrophysics and Supercomputing Swinburne University of Technology HawthornVIC3122 Australia OzGrav: The ARC Centre of Excellence for Gravitational-Wave Discovery HawthornVIC3122 Australia

Core-collapse supernova (CCSN) explosions powered by rotation and magnetic fields present an interesting astrophysical site for nucleosynthesis that potentially contributes to the production of r-process elements. Here we present yields of the innermost ejecta in 3D magnetorotational CCSN models simulated using the CoCoNuT-FMT code. Strong magnetic fields tap the rotational energy of the proto-neutron star and lead to earlier and more energetic (∼ 3 × 1051 erg) explosions than typical neutrino-driven CCSNe. Compared to a reference non-magnetic model, the ejecta in the magnetorotational models have much more neutron-rich components with Ye down to ∼ 0.25. Our post-processing calculations with the reaction network SkyNet show significant production of weak r-process elements up to mass number ∼130. We find negligible differences in the synthesis of heavy elements between two magnetorotational models with different initial field strength of 1010 and 1012 G, in accord with their similar explosion dynamics. The magnetorotational models produce about ∼ 0.19 and 0.14 M☉ of radioactive 56Ni, on the low end of inferred hypernova nickel masses. The yields are publicly available at Zenodo: doi:10.5281/zenodo.10578981 for comparison with stellar abundance patterns, inclusion in modelling galactic chemical evolution, and comparison with other yield calculations. Our results add to the yet restricted corpus of nucleosynthesis yields from 3D magnetorotational supernova simulations and will help quantify yield uncertainties. Copyright © 2024, The Authors. All rights reserved.

关键词： Explosions

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Investigation of superhumps in SU UMa-type dwarf novae based on the observations of TESS

arXiv

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arXiv 2024年

作者： Liu, Wei Qian, Shengbang Yunnan Observatories Chinese Academy of Sciences PO Box 110 Kunming650216 China Department of Astronomy Key Laboratory of Astroparticle Physics of Yunnan Province Yunnan University Kunming650091 China University of Chinese Academy of Sciences No.1 Yanqihu East Rd Huairou District Beijing101408 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences PO Box 110 Kunming650216 China

We report the superhumps analysis of seven SU UMa-type dwarf novae based on the observations of Transiting Exoplanet Survey Satellite (TESS). Superhumps are seen during superoutbursts of SU UMa-type dwarf novae. The month-long data sets of TESS are well suited for studying the variation of superhumps. We selected seven non-eclipsing SU UMa-type dwarf novae with superhumps in which TESS light curves are available and have not yet been studied. The stages A, B, and C of superhumps in superoutbursts were determined by O-C method. The results indicate that not all complete superoutbursts show obvious three stages, such as DT Oct and the second superoutburst of J1730+6247. We calculated the superhump periods for each stage and the mean periods for whole superoutbursts. Taking the stage A superhump method, the mass ratios (M2/M1) were estimated. According to the results, the seven stars are pre-bounce systems with mass ratios ranging from 0.1 to 0.2. By combining the orbital periods and the mean superhump periods, the precession periods were calculated. The results show that the precession periods of the seven SU UMa stars are about 2 days. © 2024, CC BY.

关键词： Stars

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AT 2023clx: the Faintest and Closest Optical Tidal Disruption Event Discovered in Nearby Star-forming Galaxy NGC 3799

arXiv

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arXiv 2023年

作者： Zhu, Jiazheng Jiang, Ning Wang, Tinggui Huang, Shifeng Lin, Zheyu Wang, Yibo Wang, Jian-Guo CAS Key Laboratory for Research in Galaxies and Cosmology Department of Astronomy University of Science and Technology of China Hefei230026 China School of Astronomy and Space Sciences University of Science and Technology of China Hefei230026 China Yunnan Observatories Chinese Academy of Sciences Kunming650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatories Kunming650011 China

We report the discovery of a faint optical tidal disruption event (TDE) in the nearby star-forming galaxy NGC 3799. Identification of the TDE is based on its position at the galaxy nucleus, a light curve declining as t−5/3, a blue continuum with an almost constant blackbody temperature of ∼12,000 K, and broad (≈ 15, 000 km s−1) Balmer lines and characteristic He II 4686 Å emission. The light curve of AT 2023clx peaked at an absolute magnitude of −17.16 mag in the g band and a maximum blackbody bolometric luminosity of 4.56 × 1042 erg s−1, making it the faintest TDE discovered to date. With a redshift of 0.01107 and a corresponding luminosity distance of 47.8 Mpc, it is also the closest optical TDE ever discovered to our best knowledge. Furthermore, our analysis of Swift/XRT observations of AT 2023clx yields a very tight 3σ upper limit of 9.53×1039 erg s−1 in the range 0.3–10 keV. AT2023clx, together with very few other faint TDEs such as AT 2020wey, prove that there are probably a large number of faint TDEs yet to be discovered at higher redshifts, which is consistent with the prediction of luminosity functions (LFs). The upcoming deeper optical time-domain surveys, such as the Legacy Survey of Space and Time (LSST) and the Wide-Field Survey Telescope (WFST) will discover more TDEs at even lower luminosities, allowing for a more precise constraint of the low-end of the LF. © 2023, CC BY.

关键词： Luminance

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An upgraded interpolator of the radial basis function network for spectral calculation based on empirical stellar spectral library

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Research in Astronomy and Astrophysics 2020年第9期20卷 277-290页

作者： Lian-Tao Cheng Feng-Hui Zhang Yunnan Observatories Chinese Academy of SciencesKunming 650216China Center for Astronomical Mega Science Chinese Academy of SciencesBeijing 100012China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China University of Chinese Academy of Sciences Beijing 100049China

Stellar population synthesis is an important method in galaxy and star-cluster *** stellar population synthesis models,a stellar spectral library is necessary for the integrated spectra of the stellar ***,the stellar spectral library is utilized for the transformation between the stellar atmospheric parameters and stellar *** empirical stellar spectral library has distinct advantages over the theoretical ***,for the empirical spectral library,the distribution of stars is irregular in the stellar atmospheric parameter space,which makes the traditional interpolator difficult to get accurate *** this work,we will provide an improved radial basis function interpolator which is implemented to obtain the interpolated stellar spectra based on the empirical stellar spectral *** this interpolator,we use the relation between the standard varianceσin the Gaussian radial basis function and the density distribution of stars in the stellar atmospheric parameter space to give the prior constraint on thisσ.Moreover,we also consider the anisotropic radial basis function by the advantage of the local dispersion of stars in the stellar atmospheric parameter ***,we use the empirical stellar spectral library MILES to test this *** the whole,the interpolator has a good performance except for the edge of the low-temperature *** last,we compare this interpolator with our work in 2018,and the interpolation result shows an obvious *** can apply this interpolator to retrieve the interpolated spectra based on the stellar spectral library quickly and easily.

关键词： stars:fundamental parameters stars:atmospheres (Galaxy:)globular clusters:general methods:numerical

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Absolute parameters and observed flares in the M-type detached eclipsing binary 2MASS J04100497+2931023

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Research in Astronomy and Astrophysics 2021年第5期21卷 130-138页

作者： Gang Meng Li-Yun Zhang Qing-Feng Pi Liu Long Xianming L.Han Misra Prabhakar College of Physics&Guizhou Provincial Key Laboratory of Public Big Data Guizhou UniversityGuiyang 550025China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650011China College of Medicine Guizhou University of Traditional Chinese MedicineGuiyang 550025China Department of Astronomy Beijing Normal UniversityBeijing 100875China Dept.of Physics and Astronomy Butler UniversityIndianapolisIN 46208USA Department of Physics&Astronomy Howard UniversityWashington DC 20059USA

The eclipsing binary 2 MASS J04100497+2931023(J04100497+2931023) is classified its spectral type of M0±2 V on basis of a low-resolution spectral survey by the Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST). The low-resolution spectra exhibit strong single-peak emission in the Hα line. We obtained the radial velocities of this binary by means of the Cross-Correlation Function method from the LAMOST medium-resolution spectra. Both components of J04100497+2931023 indicate strong emissions in the Hα line. We performed follow-up photometric observations of J04100497+2931023 using the Xinglong 85 cm telescope of National Astronomical Observatories, Chinese Academy of Sciences. We obtained its full light curve in V RI filters. We first determined their absolute parameters from simultaneously radial velocity and light curves by the Wilson-Devinney program. From our new light curves, we detected three flares for the first time, including one convective flare. The amplitudes,durations, energies, and spectral indices of three flares were also determined. J04100497+2931023 was monitored for approximately 29 h, which indicates that the flare rate is 0.1 flare per hour. We conclude that J04100497+2931023 is a low-mass detached eclipsing binary with strong magnetic activity.

关键词： binaries:eclipsing stars:flare star:low-mass stars:J04100497+2931023

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Dark Matter (S)pins the Planet

arXiv

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arXiv 2025年

作者： Shi, Haihao Zhou, Junda Huang, Zhenyang Lü, Guoliang Chen, Xuefei Xinjiang Astronomical Observatory Chinese Academy of Sciences Urumqi830011 China College of Astronomy and Space Science University of Chinese Academy of Sciences Beijing101408 China Yunnan Observatories Chinese Academy of Sciences Kunming650216 China School of Physical Science and Technology Xinjiang University Urumqi830046 China Key Laboratory for Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China

Dark matter heating in planets has been proposed as a potential probe for dark matter detection. Assuming near-equilibrium, we find that dark matter energy input raises planetary temperature and accelerates rotation. The energy distribution depends on planetary properties and external input, suggesting that previous studies have overestimated its heating effect. When dark matter density is high, planetary rotation stabilizes earlier and is primarily governed by dark matter. For Earth, our model predicts a 0.015 K temperature increase and a 10−8 rad/s angular velocity increase over 100 years. Copyright © 2025, The Authors. All rights reserved.

关键词： Dark energy

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Detection of [CI] Emission in Nebular Spectra of a Peculiar TypeIa Supernova 2022pul

arXiv

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arXiv 2025年

作者： Liu, Jialian Wang, Xiaofeng Yang, Yi Filippenko, Alexei V. Brink, Thomas G. Zheng, WeiKang Zhang, Jujia Li, Gaici Yan, Shengyu Physics Department Tsinghua University Beijing100084 China Purple Mountain Observatory Chinese Academy of Sciences Nanjing210023 China Department of Astronomy University of California BerkeleyCA94720-3411 United States Yunnan Observatories Chinese Academy of Sciences Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China

SN 2022pul gains special attention due to its possible origin as a super-Chandrasekhar-mass white dwarf (WD) explosion (also called a 03fg-like Type Ia supernova), which shows prominent [O I], [Ne I], and [Ca II] lines in its late-time spectra taken at ∼+300 days after the time of peak brightness. In this Letter, we present new optical observations of this peculiar object, extending up to over 500 days after peak brightness. In particular, in the t ∼ +515 days spectrum, we identified for the first time the presence of narrow emission from [C I] λλ9824, 9850, which appears asymmetric and quite similar to the accompanied [O I] λ6300 line in strength and profile. Based on the violent merger model that accounts well for previous observations but leaves little carbon in the center of the ejecta, this carbon line can be reproduced by increasing the degree of clumping in the ejecta and setting the carbon mass the same as that of oxygen (∼0.06 Me) in the innermost region (2000 km s−1). In principle, the central carbon could come from the secondary WD if it is ignited when hit by the shock wave of the explosion of the primary WD and explodes as a Ca-rich supernova, whereas pure deflagration of a super-Chandrasekhar-mass WD can account for such unburnt carbon more naturally. Copyright © 2025, The Authors. All rights reserved.

关键词： Supernovae

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A possible explanation of W-type phenomena in V694 Peg

arXiv

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arXiv 2024年

作者： Xu, Hu-Shan Zhu, Li-Ying Physics Department Yuxi Normal University Yuxi653100 China P. O. Box 110 Kunming650216 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences P. O. Box 110 Kunming650216 China Graduate University of the Chinese Academy of Sciences Yuquan Road 19 Sijingshang Block Beijing City100049 China

Three sets of complete multi-color light curves of V694 Peg observed in 2013, 2015 and 2019 were presented and analyzed. Our photometric solutions show that this system is an A-type shallow contact binary in 2013 and 2015, while it converted to a W-type one in 2019. A large cool spot on the component of this binary could explain the conversion, implying the W-type phenomena may be caused by magnetic activity of the components. We have collected available data of this binary and calculated 505 times of light minimum, which span 17 years. The orbital period investigation based on these timings shows there is a long-term period increase at a rate of dP/dt = 4.3(± 0.3)× 10−9 d yr−1 superposed on a periodic variation with a period of 11.81(± 0.06) years. The cyclic orbital variation may be the result of magnetic activity cycles or the existence of a third body. Till now, only 8 transformed systems including V694 Peg have been reported. Compared with other converting contact systems between A-type and W-type, V694 Peg is recorded as the shortest-period one. All of these converting systems are late-type (later than F7) contact binaries with O’Connell effect and show cyclic period variation, which indicates that magnetic activity may be the reason for the conversion between the two types of contact binaries. For investigating the nature of A-type and W-type phenomena, the discovery of more converting contact binaries is essential. Copyright © 2024, The Authors. All rights reserved.

关键词： Stars

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One model to rule them all: magnetic braking from CVs to low-mass stars

arXiv

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arXiv 2024年

作者： Sarkar, Arnab Ge, Hongwei Yungelson, Lev Tout, Christopher A. Institute of Astronomy University of Cambridge The Observatories Madingley Road CambridgeCB3 OHA United Kingdom Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for Structure and Evolution of Celestial Objects CAS Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China Institute of Astronomy of the Russian Academy of Sciences 48 Pyatnitskaya Str. Moscow119017 Russia

We present the results of the study of the secular evolution of donor stars in cataclysmic variables (CVs) and AM Canum Venaticorum (AM CVn) stars with our double dynamo (DD) formalism of angular momentum loss (AML) by magnetic braking (MB). In our DD model, MB is driven by an interplay between two ∝ − Ω dynamos, one in the convective envelope and the other at the boundary of the radiative core and the convective envelope. We show that (1) our MB model reproduces the period gap (2 Porb/ hr 3) and the period minimum spike (Porb ≈ 80 min) in the distribution of non-magnetic CVs, (2) evolved CVs, where the donor star commences Roche lobe overflow (RLOF) close to or just beyond the end of the main-sequence, populate the region in and beyond the period gap, and are more likely to be detected at Porb ≥ 5.5 hr. This likely contaminates the mass-radius fit of long-period CV donors. We show that (3) some of the evolved CVs become AM CVn stars with 10 Porb/ min 65. Their evolution, driven by AMLMB and AML by gravitational radiation (GR, AMLGR), leaves them extremely H-exhausted to the point of being indistinguishable from AM CVn systems formed via the He-star and the White Dwarf (WD) channels in terms of the absence of H in their spectra. We further show that (4) owing to the presence of a significant radiative region, intermediate-mass giants/sub-giants, which are progenitors of AM CVn stars formed through the He-star channel, may undergo common envelope evolution that does not behave classically, (5) several AM CVn systems with extremely bloated donors, such as Gaia14aae, ZTFJ1637+49 and SRGeJ045359.9+622444 do not match any modelled trajectories if these systems are modelled only with AMLGR without incorporating AMLMB, (6) the uncertainties in MB estimates greatly affect modelling results. This, in turn, affects our efforts to distinguish between different AM CVn formation channels and their relative importance. Finally, we find that (7) a similar MB prescription also expl

关键词： Uncertainty analysis

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Identification of temperature anomaly RR Lyrae stars in LAMOST survey,misclassification and binarities

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Research in Astronomy and Astrophysics 2020年第6期20卷 239-252页

作者： Lin-Jia Li Sheng-Bang Qian Jia Zhang Jia-Jia He Li-Ying Zhu Yunnan Observatories Chinese Academy of SciencesKunming 650216China Key laboratory of the structure and evolution of celestial objects Chinese Academy of SciencesKunming 650216China Center for Astronomical Mega-Science Chinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China

RR Lyrae stars,a well-known type of pulsating variable stars,have been known about for more than a century.A large amount of photometric data on RR Lyrae stars has been accumulated by space-and ground-based sky surveys,but the spectral data are relatively ***,the LAMOST sky survey project provides an opportunity to view them from the point of view of *** collect the atmospheric parameters of 1685 RR Lyrae stars provided by the LAMOST catalog,and carry out research by using the reliable *** find that there is a clear correlation between their Teff and pulsation periods,which is consistent with the pulsation and evolution theories of RR Lyrae *** addition,we focus on those RR Lyrae stars with abnormal *** analyzing the data from several photometric surveys,we find that some of these temperature anomalies are misclassified variable stars(e.g.,eclipsing binaries,pulsating stars on main sequence),and some are RR Lyrae binary *** the latter,the temperatures of potential companions should be lower and their luminosities should not be neglected(e.g.,red giant stars).We obtain that the ratio of temperature anomaly stars to all the sample stars is 4%,which means that the impact on the further analysis(e.g.,kinematics analysis)is *** also present the catalogs of spectral anomaly RR Lyrae stars.

关键词： techniques spectroscopic-techniques photometric-stars fundamental parameters-stars variables RR Lyrae

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