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A γ-ray quasi-periodic modulation in the blazar pks 0301−243

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arXiv 2017年

作者： Zhang, Peng-Fei Yan, Da-Hai Zhou, Jia-Neng Fan, Yi-Zhong Wang, Jian-Cheng Zhang, Li Key Laboratory of Dark Matter and Space Astronomy Purple Mountain Observatory Chinese Academy of Sciences Nanjing210008 China Key Laboratory of Astroparticle Physics of Yunnan Province Yunnan University Kunming650091 China Yunnan Observatory Chinese Academy of Sciences Kunming650011 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China Shanghai Astronomical Observatory Chinese Academy of Sciences 80 Nandan Road Shanghai200030 China

We report a nominally high-confidence γ-ray quasi-periodic modulation in the blazar PKS 0301−243. For this target, we analyze its Fermi-LAT Pass 8 data covering from 2008 August to 2017 May. Two techniques, i.e., the maximum likelihood optimization and the exposure-weighted aperture photometry, are used to build the γ-ray light curves. Then both the Lomb-Scargle Periodogram and the Weighted Wavelet Z-transform are applied to the light curves to search for period signals. A quasi-periodicity with a period of 2.1 ± 0.3 yr appears at the significance level of ∼ 5σ, although it should be noted that this putative quasi-period variability is seen in a data set barely four times longer. We speculate that this γ-ray quasi-periodic modulation might be evidence of a binary supermassive black hole. Copyright © 2017, The Authors. All rights reserved.

关键词： Z transforms

LAMOST Views δ Scuti Pulsating Stars

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arXiv 2017年

作者： Qian, S.-B. Li, L.-J. He, J.-J. Zhang, J. Zhu, L.-Y. Han, Z.-T. 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 Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang Dis- trict Beijing100012 China University of Chinese Academy of Sciences Yuquan Road 19# Sijingshang Block Beijing100049 China

About 766 δ Scuti stars were observed by LAMOST by 2017 June 16. Stellar atmospheric parameters of 525 variables were determined, while spectral types were obtained for all samples. In the paper, those spectroscopic data are catalogued. We detect a group of 131 unusual and cool variable stars (UCVs) that are distinguished from the normal δ Scuti stars (NDSTs). On the H−R diagram and the log g − T diagram, the UCVs are far beyond the red edge of pulsational instability trip. Their effective temperatures are lower than 6700 K with periods in the range from 0.09 to 0.22 d. NDSTs have metallicity close to that of the Sun as expected, while UCVs are slightly metal poor than NDSTs. The two peaks on the distributions of the period and stellar atmospheric parameters are all caused by the existence of UCVs. When those UCVs are excluded, it is discovered that the effective temperature, the gravitational acceleration, and the metallicity all are correlated with the pulsating period for NDSTs and their physical properties and evolutionary states are discussed. Detection of those UCVs indicates that about 25% of the known δ Scuti stars may be misclassified. However, if some of them are confirmed to be pulsating stars, they will be a new-type pulsator and their investigations will shed light on theoretical instability domains and on the theories of interacting between the pulsation and the convection of solar-type stars. Meanwhile, 88 δ Scuti stars are detected to be the candidates of binary or multiple systems. Copyright © 2017, The Authors. All rights reserved.

关键词： Temperature

Multi-band analyses of the bright GRB 230812B and the associated SN2023pel

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arXiv 2023年

作者： Hussenot-Desenonges, T. Wouters, T. Guessoum, N. Abdi, I. Abulwfa, A. Adami, C. Fernández, J.F. Agüí Ahumada, T. Aivazyan, V. Akl, D. Anand, S. Andrade, C.M. Antier, S. Ata, S.A. D’Avanzo, P. Azzam, Y.A. Baransky, A. Basa, S. Blazek, M. Bendjoya, P. Beradze, S. Boumis, P. Bremer, M. Brivio, R. Buat, V. Bulla, M. Burkhonov, O. Burns, E. Cenko, S.B. Coughlin, M.W. Corradi, W. Daigne, F. Dietrich, T. Dornic, D. Ducoin, J.-G. Duverne, P.-A. Elhosseiny, E.G. Elnagahy, F.I. El-Sadek, M.A. Ferro, M. Le Floc’h, E. Freeberg, M. Fynbo, J.P.U. Götz, D. Gurbanov, E. Hamed, G.M. Hasanov, E. Healy, B.F. Heintz, K.E. Hello, P. Inasaridze, R. Iskandar, A. Ismailov, N. Izzo, L. Jhawar, S. du Laz, T. Jegou Kamel, T.M. Karpov, S. Klotz, A. Koulouridis, E. Kuin, N.P. Kochiashvili, N. Leonini, S. Lu, K.-X. Malesani, D.B. Mašek, M. Mao, J. Melandri, A. Mihov, B.M. Natsvlishvili, R. Navarete, F. Nedora, V. Nicolas, J. Odeh, M. Palmerio, J. Pang, P.T.H. De Pasquale, M. Peng, H.W. Pormente, S. Peloton, J. Pradier, T. Pyshna, O. Rajabov, Y. Rakotondrainibe, N.A. Rivet, J.-P. Rousselot, L. Saccardi, A. Sasaki, N. Schneider, B. Serrau, M. Shokry, A. Slavcheva-Mihova, L. Simon, A. Sokoliuk, O. Srinivasaragavan, G. Strausbaugh, R. Takey, A. Tanvir, N.R. Thöne, C.C. Tillayev, Y. Tosta e Melo, I. Turpin, D. de Ugarte Postigo, A. Vasylenko, V. Vergani, S.D. Vidadi, Z. Xu, D. Wang, L.T. Wang, X.F. Winters, J.M. Zhang, X.-L. Zhu, Z. IJCLab Univ Paris-Saclay CNRS IN2P3 Orsay France Nikhef Science Park 105 Amsterdam1098 XG Netherlands Utrecht University Princetonplein 1 Utrecht3584 CC Netherlands Physics Department American University of Sharjah Sharjah United Arab Emirates 1 El-marsad St. Helwan Cairo11421 Egypt Aix Marseille Univ CNRS CNES LAM Marseille France Instituto de Astrofísica de Andalucía Glorieta de la Astronomía s/n Granada18008 Spain Cahill Center for Astrophysics California Institute of Technology PasadenaCA91125 United States E. Kharadze Georgian National Astrophysical Observatory Mt. Kanobili Abastumani Adigeni0301 Georgia Samtskhe-Javakheti State University Rustaveli Str. 113 Akhaltsikhe0080 Georgia School of Physics and Astronomy University of Minnesota MinneapolisMN55455 United States Observatoire de la Côte d’Azur Université Côte d’Azur Boulevard de l’Observatoire Nice06304 France INAF–Osservatorio Astronomico di Brera Via E. Bianchi 46 LC Merate23807 Italy Astronomical Observatory Taras Shevchenko National University of Kyiv Observatorna Str. 3 Kyiv04053 Ukraine CEICO Institute of Physics The Czech Academy of Sciences Na Slovance 1999/2 PrahaCZ-182 21 Czech Republic Centro Astronómico Hispano en Andalucía Observatorio de Calar Alto Sierra de los Filabres Gérgal Almería04550 Spain Laboratoire J.-L. Lagrange Université de Nice Sophia-Antipolis CNRS Observatoire de la Côte d’Azur Nice06304 France National Observatory of Athens Institute for Astronomy Astrophysics Space Applications and Remote Sensing Greece Institut de Radioastronomie Millimétrique France Università degli Studi dell’Insubria Dipartimento di Scienza e Alta Tecnologia Via Valleggio 11 Como22100 Italy Department of Physics and Earth Science University of Ferrara via Saragat 1 FerraraI-44122 Italy INFN Sezione di Ferrara via Saragat 1 FerraraI-44122 Italy INAF Osservatorio Astronomico d’Abruzzo via Mentore Maggini snc TeramoI-64100 Italy Ulugh Beg Astrono

GRB 230812B is a bright and relatively nearby (z = 0.36) long gamma-ray burst (GRB) that has generated significant interest in the community and has thus been observed over the entire electromagnetic spectrum. We report over 80 observations in X-ray, ultraviolet, optical, infrared, and sub-millimeter bands from the GRANDMA (Global Rapid Advanced Network for Multi-messenger Addicts) network of observatories and from observational partners. Adding complementary data from the literature, we then derive essential physical parameters associated with the ejecta and external properties (i.e. the geometry and environment) of the GRB and compare with other analyses of this event. We spectroscopically confirm the presence of an associated supernova, SN2023pel, and we derive a photospheric expansion velocity of v ∼ 17×103 km s-1. We analyze the photometric data first using empirical fits of the flux and then with full Bayesian Inference. We again strongly establish the presence of a supernova in the data, with a maximum (pseudo-)bolometric luminosity of 5.75×1042 erg/s, at 15.76+0.81-1.21 days (in the observer frame) after the trigger, with a half-max time width of 22.0 days. We compare these values with those of SN1998bw, SN2006aj, and SN2013dx. Our best-fit model favours a very low density environment (log10(nISM/cm-3) = -2.38+1.45-1.60) and small values for the jet’s core angle θcore = 1.54+1.02-0.81 deg and viewing angle θobs = 0.76+1.29-0.76 deg. GRB 230812B is thus one of the best observed afterglows with a distinctive supernova bump. © 2023, CC BY.

关键词： Supernovae

A new mechanism of long-term period variations for W UMa-type contact binaries

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arXiv 2017年

作者： Liu, L. Qian, S.-B. Xiong, X. Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China University of Chinese Academy of Sciences Yuquan Road 19# Sijingshang Block Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China

W UMa-type contact binaries belong to close binary systems whose components exactly overflow their Roche lobes and share a common convective envelope (CCE). In the last twenty years, the long-term variations of their orbital periods have been thought to depend on several mechanisms. Now, we suggest a new mechanism: CCE-dominated mechanism. The CCE-dominated mechanism is found based on our numerical result, especially at high mass ratios, that the orbital periods (P) of contact binaries change very much with their fill-out factors (f). Because f is taken as a measurement of the thickness of CCE, the physical cause for the variation of P is a mass transfer between CCE and components. Further, an f-dominated simplification model for this mechanism is introduced. According to it, P may change in a long-term oscillation way with a similar time scale of the thermal modulation, meanwhile q is decreasing slowly till the two components merge. It could be also applied to explain the presence of extremely short period, high mass ratio and deep contact binaries. Moreover, the CCE-dominated mechanism should always work due to mass transfer and mass loss both occurring via CCE. Therefor, the effect of CCE on the variations of orbital periods may have been underestimated before. Copyright © 2017, The Authors. All rights reserved.

关键词： Mass transfer

Ready for O4 II: GRANDMA Observations of Swift GRBs during eight-weeks of Spring 2022

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arXiv 2023年

作者： Tosta e Melo, I. Ducoin, J.-G. Vidadi, Z. Andrade, C. Rupchandani, V. Agayeva, S. Abdelhadi, J. Abe, L. Aguerre-Chariol, O. Aivazyan, V. Alishov, S. Antier, S. Bai, J.-M. Baransky, A. Bednarz, S. Bendjoya, Ph. Benkhaldoun, Z. Beradze, S. Bizouard, M.A. Bhardwaj, U. Blazek, M. Boër, M. Broens, E. Burkhonov, O. Christensen, N. Cooke, J. Corradi, W. Coughlin, M.W. Culino, T. Daigne, F. Dornic, D. Duverne, P.-A. Ehgamberdiev, S. Eymar, L. Fouad, A. Freeberg, M. Gendre, B. Guo, F. Gokuldass, P. Guessoum, N. Gurbanov, E. Hainich, R. Hasanov, E. Hello, P. Inasaridze, R. Iskandar, A. Ismailov, N. Janati, A. Jegou du Laz, T. Kann, D.A. Karpov, S. Kiendrebeogo, R.W. Klotz, A. Kneip, R. Kochiashvili, N. Kaeouach, A. Kruiswijk, K. Lamoureux, M. Leroy, N. Lin, W.L. Mao, J. Marchais, D. Mašek, M. Midavaine, T. Moller, A. Morris, D. Natsvlishvili, R. Navarete, F. Nicuesa Guelbenzu, A. Noonan, K. Noysena, K. Oksanen, A. Orange, N.B. Pellouin, C. Peloton, J. Peng, H.W. Pilloix, M. Popowicz, A. Pradier, T. Pyshna, O. Raaijmakers, G. Rajabov, Y. Rau, A. Rinner, C. Rivet, J.-P. Ryh, A.S. Sabil, M. Sadibekova, T. Sasaki, N. Serrau, M. Simon, A. Shokry, Ahmed Smith, K. Sokoliuk, O. Song, X. Takey, A. Thierry, P. Tillayev, Y. Turpin, D. de Ugarte Postigo, A. Vasylenko, V. Vernet, D. Wang, L. Vachier, F. Vignes, J.P. Wang, X.F. Zeng, X. Zhang, J. Zhu, Y. Department of Physics and Astronomy University of Catania Catania95125 Italy Sorbonne Université CNRS UMR 7095 Institut d'Astrophysique de Paris 98 bis bd Arago Paris75014 France N.Tusi Shamakhy Astrophysical Observatory Azerbaijan National Academy of Sciences settl.Y. Mammadaliyev ShamakhyAZ 5626 Azerbaijan School of Physics and Astronomy University of Minnesota MinneapolisMN55455 United States Brown University RI ProvidenceRI02912 United States Oukaimeden Observatory High Energy Physics and Astrophysics Laboratory FSSM Cadi Ayyad University Av. Prince My Abdellah MarrakeshBP 2390 Morocco Université Côte d'Azur Observatoire de la Côte d'Azur CNRS Laboratoire J.-L. Lagrange Boulevard de l'Observatoire Nice06304 France 14 rue Saint-Hubert Orry-la-VilleF-60560 France E. Kharadze Georgian National Astrophysical Observatory Mt.Kanobili Abastumani Adigeni0301 Georgia Samtskhe-Javakheti State University Rustaveli Str. 113 Akhaltsikhe0080 Georgia N.Tusi Shamakhy astrophysical Observatory Azerbaijan National Academy of Sciences settl.Mamedaliyev ShamakhyAZ 5626 Azerbaijan Université Côte d'Azur Observatoire de la Côte d'Azur CNRS Artemis Boulevard de l'Observatoire Nice06304 France Astronomical Observatory Taras Shevshenko National University of Kyiv Observatorna str. 3 Kyiv04053 Ukraine Silesian University of Technology Faculty of Automatic Control Electronics and Computer Science Akademicka 16 Gliwice44-100 Poland GRAPPA Anton Pannekoek Institute for Astronomy Institute of High-Energy Physics University of Amsterdam Science Park 904 Amsterdam1098 XH Netherlands FZU - Institute of Physics The Czech Academy of Sciences Na Slovance 1999/2 PrahaCZ-182 21 Czech Republic Vereniging or Sterrenkunde Balen-Neetlaan 18A Mol2400 Belgium Ulugh Beg Astronomical Institute Uzbekistan Academy of Sciences Astronomy str. 33 Tashkent100052 Uzbekistan Centre for Astrophysics and Supercomputing Swinburne University of Technology HawthornVIC3122

Aims. We present a campaign designed to train the GRANDMA network and its infrastructure to follow up on transient alerts and detect their early afterglows. In preparation for O4 II campaign, we focused on GRB alerts as they are expected to be an electromagnetic counterpart of gravitational-wave events. Our goal was to improve our response to the alerts and start prompt observations as soon as possible to better prepare the GRANDMA network for the fourth observational run of LIGO-Virgo-Kagra (which started at the end of May 2023), and future missions such as SM. Methods. To receive, manage and send out observational plans to our partner telescopes we set up dedicated infrastructure and a rota of follow-up adcates were organized to guarantee round-the-clock assistance to our telescope teams. To ensure a great number of observations, we focused on Swift GRBs whose localization errors were generally smaller than the GRANDMA telescopes' field of view. This allowed us to bypass the transient identification process and focus on the reaction time and efficiency of the network. Results. During'Ready for O4 II', 11 Swift/INTEGRAL GRB triggers were selected, nine fields had been observed, and three afterglows were detected (GRB 220403B, GRB 220427A, GRB 220514A), with 17 GRANDMA telescopes and 17 amateur astronomers from the citizen science project Kilonova-Catcher. Here we highlight the GRB 220427A analysis where our long-term follow-up of the host galaxy allowed us to obtain a photometric redshift of z = 0.82 ± 0.09, its lightcurve elution, fit the decay slope of the afterglows, and study the properties of the host galaxy. Conclusions. During this 8-week-long GRB follow-up campaign, we successfully fulfilled our goal of training telescope teams for O4 and the improvement of the associated technical toolkits. For seven of the GRB alerts, our network was able to start the first observations less than one hour after the GRB trigger time. We also characterized the network effic

关键词： Telescopes

Light curve inversion of asteroid(585)Bilkis with Lommel-Seeliger ellipsoid method

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Research in Astronomy and Astrophysics 2016年第12期16卷 19-26页

作者： Ao Wang Xiao-Bin Wang Karri Muinonen Xianming L.Han Yi-Bo Wang Yunnan Observatories Chinese Academy of SciencesKunming 650011China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650011China University of Chinese Academy of Sciences Beijing 100049China Department of Physics University of HelsinkiGustaf Hallstromin katu 2aEO.Box 64FI-00014 U.HelsinkiFinland Finnish Geospatial Research Institute Geodeetinrinne 2FI-02430 MasalaFinland Department of Physics and Astronomy Butler UniversityIndianapolisIN 46208USA

The basic physical parameters of asteroids, such as spin parameters, shape and scattering parameters, can provide us with information on the formation and evolution of both the asteroids themselves and the entire solar system. In a majority of asteroids, the disk-integrated photometry measurement constitutes the primary source of the above knowledge. In the present paper, newly observed photometric data and existing data on（585） Bilkis are analyzed based on a Lommel-Seeliger ellipsoid model. With a Markov chain Monte Carlo（MCMC） method, we have determined the spin parameters（period, pole orientation）and shape（b/a, c/a） of（585） Bilkis and their uncertainties. As a result, we obtained a rotational period of 8.5738209 h with an uncertainty of 9×10^-7h, and derived a pole of（136.46°, 29.0°） in the ecliptic frame of J2000.0 with uncertainties of 0.67°and 1.1°in longitude and latitude respectively. We also derived triaxial ratios b/a and c/a of（585） Bilkis as 0.736 and 0.70 with uncertainties of 0.003 and 0.03 respectively.

关键词： asteroids -- photometric observation -- spin parameter -- shape -- MCMC method

Optical Observations of the 2002cx-like Supernova 2014ek, and Characterizations of SNe Iax

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arXiv 2018年

作者： Li, Linyi Wang, Xiaofeng Zhang, Jujia Arcavi, Iair Zhang, Tianmeng Rui, Liming Hosseinzadeh, Griffin Howell, D. Andrew McCully, Curtis Zhang, Kaicheng Valenti, Stefano Mo, Jun Li, Wenxiong Huang, Fang Xiang, Danfeng Wang, Lifan Zhou, Xu Tsinghua University Beijing100084 China Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Las Cumbres Observatory 6740 Cortona Dr Suite 102 GoletaCA93117-5575 United States Department of Physics University of California Santa BarbaraCA93106-9530 United States Key Laboratory of Optical Astronomy National Astronomical Observatories of China Chinese Academy of Sciences Beijing100012 China School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing101408 China Department of Physics University of California DavisCA95616 United States Department of Astronomy Shanghai Jiao Tong University Shanghai200240 China George P. and Cynthia Woods Mitchell Institute for Fundamental Physics & Astronomy Texas A. & M. University College StationTX77843 United States Purple Mountain Observatory Chinese Academy of Sciences Nanjing210034 China

We present optical observations of supernova (SN) 2014ek discovered during the Tsinghua-NAOC Transient Survey (TNTS), which shows properties that are consistent with those of SN 2002cx-like events (dubbed as SNe Iax). The photometry indicates that it is underluminous compared to normal SNe Ia, with the absolute V-band peak magnitude being as −17.66±0.20 mag. The spectra are characterized by highly ionized Fe iii and intermediate-mass elements (IMEs). The expansion velocity of the ejecta is found to be ∼5000 km s−1 near the maximum light, only half of that measured for normal SNe Ia. The overall spectral evolution is quite similar to SN 2002cx and SN 2005hk, while the absorption features of the main IMEs seem to be relatively weaker. The 56Ni mass synthesized in the explosion is estimated to be about 0.08 M from the pseudo bolometric light curve. Based on a large sample of SNe Iax, we examined the relations between peak luminosity, ejecta velocity, decline rate, and peak V−R color but did not find noticeable correlations between these observables, in particular when a few extreme events like SN 2008ha are excluded in the analysis. For this sample, we also studied the birthplace environments and confirm that they still hold the trend of occurring preferentially in late-type spiral galaxies. Moreover, SNe Iax tend to occur in large star-forming regions of their host galaxies, more similar to SNe Ibc than SNe II, favoring that their progenitors should be associated with very young stellar populations. Copyright © 2018, The Authors. All rights reserved.

关键词： Supernovae

Panchromatic evolution of three luminous red novae: Forbidden hugs in pandemic times - IV

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arXiv 2022年

作者： Pastorello, A. Valerin, G. Fraser, M. Reguitti, A. Elias-Rosa, N. Filippenko, A.V. Rojas-Bravo, C. Tartaglia, L. Reynolds, T.M. Valenti, S. Andrews, J.E. Ashall, C. Bostroem, K.A. Brink, T.G. Burke, J. Cai, Y.-Z. Cappellaro, E. Coulter, D.A. Dastidar, R. Davis, K.W. Dimitriadis, G. Fiore, A. Foley, R.J. Fugazza, D. Galbany, L. Gangopadhyay, A. Geier, S. Gutiérrez, C.P. Haislip, J. Hiramatsu, D. Holmbo, S. Howell, D.A. Hsiao, E.Y. Hung, T. Jha, S.W. Kankare, E. Karamehmetoglu, E. Kilpatrick, C.D. Kotak, R. Kouprianov, V. Kravtsov, T. Kumar, S. Li, Z.-T. Lundquist, M.J. Lundqvist, P. Matilainen, K. Mazzali, P.A. McCully, C. Misra, K. Morales-Garoffolo, A. Moran, S. Morrell, N. Newsome, M. Gonzalez, E. Padilla Pan, Y.-C. Pellegrino, C. Phillips, M.M. Pignata, G. Piro, A.L. Reichart, D.E. Rest, A. Salmaso, I. Sand, D.J. Siebert, M.R. Smartt, S.J. Smith, K.W. Srivastav, S. Stritzinger, M.D. Taggart, K. Tinyanont, S. Yan, S.-Y. Wang, L. Wang, X.-F. Williams, S.C. Wyatt, S. Zhang, T.-M. de Boer, T. Chambers, K. Gao, H. Magnier, E. INAF Osservatorio Astronomico di Padova Vicolo dell’Osservatorio 5 PadovaI-35122 Italy Universitá degli Studi di Padova Dipartimento di Fisica e Astronomia Vicolo dell’Osservatorio 2 Padova35122 Italy School of Physics O’Brien Centre for Science North University College Dublin Belfield Dublin 4 Ireland Instituto de astrofísica Facultad de Ciencias Exactas Universidad Andres Bello Fernández Concha 700 Las Condes Santiago Chile Nuncio Monsenor Sótero Sanz 100 Providencia Santiago8320000 Chile Campus UAB Carrer de Can Magrans s/n BarcelonaE-08193 Spain Department of Astronomy University of California BerkeleyCA94720-3411 United States Miller Institute for Basic Research in Science University of California BerkeleyCA94720 United States Department of Astronomy and Astrophysics University of California Santa CruzCA95064 United States Tuorla Observatory Department of Physics and Astronomy University of Turku TurkuFI-20014 Finland Niels Bohr Institute University of Copenhagen Jagtvej 128 København N2200 Denmark Department of Physics and Astronomy University of California Davis 1 Shields Avenue DavisCA95616-5270 United States Gemini Observatory 670 North A’ohoku Place HiloHI96720-2700 United States Department of Physics Virginia Tech 850 West Campus Drive BlacksburgVA24061 United States DIRAC Institute Department of Astronomy University of Washington 3910 15th Avenue NE SeattleWA98195-0002 United States Las Cumbres Observatory 6740 Cortona Dr. Suite 102 GoletaCA93117 United States Department of Physics University of California Santa BarbaraCA93106 United States Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Tsinghua University Beijing100084 China School of Physics Trinity College Dublin The University of Dublin Dublin 2 Ireland Fondazione Bruno Kessler TrentoI-38123 Italy

We present photometric and spectroscopic data on three extragalactic luminous red novae (LRNe): AT 2018bwo, AT 2021afy, and AT 2021blu. AT 2018bwo was discovered in NGC 45 (at about 6.8 Mpc) a few weeks after the outburst onset. During the monitoring period, the transient reached a peak luminosity of 1040 erg s−1. AT 2021afy, hosted by UGC 10043 (∼ 49.2 Mpc), showed a double-peaked light curve, with the two peaks reaching a similar luminosity of 2.1(±0.6) × 1041 erg s−1. Finally, for AT 2021blu in UGC 5829 (∼ 8.6 Mpc), the pre-outburst phase was well-monitored by several photometric surveys, and the object showed a slow luminosity rise before the outburst. The light curve of AT 2021blu was sampled with an unprecedented cadence until the object disappeared behind the Sun, and it was then recovered at late phases. The light curve of LRN AT 2021blu shows a double peak, with a prominent early maximum reaching a luminosity of 6.5 × 1040 erg s−1, which is half of that of AT 2021afy. The spectra of AT 2021afy and AT 2021blu display the expected evolution for LRNe: a blue continuum dominated by prominent Balmer lines in emission during the first peak, and a redder continuum consistent with that of a K-type star with narrow absorption metal lines during the second, broad maximum. The spectra of AT 2018bwo are markedly different, with a very red continuum dominated by broad molecular features in absorption. As these spectra closely resemble those of LRNe after the second peak, AT 2018bwo was probably discovered at the very late evolutionary stages. This would explain its fast evolution and the spectral properties compatible with that of an M-type star. From the analysis of deep frames of the LRN sites years before the outburst, and considerations of the light curves, the quiescent progenitor systems of the three LRNe were likely massive, with primaries ranging from about 13 M for AT 2018bwo, to 14+−41 M for AT 2021blu, and over 40 M for AT 2021afy. Copyright © 2022, The Autho

关键词： Luminance

Effects of magnetic fields on equation of state of rotating stars

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Science China(Physics,Mechanics & Astronomy) 2015年第2期58卷 109-113页

作者： NA WeiWei LIN GuiFang HUANG RunQian Department of Physics Yunnan University Department of Physics Yuxi Normal University Yunnan Observatories Chinese Academy of Sciences Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences

The evolution of rotating stars with magnetic fields has been studied with focus given to the following aspects: the effects of magnetic fields on equation of state for stellar matter and the thermodynamic quantities; the effects of magnetic energy and pressure on the internal structure of stars. The differences between the structure and evolution of a 15M⊙rotating star with and without magnetic fields are discussed. Our results show that the magnetic fields have an effect on the structure and evolution of the star mainly during the central helium burning phase; and this influences the physical quantities in the stellar envelope where hydrogen and helium are partially ionized. This may influence stellar pulsation.

关键词： stars： magnetic fields stars： evolution stars： equation of state