检索结果-内蒙古大学图书馆

arXiv 2017年

作者： Song, H.F. Meynet, G. Maeder, A. Ekström, S. Eggenberger, P. Georgy, C. Qin, Y. Fragos, T. Soerensen, M. Barblan, F. Wade, G.A. College of Physics Guizhou University Guiyang CityGuizhou Province550025 China Geneva Observatory Geneva University SauvernyCH-1290 Switzerland Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 Guangxi Key Laboratory for Relativistic Astrophysics Department of Physics Guangxi University Nanning530004 China Department of Physics Royal Military College of Canada Ontario Canada

Context. Massive stars with solar metallicity lose important amounts of rotational angular momentum through their winds. When a magnetic field is present at the surface of a star, efficient angular momentum losses can still be achieved even when the mass-loss rate is very modest, at lower metallicities, or for lower-initial-mass stars. In a close binary system, the effect of wind magnetic braking also interacts with the influence of tides, resulting in a complex evolution of rotation. Aims. We study the interactions between the process of wind magnetic braking and tides in close binary systems. Methods. We discuss the evolution of a 10 M☉ star in a close binary system with a 7 M☉ companion using the Geneva stellar evolution code. The initial orbital period is 1.2 days. The 10 M☉ star has a surface magnetic field of 1 kG. Various initial rotations are considered. We use two different approaches for the internal angular momentum transport. In one of them, angular momentum is transported by shear and meridional currents. In the other, a strong internal magnetic field imposes nearly perfect solid-body rotation. The evolution of the primary is computed until the first mass-transfer episode occurs. The cases of different values for the magnetic fields and for various orbital periods and mass ratios are briefly discussed. Results. We show that, independently of the initial rotation rate of the primary and the efficiency of the internal angular momentum transport, the surface rotation of the primary will converge, in a time that is short with respect to the main-sequence lifetime, towards a slowly evolving velocity that is different from the synchronization velocity. This "equilibrium angular velocity" is always inferior to the angular orbital velocity. In a given close binary system at this equilibrium stage, the difference between the spin and the orbital angular velocities becomes larger when the mass losses and/or the surface magnetic field increase. The treatment of th

关键词： Angular momentum

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A study in scarlet - II. Spectroscopic properties of a sample of Intermediate Luminosity Red Transients

arXiv

引用

arXiv 2024年

作者： Valerin, G. Pastorello, A. Mason, E. Reguitti, A. Benetti, S. Cai, Y.-Z. Chen, T.-W. Eappachen, D. Elias-Rosa, N. Fraser, M. Gangopadhyay, A. Hsiao, E.Y. Howell, D.A. Inserra, C. Izzo, L. Jencson, J. Kankare, E. Kotak, R. Lundqvist, P. Mazzali, P.A. Misra, K. Pignata, G. Prentice, S.J. Sand, D.J. Smartt, S.J. Stritzinger, M.D. Tartaglia, L. Valenti, S. Anderson, J.P. Andrews, J.E. Amaro, R.C. Barbarino, C. Brennan, S. Bufano, F. Callis, E. Cappellaro, E. Dastidar, R. Valle, M. Della Fiore, A. Fulton, M.D. Galbany, L. Gromadzki, M. Heikkilä, T. Hiramatsu, D. Karamehmetoglu, E. Kuncarayakti, H. Leloudas, G. Limongi, M. Lundquist, M. Müller-Bravo, T.E. Nicholl, M. Ochner, P. Gonzalez, E. Padilla Paraskeva, E. Pellegrino, C. Rau, A. Reichart, D.E. Reynolds, T.M. Roy, R. Salmaso, I. Shahbandeh, M. Singh, M. Sollerman, J. Turatto, M. Tomasella, L. Wyatt, S. Young, D.R. INAF – Osservatorio Astronomico di Padova Vicolo dell’Osservatorio 5 PadovaI-35122 Italy INAF – OATS Via G.B. Tiepolo 11 Trieste34143 Italy INAF – Osservatorio Astronomico di Brera Via E. Bianchi 46 LC Merate23807 Italy 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 Graduate Institute of Astronomy National Central University 300 Jhongda Road Jhongli32001 Taiwan SRON Netherlands Institute for Space Research Niels Bohrweg 4 Leiden2333 CA Netherlands Department of Astrophysics IMAPP Radboud University Nijmegen P.O. Box 9010 Nijmegen6500 GL Netherlands Campus UAB Carrer de Can Magrans s/n BarcelonaE-08193 Spain School of Physics O’Brien Centre for Science North University College Dublin BelfieldDublin 4 Ireland The Oskar Klein Centre Department of Astronomy Stockholm University AlbaNova StockholmSE-10691 Sweden Hiroshima Astrophysical Science Center Hiroshima University Japan Department of Physics Florida State University 77 Chieftan Way TallahasseeFL32306 United States Las Cumbres Observatory 6740 Cortona Dr. Suite 102 GoletaCA93117 United States Department of Physics University of California Santa BarbaraCA93106 United States Cardiff Hub for Astrophysics Research and Technology School of Physics & Astronomy Cardiff University Queens Buildings The Parade CardiffCF24 3AA United Kingdom INAF Osservatorio Astronomico di Capodimonte Salita Moiariello 16 NapoliI-80131 Italy DARK Niels Bohr Institute University of Copenhagen Jagtvej 128 Copenhagen2200 Denmark Caltech/IPAC Mailcode 100-22 PasadenaCA91125 United States Tuorla Observatory Department of Physics and Astronomy University of Turku Turku20014 Finland Department of Astronomy AlbaNova University Center Stockholm University StockholmSE-10691 Swede

Aims. We investigate the spectroscopic characteristics of Intermediate Luminosity Red Transients (ILRTs), a class of elusive objects with peak luminosity between that of classical novae and standard supernovae. Our goal is to provide a stepping stone in the path to unveil the physical origin of such events, thanks to the analysis of the datasets collected. Methods. We present the extensive optical and near-infrared (NIR) spectroscopic monitoring of four ILRTs, namely NGC 300 2008OT-1, AT 2019abn, AT 2019ahd and AT 2019udc. First we focus on the evolution of the most prominent spectral features observed in the low resolution spectra, then we discuss more in detail the high resolution spectrum collected for NGC 300 2008OT-1 with the Very Large Telescope equipped with UVES. Finally we analyse late time spectra of NGC 300 2008OT-1 and AT 2019ahd through comparisons with both synthetic and observed spectra. Results. Balmer and Ca lines dominate the optical spectra, revealing the presence of slowly moving circumstellar medium (CSM) around the objects. The line luminosity of Hα, Hβ and Ca II NIR triplet presents a double peaked evolution with time, possibly indicative of interaction between fast ejecta and the slow CSM. The high resolution spectrum of NGC 300 2008OT-1 reveals a complex circumstellar environment, with the transient being surrounded by a slow (∼30 km s−1) progenitor wind. At late epochs, optical spectra of NGC 300 2008OT-1 and AT 2019ahd show broad (∼2500 km s−1) emission features at ∼6170Å and ∼7000Å which are unprecedented for ILRTs. We find that these lines originate most likely from the blending of several narrow lines, possibly of iron-peak elements. © 2024, CC BY.

关键词： Infrared devices

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Strong Carbon Features and a Red Early Color in the Underluminous Type Ia SN 2022xkq

arXiv

引用

arXiv 2023年

作者： Pearson, Jeniveve Sand, David J. Lundqvist, Peter Galbany, Lluís Andrews, Jennifer E. Bostroem, K. Azalee Dong, Yize Hoang, Emily Hosseinzadeh, Griffin Janzen, Daryl Jencson, Jacob E. Lundquist, Michael J. Mehta, Darshana Retamal, Nicolás Meza Shrestha, Manisha Valenti, Stefano Wyatt, Samuel Anderson, Joseph P. Ashall, Chris Auchettl, Katie Baron, Eddie Blondin, Stéphane Burns, Christopher R. Cai, Yongzhi Chen, Ting-Wan Chomiuk, Laura Coulter, David A. Cross, Dane Davis, Kyle W. de Jaeger, Thomas DerKacy, James M. Desai, Dhvanil D. Dimitriadis, Georgios Do, Aaron Farah, Joseph R. Foley, Ryan J. Gromadzki, Mariusz Gutiérrez, Claudia P. Haislip, Joshua González Hernández, Jonay I. Hinkle, Jason T. Hoogendam, Willem B. Howell, D. Andrew Hoeflich, Peter Hsiao, Eric Huber, Mark E. Jha, Saurabh W. Palau, Cristina Jiménez Kilpatrick, Charles D. Kouprianov, Vladimir Kumar, Sahana Kwok, Lindsey A. Larison, Conor LeBaron, Natalie Le Saux, Xavier Lu, Jing McCully, Curtis Evans, Tycho Mera Milne, Peter Modjaz, Maryam Morrell, Nidia Müller-Bravo, Tomás E. Newsome, Megan Nicholl, Matt Gonzalez, Estefania Padilla Payne, Anna V. Pellegrino, Craig Phan, Kim Pineda-García, Jonathan Piro, Anthony L. Piscarreta, Lara Polin, Abigail Reichart, Daniel E. Rojas-Bravo, César Ryder, Stuart D. Salmaso, Irene Schwab, Michaela Shahbandeh, Melissa Shappee, Benjamin J. Siebert, Matthew R. Smith, Nathan Strader, Jay Taggart, Kirsty Terreran, Giacomo Tinyanont, Samaporn Tucker, M.A. Valerin, Giorgio Young, D.R. Steward Observatory University of Arizona 933 North Cherry Avenue TucsonAZ85721-0065 United States Oskar Klein Centre Department of Astronomy Stockholm University Albanova University Centre StockholmSE-106 91 Sweden Campus UAB Carrer de Can Magrans s/n BarcelonaE-08193 Spain Institut d’Estudis Espacials de Catalunya Gran Capità 2-4 Edifici Nexus Desp. 201 BarcelonaE-08034 Spain Gemini Observatory 670 North A‘ohoku Place HiloHI96720-2700 United States Department of Physics and Astronomy University of California Davis 1 Shields Avenue DavisCA95616-5270 United States Department of Physics & Engineering Physics University of Saskatchewan 116 Science Place SaskatoonSKS7N 5E2 Canada Department of Physics and Astronomy The Johns Hopkins University 3400 North Charles Street BaltimoreMD21218 United States W. M. Keck Observatory 65-1120 Māmalahoa Highway KamuelaHI96743-8431 United States Department of Astronomy University of Washington 3910 15th Avenue NE SeattleWA98195-0002 United States European Southern Observatory Alonso de Córdova 3107 Casilla 19 Santiago Chile Millennium Institute of Astrophysics MAS Nuncio Monsenor Sotero Sanz 100 Off. 104 Providencia Santiago Chile Department of Physics Virginia Tech 850 West Campus Drive BlacksburgVA24061 United States School of Physics The University of Melbourne ParkvilleVIC3010 Australia Department of Astronomy and Astrophysics University of California Santa CruzCA95064-1077 United States Planetary Science Institute 1700 East Fort Lowell Road Suite 106 TucsonAZ85719-2395 United States Hamburger Sternwarte Gojenbergsweg 112 Hamburg21029 Germany Homer L. Dodge Department of Physics and Astronomy University of Oklahoma 440 W. Brooks NormanOK73019-2061 United States Aix-Marseille Univ CNRS CNES LAM Marseille13388 France Observatories of the Carnegie Institute for Science 813 Santa Barbara Street PasadenaCA91101-1232 United States Yunnan Observatories Chinese Academy of

We present optical, infrared, ultraviolet, and radio observations of SN 2022xkq, an underluminous fast-declining type Ia supernova (SN Ia) in NGC 1784 (D ≈ 31 Mpc), from Copyright © 2023, The Authors. All rights... 详细信息

关键词： Explosions

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The YNEV stellar evolution and oscillation code

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Research in Astronomy and Astrophysics 2015年第4期15卷 549-568页

作者： Qian-Sheng Zhang Yunnan Observatories Chinese Academy of Sciences Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences

We have developed a new stellar evolution and oscillation code YNEV, which calculates the structures and evolutions of stars, taking into account hydrogen and helium burning. A nonlocal turbulent convection theory and an updated over- shoot mixing model are optional in this code. The YNEV code can evolve low- and intermediate-mass stars from the pre-main sequence to a thermally pulsing asymptotic branch giant or white dwarf. The YNEV oscillation code calculates the eigenfrequen- cies and eigenfunctions of the adiabatic oscillations for a given stellar structure. The input physics and numerical scheme adopted in the code are introduced. Examples of solar models, stellar evolutionary tracks of low- and intermediate-mass stars with different convection theories （i.e. mixing-length theory and nonlocal turbulent con- vection theory）, and stellar oscillations are shown.

关键词： stars -- stellar structure -- stellar evolution -- stellar oscillations

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The rate of period change in DAV stars

arXiv

引用

arXiv 2017年

作者： Chen, Y.H. Ding, C.Y. Na, W.W. Shu, H. Institute of Astrophysics Chuxiong Normal University Chuxiong675000 China School of Physics and Electronical Science Chuxiong Normal University Chuxiong675000 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O. Box 110 Kunming650011 China School of Physics and Electronic Engineering Yuxi Normal University Yuxi653100 China

Grids of DAV star models are evolved by WDEC, taking the element diffusion effect into account. The grid parameters are hydrogen mass log(MH/M*), helium mass log(MH/M*), stellar mass M., and effective temperature Teff for DAV stars. The core compositions are from white dwarf models evolved by MESA. Therefore, those DAV star models evolved by WDEC have historically viable core compositions. Based on those DAV star models, we studied the rate of period change (P(k)) for different values of H, He, M., and Teff. The results are consistent with previous work. Two DAV stars G117-B15A and R548 have been observed around forty years. The rates of period change of two largeamplitude modes were obtained through O-C method. We did asteroseismological study on the two DAV stars and then obtained a best-fittingmodel for each star. Based on the two best-fitting models, the mode identifications (l, k) of the observed modes for G117-B15A and R548 are consistent with previous work. Both the observed modes and the observed Ps can be fitted by calculated ones. The results indicate that our method of evolving DAV star models is feasible. Copyright © 2017, The Authors. All rights reserved.

关键词： White dwarfs

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The peculiar transient AT2018cow: A possible origin of A type Ibn/IIn supernova

arXiv

引用

arXiv 2021年

作者： Xiang, Danfeng Wang, Xiaofeng Lin, Weili Mo, Jun Lin, Han Burke, Jamison Hiramatsu, Daichi Hosseinzadeh, Griffin Howell, D. Andrew McCully, Curtis Valenti, Stefan Vinkó, József Wheeler, J. Craig Ehgamberdiev, Shuhrat A. Mirzaqulov, Davron Bódi, Attila Bognár, Zsófia Cseh, Borbála Hanyecz, Ottó Ignácz, Bernadett Kalup, Csilla Könyves-Tóth, Réka Kriskovics, Levente Ordasi, András Pál, András Sárneczky, Krisztián Seli, Bálint Szakáts, Róbert Arranz-Heras, T. Benavides-Palencia, R. Cejudo-Martínez, D. de la Fuente-Fernández, P. Escartín-Pérez, A. la Cuesta, F. García-De González-Carballo, J.L. González-Farfán, R. Limón-Martínez, F. Mantero, A. Naves-Nogués, R. Morales-Aimar, M. Ruíz-Ruíz, V.R. Soldán-Alfaro, F.C. Valero-Pérez, J. Violat-Bordonau, F. Zhang, Tianmeng Zhang, Jujia Li, Xue Chen, Zhihao Sai, Hanna Li, Wenxiong Tsinghua University Beijing100084 China Beijing Planetarium Beijing Academy of Sciences and Technology Beijing100044 China Purple Mountain Observatory Chinese Academy of Sciences Nanjing210023 China Las Cumbres Observatory 6740 Cortona Drive Suite 102 GoletaCA93117-5575 United States Department of Physics University of California Santa BarbaraCA93106-9530 United States Center for Astrophysics | Harvard & Smithsonian 60 Garden Street CambridgeMA02138-1516 United States Department of Physics and Astronomy University of California 1 Shields Avenue DavisCA95616-5270 United States Konkoly Observatory Research Centre for Astronomy and Earth Sciences Konkoly-Thege M. út 15-17 Budapest1121 Hungary ELTE Eötvös Loránd University Institute of Physics Pázmany Péter sétány 1/A Budapest1117 Hungary Department of Optics & Quantum Electronics University of Szeged Dóm tér 9 Szeged6720 Hungary Department of Astronomy University of Texas at Austin AustinTX78712 United States Ulugh Beg Astronomical Institute Uzbekistan Academy of Sciences Uzbekistan Tashkent100052 Uzbekistan CSFK Lendület Near-Field Cosmology Research Group Eötvös Loránd University Institute of Physics Pázmany Péter sétány 1/A Budapest1117 Hungary Eötvös Loránd University Department of Astronomy Pázmany Péter sétány 1/A Budapest1117 Hungary Spain Obs. Las Pequeras Navas de Oro Segovia40470 Spain Obs. Posadas MPC J53 Posadas Córdoba14730 Spain Obs. El Gallinero El Berrueco Madrid28192 Spain Obs. Llanes Llanes Asturias33784 Spain Obs. Belako Mungia Vizcaya48100 Spain Obs. La Vara MPC J38 Muñas de Arriba Asturias33784 Spain Obs. Cerro del Viento MPC I84 Badajoz06010 Spain Obs. Uraniborg MPC Z55 Écija Sevilla41400 Spain Obs. Mazariegos MPC I99 Mazariegos Palencia34170 Spain Obs. Bernezzo MPC C77 Bernezzo Cuneo12010 Italy Obs. Montcabrer MPC 213 Cabrils Barcelona08348 Spain Obs. Sencelles MPC K14 Sencelles Islas Baleares07140 Spain New Mexico Skies Unit

We present our photometric and spectroscopic observations on the peculiar transient AT2018cow. The multi-band photometry covers from peak to ∼70 days and the spectroscopy ranges from 5 to ∼50 days. The rapid rise (tr.2.9 days), high luminosity (MVpeak ∼ −20.8 mag) and fast decline after peak make AT2018cow stand out of any other optical transients. While we find that its light curves show high resemblance to those of type Ibn supernovae. Moreover, the spectral energy distribution remains high temperature of ∼14,000 K after ∼15 days since discovery. The spectra are featureless in the first 10 days, while some broad emission lines due to H, He, C and O emerge later, with velocity declining from ∼ 14, 000 km s−1 to ∼3000 km s−1 at the end of our observations. Narrow and weak He I emission lines emerge in the spectra at t >20 days since discovery. These emission lines are reminiscent of the features seen in interacting supernovae like type Ibn and IIn subclasses. We fit the bolometric light curves with a model of circumstellar interaction (CSI) and radioactive decay (RD) of 56Ni and find a good fit with ejecta mass Mej ∼ 3.16 M☉, circumstellar material mass MCSM ∼ 0.04 M☉, and ejected 56Ni mass M56Ni ∼ 0.23 M☉. The CSM shell might be formed in an eruptive mass ejection of the progenitor star. Furthermore, host environment of AT2018cow implies connection of AT2018cow with massive stars. Combining observational properties and the light curve fitting results, we conclude that AT2018cow might be a peculiar interacting supernova originated from a massive star. © 2021, CC BY.

关键词： Electromagnetic wave emission

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An unexpected detection of bifurcated blue straggler sequences in the young globular cluster ngc 2173

arXiv

引用

arXiv 2018年

作者： Li, Chengyuan Deng, Licai Grijs, Richard De Jiang, Dengkai Xin, Yu Department of Physics and Astronomy Macquarie University Balaclava Road North RydeNSW2109 Australia Department of Astronomy China West Normal University Nanchong637002 China School of Astronomy and Space Science University of Chinese Academy of Sciences 20A Datun Road Beijing100012 China Kavli Institute for Astronomy and Astrophysics and Department of Astronomy Peking University Yi He Yuan Lu 5 Beijing100871 China International Space Science Institute-Beijing 1 Nanertiao Zhongguancun Beijing100190 China Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China

Bifurcated patterns of blue straggler stars in their color-magnitude diagrams have atracted significant attention. This type of special (but rare) pattern of two distinct blue straggler sequences is commonly interpreted as evidence of cluster core-collapse-driven stellar collisions as an efficient formation mechanism. Here, we report the detection of a bifurcated blue straggler distribution in a young LargeMagellanic Cloud cluster, NGC 2173. Because of the cluster's low central stellar number density and its young age, dynamical analysis shows that stellar collisions alone cannot explain the observed blue straggler stars. Therefore, binary evolution is instead the most viable explanation of the origin of these blue straggler stars. However, the reason why binary evolution would render the color-magnitude distribution of blue straggler stars bifurcated remains unclear. Copyright © 2018, The Authors. All rights reserved.

关键词： Stars

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A method for locating high energy dissipation region in blazar

arXiv

引用

arXiv 2017年

作者： Yan, Dahai Wu, Qingwen Fan, Xuliang Wang, Jiancheng Zhang, Li Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatory Chinese Academy of Sciences Kunming650011 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China School of Physics Huazhong University of Science and Technology Wuhan430074 China Key Laboratory of Astroparticle Physics of Yunnan Province Yunnan University Kunming650091 China

The production site of gamma-rays in blazar jet is an unresolved problem. We present a method to locate gamma-ray emission region in the framework of one-zone emission model. From measurements of core-shift effect, the relation between the magnetic field strengths (B′) in the radio cores of jet and the distances (R) of these radio cores from central supermassive black hole (SMBH) can be inferred. Therefore once the magnetic field strength in gamma-ray emission region (Bdiss′ ) is obtained, one can use the relation of B′-R to derive the distance (Rdiss) of gamma-ray emission region from SMBH. Here we evaluate the lower limit of Bdiss′ by using the criteria that the optical variability timescale tvar should be longer or equal to the synchrotron radiation cooling timescale of the electrons that emit optical photons. We test the method with the observations of PSK 1510-089 and BL Lacertae, and derive Rdiss D1/3(1 + A)2/3 pc for PSK 1510-089 with tvar ∼ a few hours, and Rdiss D1/3(1 + A)2/3 pc for BL Lacertae with tvar ∼ a few minutes. Here δD is the Doppler factor and A is the Compton dominance (i.e., the ratio of the Compton to the synchrotron peak luminosities). Copyright © 2017, The Authors. All rights reserved.

关键词： Synchrotron radiation

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Insight-Hxmt Observations of The New Black Hole Candidate Maxi J1535-571: Timing Analysis

arXiv

引用

arXiv 2018年

作者： Huang, Y. Qu, J.L. Zhang, S.N. Bu, Q.C. Chen, Y.P. Tao, L. Zhang, S. Lu, F.J. Li, T.P. Song, L.M. Xu, Y.P. Cao, X.L. Chen, Y. Liu, C.Z. Chang, H.-K. Yu, W.F. Weng, S.S. Hou, X. Kong, A.K.H. Xie, F.G. Zhang, G.B. Zhou, J.F. Chang, Z. Chen, G. Chen, L. Chen, T.X. Chen, Y.B. Cui, W. Cui, W.W. Deng, J.K. Dong, Y.W. Du, Y.Y. Fu, M.X. Gao, G.H. Gao, H. Gao, M. Ge, M.Y. Gu, Y.D. Guan, J. Gungor, C. Guo, C.C. Han, D.W. Hu, W. Huo, J. Ji, J.F. Jia, S.M. Jiang, L.H. Jiang, W.C. Jin, J. Jin, Y.J. Li, B. Li, C.K. Li, G. Li, M.S. Li, W. Li, X. Li, X.B. Li, X.F. Li, Y.G. Li, Z.J. Li, Z.W. Liang, X.H. Liao, J.Y. Liu, G.Q. Liu, H.W. Liu, S.Z. Liu, X.J. Liu, Y. Liu, Y.N. Lu, B. Lu, X.F. Luo, T. Ma, X. Meng, B. Nang, Y. Nie, J.Y. Ou, G. Sai, N. Shang, R.C. Sun, L. Tan, Y. Tao, W. Tuo, Y.L. Wang, G.F. Wang, H.Y. Wang, J. Wang, W.S. Wang, Y.S. Wen, X.Y. Wu, B.B. Wu, M. Xiao, G.C. Xiong, S.L. Xu, H. Yan, L.L. Yang, J.W. Yang, S. Yang, Y.J. Zhang, A.M. Zhang, C.L. Zhang, C.M. Zhang, F. Zhang, H.M. Zhang, J. Zhang, Q. Zhang, T. Zhang, W. Zhang, W.C. Zhang, W.Z. Zhang, Y. Zhang, Y. Zhang, Y.F. Zhang, Y.J. Zhang, Z. Zhang, Z. Zhang, Z.L. Zhao, H.S. Zhao, J.L. Zhao, X.F. Zheng, S.J. Zhu, Y. Zhu, Y.X. Zou, C.L. Key Laboratory of Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing100049 China University of Chinese Academy of Sciences Chinese Academy of Sciences Beijing100049 China Department of Physics Tsinghua University Beijing100084 China Department of Astronomy Beijing Normal University Beijing100088 China Department of Engineering Physics Tsinghua University Beijing100084 China Institute of Astronomy National Tsing Hua University Hsinchu30013 Taiwan Department of Physics National Tsing Hua University Hsinchu30013 Taiwan Key Laboratory for Research in Galaxies and Cosmology Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai200030 China Department of Physics Institute of Theoretical Physics Nanjing Normal University Nanjing210023 China Yunnan Observatories 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 Beijing100012 China

We present the X-ray timing results of the new black hole candidate (BHC) MAXI J1535-571 during its 2017 outburst from Hard X-ray Modulation Telescope (Insight-HXMT) observations taken from 2017 September 6 to 23. Following the definitions given by Belloni (2010), we find that the source exhibits state transitions from Low/Hard state (LHS) to Hard Intermediate state (HIMS) and eventually to Soft Intermediate state (SIMS). Quasi-periodic oscillations (QPOs) are found in the intermediate states, which suggest different types of QPOs. With the large effective area of Insight-HXMT at high energies, we are able to present the energy dependence of the QPO amplitude and centroid frequency up to 100 keV which is rarely explored by previous satellites. We also find that the phase lag at the type-C QPOs centroid frequency is negative (soft lags) and strongly correlated with the centroid frequency. By assuming a geometrical origin of type-C QPOs, the source is consistent with being a high inclination system. Copyright © 2018, The Authors. All rights reserved.

关键词： Stars

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Synchrotron spectrum of fast cooling electrons in GRBs

arXiv

引用

arXiv 2017年

作者： Zhao, Xiao-Hong Bai, Jin-Ming Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 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 396 Yangfangwang Guandu District Kunming650216 China

We discuss the synchrotron emission of fast cooling electrons in shocks. The fast cooling electrons behind the shocks can generate a position-dependent inhomogeneous electron distribution if they have not enough time to mix homogeneously. This would lead to a very different synchrotron spectrum in low frequency bands from that in the homogeneous case due to the synchrotron absorption. In this paper, we calculate the synchrotron spectrum in this inhomogeneous case in a gamma-ray burst (GRB). Both the forward shock and the reverse shock are considered. We find for the reverse shock dominated case, we would expect a "reverse shock bump" in the low frequency spectrum. The spectral bump is due to the combining synchrotron absorption in both the forward and reverse shock regions. In the forward shock spectrum in the low frequencies has two unconventional segments with spectral slopes of 1 and 11/8. The slope of 11/8 has been found by some authors, while the slope of 1 is new, which is due to the approximately constant electron temperature in the optically thick region. In the future, simultaneous observations in multiple bands (especially in the low frequency bands) in the GRB early afterglow or prompt emission phases will possibly reveal these spectral characteristics and enable us to identify the reverse shock component and distinguish between the forward and reverse shock emissions. This also may be as a method to diagnose the electron distribution status (homogeneous or inhomogeneous) after fast cooling in relativistic shock region. Copyright © 2017, The Authors. All rights reserved.

关键词： Cooling

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