arXiv: Solar and Stellar Astrophysics最新文献

Found: a rapidly spinning white dwarf in LAMOST J024048.51+195226.9 发现:LAMOST J024048.51+195226.9中的一颗快速旋转的白矮星

arXiv: Solar and Stellar Astrophysics Pub Date : 2021-08-25 DOI: 10.1093/mnrasl/slab116

I. Pelisoli, T. Marsh, V. Dhillon, E. Breedt, A. Brown, M. Dyer, M. Green, P. Kerry, S. Littlefair, S. Parsons, D. Sahman, J. F. Wild

{"title":"Found: a rapidly spinning white dwarf in LAMOST J024048.51+195226.9","authors":"I. Pelisoli, T. Marsh, V. Dhillon, E. Breedt, A. Brown, M. Dyer, M. Green, P. Kerry, S. Littlefair, S. Parsons, D. Sahman, J. F. Wild","doi":"10.1093/mnrasl/slab116","DOIUrl":"https://doi.org/10.1093/mnrasl/slab116","url":null,"abstract":"We present optical photometry of the cataclysmic variable LAMOST J024048.51+195226.9 taken with the high-speed, five-band CCD camera HiPERCAM on the 10.4 m Gran Telescopio Canarias (GTC). We detect pulsations originating from the spin of its white dwarf, finding a spin period of 24.9328(38)s. The pulse amplitude is of the order of 0.2% in the g-band, below the detection limits of previous searches. This detection establishes LAMOST J024048.51+195226.9 as only the second white dwarf magnetic propeller system, a twin of its long-known predecessor, AE Aquarii. At 24.93s, the white dwarf in LAMOST J024048.51+195226.9 has the shortest known spin period of any cataclysmic variable star. The white dwarf must have a mass of at least 0.7MSun to sustain so short a period. The observed faintest u-band magnitude sets an upper limit on the white dwarf's temperature of ~25000K. The pulsation amplitudes measured in the five HiPERCAM filters are consistent with an accretion spot of ~30000K covering ~2% of the white dwarf's visible area, although much hotter and smaller spots cannot be ruled out.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90462575","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 5

Magnetic helicity and energy budget around large confined and eruptive solar flares. 大的受限的和喷发的太阳耀斑周围的磁螺旋度和能量收支。

arXiv: Solar and Stellar Astrophysics Pub Date : 2021-06-16 DOI: 10.1051/0004-6361/202140591

M. Gupta, J. Thalmann, A. Veronig

{"title":"Magnetic helicity and energy budget around large confined and eruptive solar flares.","authors":"M. Gupta, J. Thalmann, A. Veronig","doi":"10.1051/0004-6361/202140591","DOIUrl":"https://doi.org/10.1051/0004-6361/202140591","url":null,"abstract":"We investigate the coronal magnetic energy and helicity budgets of ten solar ARs, around the times of large flares. In particular, we are interested in a possible relation of the derived quantities to the particular type of the flares that the AR produces, i.e., whether they are associated with a CME or they are confined. Using an optimization approach, we employ time series of 3D nonlinear force-free magnetic field models of ten ARs, covering a time span of several hours around the time of occurrence of large solar flares (GOES class M1.0 and larger). We subsequently compute the 3D magnetic vector potentials associated to the model 3D coronal magnetic field using a finite-volume method. This allows us to correspondingly compute the coronal magnetic energy and helicity budgets, as well as related (intensive) quantities such as the relative contribution of free magnetic energy, $E_{mathrm{F}}/{E}$ (energy ratio), the fraction of non-potential (current-carrying) helicity, $|H_{mathrm{J}}|/|{H_{V}}|$ (helicity ratio), and the normalized current-carrying helicity, $|H_{mathrm{J}}|/{phi^{prime}}^{2}$. The total energy and helicity budgets of flare-productive ARs (extensive parameters) cover a broad range of magnitudes, with no obvious relation to the eruptive potential of the individual ARs, i.e., whether or not a CME is produced in association with the flare. The intensive eruptivity proxies, $E_{mathrm{F}}/{E}$ and $|H_{mathrm{J}}|/|{H_{V}}|$, and $|H_{mathrm{J}}|/{phi^{prime}}^{2}$, however, seem to be distinctly different for ARs that produced CME-associated large flares compared to those which produced confined flares. For the majority of ARs in our sample, we are able to identify characteristic pre-flare magnitudes of the intensive quantities, clearly associated to subsequent CME-productivity.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80197286","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 15

On the Periods and Nature of Superhumps 关于超级驼峰的周期和性质

arXiv: Solar and Stellar Astrophysics Pub Date : 2021-02-21 DOI: 10.32023/0001-5237/70.4.6

J. Smak

引用次数: 2

Deciphering Solar Magnetic Activity. II. The Solar Cycle Clock and the Onset of Solar Minimum Conditions 解读太阳磁场活动。2太阳周期钟与太阳极小期的开始

arXiv: Solar and Stellar Astrophysics Pub Date : 2021-02-05 DOI: 10.13016/M2R4TI-G532

R. Leamon, S. McIntosh, S. Chapman, N. Watkins, Subhamoy Chatterjee, A. Title

引用次数: 1

Mapping the Youngest and Most Massive Stars in the Tarantula Nebula with MUSE-NFM 用MUSE-NFM绘制狼蛛星云中最年轻和最大质量的恒星

arXiv: Solar and Stellar Astrophysics Pub Date : 2021-02-01 DOI: 10.18727/0722-6691/5223

N. Castro, M. Roth, P. Weilbacher, G. Micheva, A. Monreal-Ibero, A. Kelz, S. Kamann, M. Maseda, M. Wendt, T. M. C. L. F. A. Potsdam, Instituto de Astrof'isica de Canarias, U. L. Laguna, Liverpool John Moores University, Leiden University, U. Potsdam

引用次数: 2

SWELTO - Space WEather Laboratory in Turin Observatory 位于都灵天文台的空间气象实验室

arXiv: Solar and Stellar Astrophysics Pub Date : 2021-01-18 DOI: 10.20371/INAF/TECHREP/40

A. Bemporad, L. Abbo, D. Barghini, C. Benna, R. Biondo, D. Bonino, G. Capobianco, F. Carella, A. Cora, S. Fineschi, F. Frassati, D. Gardiol, S. Giordano, A. Liberatore, S. Mancuso, A. Mignone, S. Rasetti, F. Reale, A. Riva, F. Salvati, R. Susino, A. Volpicelli, L. Zangrilli

引用次数: 0

The chromospheric component of coronal bright points 日冕亮点的色球成分

arXiv: Solar and Stellar Astrophysics Pub Date : 2020-12-17 DOI: 10.1051/0004-6361/202039329

M. Madjarska, J. Chae, F. Moreno-Insertis, Zhenyong Hou, D. Nóbrega-Siverio, Hannah Kwak, K. Galsgaard, Kyuhyoun Cho

{"title":"The chromospheric component of coronal bright points","authors":"M. Madjarska, J. Chae, F. Moreno-Insertis, Zhenyong Hou, D. Nóbrega-Siverio, Hannah Kwak, K. Galsgaard, Kyuhyoun Cho","doi":"10.1051/0004-6361/202039329","DOIUrl":"https://doi.org/10.1051/0004-6361/202039329","url":null,"abstract":"We investigate the chromospheric counterpart of small-scale coronal loops constituting a coronal bright point (CBP) and its response to a photospheric magnetic-flux increase accompanied by co-temporal CBP heating. We used co-observations from the AIA and HMI/SDO, together with data from the Fast Imaging Solar Spectrograph taken in the Halpha and Ca II 8542 lines. We used a new multi-layer spectral inversion technique to derive the temporal variations of the temperature of the Halpha loops (HLs). We find that the counterpart of the CBP, as seen at chromospheric temperatures, is composed of a bundle of dark elongated features named in this work Halpha loops, which constitute an integral part of the CBP loop magnetic structure. An increase in the photospheric magnetic flux due to flux emergence is accompanied by a rise of the coronal emission of the CBP loops, that is a heating episode. We also observe enhanced chromospheric activity associated with the occurrence of new HLs and mottles. While the coronal emission and magnetic flux increases appear to be co-temporal, the response of the Halpha counterpart of the CBP occurs with a small delay of less than 3 min. A sharp temperature increase is found in one of the HLs and in one of the CBP footpoints estimated at 46% and 55% with respect to the pre-event values, also starting with a delay of less than 3~min following the coronal heating episode. The low-lying CBP loop structure remains non-potential for the entire observing period. The magnetic topological analysis of the overlying corona reveals the presence of a coronal null point at the beginning and towards the end of the heating episode. The delay in the response of the chromospheric counterpart of the CBP suggests that the heating may have occurred at coronal heights.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83843236","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 7

The Impact of a Fossil Magnetic Field on Dipolar Mixed-Mode Frequencies in Sub- and Red-Giant Stars 化石磁场对亚巨星和红巨星中偶极混合模频率的影响

arXiv: Solar and Stellar Astrophysics Pub Date : 2020-12-16 DOI: 10.1007/978-3-030-55336-4_33

L. Bugnet, V. Prat, S. Mathis, R. Garc'ia, S. Mathur, K. Augustson, C. Neiner, M. Thompson

引用次数: 0

Detecting prolonged activity minima in binary stars 探测双星中持续活动极小值

arXiv: Solar and Stellar Astrophysics Pub Date : 2020-12-16 DOI: 10.1051/0004-6361/202039902

M. Flores, M. J. Arancibia, R. Bustos, A. Buccino, J. Y. Galarza, N. Nuñez, P. Miquelarena, J. Alacoria, C. Saffe, P. Mauas

{"title":"Detecting prolonged activity minima in binary stars","authors":"M. Flores, M. J. Arancibia, R. Bustos, A. Buccino, J. Y. Galarza, N. Nuñez, P. Miquelarena, J. Alacoria, C. Saffe, P. Mauas","doi":"10.1051/0004-6361/202039902","DOIUrl":"https://doi.org/10.1051/0004-6361/202039902","url":null,"abstract":"Context. It is well known that from 1645 to 1715 solar activity was notably low and the number of sunspots was extremely reduced. This epoch is known as the Maunder Minimum (MM). The study of stars in prolonged activity minima like the MM could help to shed light on this enigmatic epoch. \u0000Aims. To explore if the star $zeta^{2}$ Ret, which belongs to a binary system, is in a state similar to the MM. We have collected more than 430 spectra acquired between 2000 and 2019 with the HARPS, REOSC, UVES, and FEROS spectrographs. \u0000Methods. We performed a detailed long-term activity study of both components using the Mount Wilson index, which is obtained from the Ca II H&K lines. To search for signs of an activity cycle, we analyzed the resulting time-series with the Generalized Lomb-Scargle and CLEAN periodograms. \u0000Results. Our spectroscopic analysis shows a high activity level for zet01 Ret and a significant decrease in the magnetic activity cycle amplitude of $zeta^{2}$ Ret. Thus, the activity difference between both components has been slightly increased ($Delta$log (RHK) $sim$0.24 dex), when compared to the previously reported value. The long series analyzed here allowed us to recalculate and constrain the period of $zeta^{2}$ Ret to $sim$7.9 yr. We also detected a long-term activity cycle of $sim$4.2 yr in $zeta^{1}$ Ret. \u0000Conclusions. By analogy with the scenario that proposes a weak solar cycle during the MM, we suggest that activity signatures showed by $zeta^{2}$ Ret, i.e., a very low activity level when compared to its stellar companion, a notably decreasing amplitude ($sim$47%), and a cyclic behaviour, are possible evidence that this star could be in a MM state. It is, to our knowledge, the first MM candidate star detected through a highly discrepant activity behaviour in a binary system.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75247756","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Pebbles in an embedded protostellar disk: the case of CB 26 嵌在原恒星盘中的鹅卵石:CB 26的例子

arXiv: Solar and Stellar Astrophysics Pub Date : 2020-12-15 DOI: 10.1051/0004-6361/202039536

Chuan-peng Zhang, R. Launhardt, Yao Liu, J. Tobin, T. Henning

{"title":"Pebbles in an embedded protostellar disk: the case of CB 26","authors":"Chuan-peng Zhang, R. Launhardt, Yao Liu, J. Tobin, T. Henning","doi":"10.1051/0004-6361/202039536","DOIUrl":"https://doi.org/10.1051/0004-6361/202039536","url":null,"abstract":"Planetary cores are thought to form in proto-planetary disks via the growth of dusty solid material. However, it is unclear how early this process begins. We study the physical structure and grain growth in the edge-on disk that surrounds the ~1 Myr old low-mass (~0.55 Msun) protostar embedded in the Bok Globule CB26 to examine how much grain growth has already occurred in the protostellar phase. We combine the SED between 0.9 ${mu}$m and 6.4 cm with high angular resolution continuum maps at 1.3, 2.9, and 8.1 mm, and use the radiative transfer code RADMC-3D to conduct a detailed modelling of the dust emission from the disk and envelope of CB 26. We infer inner and outer disk radii of around 16 au and 172$pm$22 au, respectively. The total gas mass in the disk is ~0.076 Msun, which amounts to ~14% of the mass of the central star. The inner disk contains a compact free-free emission region, which could be related to either a jet or a photoevaporation region. The thermal dust emission from the outer disk is optically thin at mm wavelengths, while the emission from the inner disk midplane is moderately optically thick. Our best-fit radiative transfer models indicate that the dust grains in the disk have already grown to pebbles with diameters of the order of 10 cm in size. Residual 8.1 mm emission suggests the presence of even larger particles in the inner disk. For the optically thin mm dust emission from the outer disk, we derive a mean opacity slope of 0.6$pm$0.4, which is consistent with the presence of large dust grains. The presence of cm-sized bodies in the CB 26 disk indicates that solids grow rapidly already during the first million years in a protostellar disk. It is thus possible that Class II disks are already seeded with large particles and may contain even planetesimals.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80431087","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 5