Pub Date : 2020-10-07DOI: 10.1051/0004-6361/202039000
Ritesh Patel, V. Pant, K. Chandrashekhar, D. Banerjee
We investigate the properties of plasmoids observed in the current sheet formed after an X-8.3 flare followed by a fast CME eruption on September 10, 2017 using Extreme Ultraviolet (EUV) and white-light coronagraph images. The main aim is to understand the evolution of plasmoids at different spatio-temporal scales using existing ground- and space-based instruments. We identified the plasmoids in current sheet observed in the successive images of {it Atmospheric Imaging Assembly} (AIA) and white-light coronagraphs, K-Cor and LASCO/C2. We found that the current sheet is accompanied by several plasmoids moving upwards and downwards. Our analysis showed that the downward and upward moving plasmoids have average width of 5.92 Mm and 5.65 Mm, respectively in the AIA field of view (FOV). However, upward moving plasmoids have average width of 64 Mm in the K-Cor which evolves to a mean width of 510 Mm in the LASCO/C2 FOV. Upon tracking the plasmoids in successive images, we observe that downward and upward moving plasmoids have average speeds of $sim$272 km s$^{-1}$ and $sim$191 km s$^{-1}$ respectively in the EUV passbands. We note that the plasmoids become super-Alfvenic when they reach at LASCO FOV. Furthermore, we estimate that the null-point of the current sheet at $approx$ 1.15 R$_odot$ where bidirectional plasmoid motion is observed. We study the width distribution of plasmoids formed and notice that it is governed by a power law with a power index of -1.12. Unlike previous studies there is no difference in trend for small and large scale plasmoids. The presence of accelerating plasmoids near the neutral point indicates a longer diffusion region as predicted by MHD models.
我们利用极紫外(EUV)和白光日冕仪图像研究了2017年9月10日X-8.3耀斑和快速CME爆发后形成的电流片中观测到的等离子体的性质。主要目的是利用现有的地面和天基仪器了解等离子体在不同时空尺度上的演化。我们在{it大气成像}组件(AIA)和白光日冕仪、K-Cor和LASCO/C2的连续图像中发现了电流片中的等离子体。我们发现电流片伴随着几个向上和向下移动的等离子体。我们的分析表明，在AIA视场(FOV)中，向下和向上运动的等离子体流场的平均宽度分别为5.92 Mm和5.65 Mm。然而，向上移动的等离子体在K-Cor中平均宽度为64 Mm，在LASCO/C2视场中平均宽度为510 Mm。在连续图像中跟踪等离子体，我们观察到等离子体向上和向下运动的平均速度分别为$sim$ 272 km ($^{-1}$)和$sim$ 191 km ($^{-1}$)。我们注意到等离子体在到达LASCO视场时变得超级阿尔芬尼克。此外，我们估计电流片的零点为$approx$ 1.15 R $_odot$，在那里观察到双向等离子体运动。我们研究了形成的等离子体的宽度分布，注意到它受幂指数为-1.12的幂律支配。与以往的研究不同，小型和大型等离子体的趋势没有差异。中性点附近加速等离子体的存在表明MHD模型预测的扩散区域更长。
{"title":"A statistical study of plasmoids associated with a post-CME current sheet","authors":"Ritesh Patel, V. Pant, K. Chandrashekhar, D. Banerjee","doi":"10.1051/0004-6361/202039000","DOIUrl":"https://doi.org/10.1051/0004-6361/202039000","url":null,"abstract":"We investigate the properties of plasmoids observed in the current sheet formed after an X-8.3 flare followed by a fast CME eruption on September 10, 2017 using Extreme Ultraviolet (EUV) and white-light coronagraph images. The main aim is to understand the evolution of plasmoids at different spatio-temporal scales using existing ground- and space-based instruments. We identified the plasmoids in current sheet observed in the successive images of {it Atmospheric Imaging Assembly} (AIA) and white-light coronagraphs, K-Cor and LASCO/C2. We found that the current sheet is accompanied by several plasmoids moving upwards and downwards. Our analysis showed that the downward and upward moving plasmoids have average width of 5.92 Mm and 5.65 Mm, respectively in the AIA field of view (FOV). However, upward moving plasmoids have average width of 64 Mm in the K-Cor which evolves to a mean width of 510 Mm in the LASCO/C2 FOV. Upon tracking the plasmoids in successive images, we observe that downward and upward moving plasmoids have average speeds of $sim$272 km s$^{-1}$ and $sim$191 km s$^{-1}$ respectively in the EUV passbands. We note that the plasmoids become super-Alfvenic when they reach at LASCO FOV. Furthermore, we estimate that the null-point of the current sheet at $approx$ 1.15 R$_odot$ where bidirectional plasmoid motion is observed. We study the width distribution of plasmoids formed and notice that it is governed by a power law with a power index of -1.12. Unlike previous studies there is no difference in trend for small and large scale plasmoids. The presence of accelerating plasmoids near the neutral point indicates a longer diffusion region as predicted by MHD models.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72719376","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}
From Gaia DR 2 data of eight high velocity hot post-AGB candidates LS 3593, LSE 148, LS 5107, HD 172324, HD 214539, LS IV -12 111, LS III +52 24, and LS 3099, we found that six of them have accurate parallaxes which made it possible to derive their distances, absolute visual magnitudes (M_V) and luminosity (log L/L_sun). Except LS 5107 all the remaining seven stars have accurate effective temperature (T_eff) in the literature. Some of these stars are metal-poor and some of them do not have circumstellar dust shells. In the past the distances of some stars were estimated to be 6~kpc which we find it to be incorrect. The accurate Gaia DR2 parallaxes show that they are relatively nearby post-AGB stars. When compared with post-AGB evolutionary tracks we find their initial masses in the range of 1M_sun to 2M_sun. We find the luminosity of LSE 148 to be significantly lower than that of post-AGB stars, suggesting that this is a post-horizontal branch star or post-early-AGB star. LS 3593 and LS 5107 are new high velocity hot post-AGB stars from Gaia DR2.
从Gaia DR 2对8颗高速热后agb候选恒星LS 3593、LSE 148、LS 5107、HD 172324、HD 214539、LS IV -12 111、LS III +52 24和LS 3099的观测数据中，我们发现其中6颗具有精确的视差，从而可以推算出它们的距离、绝对视星等(M_V)和光度(log L/L_sun)。除LS 5107外，其余7颗星均有准确的有效温度(T_eff)。这些恒星中有些是金属贫乏的，有些没有星周尘埃壳。过去一些恒星的距离被估计为6~kpc，我们发现这是不正确的。精确的盖亚DR2视差显示它们相对较近。当与agb后的演化轨迹进行比较时，我们发现它们的初始质量在1M_sun到2M_sun之间。我们发现LSE 148的光度明显低于agb后恒星，这表明它是一颗后水平分支星或后早期agb星。LS 3593和LS 5107是来自盖亚DR2的新的高速热后agb恒星。
{"title":"Gaia DR2 data and the evolutionary status of eight high-velocity hot post-AGB candidates","authors":"M. Parthasarathy, T. Matsuno, W. Aoki","doi":"10.1093/pasj/psaa097","DOIUrl":"https://doi.org/10.1093/pasj/psaa097","url":null,"abstract":"From Gaia DR 2 data of eight high velocity hot post-AGB candidates LS 3593, LSE 148, LS 5107, HD 172324, HD 214539, LS IV -12 111, LS III +52 24, and LS 3099, we found that six of them have accurate parallaxes which made it possible to derive their distances, absolute visual magnitudes (M_V) and luminosity (log L/L_sun). Except LS 5107 all the remaining seven stars have accurate effective temperature (T_eff) in the literature. Some of these stars are metal-poor and some of them do not have circumstellar dust shells. In the past the distances of some stars were estimated to be 6~kpc which we find it to be incorrect. The accurate Gaia DR2 parallaxes show that they are relatively nearby post-AGB stars. When compared with post-AGB evolutionary tracks we find their initial masses in the range of 1M_sun to 2M_sun. We find the luminosity of LSE 148 to be significantly lower than that of post-AGB stars, suggesting that this is a post-horizontal branch star or post-early-AGB star. LS 3593 and LS 5107 are new high velocity hot post-AGB stars from Gaia DR2.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73856719","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}
Pub Date : 2020-10-01DOI: 10.1051/0004-6361/202038717
Phillip A. B. Galli, Hervé Bouy, J. Olivares, N. Miret-Roig, R. Vieira, L. M. Sarro, David Barrado, A. Berihuete, C. Bertout, Emmanuel Bertin, Jean-Charles Cuillandre
Context: Lupus is recognised as one of the closest star-forming regions, but the lack of trigonometric parallaxes in the pre-Gaia era hampered many studies on the kinematic properties of this region and led to incomplete censuses of its stellar population. Aims: We use the second data release of the Gaia space mission combined with published ancillary radial velocity data to revise the census of stars and investigate the 6D structure of the Lupus complex. Methods: We performed a new membership analysis of the Lupus association based on astrometric and photometric data over a field of 160 deg2 around the main molecular clouds of the complex and compared the properties of the various subgroups in this region. Results: We identified 137 high-probability members of the Lupus association of young stars, including 47 stars that had never been reported as members before. Many of the historically known stars associated with the Lupus region identified in previous studies are more likely to be field stars or members of the adjacent Scorpius-Centaurus association. Our new sample of members covers the magnitude and mass range from G=8 to G=18 mag and from 0.03 to 2.4Msun, respectively. We compared the kinematic properties of the stars projected towards the molecular clouds Lupus 1 to 6 and showed that these subgroups are located at roughly the same distance (about 160~pc) and move with the same spatial velocity. Our age estimates inferred from stellar models show that the Lupus subgroups are coeval (with median ages ranging from about 1 to 3 Myr). The Lupus association appears to be younger than the population of young stars in the Corona-Australis star-forming region recently investigated by our team using a similar methodology. The initial mass function of the Lupus association inferred from the distribution of spectral types shows little variation compared to other star-forming regions.
{"title":"Lupus DANCe","authors":"Phillip A. B. Galli, Hervé Bouy, J. Olivares, N. Miret-Roig, R. Vieira, L. M. Sarro, David Barrado, A. Berihuete, C. Bertout, Emmanuel Bertin, Jean-Charles Cuillandre","doi":"10.1051/0004-6361/202038717","DOIUrl":"https://doi.org/10.1051/0004-6361/202038717","url":null,"abstract":"Context: Lupus is recognised as one of the closest star-forming regions, but the lack of trigonometric parallaxes in the pre-Gaia era hampered many studies on the kinematic properties of this region and led to incomplete censuses of its stellar population. Aims: We use the second data release of the Gaia space mission combined with published ancillary radial velocity data to revise the census of stars and investigate the 6D structure of the Lupus complex. Methods: We performed a new membership analysis of the Lupus association based on astrometric and photometric data over a field of 160 deg2 around the main molecular clouds of the complex and compared the properties of the various subgroups in this region. Results: We identified 137 high-probability members of the Lupus association of young stars, including 47 stars that had never been reported as members before. Many of the historically known stars associated with the Lupus region identified in previous studies are more likely to be field stars or members of the adjacent Scorpius-Centaurus association. Our new sample of members covers the magnitude and mass range from G=8 to G=18 mag and from 0.03 to 2.4Msun, respectively. We compared the kinematic properties of the stars projected towards the molecular clouds Lupus 1 to 6 and showed that these subgroups are located at roughly the same distance (about 160~pc) and move with the same spatial velocity. Our age estimates inferred from stellar models show that the Lupus subgroups are coeval (with median ages ranging from about 1 to 3 Myr). The Lupus association appears to be younger than the population of young stars in the Corona-Australis star-forming region recently investigated by our team using a similar methodology. The initial mass function of the Lupus association inferred from the distribution of spectral types shows little variation compared to other star-forming regions.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84557518","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}
H. Maehara, Y. Notsu, K. Namekata, S. Honda, A. Kowalski, Noriyuki Katoh, T. Ohshima, K. Iida, M. Oeda, K. Murata, M. Yamanaka, K. Takagi, M. Sasada, H. Akitaya, K. Ikuta, Soshi Okamoto, D. Nogami, K. Shibata
In this paper, we present the results from spectroscopic and photometric observations of the M-type flare star YZ CMi in the framework of the Optical and Infrared Synergetic Telescopes for Education and Research (OISTER) collaborations during the Transiting Exoplanet Survey Satellite (TESS) observation period. We detected 145 white-light flares from the TESS light curve and 4 H$alpha$ flares from the OISTER observations performed between 2019-01-16 and 2019-01-18. Among them, 3 H$alpha$ flares were associated with white-light flares. However, one of them did not show clear brightening in continuum; during this flare, the H$alpha$ line exhibited blue-asymmetry which has lasted for $sim 60$ min. The line of sight velocity of the blue-shifted component is $-80$ - $-100$ km s$^{-1}$. This suggests that there can be upward flows of chromospheric cool plasma even without detectable red/NIR continuum brightening. By assuming that the blue-asymmetry in H$alpha$ line was caused by a prominence eruption on YZ CMi, we estimated the mass and kinetic energy of the upward-moving material to be $10^{16}$ - $10^{18}$ g and $10^{29.5}$ - $10^{31.5}$ erg, respectively. The estimated mass is comparable to expectations from the empirical relation between the flare X-ray energy and mass of upward-moving material for stellar flares and solar CMEs. In contrast, the estimated kinetic energy for the non-white-light flare on YZ CMi is roughly $2$ orders of magnitude smaller than that expected from the relation between flare X-ray energy and kinetic energy for solar CMEs. This could be understood by the difference in the velocity between CMEs and prominence eruptions.
本文介绍了凌日系外行星巡天卫星(TESS)观测期间，在光学和红外教育与研究协同望远镜(OISTER)合作框架下对m型耀斑星YZ CMi的光谱和光度观测结果。我们在2019年01月16日至2019年01月18日的OISTER观测中检测到145个白光耀斑和4个H $alpha$耀斑。其中，3h $alpha$耀斑与白光耀斑相关。但其中一个在连续体中没有明显的增亮;在这次耀斑期间，H $alpha$线表现出蓝色不对称，持续了$sim 60$分钟。蓝移分量的视线速度为$-80$ - $-100$ km s $^{-1}$。这表明，即使没有可检测到的红色/近红外连续体增亮，色球冷等离子体也可能向上流动。假设H $alpha$线上的蓝色不对称是由YZ CMi上的日珥喷发引起的，我们估计向上移动的物质的质量和动能分别为$10^{16}$ - $10^{18}$ g和$10^{29.5}$ - $10^{31.5}$ erg。估计的质量与耀斑x射线能量与恒星耀斑和太阳日冕物质向上运动物质质量之间的经验关系的期望相当。相比之下，YZ CMi上的非白光耀斑的估计动能大约比耀斑x射线能量与太阳cme动能之间的关系估计的要小$2$个数量级。这可以通过日冕物质抛射和日珥喷发之间的速度差异来理解。
{"title":"Time-resolved spectroscopy and photometry of an M dwarf flare star YZ Canis Minoris with OISTER and TESS: Blue asymmetry in H$alpha$ line during the non-white light flare","authors":"H. Maehara, Y. Notsu, K. Namekata, S. Honda, A. Kowalski, Noriyuki Katoh, T. Ohshima, K. Iida, M. Oeda, K. Murata, M. Yamanaka, K. Takagi, M. Sasada, H. Akitaya, K. Ikuta, Soshi Okamoto, D. Nogami, K. Shibata","doi":"10.5281/ZENODO.4564272","DOIUrl":"https://doi.org/10.5281/ZENODO.4564272","url":null,"abstract":"In this paper, we present the results from spectroscopic and photometric observations of the M-type flare star YZ CMi in the framework of the Optical and Infrared Synergetic Telescopes for Education and Research (OISTER) collaborations during the Transiting Exoplanet Survey Satellite (TESS) observation period. We detected 145 white-light flares from the TESS light curve and 4 H$alpha$ flares from the OISTER observations performed between 2019-01-16 and 2019-01-18. Among them, 3 H$alpha$ flares were associated with white-light flares. However, one of them did not show clear brightening in continuum; during this flare, the H$alpha$ line exhibited blue-asymmetry which has lasted for $sim 60$ min. The line of sight velocity of the blue-shifted component is $-80$ - $-100$ km s$^{-1}$. This suggests that there can be upward flows of chromospheric cool plasma even without detectable red/NIR continuum brightening. By assuming that the blue-asymmetry in H$alpha$ line was caused by a prominence eruption on YZ CMi, we estimated the mass and kinetic energy of the upward-moving material to be $10^{16}$ - $10^{18}$ g and $10^{29.5}$ - $10^{31.5}$ erg, respectively. The estimated mass is comparable to expectations from the empirical relation between the flare X-ray energy and mass of upward-moving material for stellar flares and solar CMEs. In contrast, the estimated kinetic energy for the non-white-light flare on YZ CMi is roughly $2$ orders of magnitude smaller than that expected from the relation between flare X-ray energy and kinetic energy for solar CMEs. This could be understood by the difference in the velocity between CMEs and prominence eruptions.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90786058","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}
IW And-type dwarf novae are recently recognized group of cataclysmic variables which are characterized by a sequence of brightening from a standstill-like phase with damping oscillations often followed by a deep dip. We found that the supposed classical nova BC Cas which erupted in 1929 experienced a state of an IW And-type dwarf nova in 2018, 89 yr after the eruption. This finding suggests that high mass-transfer rate following the nova eruption is associated with the IW And-type phenomenon. The mass of the white dwarf inferred from the decline rate of the nova is considerably higher than the average mass of the white dwarfs in cataclysmic variables and the massive white dwarfs may be responsible for the manifestation of the IW And-type phenomenon.
{"title":"BC Cassiopeiae: First detection of IW Andromedae-type phenomenon among post-eruption novae","authors":"Taichi Kato, N. Kojiguchi","doi":"10.1093/PASJ/PSAA096","DOIUrl":"https://doi.org/10.1093/PASJ/PSAA096","url":null,"abstract":"IW And-type dwarf novae are recently recognized group of cataclysmic variables which are characterized by a sequence of brightening from a standstill-like phase with damping oscillations often followed by a deep dip. We found that the supposed classical nova BC Cas which erupted in 1929 experienced a state of an IW And-type dwarf nova in 2018, 89 yr after the eruption. This finding suggests that high mass-transfer rate following the nova eruption is associated with the IW And-type phenomenon. The mass of the white dwarf inferred from the decline rate of the nova is considerably higher than the average mass of the white dwarfs in cataclysmic variables and the massive white dwarfs may be responsible for the manifestation of the IW And-type phenomenon.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80964750","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}
Pub Date : 2020-09-28DOI: 10.1051/0004-6361/202038966
C. Mininni, M. Beltrán, V. Rivilla, Á. Sánchez-Monge, F. Fontani, T. Möller, R. Cesaroni, P. Schilke, S. Viti, I. Jímenez-Serra, L. Colzi, A. Lorenzani, L. Testi
Understanding the degree of chemical complexity that can be reached in star-forming regions, together with the identification of precursors of the building blocks of life in the interstellar medium, is one of the goals of astrochemistry. Unbiased spectral surveys with large bandwidth and high spectral resolution are thus needed, to resolve line blending in chemically rich sources and identify complex organic molecules. This kind of observations has been successfully carried out, mainly towards the Galactic Center, a region that shows peculiar environmental conditions. We present an unbiased spectral survey at 3mm of one of the most chemically rich hot molecular cores located outside the Galactic Center, in the high-mass star-forming region G31.41+0.31. In this first paper, we present the survey and discuss the detection of the 3 isomers of C$_{2}$H$_{4}$O$_{2}$: methyl formate, glycolaldehyde and acetic acid. Observations were carried out with ALMA and cover the entire Band 3 from 84 to 116 GHz with an angular resolution of $1.2^{''}$x$1.2^{''}$ and a spectral resolution of $sim0.488$ MHz. The transitions of the 3 molecules have been analyzed with the software XCLASS. All three isomers were detected and methyl formate and acetic acid abundances in G31 are the highest detected up to now, if compared to sources in literature. The size of the emission varies among the three isomers with acetic acid showing the most compact emission while methyl formate the most extended. The comparison with chemical models suggests the necessity of grain-surface routes for the formation of methyl formate in G31, while for glycolaldehyde both scenarios could be feasible. Proposed grain-surface reaction for acetic acid is not able to reproduce the observed abundance in this work, while gas-phase scenario should be further tested due to large uncertainties.
{"title":"The GUAPOS project: G31.41+0.31 Unbiased ALMA sPectral Observational Survey","authors":"C. Mininni, M. Beltrán, V. Rivilla, Á. Sánchez-Monge, F. Fontani, T. Möller, R. Cesaroni, P. Schilke, S. Viti, I. Jímenez-Serra, L. Colzi, A. Lorenzani, L. Testi","doi":"10.1051/0004-6361/202038966","DOIUrl":"https://doi.org/10.1051/0004-6361/202038966","url":null,"abstract":"Understanding the degree of chemical complexity that can be reached in star-forming regions, together with the identification of precursors of the building blocks of life in the interstellar medium, is one of the goals of astrochemistry. Unbiased spectral surveys with large bandwidth and high spectral resolution are thus needed, to resolve line blending in chemically rich sources and identify complex organic molecules. This kind of observations has been successfully carried out, mainly towards the Galactic Center, a region that shows peculiar environmental conditions. We present an unbiased spectral survey at 3mm of one of the most chemically rich hot molecular cores located outside the Galactic Center, in the high-mass star-forming region G31.41+0.31. In this first paper, we present the survey and discuss the detection of the 3 isomers of C$_{2}$H$_{4}$O$_{2}$: methyl formate, glycolaldehyde and acetic acid. Observations were carried out with ALMA and cover the entire Band 3 from 84 to 116 GHz with an angular resolution of $1.2^{''}$x$1.2^{''}$ and a spectral resolution of $sim0.488$ MHz. The transitions of the 3 molecules have been analyzed with the software XCLASS. All three isomers were detected and methyl formate and acetic acid abundances in G31 are the highest detected up to now, if compared to sources in literature. The size of the emission varies among the three isomers with acetic acid showing the most compact emission while methyl formate the most extended. The comparison with chemical models suggests the necessity of grain-surface routes for the formation of methyl formate in G31, while for glycolaldehyde both scenarios could be feasible. Proposed grain-surface reaction for acetic acid is not able to reproduce the observed abundance in this work, while gas-phase scenario should be further tested due to large uncertainties.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90848323","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}
P. Benni, A. Burdanov, V. Krushinsky, A. Bonfanti, G. H'ebrard, J. Almenara, S. Dalal, O. Demangeon, M. Tsantaki, J. Pepper, K. Stassun, A. Vanderburg, A. Belinski, F. Kashaev, K. Barkaoui, T. Kim, W. Kang, K. Antonyuk, V. Dyachenko, D. Rastegaev, A. Beskakotov, A. Mitrofanova, F. Pozuelos, E. D. Kuznetsov, A. Popov, F. Kiefer, P. Wilson, G. Ricker, R. Vanderspek, D. Latham, S. Seager, J. Jenkins, E. Sokov, I. Sokova, A. Marchini, R. Papini, F. Salvaggio, M. Banfi, Ö. Baştürk, Ş. Torun, S. Yalçınkaya, K. Ivanov, G. Valyavin, E. Jehin, M. Gillon, E. Pakštienė, V. Hentunen, S. Shadick, M. Bretton, A. Wünsche, J. Garlitz, Y. Jongen, D. Molina, E. Girardin, F. Grau Horta, R. Naves, Z. Benkhaldoun, M. Joner, M. Spencer, A. Bieryla, D. Stevens, E. Jensen, K. Collins, D. Charbonneau, E. Quintana, S. Mullally, C. Henze
We announce the discovery of GPX-1b, a transiting brown dwarf with a mass of $19.7pm 1.6$ $M_{mathrm{Jup}}$ and a radius of $1.47pm0.10$ $R_{mathrm{Jup}}$, the first sub-stellar object discovered by the Galactic Plane eXoplanet (GPX) survey. The brown dwarf transits a moderately bright ($V$ = 12.3 mag) fast-rotating F-type star with a projected rotational velocity $vsin{ i_*}sim$40 km/s, effective temperature $7000pm200$ K, mass $1.68pm0.10$ $M_{Sun}$, radius $1.56pm0.10$ $R_{Sun}$ and approximate age $0.27_{-0.15}^{+0.09}$ Gyr. GPX-1b has an orbital period of $1.744579pm0.000008$ d, mid-transit time $T_0 = 2458770.23823pm0.00040$ ${mathrm{BJD_{TDB}}}$ and a transit depth of $0.90pm0.03$%. We describe the GPX transit detection observations, subsequent photometric and speckle-interferometric follow-up observations, and SOPHIE spectroscopic measurements, which allowed us to establish the presence of a sub-stellar object around the host star. GPX-1 was observed at 30-min integrations by TESS in Sector 18, but the data is affected by blending with a 3.4 mag brighter star 42 arcsec away. GPX-1b is one of about two dozen transiting brown dwarfs known to date, with a mass close to the theoretical brown dwarf/gas giant planet mass transition boundary. Since GPX-1 is a moderately bright and fast-rotating star, it can be followed-up by the means of Doppler tomography.
我们宣布发现GPX-1b，这是一颗凌日褐矮星，质量为$19.7pm 1.6$$M_{mathrm{Jup}}$，半径为$1.47pm0.10$$R_{mathrm{Jup}}$，是银河面系外行星(GPX)调查发现的第一个亚恒星物体。这颗褐矮星是一颗中等亮度($V$ = 12.3等)的快速旋转的f型恒星，预计旋转速度为$vsin{ i_*}sim$ 40 km/s，有效温度为$7000pm200$ K，质量为$1.68pm0.10$$M_{Sun}$，半径为$1.56pm0.10$$R_{Sun}$，年龄为$0.27_{-0.15}^{+0.09}$ Gyr。GPX-1b的轨道周期为$1.744579pm0.000008$ d，中凌日时间为$T_0 = 2458770.23823pm0.00040$${mathrm{BJD_{TDB}}}$，凌日深度为 $0.90pm0.03$%. We describe the GPX transit detection observations, subsequent photometric and speckle-interferometric follow-up observations, and SOPHIE spectroscopic measurements, which allowed us to establish the presence of a sub-stellar object around the host star. GPX-1 was observed at 30-min integrations by TESS in Sector 18, but the data is affected by blending with a 3.4 mag brighter star 42 arcsec away. GPX-1b is one of about two dozen transiting brown dwarfs known to date, with a mass close to the theoretical brown dwarf/gas giant planet mass transition boundary. Since GPX-1 is a moderately bright and fast-rotating star, it can be followed-up by the means of Doppler tomography.
{"title":"Discovery of a young low-mass brown dwarf transiting a fast-rotating F-type star by the Galactic Plane eXoplanet (GPX) survey","authors":"P. Benni, A. Burdanov, V. Krushinsky, A. Bonfanti, G. H'ebrard, J. Almenara, S. Dalal, O. Demangeon, M. Tsantaki, J. Pepper, K. Stassun, A. Vanderburg, A. Belinski, F. Kashaev, K. Barkaoui, T. Kim, W. Kang, K. Antonyuk, V. Dyachenko, D. Rastegaev, A. Beskakotov, A. Mitrofanova, F. Pozuelos, E. D. Kuznetsov, A. Popov, F. Kiefer, P. Wilson, G. Ricker, R. Vanderspek, D. Latham, S. Seager, J. Jenkins, E. Sokov, I. Sokova, A. Marchini, R. Papini, F. Salvaggio, M. Banfi, Ö. Baştürk, Ş. Torun, S. Yalçınkaya, K. Ivanov, G. Valyavin, E. Jehin, M. Gillon, E. Pakštienė, V. Hentunen, S. Shadick, M. Bretton, A. Wünsche, J. Garlitz, Y. Jongen, D. Molina, E. Girardin, F. Grau Horta, R. Naves, Z. Benkhaldoun, M. Joner, M. Spencer, A. Bieryla, D. Stevens, E. Jensen, K. Collins, D. Charbonneau, E. Quintana, S. Mullally, C. Henze","doi":"10.1093/mnras/stab1567","DOIUrl":"https://doi.org/10.1093/mnras/stab1567","url":null,"abstract":"We announce the discovery of GPX-1b, a transiting brown dwarf with a mass of $19.7pm 1.6$ $M_{mathrm{Jup}}$ and a radius of $1.47pm0.10$ $R_{mathrm{Jup}}$, the first sub-stellar object discovered by the Galactic Plane eXoplanet (GPX) survey. The brown dwarf transits a moderately bright ($V$ = 12.3 mag) fast-rotating F-type star with a projected rotational velocity $vsin{ i_*}sim$40 km/s, effective temperature $7000pm200$ K, mass $1.68pm0.10$ $M_{Sun}$, radius $1.56pm0.10$ $R_{Sun}$ and approximate age $0.27_{-0.15}^{+0.09}$ Gyr. GPX-1b has an orbital period of $1.744579pm0.000008$ d, mid-transit time $T_0 = 2458770.23823pm0.00040$ ${mathrm{BJD_{TDB}}}$ and a transit depth of $0.90pm0.03$%. We describe the GPX transit detection observations, subsequent photometric and speckle-interferometric follow-up observations, and SOPHIE spectroscopic measurements, which allowed us to establish the presence of a sub-stellar object around the host star. GPX-1 was observed at 30-min integrations by TESS in Sector 18, but the data is affected by blending with a 3.4 mag brighter star 42 arcsec away. GPX-1b is one of about two dozen transiting brown dwarfs known to date, with a mass close to the theoretical brown dwarf/gas giant planet mass transition boundary. Since GPX-1 is a moderately bright and fast-rotating star, it can be followed-up by the means of Doppler tomography.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85353857","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}
A curious rotation period distribution in the Color-Magnitude-Period Diagram (CMPD) of the Kepler field was recently revealed, thanks to data from Gaia and Kepler spacecraft. It was found that redder and brighter stars are spinning slower than the rest of the main sequence. On the theoretical side, it was demonstrated that metallicity should affect the rotational evolution of stars as well as their evolution in the Hertzprung-Russel or Color-Magnitude diagram. In this work we combine this dataset with medium and high resolution spectroscopic metallicities and carefully select main sequence single stars in a given mass range. We show that the structure seen in the CMPD also corresponds to a broad correlation between metallicity and rotation, such that stars with higher metallicity rotate on average more slowly than those with low metallicity. We compare this sample to theoretical rotational evolution models that include a range of different metallicities. They predict a correlation between rotation rate and metallicity that is in the same direction and of about the same magnitude as that observed. Therefore metallicity appears to be a key parameter to explain the observed rotation period distributions. We also discuss a few different ways in which metallicity can affect the observed distribution of rotation period, due to observational biases and age distributions, as well as the effect on stellar wind torques.
{"title":"Evidence for metallicity-dependent spin evolution in the Kepler field","authors":"L. Amard, J. Roquette, S. Matt","doi":"10.1093/mnras/staa3038","DOIUrl":"https://doi.org/10.1093/mnras/staa3038","url":null,"abstract":"A curious rotation period distribution in the Color-Magnitude-Period Diagram (CMPD) of the Kepler field was recently revealed, thanks to data from Gaia and Kepler spacecraft. It was found that redder and brighter stars are spinning slower than the rest of the main sequence. On the theoretical side, it was demonstrated that metallicity should affect the rotational evolution of stars as well as their evolution in the Hertzprung-Russel or Color-Magnitude diagram. In this work we combine this dataset with medium and high resolution spectroscopic metallicities and carefully select main sequence single stars in a given mass range. We show that the structure seen in the CMPD also corresponds to a broad correlation between metallicity and rotation, such that stars with higher metallicity rotate on average more slowly than those with low metallicity. We compare this sample to theoretical rotational evolution models that include a range of different metallicities. They predict a correlation between rotation rate and metallicity that is in the same direction and of about the same magnitude as that observed. Therefore metallicity appears to be a key parameter to explain the observed rotation period distributions. We also discuss a few different ways in which metallicity can affect the observed distribution of rotation period, due to observational biases and age distributions, as well as the effect on stellar wind torques.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87394629","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}
Pub Date : 2020-09-22DOI: 10.32023/0001-5237/70.3.4
B. Ulaş, K. Gazeas, A. Liakos, C. Ulusoy, I. Stateva, N. Erkan, M. Napetova, I. Iliev
We present new photometric and spectroscopic observations and analyses for the eclipsing binary systems V1241 Tau and GQ Dra. Our photometric light and radial velocity curves analyses combining with the TESS light curves show that both are conventional semi-detached binary systems. Their absolute parameters are also derived. We present the $O-C$ analyses of the systems and we propose the most possible orbital period modulating mechanisms. Furthermore, Fourier analyses are applied to the photometric residual data of the systems to check for the pulsational behavior of the components. We conclude that the primary component of the system GQ Dra is a $delta$ Sct type pulsator with a dominant pulsation frequency of 18.58 d$^{-1}$ based on our $B$ filter residual light curve although it can not be justified by 30-minute cadence TESS data. No satisfactory evidence of pulsational behaviour for V1241 Tau was verified. Finally, the evolutionary tracks of the components of both systems are calculated, while their locations within evolutionary diagrams are compared with other Algol-type systems.
{"title":"A comprehensive study of the eclipsing binaries V1241 Tau and GQ Dra","authors":"B. Ulaş, K. Gazeas, A. Liakos, C. Ulusoy, I. Stateva, N. Erkan, M. Napetova, I. Iliev","doi":"10.32023/0001-5237/70.3.4","DOIUrl":"https://doi.org/10.32023/0001-5237/70.3.4","url":null,"abstract":"We present new photometric and spectroscopic observations and analyses for the eclipsing binary systems V1241 Tau and GQ Dra. Our photometric light and radial velocity curves analyses combining with the TESS light curves show that both are conventional semi-detached binary systems. Their absolute parameters are also derived. We present the $O-C$ analyses of the systems and we propose the most possible orbital period modulating mechanisms. Furthermore, Fourier analyses are applied to the photometric residual data of the systems to check for the pulsational behavior of the components. We conclude that the primary component of the system GQ Dra is a $delta$ Sct type pulsator with a dominant pulsation frequency of 18.58 d$^{-1}$ based on our $B$ filter residual light curve although it can not be justified by 30-minute cadence TESS data. No satisfactory evidence of pulsational behaviour for V1241 Tau was verified. Finally, the evolutionary tracks of the components of both systems are calculated, while their locations within evolutionary diagrams are compared with other Algol-type systems.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79778980","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}
B. Zhao, P. Caselli, Zhi-Yun Li, R. Krasnopolsky, H. Shang, K. H. Lam
Non-ideal MHD effects have been shown recently as a robust mechanism of averting the magnetic braking "catastrophe" and promoting protostellar disc formation. However, the magnetic diffusivities that determine the efficiency of non-ideal MHD effects are highly sensitive to microphysics. We carry out non-ideal MHD simulations to explore the role of microphysics on disc formation and the interplay between ambipolar diffusion (AD) and Hall effect during the protostellar collapse. We find that removing the smallest grain population ($lesssim$10 nm) from the standard MRN size distribution is sufficient for enabling disc formation. Further varying the grain sizes can result in either a Hall-dominated or an AD-dominated collapse; both form discs of tens of AU in size regardless of the magnetic field polarity. The direction of disc rotation is bimodal in the Hall dominated collapse but unimodal in the AD-dominated collapse. We also find that AD and Hall effect can operate either with or against each other in both radial and azimuthal directions, yet the combined effect of AD and Hall is to move the magnetic field radially outward relative to the infalling envelope matter. In addition, microphysics and magnetic field polarity can leave profound imprints both on observables (e.g., outflow morphology, disc to stellar mass ratio) and on the magnetic field characteristics of protoplanetary discs. Including Hall effect relaxes the requirements on microphysics for disc formation, so that prestellar cores with cosmic-ray ionization rate of $lesssim$2--3$times10^{-16}$ s$^{-1}$ can still form small discs of $lesssim$10 AU radius. We conclude that disc formation should be relatively common for typical prestellar core conditions, and that microphysics in the protostellar envelope is essential to not only disc formation, but also protoplanetary disc evolution.
{"title":"The interplay between ambipolar diffusion and Hall effect on magnetic field decoupling and protostellar disc formation","authors":"B. Zhao, P. Caselli, Zhi-Yun Li, R. Krasnopolsky, H. Shang, K. H. Lam","doi":"10.1093/mnras/stab1295","DOIUrl":"https://doi.org/10.1093/mnras/stab1295","url":null,"abstract":"Non-ideal MHD effects have been shown recently as a robust mechanism of averting the magnetic braking \"catastrophe\" and promoting protostellar disc formation. However, the magnetic diffusivities that determine the efficiency of non-ideal MHD effects are highly sensitive to microphysics. We carry out non-ideal MHD simulations to explore the role of microphysics on disc formation and the interplay between ambipolar diffusion (AD) and Hall effect during the protostellar collapse. We find that removing the smallest grain population ($lesssim$10 nm) from the standard MRN size distribution is sufficient for enabling disc formation. Further varying the grain sizes can result in either a Hall-dominated or an AD-dominated collapse; both form discs of tens of AU in size regardless of the magnetic field polarity. The direction of disc rotation is bimodal in the Hall dominated collapse but unimodal in the AD-dominated collapse. We also find that AD and Hall effect can operate either with or against each other in both radial and azimuthal directions, yet the combined effect of AD and Hall is to move the magnetic field radially outward relative to the infalling envelope matter. In addition, microphysics and magnetic field polarity can leave profound imprints both on observables (e.g., outflow morphology, disc to stellar mass ratio) and on the magnetic field characteristics of protoplanetary discs. Including Hall effect relaxes the requirements on microphysics for disc formation, so that prestellar cores with cosmic-ray ionization rate of $lesssim$2--3$times10^{-16}$ s$^{-1}$ can still form small discs of $lesssim$10 AU radius. We conclude that disc formation should be relatively common for typical prestellar core conditions, and that microphysics in the protostellar envelope is essential to not only disc formation, but also protoplanetary disc evolution.","PeriodicalId":8493,"journal":{"name":"arXiv: Solar and Stellar Astrophysics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85539859","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}
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