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Examining the M67 Classification as an Open Cluster

International Journal of Astronomy and Astrophysics 2012年第3期2卷 167-173页

作者： Shimmon Naim evgeny griv Department of Physics Ben-Gurion University of the Negev Beer-Sheva Israel Ilan Ramon Physics Center Ben-Gurion University of the Negev Beer-Sheva Israel

The cluster M67 (= NGC 2682) in Cancer is a rich stellar cluster, usually classified as an open cluster. Using our own observations with the 0.4 m telescope, we show that M67 is a tight group of about 1200 stars. The actual radius of the cluster is about 3.1 pc and the average mass of a star in the system is about . We also show that the ratio of the mean kinetic energy of the cluster to its mean gravitational potential energy , while the value predicted by the virial theorem is equal to . So the system is a gravitationally bound. This value of is considered as an evidence of quasi-stability of the cluster and allows us to use the Chandrasekhar-Spitzer relaxation time for M67 Myr as a characteristic dynamical relaxation time of the system. As the cluster is almost twice older its half-life time , it is argued that M67 was in the past (about 4 Gyr ago, close to its forma-tion) a relatively small ( stars) globular cluster, but got “open cluster” shape due to the dynamical evapora-tion of the majority of its stars.

关键词： Photometers Techniques Photometric Open Clusters and Associations M67 Galaxies Star Clusters

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Non-sinusoidal transit timing variations for the exoplanet HAT-P-12b

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Research in Astronomy and Astrophysics 2021年第4期21卷 253-263页

作者： Devesh P.Sanya Ing-Guey Jiang Li-Hsin Su Li-Chin Yeh Tze-En Chang V.V.Moskvin A.A.Shlyapnikov V.Ignatov David Mkrtichian evgeny griv Vineet Kumar Mannaday Parijat Thakur D.K.Sahu Swadesh Chand D.Bisht Zhao Sun Jianghui Ji Department of Physics and Institute of Astronomy “National Tsing-Hua University”HsinChu 30013China Institute of Computational and Modeling Science “National Tsing-Hua University”HsinChu 30013China Crimean Astrophysical Observatory 298409NauchnyCrimea National Astronomical Research Institute of Thailand(NARIT) Siripanich Building191 Huaykaew RoadMuang DistrictChiangmaiThailand Department of Physics Ben-Gurion UniversityBeer-Sheva 84105Israel Department of Pure&Applied Physics Guru Ghasidas Vishwavidyalaya(A Central University)Bilaspur(C.G.)-495009India Indian Institute of Astrophysics Bangalore 560034India Key Laboratory for Researches in Galaxies and Cosmology University of Science and Technology of ChinaChinese Academy of Sciences Purple Mountain Observatory Chinese Academy of SciencesNanjing 210008China

Considering the importance of investigating the transit timing variations(TTVs)of transiting exoplanets,we present a follow-up study of HAT-P-12 *** include six new light curves observed between2011 and 2015 from three different observatories,in association with 25 light curves taken from the published *** sample of the data used thus covers a time span of~10.2 years with a large coverage of epochs(1160)for the transiting events of the exoplanet HAT-P-12 *** light curves are utilized to determine the orbital parameters and conduct an investigation of possible *** new linear ephemeris shows a large value of reducedχ^(2),i.e.X_(red)^(2)(23)=7.93,and the sinusoidal fitting using the prominent frequency coming from a periodogram shows a reducedχ^(2) around *** on these values and the corresponding O-C diagrams,we suspect the presence of a possible non-sinusoidal TTV in this planetary ***,we find that a scenario with an additional non-transiting exoplanet could explain this TTV with an even smaller reducedχ^(2) value of around 2.

关键词： planetary systems techniques photometric

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Cortical laminar necrosis related to migrainous cerebral infarction

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World Journal of Clinical Cases 2013年第8期1卷 256-259页

作者： Adrià Arboix Sebastià González-Peris Elisenda grivé María-José Sánchez Emili Comes Cerebrovascular Division Department of NeurologyHospital Universitari del Sagrat Cor.Universitat de BarcelonaE-08029 BarcelonaSpain Department of Neuroradiology Hospital Universitari Sagrat Cor.E-08029 BarcelonaSpain Medical Library Hospital Universitari Sagrat Cor.E-08029 BarcelonaSpain

We present a 29-year-old woman with a long history of attacks of migraine with and without visual *** was a heavy smoker(20 cigarettes/d) and was currently taking oral contraceptives. During a typical migraine attack with aura, she developed dysarthria,left brachial hemiparesis and hemihypoesthesia and brief and autolimited left clonic facial movements. Four hours after onset, vascular headache and focal sensorimotor neurological deficit were the only persisting symptoms and, on seventh day, she was completely recovered. Brain magnetic resonance imaging on day 20 after onset showed a subacute ischemic lesion in the right temporo-parietal cortex compatible with cortical laminar necrosis(CLN). Extensive neurological work-up done to rule out other known causes of cerebral infarct with CLN was unrevealing. Only ten of 3.808 consecutive stroke patients included in our stroke registry over a 19-year period fulfilled the strictly defined International Headache Society criteria for migrainous stroke. The present case is the unique one in our stroke registry that presents CLN related to migrainous cerebral infarction. Migrainous infarction can result in CLN.

关键词： Cortical laminar necrosis Migrainous stroke Migraine Cerebrovascular diseases Stroke

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