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V. V. Bobylev - One of the best experts on this subject based on the ideXlab platform.
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Search for close stellar encounters with the Solar system from data on nearby dwarfs
Astronomy Reports, 2017Co-Authors: V. V. BobylevAbstract:Trigonometric parallaxesmeasuredwith ground-based telescopes of the RECONS consortium as part of the CTIOPI program are used to search for stars that have either had an encounter with the Solar system in the past or will have such an encounter in the future, at distances of less than a few parsecs. These are mainly low-mass dwarfs and subdwarfs of types M, L, and T currently at distances of less than 30 pc from the Sun. Six stars for which encounters with the Solar Orbit at distances of less than 1 pc are possible have been identified for the first time. For example, the minimum distance for the star **SOZ 3A will be 0.72 ± 0.11 pc at an epoch of 103 ± 44 thousand years in the future.
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Searching for possible siblings of the sun from a common cluster based on stellar space velocities
Astronomy Letters, 2011Co-Authors: V. V. Bobylev, A. T. Bajkova, A. Mylläri, M. ValtonenAbstract:We propose a kinematic approach to searching for the stars that could be formed with the Sun in a common “parent” open cluster. The approach consists in preselecting suitable candidates by the closeness of their space velocities to the Solar velocity and analyzing the parameters of their encounters with the Solar Orbit in the past in a time interval comparable to the lifetime of stars. We consider stars from the Hipparcos catalog with available radial velocities. The Galactic Orbits of stars have been constructed in the Allen-Santillan potential by taking into account the perturbations from the spiral density wave. We show that two stars, HIP 87382 and HIP 47399, are of considerable interest in our problem. Their Orbits oscillate near the Solar Orbit with an amplitude of ≈250 pc; there are short-term close encounters to distances
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Stars outside the Hipparcos list closely encountering the Solar system
Astronomy Letters, 2010Co-Authors: V. V. BobylevAbstract:Based on currently available kinematic data, we have searched for stars outside the Hipparcos list that either closely encountered in the past or will encounter in the future the Solar system within several parsecs. For the first time, we have identified two single stars, GJ 3379 (G 099-049) and GJ 3323 (LHS 1723), as candidate for a close encounter with the Solar Orbit. The star GJ 3379 could encounter the Sunmore closely to aminimumdistance d _min = 1.32±0.03 pc at time t _min = −163 ± 3 thousand years. We have found two potential candidates for a close encounter that have only photometrical distances: the white dwarf SSSPM J1549-3544 without any data on its radial velocity and the L-dwarf SDSS J1416+1348. The probabilities of their penetration into the Oort cloud region are 0.09 (at a model radial velocity
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Searching for stars closely encountering with the Solar system
Astronomy Letters, 2010Co-Authors: V. V. BobylevAbstract:Based on a new version of the Hipparcos catalog and currently available radial velocity data, we have searched for stars that either have encountered or will encounter the Solar neighborhood within less than 3 pc in the time interval from −2 Myr to +2 Myr. Nine new candidates within 30 pc of the Sun have been found. To construct the stellar Orbits relative to the Solar Orbit, we have used the epicyclic approximation. We show that, given the errors in the observational data, the probability that the well-known star HIP 89 825 (GL 710) encountering with the Sun most closely falls into the Oort cloud is 0.86 in the time interval 1.45 ± 0.06 Myr. This star also has a nonzero probability, 1 × 10^−4, of falling into the region d < 1000 AU, where its influence on Kuiper Belt objects becomes possible.
Abe Fumio - One of the best experts on this subject based on the ideXlab platform.
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OGLE-2017-BLG-0406: ${\it Spitzer}$ Microlens Parallax Reveals Saturn-mass Planet Orbiting M-dwarf Host in the Inner Galactic Disk
'American Astronomical Society', 2020Co-Authors: Hirao Yuki, Bennett, David P., Ryu Yoon-hyun, Koshimoto Naoki, Udalski Andrzej, Yee, Jennifer C., Sumi Takahiro, Bond, Ian A., Shvartzvald Yossi, Abe FumioAbstract:We report the discovery and analysis of the planetary microlensing event OGLE-2017-BLG-0406, which was observed both from the ground and by the ${\it Spitzer}$ satellite in a Solar Orbit. At high magnification, the anomaly in the light curve was densely observed by ground-based-survey and follow-up groups, and it was found to be explained by a planetary lens with a planet/host mass ratio of $q=7.0 \times 10^{-4}$ from the light-curve modeling. The ground-only and ${\it Spitzer}$-"only" data each provide very strong one-dimensional (1-D) constraints on the 2-D microlens parallax vector $\bf{\pi_{\rm E}}$. When combined, these yield a precise measurement of $\bf{\pi_{\rm E}}$, and so of the masses of the host $M_{\rm host}=0.56\pm0.07\,M_\odot$ and planet $M_{\rm planet} = 0.41 \pm 0.05\,M_{\rm Jup}$. The system lies at a distance $D_{\rm L}=5.2 \pm 0.5 \ {\rm kpc}$ from the Sun toward the Galactic bulge, and the host is more likely to be a disk population star according to the kinematics of the lens. The projected separation of the planet from the host is $a_{\perp} = 3.5 \pm 0.3 \ {\rm au}$, i.e., just over twice the snow line. The Galactic-disk kinematics are established in part from a precise measurement of the source proper motion based on OGLE-IV data. By contrast, the ${\it Gaia}$ proper-motion measurement of the source suffers from a catastrophic $10\,\sigma$ error.Comment: 40 pages, 12 figures, 10 tables, accepted for publication in The Astronomical Journa
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OGLE-2017-BLG-0406: Spitzer microlens parallax reveals Saturn-mass planet Orbiting M-dwarf host in the inner galactic disk
'American Astronomical Society', 2020Co-Authors: Hirao Yuki, Bennett, David P., Ryu Yoon-hyun, Koshimoto Naoki, Udalski Andrzej, Yee, Jennifer C., Sumi Takahiro, Bond, Ian A., Shvartzvald Yossi, Abe FumioAbstract:Funding: Work by Y.H. was supported by JSPS KAKENHI Grant Number 17J02146. DPB, AB, and CR were supported by NASA through grant NASA-80NSSC18K0274. Work by N.K. is supported by JSPS KAKENHI Grant Number JP18J00897. Work by AG was supported by AST-1516842 from the US NSF and by JPL grant 1500811. AG received support from the European Research Council under the European Unions Seventh Framework Programme (FP 7) ERC Grant Agreement n.[321035]. Work by C.H. was supported by the grants of the National Research Foundation of Korea (2017R1A4A1015178 and 2019R1A2C2085965). YT acknowledges the support of DFG priority program SPP 1992 ”Exploring the Diversity of ExtraSolar Planets” (WA 1047/11-1).We report the discovery and analysis of the planetary microlensing event OGLE-2017-BLG-0406, which was observed both from the ground and by the Spitzer satellite in a Solar Orbit. At high magnification, the anomaly in the light curve was densely observed by ground-based-survey and follow-up groups, and it was found to be explained by a planetary lens with a planet/host mass ratio of q = 7.0 x 10-4 from the light-curve modeling. The ground-only and Spitzer-"only" data each provide very strong one-dimensional (1-D) constraints on the 2-D microlens parallax vector πE. When combined, these yield a precise measurement of πE, and so of the masses of the host Mhost = 0.56 ± 0.07 M⊙ and planet Mplanet = 0.41 ± 0.05 MJup. The system lies at a distance DL = 5.2 ± 0.5 kpc from the Sun toward the Galactic bulge, and the host is more likely to be a disk population star according to the kinematics of the lens. The projected separation of the planet from the host is a⊥ = 3.5 ± 0.3 au, i.e., just over twice the snow line. The Galactic-disk kinematics are established in part from a precise measurement of the source proper motion based on OGLE-IV data. By contrast, the Gaia proper-motion measurement of the source suffers from a catastrophic 10σ error.PostprintPeer reviewe
Gerald A Lincoln - One of the best experts on this subject based on the ideXlab platform.
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photoperiodic variation in cd45 positive cells and cell proliferation in the mediobasal hypothalamus of the soay sheep
Chronobiology International, 2013Co-Authors: David G Hazlerigg, C A Wyse, Hugues Dardente, E A Hanon, Gerald A LincolnAbstract:The Earth's Solar Orbit induces annual climatic changes challenging to survival. Many animals have evolved to cope with seasonal variability through compensatory annual changes in their physiology ...
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Photoperiodic variation in CD45-positive cells and cell proliferation in the mediobasal hypothalamus of the Soay sheep
Chronobiology International, 2013Co-Authors: David G Hazlerigg, C A Wyse, Hugues Dardente, E A Hanon, Gerald A LincolnAbstract:The Earth's Solar Orbit induces annual climatic changes challenging to survival. Many animals have evolved to cope with seasonal variability through compensatory annual changes in their physiology and behavior, which involve innate long-term timing and photoperiodic synchronization to anticipate the environmental seasonal cycles. Here we considered the potential involvement of cyclical histogenesis in seasonal timing mechanisms in the sheep. Adult Soay rams were established in three distinctive seasonal states by controlled photoperiod exposure. A first group, representing the condition in late spring (long-photoperiod [LP] group), was taken indoors in May and exposed to 4 wks of 16 h light/day (LP). A second group was exposed to 20 wks of LP to establish a late-summer/long-day refractory condition (LPR group). A third group of animals was brought indoors in August and exposed to 4 wks of LP followed by 4 wks of 8 h light/day (short photoperiod [SP]) to establish an autumn-like condition (SP group). At the end of these regimes, we injected 5-bromo-2-deoxyuridine (BrdU), and animals were killed 24 h or 4 wks later. When BrdU was administered 24 h before death, more BrdU-immunopositive cells were detected in the hilus of the hippocampus in LP compared with SP animals, indicative of a higher proliferation rate. When BrdU was administered 4 wks before death, more BrdU-positive cells were detected in the hippocampus under LP, compared with SP, indicating increased cell survival. These mitotic cells were occasionally seen to adopt a neuronal phenotype in the hippocampus, but not in the hypothalamus. Approximately 10% of BrdU-positive cells in the basal hypothalamus coexpressed the pan-leukocytic marker CD45, and showed morphological features and regional distribution consistent with ameboid microglia. Increased numbers of these cells were detected in the region of the median eminence and tuberoinfundibular sulcus of animals kept in SP compared with LP or LPR. These data suggest that neuroimmune mechanisms may be involved in photoperiod-dependent seasonal remodeling of the adult brain.
Hirao Yuki - One of the best experts on this subject based on the ideXlab platform.
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OGLE-2017-BLG-0406: ${\it Spitzer}$ Microlens Parallax Reveals Saturn-mass Planet Orbiting M-dwarf Host in the Inner Galactic Disk
'American Astronomical Society', 2020Co-Authors: Hirao Yuki, Bennett, David P., Ryu Yoon-hyun, Koshimoto Naoki, Udalski Andrzej, Yee, Jennifer C., Sumi Takahiro, Bond, Ian A., Shvartzvald Yossi, Abe FumioAbstract:We report the discovery and analysis of the planetary microlensing event OGLE-2017-BLG-0406, which was observed both from the ground and by the ${\it Spitzer}$ satellite in a Solar Orbit. At high magnification, the anomaly in the light curve was densely observed by ground-based-survey and follow-up groups, and it was found to be explained by a planetary lens with a planet/host mass ratio of $q=7.0 \times 10^{-4}$ from the light-curve modeling. The ground-only and ${\it Spitzer}$-"only" data each provide very strong one-dimensional (1-D) constraints on the 2-D microlens parallax vector $\bf{\pi_{\rm E}}$. When combined, these yield a precise measurement of $\bf{\pi_{\rm E}}$, and so of the masses of the host $M_{\rm host}=0.56\pm0.07\,M_\odot$ and planet $M_{\rm planet} = 0.41 \pm 0.05\,M_{\rm Jup}$. The system lies at a distance $D_{\rm L}=5.2 \pm 0.5 \ {\rm kpc}$ from the Sun toward the Galactic bulge, and the host is more likely to be a disk population star according to the kinematics of the lens. The projected separation of the planet from the host is $a_{\perp} = 3.5 \pm 0.3 \ {\rm au}$, i.e., just over twice the snow line. The Galactic-disk kinematics are established in part from a precise measurement of the source proper motion based on OGLE-IV data. By contrast, the ${\it Gaia}$ proper-motion measurement of the source suffers from a catastrophic $10\,\sigma$ error.Comment: 40 pages, 12 figures, 10 tables, accepted for publication in The Astronomical Journa
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OGLE-2017-BLG-0406: Spitzer microlens parallax reveals Saturn-mass planet Orbiting M-dwarf host in the inner galactic disk
'American Astronomical Society', 2020Co-Authors: Hirao Yuki, Bennett, David P., Ryu Yoon-hyun, Koshimoto Naoki, Udalski Andrzej, Yee, Jennifer C., Sumi Takahiro, Bond, Ian A., Shvartzvald Yossi, Abe FumioAbstract:Funding: Work by Y.H. was supported by JSPS KAKENHI Grant Number 17J02146. DPB, AB, and CR were supported by NASA through grant NASA-80NSSC18K0274. Work by N.K. is supported by JSPS KAKENHI Grant Number JP18J00897. Work by AG was supported by AST-1516842 from the US NSF and by JPL grant 1500811. AG received support from the European Research Council under the European Unions Seventh Framework Programme (FP 7) ERC Grant Agreement n.[321035]. Work by C.H. was supported by the grants of the National Research Foundation of Korea (2017R1A4A1015178 and 2019R1A2C2085965). YT acknowledges the support of DFG priority program SPP 1992 ”Exploring the Diversity of ExtraSolar Planets” (WA 1047/11-1).We report the discovery and analysis of the planetary microlensing event OGLE-2017-BLG-0406, which was observed both from the ground and by the Spitzer satellite in a Solar Orbit. At high magnification, the anomaly in the light curve was densely observed by ground-based-survey and follow-up groups, and it was found to be explained by a planetary lens with a planet/host mass ratio of q = 7.0 x 10-4 from the light-curve modeling. The ground-only and Spitzer-"only" data each provide very strong one-dimensional (1-D) constraints on the 2-D microlens parallax vector πE. When combined, these yield a precise measurement of πE, and so of the masses of the host Mhost = 0.56 ± 0.07 M⊙ and planet Mplanet = 0.41 ± 0.05 MJup. The system lies at a distance DL = 5.2 ± 0.5 kpc from the Sun toward the Galactic bulge, and the host is more likely to be a disk population star according to the kinematics of the lens. The projected separation of the planet from the host is a⊥ = 3.5 ± 0.3 au, i.e., just over twice the snow line. The Galactic-disk kinematics are established in part from a precise measurement of the source proper motion based on OGLE-IV data. By contrast, the Gaia proper-motion measurement of the source suffers from a catastrophic 10σ error.PostprintPeer reviewe
X X Zhang - One of the best experts on this subject based on the ideXlab platform.
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interplanetary coronal mass ejections observed by ulysses through its three Solar Orbits
Solar Physics, 2010Co-Authors: Pingbing Zuo, X X ZhangAbstract:An extended Ulysses interplanetary coronal mass ejections (ICMEs) list is used to statistically study the occurrence rate of ICMEs, the interaction of ICMEs with Solar wind, and the magnetic field properties in ICMEs. About 43% of the ICMEs are identified as magnetic clouds (MCs). It is found that the occurrence rate of ICMEs approximately follows the Solar activity level, except for the second Solar Orbit; the rate is higher in the southern heliolatitude than in the northern heliolatitude; and it roughly decreases with the increase of ICME speeds. Our results show that the speed difference between the ICME and the Solar wind in front of it shows a slight decrease with increasing heliocentric distance for ICMEs preceded by a shock, whereas no such dependence is found for the ICMEs without shock association. It is also found that approximately 23% of the ICMEs are associated with radial field events, in which the interplanetary magnetic field with near-radial direction lasts for many hours, in the Ulysses detected range, and these associated events are not necessarily confined to fast ICMEs or the trailing portions of ICMEs. Nearly all these associated events occur during the period of declining Solar wind speed and most of them occur at low heliolatitudes.