scholarly journals Distance, Luminosity and evolutionary status of epsilon Aurigae (F0Iaep) from Gaia DR2 parallax

2019 ◽  
Author(s):  
M. Parthasarathy ◽  
S. Muneer
Keyword(s):  
Evolutionary Status ◽  
Epsilon Aurigae ◽  
Gaia Dr2

scholarly journals Gaia DR2 data and the evolutionary status of eight high-velocity hot post-AGB candidates

2020 ◽  
Vol 72 (6) ◽  
Author(s):  
Mudumba Parthasarathy ◽  
Tadafumi Matsuno ◽  
Wako Aoki
Keyword(s):  
Effective Temperature ◽  
High Velocity ◽  
Circumstellar Dust ◽  
Evolutionary Status ◽  
Agb Stars ◽  
Horizontal Branch ◽  
Dust Shells ◽  
The Past ◽  
Gaia Dr2 ◽  
Branch Star

Abstract From Gaia DR2 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 (MV) and luminosity (log L/L⊙). All the stars except LS 5107 have an accurate effective temperature (Teff) 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 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 to be in the range 1 M⊙ to 2 M⊙. 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.

scholarly journals Searching for correlations in Gaia DR2 unbound star trajectories

2019 ◽  
Vol 490 (4) ◽  
pp. 5647-5657
Author(s):  
F Montanari ◽  
D Barrado ◽  
J García-Bellido
Keyword(s):  
Globular Clusters ◽  
Cold Dark Matter ◽  
Dwarf Galaxies ◽  
Compact Objects ◽  
Evolutionary Status ◽  
Primordial Black Hole ◽  
Full Phase Space ◽  
Nearby Galaxies ◽  
Gaia Dr2 ◽  
Scattering Events

ABSTRACT Scattering events with compact objects are expected in the primordial black hole (PBH) cold dark matter (CDM) scenario, due to close encounters between stars and PBHs in the dense environments of dwarf spheroidals. We develop a Bayesian framework to search for correlations among Milky Way stellar trajectories and those of globular clusters and dwarf galaxies in the halo and in other nearby galaxies. We apply the method to a selection of hypervelocity stars (HVS) and globular clusters from the Gaia DR2 catalogue and known nearby (mostly dwarf) galaxies with full phase-space and size measurements. We report positive evidence for trajectory intersection ∼20–40 Myr ago of up to two stars, depending on priors, with the Sagittarius dwarf spheroidal galaxy (dSph) when assuming the distance estimates of Marchetti, Rossi & Brown (2018). We verify that the result is compatible with their evolutionary status, setting a lower bound for their stellar age of ∼100 Myr. However, such scattering events are not confirmed when assuming Anders et al. (2019) distance estimates. We discuss shortcomings related to present data quality and future prospects for detection of HVS with the full Gaia catalogue and Sagittarius dSph.

Sixteen Open Clusters Discovered with Sample-based Clustering Search of Gaia DR2

2020 ◽  
Vol 132 (1009) ◽  
pp. 034502 ◽  
Author(s):  
ChaoJie Hao ◽  
Ye Xu ◽  
ZhenYu Wu ◽  
ZhiHong He ◽  
ShuaiBo Bian
Keyword(s):  
Open Clusters ◽  
Clustering Search ◽  
Gaia Dr2

Twin stars as tracers of binary evolution in the Kepler era

2021 ◽  
Author(s):  
Sara Bulut ◽  
Baris Hoyman ◽  
Ahmet Dervisoglu ◽  
Orkun Özdarcan ◽  
Ömür Cakilrli
Keyword(s):  
High Resolution ◽  
Internal Structure ◽  
Spectroscopic Analysis ◽  
Independent Method ◽  
Eclipsing Binaries ◽  
Physical Parameters ◽  
Evolutionary Status ◽  
Mass Ratio ◽  
Orbital Parameters ◽  
Binary Evolution

Abstract We present results of the combined photometric and spectroscopic analysis of four systems, which are eclipsing binaries with a twin–component (mass ratio q ≃ 1). These are exceptional tools to provide information for probing the internal structure of stars. None of the systems were previously recognized as twin binaries. We used a number of high–resolution optical spectra to calculate the radial velocities and later combined them with photometry to derive orbital parameters. Temperatures and metallicities of systems were estimated from high-resolution spectra. For each binary, we obtained a full set of orbital and physical parameters, reaching precision below 3 per cent in masses and radii for whole pairs. By comparing our results with PARSEC and MIST isochrones, we assess the distance, age and evolutionary status of the researched objects. The primary and/or secondary stars of EPIC 216075815 and EPIC 202843107 are one of the cases where asteroseismic parameters of δ Sct and γ Dor pulsators were confirmed by an independent method and rare examples of the twin–eclipsing binaries, therefore the following analyses and results concern the pulsating nature of the components.

scholarly journals HD 76920 b pinned down: A detailed analysis of the most eccentric planetary system around an evolved star

2021 ◽  
Vol 38 ◽  
Author(s):  
C. Bergmann ◽  
M. I. Jones ◽  
J. Zhao ◽  
A. J. Mustill ◽  
R. Brahm ◽  
...  
Keyword(s):  
Spectroscopic Analysis ◽  
Planetary System ◽  
Continuous Phase ◽  
Minimum Mass ◽  
Orbital Elements ◽  
Stellar Envelope ◽  
Orbital Decay ◽  
Fundamental Stellar Parameters ◽  
Transit Probability ◽  
Gaia Dr2

Abstract We present 63 new multi-site radial velocity (RV) measurements of the K1III giant HD 76920, which was recently reported to host the most eccentric planet known to orbit an evolved star. We focused our observational efforts on the time around the predicted periastron passage and achieved near-continuous phase coverage of the corresponding RV peak. By combining our RV measurements from four different instruments with previously published ones, we confirm the highly eccentric nature of the system and find an even higher eccentricity of $e=0.8782 \pm 0.0025$ , an orbital period of $415.891^{+0.043}_{-0.039}\,\textrm{d}$ , and a minimum mass of $3.13^{+0.41}_{-0.43}\,\textrm{M}_{\textrm{J}}$ for the planet. The uncertainties in the orbital elements are greatly reduced, especially for the period and eccentricity. We also performed a detailed spectroscopic analysis to derive atmospheric stellar parameters, and thus the fundamental stellar parameters ( $M_*, R_*, L_*$ ), taking into account the parallax from Gaia DR2, and independently determined the stellar mass and radius using asteroseismology. Intriguingly, at periastron, the planet comes to within 2.4 stellar radii of its host star’s surface. However, we find that the planet is not currently experiencing any significant orbital decay and will not be engulfed by the stellar envelope for at least another 50–80 Myr. Finally, while we calculate a relatively high transit probability of 16%, we did not detect a transit in the TESS photometry.

Colloquial features in Word Englishes

2013 ◽  
Vol 18 (4) ◽  
pp. 479-505 ◽  
Author(s):  
Peter Collins ◽  
Xinyue Yao
Keyword(s):  
Twentieth Century ◽  
American English ◽  
World Englishes ◽  
Evolutionary Status ◽  
First Person ◽  
Functional Interpretation ◽  
Person Plural ◽  
World English ◽  
First Person Plural ◽  
Grammatical Change

A powerful discourse-pragmatic agent of grammatical change in English since the mid-twentieth century has been the increasing acceptance of colloquialism. Little is known, however, about its influence on grammatical developments in regional varieties of World English other than the two inner circle ‘supervarieties’, British and American English. This paper reports findings from a corpus-based study of three grammatical categories known to be undergoing a colloquialism-related rise in contemporary English, across a range of registers in ten World Englishes: quasi-modals (have to, have got to, be going to, want to), get-passives, and first person plural inclusive let’s. In each case comparisons are drawn with non-colloquial variants: modals (must, should, will, shall), be-passives, and let us. Subsequent functional interpretation of the data is used to explore the effect upon the quantitative patterns identified of the phenomenon of colloquialism and of further factors with which it interacts (including Americanism, prescriptivism, and evolutionary status).

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