scholarly journals High dispersion spectroscopy of solar-type superflare stars. I. Temperature, surface gravity, metallicity, andvsin i

2015 ◽  
Vol 67 (3) ◽  
pp. 32 ◽  
Author(s):  
Yuta Notsu ◽  
Satoshi Honda ◽  
Hiroyuki Maehara ◽  
Shota Notsu ◽  
Takuya Shibayama ◽  
...  
Keyword(s):  
Surface Gravity ◽  
High Dispersion ◽  
Solar Type ◽  
Temperature Surface

scholarly journals High dispersion spectroscopy of solar-type superflare stars. III. Lithium abundances

2015 ◽  
Vol 67 (5) ◽  
pp. 85 ◽  
Author(s):  
Satoshi Honda ◽  
Yuta Notsu ◽  
Hiroyuki Maehara ◽  
Shota Notsu ◽  
Takuya Shibayama ◽  
...  
Keyword(s):  
High Dispersion ◽  
Solar Type

scholarly journals Synthesis of Classification Dispersion Spectra from Stellar Atmospheres Theory and from High Dispersion Spectra

1976 ◽  
Vol 72 ◽  
pp. 17-18
Author(s):  
A. W. Irwin ◽  
C. T. Bolton ◽  
R. F. Garrison
Keyword(s):  
Spectral Synthesis ◽  
Stellar Atmospheres ◽  
Oscillator Strengths ◽  
Continuum Models ◽  
High Dispersion ◽  
University Of Toronto ◽  
Spectrum Synthesis ◽  
Effective Temperatures ◽  
The University ◽  
Temperature Surface

The ATLAS programme has been corrected and modified for use at low effective temperatures. A grid of unblanketed model atmospheres has been generated for the region G5-K5, V-II. A spectrum synthesis programme has been written for the calculation of flux vs wavelength for selected regions of the spectrum. Temperature distributions from the grid of continuum models and from published blanketed models will be used along with published oscillator strengths as input data for the spectral synthesis programme.Spectrograms of MK standards have been taken at 12 Å mm−1 and 120 Å mm−1. The University of Toronto PDS microdensitometer system has been programmed to allow comparison between the synthesized spectra and the observed spectra to determine the effects of effective temperature, surface gravity, microturbulence, and abundance on classification criteria.

Stellar Parameterisation using KPCA and SVM

2017 ◽  
Vol 14 (S339) ◽  
pp. 345-348
Author(s):  
H. Yuan ◽  
Y. Zhang ◽  
Y. Lei ◽  
Y. Dong ◽  
Z. Bai ◽  
...  
Keyword(s):  
Effective Temperature ◽  
Hybrid Approach ◽  
Principal Component ◽  
Test Sample ◽  
Surface Gravity ◽  
Kernel Principal Component Analysis ◽  
Support Vector ◽  
Stellar Spectra ◽  
The Impact ◽  
Temperature Surface

AbstractWith so many spectroscopic surveys, both past and upcoming, such as SDSS and LAMOST, the number of accessible stellar spectra is continuously increasing. There is therefore a great need for automated procedures that will derive estimates of stellar parameters. Working with spectra from SDSS and LAMOST, we put forward a hybrid approach of Kernel Principal Component Analysis (KPCA) and Support Vector Machine (SVM) to determine the stellar atmospheric parameters effective temperature, surface gravity and metallicity. For stars with both APOGEE and LAMOST spectra, we adopt the LAMOST spectra and APOGEE parameters, and then use KPCA to reduce dimensionality and SVM to measure parameters. Our method provides reliable and precise results; for example, the standard deviation of effective temperature, surface gravity and metallicity for the test sample come to approximately 47–75 K, 0.11–0.15 dex and 0.06–0.075 dex, respectively. The impact of the signal:noise ratio of the observations upon the accuracy of the results is also investigated.

scholarly journals Discovery of FK comae and RS CVn systems by observation of their X-ray emission

1987 ◽  
Vol 122 ◽  
pp. 367-367
Author(s):  
Thomas A. Fleming ◽  
Isabella Gioia ◽  
Tommaso Maccacaro
Keyword(s):  
Optical Spectroscopy ◽  
Binary Systems ◽  
Cataclysmic Variables ◽  
Radial Velocities ◽  
Surface Gravity ◽  
X Ray ◽  
Chromospheric Activity ◽  
Flare Stars ◽  
Einstein Observatory ◽  
Temperature Surface

We are currently working with a statistically complete, unbiased sample of 125 x-ray-bright stars which were serendipitously detected by the Einstein Observatory Medium Sensitivity Survey (MSS). A program of optical spectroscopy and photometry is currently underway to measure radial velocities, distances, and such stellar parameters as rotation, temperature, surface gravity, metallicity, chromospheric activity, and age and to correlate them with absolute x-ray luminosity. So far, the majority of the sample (which was defined at |bII| > 20o) appears to be composed of either flare stars (e.g. dMe, dKe) or active binary systems (e.g. cataclysmic variables, RS CVn, W UMa).

scholarly journals RAVE-Gaia and the impact on Galactic archeology

2017 ◽  
Vol 12 (S330) ◽  
pp. 176-180
Author(s):  
Andrea Kunder
Keyword(s):  
Radial Velocity ◽  
Effective Temperature ◽  
Milky Way ◽  
Radial Velocities ◽  
Surface Gravity ◽  
Individual Stars ◽  
Dynamic Analyses ◽  
Data Release ◽  
The Impact ◽  
Temperature Surface

AbstractThe new data release (DR5) of the RAdial Velocity Experiment (RAVE) includes radial velocities of 520,781 spectra of 457,588 individual stars, of which 215,590 individual stars are released in the Tycho-Gaia astrometric solution (TGAS) in Gaia DR1. Therefore, RAVE contains the largest TGAS overlap of the recent and ongoing Milky Way spectroscopic surveys. Most of the RAVE stars also contain stellar parameters (effective temperature, surface gravity, overall metallicity), as well as individual abundances for Mg, Al, Si, Ca, Ti, Fe, and Ni. Combining RAVE with TGAS brings the uncertainties in space velocities down by a factor of 2 for stars in the RAVE volume – 10 km s−1 uncertainties in space velocities are now able to be derived for the majority (70%) of the RAVE-TGAS sample, providing a powerful platform for chemo-dynamic analyses of the Milky Way. Here we discuss the RAVE-TGAS impact on Galactic archaeology as well as how the Gaia parallaxes can be used to break degeneracies within the RAVE spectral regime for an even better return in the derivation of stellar parameters and abundances.

scholarly journals Automated Extraction of DIBs from Cool Star Spectra

2013 ◽  
Vol 9 (S297) ◽  
pp. 110-112
Author(s):  
H.-Ch. Chen ◽  
R. Lallement ◽  
L. Puspitarini ◽  
P. Bonifacio ◽  
C. Babusiaux ◽  
...  
Keyword(s):  
Solar Neighborhood ◽  
Surface Gravity ◽  
Automated Extraction ◽  
Galactic Bulge ◽  
Cool Star ◽  
Extensive Data ◽  
The One ◽  
Temperature Surface

AbstractWe have developed a method allowing to extract DIBs from cool star spectra, based on combinations of stellar synthetic, telluric transmission (when necessary), and DIB profile models. It is applicable when the star temperature, surface gravity and metallicity have been previously estimated. Such a method aims at extracting extensive data from stellar spectroscopic surveys such as the Gaia-ESO Survey in progress at the VLT. The method has been applied to several strong DIBs detected towards stars from various programs and located at various distances from the solar neighborhood to the Galactic Bulge. Here we illustrate the extraction of the 8620 Å DIB, and compare its strength to the one of the 6284 Å band, both for nearby and bulge stars.

scholarly journals HD137569, a Population II Remnant of Mass Exchange Evolution

1980 ◽  
Vol 88 ◽  
pp. 575-575
Author(s):  
C. T. Bolton ◽  
J. R. Thomson
Keyword(s):  
Mass Exchange ◽  
Surface Gravity ◽  
Spectroscopic Binary ◽  
Branch Star ◽  
Temperature Surface

The temperature, surface gravity, and abundances derived for this halo B star by Danziger and Jura (1970, Ap.J., 161, 997) show that it is a field suprahorizontal branch star very similar to B29 in M13. The only difference is that HD137569 has a higher (solar) C abundance. We find that HD137569 is a spectroscopic binary with P=529.8(2) days, Vo=45.0(2) km/s, K=16.2(3) km/s, e=0.12(2), ω=233°(10), and T=JD2441922(14). The parenthesized quantities are the uncertainties (probable errors) of the last digits of the elements.

scholarly journals High dispersion spectroscopy of solar-type superflare stars. II. Stellar rotation, starspots, and chromospheric activities

2015 ◽  
Vol 67 (3) ◽  
pp. 33 ◽  
Author(s):  
Yuta Notsu ◽  
Satoshi Honda ◽  
Hiroyuki Maehara ◽  
Shota Notsu ◽  
Takuya Shibayama ◽  
...  
Keyword(s):  
High Dispersion ◽  
Stellar Rotation ◽  
Solar Type
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