scholarly journals Rotation periods of late-type dwarf stars from time series high-resolution spectroscopy of chromospheric indicators

2015 ◽  
Vol 452 (3) ◽  
pp. 2745-2756 ◽  
Author(s):  
A. Suárez Mascareño ◽  
R. Rebolo ◽  
J. I. González Hernández ◽  
M. Esposito
Keyword(s):  
Time Series ◽  
High Resolution ◽  
High Resolution Spectroscopy ◽  
Late Type ◽  
Dwarf Stars ◽  
Rotation Periods

scholarly journals The Art of Surface Imaging

1991 ◽  
Vol 130 ◽  
pp. 309-320 ◽  
Author(s):  
N.E. Piskunov
Keyword(s):  
Inverse Problem ◽  
High Resolution ◽  
Stellar Atmosphere ◽  
High Resolution Spectroscopy ◽  
Regularization Methods ◽  
Problem Solution ◽  
Surface Imaging ◽  
Late Type ◽  
Inverse Problem Solution ◽  
Additional Constraints

AbstractWe intend to analyze the reliability of surface imaging of stars based on high resolution spectroscopy and the technique of inverse problem solution. Both astrophysical and mathematical aspects including different regularization methods are reviewed. The influence of the different factors on the resulting map is discussed and it is shown that the simultaneous use of different kinds of observational data (spectroscopy, photometry, polarimetry etc.) is very useful in providing additional constraints for the solution. The recent results in the surface imaging of Cp- and late-type stars show the way for further progress: the use of more adequate mathematical description of the stellar atmosphere and the simultaneous consideration of various surface inhomogeneities.

scholarly journals Lithium Abundance in Late-Type Stars

2000 ◽  
Vol 198 ◽  
pp. 368-369
Author(s):  
L Pompéia ◽  
B Barbuy ◽  
M. Grenon
Keyword(s):  
High Resolution ◽  
Radial Velocity ◽  
Detailed Analysis ◽  
Absolute Magnitude ◽  
Late Type ◽  
Lithium Abundance ◽  
Dwarf Stars ◽  
The Absolute

We have a list of nearby bulge-like turnoff stars with metallicities in the range −0.3 ≤ [Fe/H] ≤ +0.6, for which we have the absolute magnitude from Hipparcos, Geneva photometry (therefore temperature and metallicity), and radial velocity from Coravel (Grenon 1990, 1997). From Hipparcos data, the turnoff of these field stars indicate an age of 10-11 Gyr, which would be the age of the most metal-rich component of the bulge.We obtained high resolution échelle spectra with FEROS, with the aim to carry out detailed analysis of these stars. In this paper we present the Li abundance for 40 of these metal-rich and old dwarf stars, as a function of their temperatures.

scholarly journals Transiting exocomets detected in broadband light by TESS in the β Pictoris system

2019 ◽  
Vol 625 ◽  
pp. L13 ◽  
Author(s):  
S. Zieba ◽  
K. Zwintz ◽  
M. A. Kenworthy ◽  
G. M. Kennedy
Keyword(s):  
Time Series ◽  
High Resolution ◽  
Light Curve ◽  
Frequency Analysis ◽  
Photometric Data ◽  
High Resolution Spectroscopy

Aims. We search for signs of falling evaporating bodies (FEBs, also known as exocomets) in photometric time series obtained for β Pictoris after fitting and removing its δ Scuti-type pulsation frequencies. Methods. Using photometric data obtained by the TESS satellite we determined the pulsational properties of the exoplanet host star β Pictoris through frequency analysis. We then pre-whitened the 54 identified δ Scuti p-modes and investigated the residual photometric time series for the presence of FEBs. Results. We identify three distinct dipping events in the light curve of β Pictoris over a 105-day period. These dips have depths from 0.5 to 2 millimagnitudes and durations of up to 2 days for the largest dip. These dips are asymmetric in nature and are consistent with a model of an evaporating comet with an extended tail crossing the disc of the star Conclusions. We present the first broadband detections of exocomets crossing the disc of β Pictoris, complementing the predictions made 20 years earlier by Lecavelier Des Etangs et al. (1999, A&A, 343, 916). No periodic transits are seen in this time series. These observations confirm the spectroscopic detection of exocomets in calcium H and K lines that have been seen in high resolution spectroscopy.

scholarly journals Magnetic cycles and rotation periods of late-type stars from photometric time series

2016 ◽  
Vol 595 ◽  
pp. A12 ◽  
Author(s):  
A. Suárez Mascareño ◽  
R. Rebolo ◽  
J. I. González Hernández
Keyword(s):  
Time Series ◽  
Late Type ◽  
Rotation Periods ◽  
Magnetic Cycles

scholarly journals High S/N Na I D Line Profiles in Late-Type MS Stars and their Importance for Stellar Modelling

1993 ◽  
Vol 137 ◽  
pp. 190-192 ◽  
Author(s):  
E. Covino ◽  
M.T. Gomez ◽  
G. Severino ◽  
M. Franchini
Keyword(s):  
High Resolution ◽  
Synthesis Method ◽  
Atomic Data ◽  
Line Profiles ◽  
Late Type ◽  
Stellar Spectrum ◽  
Dwarf Stars ◽  
Observational Techniques ◽  
Numerical Fit

Progress in observational techniques (i.e. high S/N spectroscopy) and modelling (e.g. RE models including convection, nonLTE codes, accurate atomic data) make significant to carry to extremes the numerical fit of a portion of the stellar spectrum and try to interpret the residual differences between calculations and observations in terms of stellar characteristics new respect to the employed model.We have started to apply this synthesis method to a set of high resolution, high S/N spectra of late-type dwarfs in the region of the Na I D lines, obtained at ESO with the 1.4m CAT on May 1989 (Franchini et al. 1992). The dwarf stars are modelled in radiative equilibrium (RE), and the Na I D line synthesis accounts for nonLTE and blend effects.

scholarly journals HADES RV Programme with HARPS-N at TNG

2019 ◽  
Vol 624 ◽  
pp. A27 ◽  
Author(s):  
E. González-Álvarez ◽  
G. Micela ◽  
J. Maldonado ◽  
L. Affer ◽  
A. Maggio ◽  
...  
Keyword(s):  
Rotation Period ◽  
High Resolution Spectroscopy ◽  
Slow Rotation ◽  
Stellar Rotation ◽  
M Dwarfs ◽  
Dwarf Stars ◽  
Rotation Periods ◽  
Coronal Activity ◽  
Low Mass ◽  
M Dwarf Stars

Aims. We extend the relationship between X-ray luminosity (Lx) and rotation period (Prot) found for main-sequence FGK stars, and test whether it also holds for early M dwarfs, especially in the non-saturated regime (Lx ∝ Prot−2) which corresponds to slow rotators. Methods. We use the luminosity coronal activity indicator (Lx) of a sample of 78 early M dwarfs with masses in the range from 0.3 to 0.75 M⊙ from the HArps-N red Dwarf Exoplanet Survey (HADES) radial velocity (RV) programme collected from ROSAT and XMM-Newton. The determination of the rotation periods (Prot) was done by analysing time series of high-resolution spectroscopy of the Ca II H & K and Hα activity indicators. Our sample principally covers the slow rotation regime with rotation periods from 15 to 60 days. Results. Our work extends to the low mass regime the observed trend for more massive stars showing a continuous shift of the Lx∕Lbol versus Prot power law towards longer rotation period values, and includes a more accurate way to determine the value of the rotation period at which the saturation occurs (Psat) for M dwarf stars. Conclusions. We conclude that the relations between coronal activity and stellar rotation for FGK stars also hold for early M dwarfs in the non-saturated regime, indicating that the rotation period is sufficient to determine the ratio Lx∕Lbol.

scholarly journals Signatures of pulsations and mass loss in the spectra of post-AGB stars

2011 ◽  
Vol 7 (S283) ◽  
pp. 526-527
Author(s):  
Laimons Začs ◽  
Julius Sperauskas ◽  
Aija Laure ◽  
Olesja Smirnova
Keyword(s):  
Time Series ◽  
High Resolution ◽  
Mass Loss ◽  
Radial Velocity ◽  
High Resolution Spectroscopy ◽  
Agb Stars ◽  
Atomic Lines ◽  
Mass Ejection

AbstractThe results of high-resolution spectroscopy and radial velocity monitoringa are presented for selected post-AGB candidate stars. Time series of high-resolution spectra for HD235858 shows spliting of low-excitation atomic lines and significant changes in the intensity of C2 and CN lines originated in the extended atmosphere significantly affected by pulsations and outflow. Mass ejection was confirmed for cool R CrB candidate stars DY Per, V1983 Cyg, and V2074 Cyg.

High-Resolution Spectroscopy of 15 Metal-Poor Stars

2005 ◽  
Vol 277-279 ◽  
pp. 851-856
Author(s):  
Hyun Jin Jeong ◽  
Jae Woo Lee ◽  
Sug Whan Kim ◽  
A Ram Kang
Keyword(s):  
High Resolution ◽  
Mean Value ◽  
Solar Neighborhood ◽  
High Resolution Spectroscopy ◽  
Chemical Abundance ◽  
Dwarf Stars ◽  
Mean Values ◽  
Elemental Abundances ◽  
The Mean ◽  
Good Agreement

We present high-resolution chemical abundance results of 15 metal-poor dwarf stars in the solar neighborhood. Our metallicity measurements are in a good agreement with previous estimates. The stars under investigation have metallicities ranging from -1.6 to -2.8 with the mean value of [Fe/H] = -2.28. The mean values of elemental abundances are [O/Fe] = 0.73, [Na/Fe] = -0.16, [Ca/Fe] = 0.28, and [Ti/Fe] = 0.60. Our results are found to be consistent with those of giant metal-poor stars.

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