Multi-object spectroscopy of stars in the CoRoT fields

Sebastian, Daniel; Guenther, E. W.; Schaffenroth, V.; Gandolfi, D.; Geier, S.; Heber, U.; Deleuil, M.; Moutou, C.

doi:10.1051/0004-6361/201118032

Cited by 38 publications

(49 citation statements)

References 33 publications

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“…In Table 3 we give the spectral types of F, G, K, and M-stars in these fields, and in Paper I (Sebastian et al 2012) the spectral types of all O, B, and A-stars. For completeness we list in Cols.…”

Section: Resultsmentioning

confidence: 99%

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Multi-object spectroscopy of stars in the CoRoT fields

Guenther¹,

Sebastian²,

Deleuil³

et al. 2012

A&A

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Context. With now more than 20 exoplanets discovered by CoRoT, it has often been considered strange that so many of them are orbiting F-stars, and so few of them K-or M-stars. Up to now, studies of the relation between the frequency of extrasolar planets and the spectral types, or masses of their host stars has been the realm of radial velocity surveys. Although transit search programs are mostly sensitive to short-period planets, they are ideal for verifying these results. This is because transit search programs have different selection biases than radial velocity surveys. To determine the frequency of planets as a function of stellar mass, we also have to characterize the sample of stars that was observed. Aims. We study the stellar content of the CoRoT-fields IRa01, LRa01 (=LRa06), and LRa02 by determining the spectral types of 11 466 stars. Nine planet-host stars have already been identified in these fields. Determing the spectral types of thousands of stars of which CoRoT obtained high-precision light-curves also makes a wide variety of other research projects possible. Methods. We used spectra obtained with the multi-object spectrograph AAOmega and derived the spectral types by using template spectra with well-known parameters. Results. We find that 34.8 ± 0.7% of the stars observed by CoRoT in these fields are F-dwarfs, 15.1 ± 0.5% G-dwarfs, and 5.0 ± 0.3% K-dwarfs. We conclude that the apparent lack of exoplanets of K-and M-stars is explained by the relatively small number of these stars in the observed sample. We also show that the apparently large number of planets orbiting F-stars is similarly explained by the large number of such stars in these fields. Given the number of F-stars, we would have expected to find even more F-stars with planets. Our study also shows that the difference between the sample of stars that CoRoT observes and a sample of randomly selected stars is relatively small, and that the yield of CoRoT specifically is the detection one hot Jupiter amongst 2100 ± 700 stars. Conclusions. We conclude that transit search programs can be used to study the relation between the frequency of planets and the mass of the host stars, and that the results obtained so far generally agree with those of radial velocity programs.

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Section: Resultsmentioning

confidence: 99%

“…In Paper I (Sebastian et al 2012), we gave a list of stars with spectral types O, B, and A in IRa01, LRa01, and LRa02. Here we analyze stars with spectral types F, G, K, and M. The LRa01-field was recently re-observed by CoRoT, the field is called LRa06 in the new observations.…”

Section: Concept Of the Surveymentioning

confidence: 99%

Multi-object spectroscopy of stars in the CoRoT fields

Guenther¹,

Sebastian²,

Deleuil³

et al. 2012

A&A

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“…(MacConnell 1988;Stephenson 1989Stephenson , 1996Alksnis et al 2001;Chen & Yang 2012;Zacharias et al 2013). We also cross-checked with previous studies using CoRoT data (Lebzelter 2011;Sebastian et al 2012;Guenther et al 2012;Sarro et al 2013;De Medeiros et al 2013). Finally, we also searched in many other databases incorporated in the International Virtual Observatory Alliance 3 , using the Tool for OPerations on Catalogues And Tables (TOPCAT 4 - Taylor 2005).…”

Section: Notesmentioning

confidence: 99%

The variability behaviour of CoRoT M-giant stars

Lopes

Neves

Leão

et al. 2015

A&A

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Context. For six years the Convection, Rotation, and planetary Transits (CoRoT) space mission has been acquiring photometric data from more than 100 000 point sources towards and directly opposite the inner and outer regions of the Galaxy. The high temporal resolution of the CoRoT data, combined with the wide time span of the observations, enabled the study of short-and long-time variations in unprecedented detail. Aims. The aim of this work is to study the variability and evolutionary behaviour of M-giant stars using CoRot data. Methods. From the initial sample of 2534 stars classified as M giants in the CoRoT databases, we selected 1428 targets that exhibit well defined variability, by visual inspection. Then, we defined three catalogues: C1 -stars with T eff < 4200 K and LCs displaying semi-sinusoidal signatures; C2 -rotating variable candidates with T eff > 4200 K; C3 -long-period variable candidates (with LCs showing a variability period up to the total time span of the observations). The variability period and amplitude of C1 stars were computed using Lomb-Scargle and harmonic fit methods. Finally, we used C1 and C3 stars to study the variability behaviour of M-giant stars. Results. The trends found in the V − I vs. J − K colour-colour diagram are in agreement with standard empirical calibrations for M giants. The sources located towards the inner regions of the Galaxy are distributed throughout the diagram, while the majority of the stars towards the outer regions of the Galaxy are spread between the calibrations of M giants and the predicted position for carbon stars. The stars classified as supergiants follow a different sequence from the one found for giant stars. We also performed a Kolmogorov-Smirnov (KS) test of the period and amplitude of stars towards the inner and outer regions of the Galaxy. We obtained a low probability that the two samples came from the same parent distribution. The observed behaviour of the period-amplitude and period-effective temperature (T eff ) diagrams are, in general, in agreement with those found for Kepler sources and ground based photometry, with pulsation being the dominant cause responsible for the observed modulation. We also conclude that short-time variations on M-giant stars do not exist or are very rare, and the few cases we found are possibly related to biases or background stars.

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“…We refer the reader to Sebastian et al (2012) and Guenther et al (2012) for details on the instrument set-up, observing strategy, and data reduction. By comparing the AAOmega spectrum with a grid of suitable templates, Guenther et al (2012) classified CoRoT 102749568 as an F1 IV star.…”

Section: Spectroscopymentioning

confidence: 99%

CoRoT 102749568: mode identification in aδScuti star based on regular spacings

Paparó

Bognár

Benkő

et al. 2013

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Context. The high accuracy of space data increased the number of the periodicities determined for pulsating variable stars, but the mode identification is still a critical point in the non-asymptotic regime. Aims. We use regularities in frequency spacings for identifying the pulsation modes of the recently discovered δ Sct star ID 102749568. Methods. In addition to analysing CoRoT light curves (15 252 datapoints spanning 131 days), we obtained and analysed both spectroscopic and extended multi-colour photometric data. We applied standard tools (MUFRAN, Period04, SigSpec, and FAMIAS) for time-series analysis. Results. A satisfactory light-curve fit was obtaining by means of 52 independent modes and 15 combination terms. The frequency spacing revealed distinct peaks around large (25.55-31.43 μHz), intermediate (9.80, 7.66 μHz), and low (2.35 μHz) separations. We directly identified 9 modes, and the l and n values of other three modes were extrapolated. The combined application of spectroscopy, multi-colour photometry, and modelling yielded the precise physical parameters and confirmed the observational mode identification. The large separation constrained the log g and related quantities. The dominant mode is the radial first overtone.

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Multi-object spectroscopy of stars in the CoRoT fields

Cited by 38 publications

References 33 publications

Multi-object spectroscopy of stars in the CoRoT fields

Multi-object spectroscopy of stars in the CoRoT fields

The variability behaviour of CoRoT M-giant stars

CoRoT 102749568: mode identification in aδScuti star based on regular spacings

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