0000000001180780
AUTHOR
E. Poretti
The GAPS Programme with HARPS-N at TNG XV. A substellar companion around a K giant star identified with quasi-simultaneous HARPS-N and GIANO measurements
Context. Identification of planetary companions of giant stars is made difficult because of the astrophysical noise, that may produce radial velocity (RV) variations similar to those induced by a companion. On the other hand any stellar signal is wavelength dependent, while signals due to a companion are achromatic. Aims. Our goal is to determine the origin of the Doppler periodic variations observed in the thick disk K giant star TYC 4282-605-1 by HARPS-N at the Telescopio Nazionale Galileo (TNG) and verify if they can be due to the presence of a substellar companion. Methods. Several methods have been used to exclude the stellar origin of the observed signal including detailed analysis of…
The B0.5IVe CoRoT target HD 49 330. II. Spectroscopic ground-based observations
Context. We present spectroscopic ground-based observations of the early Be star HD 49330 obtained simultaneously with the CoRoT-LRA1 run just before the burst observed in the CoRoT data. Aims. Ground-based spectroscopic observations of the early Be star HD 49330 obtained during the precursor phase and just before the start of an outburst allow us to disantangle stellar and circumstellar contributions and identify modes of stellar pulsations in this rapidly rotating star. Methods. Time series analysis (TSA) is performed on photospheric line profiles of He i and Si iii by means of the least squares method. Results. We find two main frequencies f1 = 11.86 c d^−1 and f2 = 16.89 c d^−1 which ca…
Pulsations in the late-type Be star HD 50 209 detected by CoRoT
The presence of pulsations in late-type Be stars is still a matter of controversy. It constitutes an important issue to establish the relationship between non-radial pulsations and the mass-loss mechanism in Be stars. To contribute to this discussion, we analyse the photometric time series of the B8IVe star HD 50209 observed by the CoRoT mission in the seismology field. We use standard Fourier techniques and linear and non-linear least squares fitting methods to analyse the CoRoT light curve. In addition, we applied detailed modelling of high-resolution spectra to obtain the fundamental physical parameters of the star. We have found four frequencies which correspond to gravity modes with az…
The pulsations of the B5IVe star HD 181 231 observed with CoRoT and ground-based spectroscopy
Context. HD 181231 is a B5IVe star, which has been observed with the CoRoT satellite during ∼5 consecutive months and simultaneously from the ground in spectroscopy and spectropolarimetry. Aims. By analysing these data, we aim to detect and characterize as many pulsation frequencies as possible, to search for the presence of beating effects possibly at the origin of the Be phenomenon. Our results will also pr ovide a basis for seismic modelling. Methods. The fundamental parameters of the star are determined from spectral fitting and from the study of the circumstellar emission. The CoRoT photometric data and ground-based spectroscopy are analysed using several Fourier Techniques: CLEAN-NG,P…
Stochastic gravito-inertial modes discovered by CoRoT in the hot Be star HD 51452
Context.Be stars are rapidly rotating stars with a circumstellar decretion disk. They usually undergo pressure and/or gravity pulsation modes excited by the κ-mechanism, i.e. an effect of the opacity of iron-peak elements in the envelope of the star. In the Milky Way,p-modes are observed in stars that are hotter than or equal to the B3 spectral type, while g-modes are observed at the B2 spectral type and cooler.Aims.We observed a B0IVe star, HD 51452,with the high-precision, high-cadence photometric CoRoT satellite and high-resolution, ground-based HARPS and SOPHIE spectrographs to study its pulsations in great detail. We also used the lower resolution spectra available in the BeSS atabase.…
Pulsations of HD 181231
HD181231 is a B5IVe star, which has been observed with the CoRoT satellite during ~5 consecutive months and simultaneously from the ground in spectroscopy and spectropolarimetry. By analysing these data, we aim to detect and characterize as many pulsation frequencies as possible, to search for the presence of beating effects possibly at the origin of the Be phenomenon. Our results will also provide a basis for seismic modelling. The fundamental parameters of the star are determined from spectral fitting and from the study of the circumstellar emission. The CoRoT photometric data and ground-based spectroscopy are analysed using several Fourier techniques: Clean-ng, Pasper, and Tisaft, as wel…
KELT-9b radial velocity curve
In the framework of the GAPS project, we observed the planet-hosting star KELT-9 (A-type star, vsini~110km/s) with the HARPS-N spectrograph at the Telescopio Nazionale Galileo. In this work we analyse the spectra and the extracted radial velocities, to constrain the physical parameters of the system and to detect the planetary atmosphere of KELT-9b. We extracted from the high-resolution optical spectra the mean stellar line profiles with an analysis based on the Least Square Deconvolution technique. Then, we computed the stellar radial velocities with a method optimized for fast rotators, by fitting the mean stellar line profile with a purely rotational profile instead of using a Gaussian f…
ESPRESSO radial velocities of HE0107-5240
The vast majority of the known stars of ultra low metallicity ([Fe/H]<-4.5) are known to be enhanced in carbon, and belong to the 'low-carbon band' (A(C)=log(C/H)+12~7.6). It is generally, although not universally, accepted that this peculiar chemical composition reflects the chemical composition of the gas cloud out of which these stars were formed. The first ultra-metal-poor star discovered, HE 0107-5240, is also enhanced in carbon and belongs to the 'low-carbon band'. It has recently been claimed to be a long-period binary, based on radial velocity measurements. It has also been claimed that this binarity may explain its peculiar composition as being due to mass transfer to a former AGB …