- ID:
- ivo://CDS.VizieR/J/A+A/533/A4
- Title:
- CoRoT photometry of three O-type stars
- Short Name:
- J/A+A/533/A4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The detection of pulsational frequencies in stellar photometry is required as input for asteroseismological modelling. The second short run (SRa02) of the CoRoT mission has provided photometric data of unprecedented quality and time-coverage for a number of O-type stars. We analyse the CoRoT data corresponding to three hot O-type stars, describing the properties of their light curves and we search for pulsational frequencies, which we then compare to theoretical model predictions. We determine the amplitude spectrum of the data, using the Lomb-Scargle and a multifrequency HMM-like technique. Frequencies are extracted by prewhitening, and their significance is evaluated under the assumption that the light curve is dominated by red noise. We search for harmonics, linear combinations and regular spacings among these frequencies. We use simulations with the same time sampling as the data as a powerful tool to judge the significance of our results. From the theoretical point of view, we use the MAD non-adiabatic pulsation code to determine the expected frequencies of excited modes. A substantial number of frequencies is listed, but none can be convincingly identified as being connected to pulsations. The amplitude spectrum is dominated by red noise. Theoretical modelling shows that all three O-type stars can have excited modes but the relation between the theoretical frequencies and the observed spectrum is not obvious. The dominant red noise component in the hot O-type stars studied here clearly points to a different origin than the pulsations seen in cooler O stars. The physical cause of this red noise is unclear, but we speculate on the possibility of sub-surface convection, granulation, or stellar wind inhomogeneities being responsible.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/597/A55
- Title:
- Corot photometry of TYC 455-791-1
- Short Name:
- J/A+A/597/A55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery and analysis of very narrow transits in the eccentric spectroscopic binary TYC 455-791-1=HSS 348 (IC 4756). We obtained high-precision CoRoT photometry over two long runs and multi-epoch high-resolution echelle spectroscopy and imaging with STELLA. Standard radial-velocity extraction, spectrum synthesis, Fourier analysis, and light-curve inversions are applied to the data. HSS 348 is found to be an eccentric (e=0.18) double-lined spectroscopic binary with a period of 12.47 d in which at least the primary component is a peculiar B star of the HgMn class. The orbital elements are such that the system undergoes a grazing eclipse with the primary in front but no secondary eclipse. The out-of-eclipse light variations show four nearly equidistant but unequal minima stable in shape and amplitude throughout our observations. Their individual photometric periods are all harmonics of the same fundamental period which happens to agree with the transit period to within the errors. We interpret the fundamental period to be the rotation period of at least one if not both stars due to surface inhomogeneities. Due to the non-zero eccentricity of the orbit the two components are rotating sub-synchronously. It appears that HSS 348 is not a member of the IC 4756 cluster but a background B8+B8.5 binary system. Its sharp eclipses every 12.47 days just mimic a small-body transit but are in reality the grazing eclipses of a B-star binary and thus a classical false positive. The system seems to be pre-main sequence with the primary possibly just arrived on the ZAMS. The light curve with four unequal minima can be explained with four cool spots of different size equidistantly positioned in longitude. Our data do not allow to uniquely assign the spots to either of the two stars.
- ID:
- ivo://CDS.VizieR/J/A+A/506/303
- Title:
- CoRoT-7 radial velocities
- Short Name:
- J/A+A/506/303
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on an intensive observational campaign carried out with HARPS at the 3.6m telescope at La Silla on the star CoRoT-7. Additional simultaneous photometric measurements carried out with the Euler Swiss telescope have demonstrated that the observed radial velocity variations are dominated by rotational modulation from cool spots on the stellar surface. Several approaches were used to extract the radial velocity signal of the planet(s) from the stellar activity signal.
- ID:
- ivo://CDS.VizieR/J/A+A/603/A43
- Title:
- CoRoT-9 radial velocity curve
- Short Name:
- J/A+A/603/A43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CoRoT-9b is one of the rare long-period (P=95.3days) transiting giant planets with a measured mass known to date. We present a new analysis of the CoRoT-9 system based on five years of radial-velocity (RV) monitoring with HARPS and three new space-based transits observed with CoRoT and Spitzer. Combining our new data with already published measurements we redetermine the CoRoT-9 system parameters and find good agreement with the published values. We uncover a higher significance for the small but non-zero eccentricity of CoRoT-9b (e=0.133^+0.042^_-0.037_) and find no evidence for additional planets in the system. We use simulations of planet-planet scattering to show that the eccentricity of CoRoT-9b may have been generated by an instability in which a ~50M_{earth}_ planet was ejected from the system. This scattering would not have produced a spin-orbit misalignment, so we predict that the CoRoT-9b orbit should lie within a few degrees of the initial plane of the protoplanetary disk. As a consequence, any significant stellar obliquity would indicate that the disk was primordially tilted.
- ID:
- ivo://CDS.VizieR/J/A+A/564/A119
- Title:
- CoRoT red giants abundances
- Short Name:
- J/A+A/564/A119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A precise characterisation of the red giants in the seismology fields of the CoRoT satellite is a prerequisite for further in-depth seismic modelling. High-resolution FEROS and HARPS spectra were obtained as part of the ground-based follow-up campaigns for 19 targets holding great asteroseismic potential. These data are used to accurately estimate in a self-consistent manner their fundamental parameters and the abundances of 16 chemical species. Some powerful probes of mixing are investigated (the Li and CNO abundances, as well as the carbon isotopic ratio in a few cases). The information provided by the spectroscopic and seismic data is combined to provide more accurate physical parameters and abundances. The stars in our sample follow the general trends between various abundance ratios and the metallicity observed in stars of the Galactic disk. After allowance is made for the chemical evolution of the interstellar medium, the observational signature of internal mixing phenomena is revealed through the detection at the stellar surface of the products of the CN and, in the case of the most massive stars, NeNa cycles. Together with the asteroseismic constraints, these data will pave the way for a detailed theoretical investigation of the physical processes responsible for the transport of chemical elements in evolved, low- and intermediate-mass stars.
3956. CoRoT space mission. I.
- ID:
- ivo://CDS.VizieR/J/A+A/482/L17
- Title:
- CoRoT space mission. I.
- Short Name:
- J/A+A/482/L17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The pioneer space mission for photometric planet searches, CoRoT, steadily monitors about 12000 stars in each of its fields of view. Transit candidates can be detected early in the processing of the data and before the end of a run of observation. We report the detection of the first planet discovered by CoRoT and characterizing it with the help of follow-up observations.
3957. CoRoT transit catalogue
- ID:
- ivo://CDS.VizieR/J/A+A/619/A97
- Title:
- CoRoT transit catalogue
- Short Name:
- J/A+A/619/A97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The CoRoT space mission observed 163665 stars over 26 stellar fields in the faint star channel. The exoplanet teams detected a total of 4123 transit-like features in the 177454 light curves. We present the complete re-analysis of all these detections carried out with the same softwares so that to ensure their homogeneous analysis. Although the vetting process involves some human evaluation, it also involves a simple binary flag system over basic tests: detection significance, presence of a secondary, difference between odd and even depths, colour dependence, V-shape transit, and duration of the transit. We also gathered the information from the large accompanying ground-based programme carried out on the planet candidates and checked how useful the flag system could have been at the vetting stage of the candidates. From the initial list of transit-like features, we identified and separated 824 false alarms of various kind, 2269 eclipsing binaries among which 616 are contact binaries and 1653 are detached ones, 37 planets and brown dwarfs, and 557 planet candidates. We provide the catalogue of all these transit-like features, including false alarms. For the planet candidates, the catalogue gives not only their transit parameters but also the products of their light curve modelling: reduced radius, reduced semi-major axis, and impact parameter, together with a summary of the outcome of follow-up observations when carried out and their current status. For the detached eclipsing binaries, the catalogue provides, in addition to their transit parameters, a simple visual classification. Among the planet candidates whose nature remains unresolved, we estimate that eight (within an error of three) planets are still to be identified. After correcting for geometric and sensitivity biases, we derived planet and brown dwarf occurrences and confirm disagreements with Kepler estimates, as previously reported by other authors from the analysis of the first runs: small-size planets with orbital period less than ten days are underabundant by a factor of three in the CoRoT fields whereas giant planets are overabundant by a factor of two. These preliminary results would however deserve further investigations using the recently released CoRoT light curves that are corrected of the various instrumental effects and a homogeneous analysis of the stellar populations observed by the two missions.
- ID:
- ivo://CDS.VizieR/J/ApJ/813/96
- Title:
- CO ro-vibrational transitions
- Short Name:
- J/ApJ/813/96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present calculated rate coefficients for ro-vibrational transitions of CO in collisions with H atoms for a gas temperature range of 10K<=T<=3000K, based on the recent three-dimensional ab initio H-CO interaction potential of Song et al. (2013JPCA..117.7571S). Rate coefficients for ro-vibrational v=1,j=0-30->v'=0,j' transitions were obtained from scattering cross sections previously computed with the close-coupling (CC) method by Song et al. (2015JChPh.142t4303S). Combining these with the rate coefficients for vibrational v=1-5->v'<v quenching obtained with the infinite-order sudden approximation, we propose a new extrapolation scheme that yields the rate coefficients for ro-vibrational v=2-5,j=0-30->v',j' de-excitation. Cross sections and rate coefficients for ro-vibrational v=2,j=0-30->v'=1,j' transitions calculated with the CC method confirm the effectiveness of this extrapolation scheme. Our calculated and extrapolated rates are very different from those that have been adopted in the modeling of many astrophysical environments. The current work provides the most comprehensive and accurate set of ro-vibrational de-excitation rate coefficients for the astrophysical modeling of the H-CO collision system. The application of the previously available and new data sets in astrophysical slab models shows that the line fluxes typically change by 20%-70% in high temperature environments (800K) with an H/H_2_ ratio of 1; larger changes occur for lower temperatures.
- ID:
- ivo://CDS.VizieR/J/AJ/154/142
- Title:
- Corrected photometry for GJ 1132 for all eclipses
- Short Name:
- J/AJ/154/142
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a search for additional bodies in the GJ 1132 system through two methods: photometric transits and transit timing variations of GJ 1132b. We collected 21 transit observations of GJ 1132b with the MEarth-South array. We obtained 100 near-continuous hours of observations with the Spitzer Space Telescope, including two transits of GJ 1132b and spanning 60% of the orbital phase of the maximum (6.9-day) period at which bodies coplanar with GJ 1132b would transit. We exclude transits of additional Mars-sized bodies, such as a second planet or a moon, with a confidence of 99.7%. We find that the planet-to-star radius ratio inferred from the MEarth and Spitzer light curves are discrepant at the 3.7{sigma} level, which we ascribe to the effects of starspots and faculae. When we combine the mass estimate of the star (obtained from its parallax and apparent K_s_ band magnitude) with the stellar density inferred from our high-cadence Spitzer light curve (assuming zero eccentricity), we measure the stellar radius of GJ 1132 to be 0.2105_-0.0085_^+0.0102^ R_{sun}_, and we refine the radius measurement of GJ 1132b to 1.130+/-0.056 R_{Earth}_. Combined with HARPS RV measurements, we determine the density of GJ 1132b to be 6.2+/-2.0 g/cm^3^. We refine the ephemeris of the system (improving the period determination by an order of magnitude) and find no evidence for transit timing variations, which would be expected if there was a second planet near an orbital resonance with GJ 1132b.
- ID:
- ivo://CDS.VizieR/J/other/Ser/182.35
- Title:
- Corrected proper motion for HIP stars
- Short Name:
- J/other/Ser/182.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- During the last century, there were many so-called independent latitude (IL) stations with the observations which were included into data of a few international organizations (like Bureau International de l'Heure - BIH, International Polar Motion Service - IPMS) and the Earth rotation programmes for determining the Earth Orientation Parameters - EOP. Because of this, nowadays, there are numerous astrometric ground-based observations (made over many decades) of some stars included in the Hipparcos Catalogue (ESA 1997, Cat. <A HREF="http://cdsarc.u-strasbg.fr/cgi-bin/Cat?I/239">I/239</A>). We used these latitude data for the inverse investigations - to improve the proper motions in declination µ<SUB>δ</SUB> of the mentioned Hipparcos stars. We determined the corrections Δµ<SUB>δ</SUB> and investigated agreement of our µ<SUB>δ</SUB> and those from the catalogues Hipparcos and new Hipparcos (van Leeuwen 2007, Cat. <A HREF="http://cdsarc.u-strasbg.fr/cgi-bin/Cat?I/311">I/311</A>). To do this we used the latitude variations of 7 stations (Belgrade, Blagoveschtschensk, Irkutsk, Poltava, Pulkovo, Warsaw and Mizusawa), covering different intervals in the period 1904.7-1992.0, obtained with 6 visual and 1 floating zenith telescopes (Mizusawa). On the other hand, with regard that about two decades have elapsed since the Hipparcos ESA mission observations (the epoch of Hipparcos catalogue is 1991.25), the error of apparent places of Hipparcos stars has increased by nearly 20mas because of proper motion errors. Also, the mission lasted less than four years which was not enough for a sufficient accuracy of proper motions of some stars (such as double or multiple ones). Our method of calculation, and the calculated µ<SUB>δ</SUB> for the common IL/Hipparcos stars are presented here. We constructed an IL catalogue of 1200 stars: there are 707 stars in the first part (with at least 20 years of IL observations) and 493 stars in the second one (less than 20 years). In the case of µ<SUB>δ</SUB> of IL stars observed at some stations (Blagoveschtschensk, Irkutsk, Mizusawa, Poltava and Pulkovo) we find the formal errors less than the corresponding Hipparcos ones and for some of them (stations Blagoveschtschensk and Irkutsk) even less than the new Hipparcos ones.