- ID:
- ivo://CDS.VizieR/J/MNRAS/399/432
- Title:
- Fitted UBV magnitude for MS stars
- Short Name:
- J/MNRAS/399/432
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We fit the colour-magnitude diagrams of stars between the zero-age main-sequence and terminal-age main sequence in young clusters and associations. The ages we derive are a factor of 1.5-2 longer than the commonly used ages for these regions, which are derived from the positions of pre-main-sequence stars in colour-magnitude diagrams. From an examination of the uncertainties in the main-sequence and pre-main-sequence models, we conclude that the longer age scale is probably the correct one, which implies that we must revise upwards the commonly used ages for young clusters and associations. Such a revision would explain the discrepancy between the observational lifetimes of protoplanetary discs and theoretical calculations of the time to form planets. It would also explain the absence of clusters with ages between 5 and 30Myr.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/506/95
- Title:
- Fourier analysis of HD 49330 CoRoT light curve
- Short Name:
- J/A+A/506/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Be stars undergo outbursts producing a circumstellar disk from the ejected material. The beating of non-radial pulsations has been put forward as a possible mechanism of ejection. We analyze the pulsational behavior of the early B0.5IVe star HD 49330 observed during the first CoRoT long run towards the Galactical anticenter (LRA1). This Be star is located close to the lower edge of the {beta} Cephei instability strip in the HR diagram and showed a 0.03mag outburst during the CoRoT observations. It is thus an ideal case for testing the aforementioned hypothesis.
- ID:
- ivo://CDS.VizieR/J/A+A/506/471
- Title:
- Frequency analysis of CoRoT B stars
- Short Name:
- J/A+A/506/471
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We search for new variable B-type pulsators in the CoRoT data assembled primarily for planet detection, as part of CoRoT's Additional Programme. We aim to explore the properties of newly discovered B-type pulsators from the uninterrupted CoRoT spacebased photometry and to compare them with those of known members of the beta Cep and slowly pulsating B star (SPB) classes. We developed automated data analysis tools which include algorithms for jump correction, light curve detrending, frequency detection, frequency combination search and frequency and period spacing search. Besides numerous new classical slowly pulsating B stars, we find evidence for a new class of low-amplitude B-type pulsators between the SPB and delta Sct instability strips, with a very broad range of frequencies and low amplitudes, as well as several slowly pulsating B stars with residual excess power at frequencies typically a factor three above their expected g-mode frequencies. The frequency data we obtained for numerous new B-type pulsators represent an appropriate starting point for further theoretical analyses of these stars, once their effective temperature, gravity, rotation velocity and abundances will be derived spectroscopically in the framework of an ongoing FLAMES survey at VLT.
- ID:
- ivo://CDS.VizieR/J/A+A/506/111
- Title:
- Frequency analysis of HD 180642 (V1449 Aql)
- Short Name:
- J/A+A/506/111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the CoRoT light curve of the beta Cep star HD 180642, assembled during the first long run of the space mission, as well as archival single-band photometry. Our goal is to analyse the detailed behaviour present in the light curve and interpret it in terms of excited-mode frequencies. After describing the noise properties in detail, we use various time series analyses and fitting techniques to model the CoRoT light curve, for various physical assumptions. We apply statistical goodness-of-fit criteria that allow us to select the most appropriate physical model fit to the data. We conclude that the light-curve model based on nonlinear resonant frequency and phase locking provides the best representation of the data. Interpretation of the residuals is dependent on the chosen physical model used to prewhiten the data. Our observational results constitute a fruitful starting point for detailed seismic stellar modelling of this large-amplitude and evolved beta Cep star.
- ID:
- ivo://CDS.VizieR/J/A+A/440/305
- Title:
- Fundamental parameters of fast-rotating B stars
- Short Name:
- J/A+A/440/305
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we develop a calculation code to account for the effects carried by fast rotation on the observed spectra of early-type stars. Stars are assumed to be in rigid rotation, and the grid of plane-parallel model atmospheres used to represent the gravitational darkening are calculated by means of a non-LTE approach. Attention is paid to the relation between the apparent and parent non-rotating counterpart stellar fundamental parameters and apparent, and true Vsini parameters as a function of the rotation rate Omega/Omega_c_, stellar mass, and inclination angle. It is shown that omitting of gravitational darkening in the analysis of chemical abundances of CNO elements can produce systematic overestimation or underestimation, depending on the lines used, rotational rate, and inclination angle.
- ID:
- ivo://CDS.VizieR/J/MNRAS/487/2771
- Title:
- Gaia-DR2 distance to the W3 Complex
- Short Name:
- J/MNRAS/487/2771
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Perseus Arm is the closest Galactic spiral arm from the Sun, offering an excellent opportunity to study in detail its stellar population. However, its distance has been controversial with discrepancies by a factor of two. Kinematic distances are in the range 3.9-4.2kpc as compared to 1.9-2.3kpc from spectrophotometric and trigonometric parallaxes, reinforcing previous claims that this arm exhibits peculiar velocities. We used the astrometric information of a sample of 31 OB stars from the star-forming W3Complex to identify another 37 W3 members and to derive its distance from their Gaia-DR2 parallaxes with improved accuracy. The Gaia-DR2 distance to the W3Complex, 2.14^+0.08^_-0.07_kpc, coincides with the previous stellar distances of ~2kpc. The Gaia-DR2 parallaxes tentatively show differential distances for different parts of the W3 Complex: W3 Main, located to the NE direction, is at 2.30^+0.19^_-0.16_kpc, the W3 Cluster (IC1795), in the central region of the complex, is at 2.17^+0.12^_-0.11_kpc, and W3(OH) is at 2.00^+0.29^_-0.23_kpc to the SW direction. The W3 Cluster is the oldest region, indicating that it triggered the formation of the other two star-forming regions located at the edges of an expanding shell around the cluster.
- ID:
- ivo://CDS.VizieR/J/A+A/585/A141
- Title:
- Galactic center early-type stars catalog
- Short Name:
- J/A+A/585/A141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It is still unclear whether the Sagittarius spiral arm is a major spiral arm in the Galaxy or whether it just outlines a region of enhanced star formation because of the local compression of gas. The best way to separate these scenarios out is to study the kinematics across the arm to determine the velocity perturbation it induces. A survey of early-type stars in the direction of the Galactic center is performed covering an area of 100 sq. deg with the aim of identifying candidates for a radial velocity study. Objective prism plates were obtained with the 4{deg} prism on the ESO Schmidt telescope using IIaO, 4415, and IIIaJ emulsions. The plates were digitized and more than 100k spectra were extracted down to a limiting magnitude of B=15m. The spectra were cross-correlated with a template with Balmer lines, which yielded a candidate list of 12675 early-type stars. Magnitudes and equivalent widths of strong lines were calculated from the spectra, which allowed us to estimate the individual extinctions and distances for 11075 stars.
- ID:
- ivo://CDS.VizieR/J/ApJS/144/21
- Title:
- Galaxy and Magellanic Clouds OB and WR stars
- Short Name:
- J/ApJS/144/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have generated a set of far-ultraviolet stellar libraries using spectra of OB and Wolf-Rayet stars in the Galaxy and the Large and Small Magellanic Cloud. The spectra were collected with the Far Ultraviolet Spectroscopic Explorer and cover a wavelength range from 1003.1 to 1182.7{AA} at a resolution of 0.127{AA}. The libraries extend from the earliest O to late-O and early-B stars for the Magellanic Cloud and Galactic libraries, respectively.
- ID:
- ivo://CDS.VizieR/J/ApJ/734/13
- Title:
- GALEX ultraviolet halos around bright stars
- Short Name:
- J/ApJ/734/13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have discovered ultraviolet (UV) halos extending as far as 5{deg} around four (of six) bright UV stars using data from the Galaxy Evolution Explorer satellite. These halos are due to scattering of the starlight from nearby thin, foreground dust clouds. We have placed limits of 0.58+/-0.12 and 0.72+/-0.06 on the phase function asymmetry factor (g) in the FUV (1521{AA}) and NUV (2320{AA}) bands, respectively. We suggest that these halos are a common feature around bright stars and may be used to explore the scattering function of interstellar grains at small angles.
- ID:
- ivo://CDS.VizieR/J/A+A/449/305
- Title:
- Geneva photometry time series of HD 203664
- Short Name:
- J/A+A/449/305
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We made a seismic study of the young massive beta Cephei star HD 203664 with the goal of constraining its interior structure. Our study is based on a time series of 328 new Geneva 7-colour photometric data of the star spread over 496.8 days. The data confirm the frequency of the dominant mode of the star, which we refined to f_1_=6.02885c/d. The mode has a large amplitude of 37mmag in V and is unambiguously identified as a dipole mode (l=2) from its amplitude ratios and non-adiabatic computations. Besides f_1_, we discovered two additional new frequencies in the star with amplitudes above 4{sigma}: f_2_=6.82902c/d and f_3_=4.81543c/d, or one of their daily aliases. The amplitudes of these two modes are only between 3 and 4mmag, which explains why they were not detected before. Their amplitude ratios are too uncertain for mode identification. We show that the observed oscillation spectrum of HD 203664 is compatible with standard stellar models but that we have insufficient information for asteroseismic inferences. Among the large-amplitude beta Cephei stars, HD 203664 stands out as the only one rotating at a significant fraction of its critical rotation velocity (~40%).
