- ID:
- ivo://CDS.VizieR/J/A+A/567/A57
- Title:
- HD 161306 H{alpha} and HeI spectra
- Short Name:
- J/A+A/567/A57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The spectrum of the Be star HD 161306 is shown to vary periodically with a period of ~100-days. The radial velocity of the HeI 6678{AA} emission peak varying in antiphase to the radial velocity of the H{alpha} emission wings component suggests that the star is a binary similar to {phi} Per, 59 Cyg, or FY CMa, i.e. a radiatively interacting Be binary - a rare case among Be stars. This type of object is also called a {phi} Per-type binary or Be + sdO binaries. The range of radial-velocity variations of the strong emission peak in the helium line observed in HD 161306 is about 180km/s, similar to what is observed for these systems. We therefore conclude that HD 161306 may represent another case of a Be star with a hot subdwarf companion.
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- ID:
- ivo://CDS.VizieR/J/A+A/542/L32
- Title:
- HD 202850 HeI and SiII spectra
- Short Name:
- J/A+A/542/L32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photospheric lines of B-type supergiants show variability in their profile shapes. In addition, their widths are much wider than can be accounted for purely by stellar rotation. This excess broadening is often referred to as macroturbulence. Both effects have been linked to stellar oscillations, but B supergiants have not been systematically searched yet for the presence of especially short-term variability caused by stellar pulsations. We have started an observational campaign to investigate the line profile variability of photospheric lines in a sample of Galactic B supergiants. These observations aim to improve our understanding of the physical effects acting in the atmospheres of evolved massive stars.
- ID:
- ivo://CDS.VizieR/J/A+A/506/85
- Title:
- HD 50844 observed by CoRoT
- Short Name:
- J/A+A/506/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This work presents the results obtained on HD 50844, the only delta Sct star observed in the CoRoT Initial Run (57.6d). The aim of these CoRoT observations was to investigate and characterize for the first time the pulsational behaviour of a delta Sct star, when observed at a level of precision and with a much better duty cycle than from the ground. The 140016 datapoints were analysed using independent approaches (SigSpec software and different iterative sine-wave fittings) and several checks performed (splitting of the timeseries in different subsets, investigation of the residual light curves and spectra. A level of 10^-5^mag was reached in the amplitude spectra of the CoRoT timeseries. The space monitoring was complemented by ground-based high-resolution spectroscopy, which allowed the mode identification of 30 terms. The frequency analysis of the CoRoT timeseries revealed hundreds of terms in the frequency range 0-30d^-1^. All the cross-checks confirmed this new result. The initial guess that delta Sct stars have a very rich frequency content is confirmed. The spectroscopic mode identification gives theoretical support since very high-degree modes (up to ell=14) are identified. We also prove that cancellation effects are not sufficient in removing the flux variations associated to these modes at the noise level of the CoRoT measurements. The ground-based observations indicate that HD 50844 is an evolved star that is slightly underabundant in heavy elements, located on the Terminal Age Main Sequence. Probably due to this unfavourable evolutionary status, no clear regular distribution is observed in the frequency set. The predominant term f1=6.92d^-1^ has been identified as the fundamental radial mode combining ground-based photometric and spectroscopic data. The CoRoT scientific programme contains other delta Sct stars, with different evolutionary statuses. The very rich and dense frequency spectrum discovered in the light curve of HD 50844 is the starting point for future investigations.
- ID:
- ivo://CDS.VizieR/J/A+A/503/945
- Title:
- HD 145788, 21 Peg and pi Cet chemical analysis
- Short Name:
- J/A+A/503/945
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Modern spectroscopy of early-type stars often aims at studying complex physical phenomena such as stellar pulsation, the peculiarity of the composition of the photosphere, chemical stratification, the presence of a magnetic field, and its interplay with the stellar atmosphere and the circumstellar environment. Comparatively less attention is paid to identifying and studying the "normal" A- and B-type stars and testing how the basic atomic parameters and standard spectral analysis allow one to fit the observations. By contrast, this kind of study is paramount for eventually allowing one to correctly quantify the impact of the various physical processes that occur inside the atmospheres of A- and B-type stars. We wish to establish whether the chemical composition of the solar photosphere can be regarded as a reference for early A- and late B-type stars.
- ID:
- ivo://CDS.VizieR/J/A+A/615/A19
- Title:
- HD54662 radial velocities and X-ray light curves
- Short Name:
- J/A+A/615/A19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- HD 54662 is an O-type binary star belonging to the CMa OB1 association. Due to its long-period orbit, this system is an interesting target to test the adiabatic wind shock model. The goal of this study is to improve our knowledge of the orbital and stellar parameters of HD 54662 and to analyze its X-ray emission to test the theoretical scaling of X-ray emission with orbital separation for adiabatic wind shocks. A spectral disentangling code is applied to a set of optical spectra to determine the radial velocities, as well as the individual spectra of the primary and secondary stars. The orbital solution of the system is established and the reconstructed individual spectra are analyzed by means of the CMFGEN model atmosphere code. Two X-ray spectra are fitted using a Markov Chain Monte Carlo algorithm and are compared to the emission expected from adiabatic shocks. We determine an orbital period of 2103.4 days, a surprisingly low orbital eccentricity of 0.11, and a mass ratio m_2/m_1 of 0.84. Combined with the orbital inclination inferred in a previous astrometric study, we obtain surprisingly low masses of 9.7 and 8.2M_{sun}_. From the disentangled primary and secondary spectra, we infer O6.5 spectral types for both stars with the primary being about two times brighter than the secondary. The softness of the X-ray spectra for the two observations, the very small variation of best-fitting spectral parameters and the comparison of the X-ray-to- bolometric luminosity ratio with the canonical value for O-type stars allow us to conclude that the X-ray emission from the wind interaction region is quite small and that the observed emission is rather dominated by the intrinsic emission from the stars. Computing the peculiar radial and intrinsic emission from the stars. Computing the peculiar radial and tangential velocities, we cannot confirm the runaway status previously attributed to HD 54662. We find no X-ray emission associated with the bow shock detected in the infrared. The lack of hard X-ray emission from the wind-shock region suggests that the mass-loss rates are lower than expected and/or that the pre-shock wind velocities are much lower than the terminal wind velocities. The bow shock associated with HD 54662 possibly corresponds to a wind-blown arc created by the interaction of the stellar winds with the ionized gas of the CMa OB1 association rather than by a large differential velocity between the binary and the surrounding interstellar medium.
- ID:
- ivo://CDS.VizieR/J/A+A/552/A68
- Title:
- HD 261711 reduced spectrum
- Short Name:
- J/A+A/552/A68
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The internal structure of pre-main-sequence (PMS) stars is poorly constrained at present. This could change significantly through high-quality asteroseismological observations of a sample of such stars. We concentrate on an asteroseismological study of HD 261711, a rather hot delta Scuti-type pulsating member of the young open cluster NGC 2264 located at the blue border of the instability region. HD 261711 was discovered to be a pre-main sequence delta Scuti star using the time series photometry obtained by the MOST satellite in 2006. High-precision, time-series photometry of HD 261711 was obtained by the MOST and CoRoT satellites in four separate new observing runs that are put into context with the star's fundamental atmospheric parameters obtained from spectroscopy. Frequency Analysis was performed using Period04. The spectral analysis was performed using equivalent widths and spectral synthesis. With the new MOST data set from 2011/12 and the two CoRoT light curves from 2008 and 2011/12, the delta Scuti variability was confirmed and regular groups of frequencies were discovered. The two pulsation frequencies identified in the data from the first MOST observing run in 2006 are confirmed and 23 new delta Scuti-type frequencies were discovered using the CoRoT data. Weighted average frequencies for each group were determined and are related to l=0 and l=1 p-modes. Evidence for amplitude modulation of the frequencies in two groups is seen. The effective temperature (Teff) was derived to be 8600+/-200K, logg is 4.1+/-0.2, and the projected rotational velocity (vsini) is 53+/-1km/s. Using our Teff value and the radius of 1.8+/-0.5R_{sun}_ derived from spectral energy distribution (SED) fitting, we get a luminosity logL/L_{sun}_ of 1.20+/-0.14 which agrees well to the seismologically determined values of 1.65 Rsun and, hence, a logL/L_{sun}_ of 1.13. The radial velocity of 14+/-2km/s we derived for HD 261711, confirms the star's membership to NGC 2264. Our asteroseismic models suggest that HD 261711 is a delta Scuti-type star close to the zero-age main sequence (ZAMS) with a mass of 1.8 to 1.9M_{sun}_. With an age of about 10 million years derived from asteroseismology, the star is either a young ZAMS star or a late PMS star just before the onset of hydrogen-core burning. The observed splittings about the l=0 and 1 parent modes may be an artifact of the Fourier derived spectrum of frequencies with varying amplitudes.
- ID:
- ivo://CDS.VizieR/J/A+A/548/A13
- Title:
- HD 50138 short-term variability
- Short Name:
- J/A+A/548/A13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- HD 50138 presents the B[e] phenomenon, but its nature is not clear yet. This star is known to present spectral variations, which have been associated with outbursts and shell phases. We analyze the line profile variability of HD 50138 and its possible origin, which provide possible hints to its evolutionary stage, so far said to be close to the end of (or slightly beyond) the main sequence.
- ID:
- ivo://CDS.VizieR/J/A+A/625/A79
- Title:
- HD199178 1994-2017 spectra
- Short Name:
- J/A+A/625/A79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-resolution spectral observations during 1994-2017 are analysed in order to reveal long- and short-term changes in the spot activity of the FK Comae-type subgiant HD 199178. Most of the observations were collected with the Nordic Optical Telescope high resolution spectrographs SOFIN (34 sets) and FIES (6 sets). One set was obtained at the NAO (Rozhen), Bulgaria. The spectra were used to calculate Doppler imaging temperature maps for HD 199178 covering the years 1994-2017.
- ID:
- ivo://CDS.VizieR/J/AZh/88/380
- Title:
- HD 192163 spectroscopic study
- Short Name:
- J/AZh/88/380
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used 46 high-resolution echelle spectra of the Wolf-Rayet star HD 192163 taken in 2005-2009 at the Cassegrain focus of the 2-m Zeiss-2000 telescope of the Shamakha Astrophysical Observatory to study profiles of the five strongest emission lines (HeII 4859, HeII 5411, CIV 5808, HeI 5875, (HeII+Halpha) 6560). We also obtained four echelle spectrograms of the Wolf-Rayet star HD 191765 for a comparative study of the NaI 5890 (D2) and NaI 5896 (D1) interstellar absorption lines. The echelle spectrograms were reduced using the DECH20 code. We determined the equivalent widths, radial velocities, central intensities, and half-widths of the emission lines. We We also studied the NaI 5890 (D2) and NaI 5896 (D1) interstellar absorption lines, which are important for understanding the nature of the nebula NGC 6888, whose origin is related to HD 192163.
- ID:
- ivo://CDS.VizieR/J/AJ/136/1557
- Title:
- HD 46703 spectroscopy and photometry
- Short Name:
- J/AJ/136/1557
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The metal-poor post-asymptotic giant branch (AGB) star HD 46703 is shown to be a single-line spectroscopic binary with a period of 600-days, a high velocity of -94km/s, and an orbital eccentricity of 0.3. Light-curve studies show that it also pulsates with a period of 29-days. High-resolution, high signal-to-noise spectra were used for a new abundance study.
