Search

Start Over Subject spectroscopy
991. HD 189733b in transit light curve
ID:
ivo://CDS.VizieR/J/ApJ/791/55
Title:
HD 189733b in transit light curve
Short Name:
J/ApJ/791/55
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report near-infrared spectroscopy of the gas giant planet HD 189733b in transit. We used the Hubble Space Telescope Wide Field Camera 3 (HST WFC3) with its G141 grism covering 1.1 {mu}m to 1.7 {mu}m and spatially scanned the image across the detector at 2''/s. When smoothed to 75 nm bins, the local maxima of the transit depths in the 1.15 {mu}m and 1.4 {mu}m water vapor features are, respectively, 83+/-53 ppm and 200+/-47 ppm greater than the local minimum at 1.3 {mu}m. We compare the WFC3 spectrum with the composite transit spectrum of HD 189733b assembled by Pont et al., extending from 0.3 {mu}m to 24 {mu}m. Although the water vapor features in the WFC3 spectrum are compatible with the model of non-absorbing, Rayleigh-scattering dust in the planetary atmosphere, we also re-interpret the available data with a clear planetary atmosphere. In the latter interpretation, the slope of increasing transit depth with shorter wavelengths from the near infrared, through the visible, and into the ultraviolet is caused by unocculted star spots, with a smaller contribution of Rayleigh scattering by molecular hydrogen in the planet's atmosphere. At relevant pressures along the terminator, our model planetary atmosphere's temperature is ~700 K, which is below the condensation temperatures of sodium- and potassium-bearing molecules, causing the broad wings of the spectral lines of Na I and K I at 0.589 {mu}m and 0.769 {mu}m to be weak.
992. HD 164922 d HARPS-N time series
ID:
ivo://CDS.VizieR/J/A+A/639/A50
Title:
HD 164922 d HARPS-N time series
Short Name:
J/A+A/639/A50
Date:
21 Oct 2021
Publisher:
CDS
Description:
Observations of exoplanetary systems show that a wide variety of architectures are possible. Determining the rate of occurrence of Solar System analogs - with inner terrestrial planets and outer gas giants - is still an open question. In the framework of the Global Architecture of Planetary Systems (GAPS) project we collected more than 300 spectra with HARPS-N at the Telescopio Nazionale Galileo for the bright G9V star HD164922. This target is known to host one gas giant planet in a wide orbit (Pb~1200-days, semi-major axis ~2au) and a Neptune-mass planet with a period Pc~76-days. Our aim was to investigate the presence of additional low-mass companions in the inner region of the system. We compared the radial velocities (RV) and the activity indices derived from the HARPS-N time series to measure the rotation period of the star and used a Gaussian process regression to describe the behaviour of the stellar activity.We exploited this information in a combined model of planetary and stellar activity signals in an RV time-series composed of almost 700 high-precision RVs, both from HARPS-N and literature data. We performed a dynamical analysis to evaluate the stability of the system and the allowed regions for additional potential companions. We performed experiments of injection and recovery of additional planetary signals to gauge the sensitivity thresholds in minimum mass and orbital separation imposed by our data. Thanks to the high sensitivity of the HARPS-N dataset, we detect an additional inner super-Earth with an RV semi-amplitude of 1.3+/-0.2m/s and a minimum mass of m_d_sini=4+/-/1M_{Earth}_. It orbits HD164922 with a period of 12.4580.003 days. We disentangle the planetary signal from activity and measure a stellar rotation period of ~42 days. The dynamical analysis shows the long term stability of the orbits of the three-planet system and allows us to identify the permitted regions for additional planets in the semi-major axis ranges 0.18-0.21au and 0.6-1.4au. The latter partially includes the habitable zone of the system. We did not detect any planet in these regions, down to minimum detectable masses of 5 and 18M_{Earth}_, respectively. A larger region of allowed planets is expected beyond the orbit of planet b, where our sampling rules-out bodies with minimum mass >50MM_{Earth}. The planetary orbital parameters and the location of the snow line suggest that this system has been shaped by a gas disk migration process that halted after its dissipation.
993. H{delta} line in globular clusters
ID:
ivo://CDS.VizieR/J/AJ/134/321
Title:
H{delta} line in globular clusters
Short Name:
J/AJ/134/321
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a cautionary study exploring the reliability of the H{delta} line in the integrated spectra of galaxies for determining galaxy ages. Our database consists of the observed integrated spectra of ~120 early-type galaxies, 7 metal-rich globular clusters in M31 and the Galactic globular cluster 47 Tuc, and the open cluster M67. We have measured H{delta} using index definitions designed to assess contamination from the CN molecule in and around H{delta} by choosing combinations of bandpasses that both avoid and include a region of CN molecular lines redward of H{delta}. We find systematic differences in the ages derived from H{delta} measurements among the various definitions when extracting ages from H{delta} in old stellar populations with enhanced CN bands due to nonsolar abundance ratios. We propose that neighboring CN lines have a strong effect on pseudocontinuum and central bandpass levels. For stellar populations that have nonsolar abundance ratios in C and/or N, population synthesis models that do not account for abundance ratio variations cannot accurately reproduce the CN 4216{AA} band, which leads to a corresponding inaccuracy in reproducing the various H{delta} indices. Hence, caution must be used when extracting galaxy ages from the H{delta} line in old stellar populations with significant nonsolar abundance ratios.
994. HD 166734 ESPRESSO spectra
ID:
ivo://CDS.VizieR/J/A+A/607/A96
Title:
HD 166734 ESPRESSO spectra
Short Name:
J/A+A/607/A96
Date:
21 Oct 2021
Publisher:
CDS
Description:
HD 166734 is an eccentric eclipsing binary system composed of two supergiant O-type stars, orbiting with a 34.5-day period. In this rare configuration for such stars, the two objects mainly evolve independently, following single-star evolution so far. This system provides a chance to study the individual parameters of two supergiant massive stars and to derive their real masses. An intensive monitoring was dedicated to HD 166734. We analyzed mid- and high-resolution optical spectra to constrain the orbital parameters of this system. We also studied its light curve for the first time, obtained in the VRI filters. Finally, we disentangled the spectra of the two stars and modeled them with the CMFGEN atmosphere code in order to determine the individual physical parameters. HD 166734 is a O7.5If+O9I(f) binary. We confirm its orbital period but we revise the other orbital parameters. In comparison to what we found in the literature, the system is more eccentric and, now, the hottest and the most luminous component is also the most massive one. The light curve exhibits only one eclipse and its analysis indicates an inclination of 63.0+/-2.7{deg}. The photometric analysis provides us with a good estimation of the luminosities of the stars, and therefore their exact positions in the Hertzsprung-Russell diagram. The evolutionary and the spectroscopic masses show good agreement with the dynamical masses of 39.5M_{sun}_ for the primary and 33.5M_{sun}_ for the secondary, within the uncertainties. The two components are both enriched in helium and in nitrogen and depleted in carbon. In addition, the primary also shows a depletion in oxygen. Their surface abundances are however not different from those derived from single supergiant stars, yielding, for both components, an evolution similar to that
995. HD 149404 FEROS, Coralie and IUE spectra
ID:
ivo://CDS.VizieR/J/A+A/588/A10
Title:
HD 149404 FEROS, Coralie and IUE spectra
Short Name:
J/A+A/588/A10
Date:
21 Oct 2021
Publisher:
CDS
Description:
Mass and momentum exchanges in close massive binaries play an important role in their evolution, and produce several observational signatures such as asynchronous rotation and altered chemical compositions, that remain after the stars detach again. We investigated these effects for the detached massive O-star binary HD 149404 (O7.5 If + ON9.7 I, P=9.81-days), which is thought to have experienced a past episode of case A Roche-lobe overflow (RLOF). Using phase-resolved spectroscopy, we performed the disentangling of the optical spectra of the two stars. The reconstructed primary and secondary spectra were then analysed with the CMFGEN model atmosphere code to determine stellar parameters, such as the effective temperatures and surface gravities, and to constrain the chemical composition of the components. We complemented the optical study with the study of IUE spectra, which we compare to the synthetic binary spectra. The properties of the stars were compared to evolutionary models.
996. HD 48977 frequency analysis
ID:
ivo://CDS.VizieR/J/A+A/551/A12
Title:
HD 48977 frequency analysis
Short Name:
J/A+A/551/A12
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the CoRoT light curve of the bright B2.5V star HD 48977 observed during a short run of the mission in 2008, as well as a high-resolution spectrum gathered with the HERMES spectrograph at the Mercator telescope. We use several time series analysis tools to explore the nature of the variations in the light curve. We performed a detailed analysis of the spectrum of the star to determine its fundamental parameters and its element abundances. We find a large number of high-order g-modes, and one rotationally induced frequency. We find stable low-amplitude frequencies in the p-mode regime as well.
997. HD 161306 H{alpha} and HeI spectra
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.
998. HD 202850 HeI and SiII spectra
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.
999. HD 50844 observed by CoRoT
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.
1000. HD 145788, 21 Peg and pi Cet chemical analysis
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.

Limit your search

more »

more »

more »

more »

more »