- ID:
- ivo://CDS.VizieR/J/ApJS/234/21
- Title:
- hCOSMOS: Hectospec survey of galaxies in COSMOS
- Short Name:
- J/ApJS/234/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe the hCOSMOS redshift survey of the COSMOS field conducted with the Hectospec spectrograph on the MMT. In the central 1deg^2^, the hCOS20.6 subset of the survey is >90% complete to a limiting magnitude r=20.6. The hCOSMOS survey includes 1701 new redshifts in the COSMOS field. We also use the total of 4362 new and remeasured objects to derive the age-sensitive D_n_4000 index over the entire redshift interval 0.001<~z<~0.6. For 85% of the quiescent galaxies in hCOS20.6, we measure the central line-of-sight velocity dispersion. To explore potential uses of this survey, we combine previously measured galaxy sizes, profiles, and stellar masses with the spectroscopy. The comparison reveals the known relations among structural, kinematic, and stellar population properties. We also compare redshift and D_n_4000 distributions of hCOS20.6 galaxies with SHELS; a complete spectroscopic survey of 4deg^2^ observed to the same depth. The redshift distributions in the two fields are very different, but the D_n_4000 distribution is remarkably similar. The relation between velocity dispersion and stellar mass for massive hCOS20.6 galaxies is consistent with the local relation from the Sloan Digital Sky Survey. Using measured velocity dispersions, we test a photometric proxy calibrated to galaxies in the local universe. The systematic differences between the measured and photometric proxy velocity dispersions are correlated with galaxy dynamical and stellar population properties highlighting the importance of direct spectroscopic measurements.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/638/A5
- Title:
- HD 285507 and AD Leo light and velocity curves
- Short Name:
- J/A+A/638/A5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The existence of hot Jupiters is still not well understood. Two main channels are thought to be responsible for their current location: a smooth planet migration through the proto-planetary disk or the circularization of an initial high eccentric orbit by tidal dissipation leading to a strong decrease of the semimajor axis. Different formation scenarios result in different observable effects, such as orbital parameters (obliquity/eccentricity), or frequency of planets at different stellar ages. In the context of the GAPS Young-Objects project, we are carrying out a radial velocity survey with the aim to search and characterize young hot-Jupiter planets. Our purpose is to put constraints on evolutionary models and establish statistical properties, such as the frequency of these planets from a homogeneous sample. Since young stars are in general magnetically very active, we performed multi-band (visible and near-infrared) spectroscopy with simultaneous GIANO-B + HARPS-N (GIARPS) observing mode at TNG. This helps to deal with stellar activity and distinguish the nature of radial velocity variations: stellar activity will introduce a wavelength-dependent radial velocity amplitude, whereas a Keplerian signal is achromatic. As a pilot study, we present here the cases of two already claimed hot Jupiters orbiting young stars: HD 285507 b and AD Leo b. Our analysis of simultaneous high-precision GIARPS spectroscopic data confirms the Keplerian nature of HD285507's radial velocities variation and refines the orbital parameters of the hot Jupiter, obtaining an eccentricity consistent with a circular orbit. On the other hand, our analysis does not confirm the signal previously attributed to a planet orbiting AD~Leo. This demonstrates the power of the multi-band spectroscopic technique when observing active stars.
- ID:
- ivo://CDS.VizieR/J/A+A/539/A102
- Title:
- HD 209458 and HD 189733 theoretical spectra
- Short Name:
- J/A+A/539/A102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We compare limb darkening laws derived from 3D hydrodynamical model atmospheres and 1D hydrostatic MARCS models for the host stars of two well-studied transiting exoplanet systems, the late-type dwarfs HD 209458 and HD 189733. The surface brightness distribution of the stellar disks is calculated for a wide spectral range using 3D LTE spectrum formation and opacity sampling. We test our theoretical predictions using least-squares fits of model light curves to wavelength-integrated primary eclipses that were observed with the Hubble Space Telescope (HST).
- ID:
- ivo://CDS.VizieR/J/A+A/297/503
- Title:
- HD 146850 atomic lines
- Short Name:
- J/A+A/297/503
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the identification of 3 Li-rich giants discovered in an ongoing survey based on IRAS colours. A detailed analysis of one of these, HD 146850, is presented here. High resolution spectra were obtained for this star, using CASPEC at the 3.6m telescope of ESO.
- 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.
- 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.
- 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.
- 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
- 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.
- 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.
