- ID:
- ivo://CDS.VizieR/J/A+A/635/A8
- Title:
- Differential abundances of open clusters
- Short Name:
- J/A+A/635/A8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Well studied Open Clusters (OCs) of the Solar neighbourhood are frequently used as reference objects to test galactic and stellar theories. For that purpose their chemical composition needs to be known with a high level of confidence. It is also important to clarify if each OC is chemically homogeneous and if it has a unique chemical signature. The aims of this work are (1) to determine accurate and precise abundances of 22 chemical species (from Na to Eu) in the Hyades, Praesepe and Rupecht 147 using a large number of stars at different evolutionary states, (2) to evaluate the level of chemical homogeneity of these OCs, (3) to compare their chemical signatures. We gathered ~800 high resolution and high signal-to-noise spectra of ~100 members in the three clusters, obtained with the latest memberships based on Gaia DR2 data. We build a pipeline which computes atmospheric parameters and strictly line-by-line differential abundances among twin stars in our sample. With this method we are able to reach a very high precision in the abundances (0.01-0.02dex in most of the elements). We find large differences in the absolute abundances in some elements, which can be attributed to diffusion, NLTE effects or systematics in the analysis. For the three OCs, we find strong correlations in the differential abundances between different pairs of elements. According to our experiment with synthetic data, this can be explained by some level of chemical inhomogeneity. We compare differential abundances of several stars from the Hyades and Praesepe tails: the stars that differ more in chemical abundances also have distinct kinematics, even though they have been identified as members of the tail. It is possible to obtain high precision abundances using a differential analysis even when mixing spectra from different instruments. With this technique we find that the Hyades and Preasepe have the same chemical signature when G dwarfs and K giants are considered. Despite a certain level of inhomogeneity in each cluster, it is still possible to clearly distinguish the chemical signature of the older cluster Ruprecht 147 when compared to the Hyades and Praesepe.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/127/1727
- Title:
- Differential magnitudes of binary stars
- Short Name:
- J/AJ/127/1727
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Five hundred seventy-six magnitude difference measures are presented for 260 binary stars. These measures are derived from CCD-based speckle observations taken at the WIYN 3.5m telescope at Kitt Peak National Observatory during the period 1997-2000. Separations of the systems range from over 1" down to near the diffraction limit of the telescope. A study of multiple measures of the same targets indicates that the measures have a typical uncertainty of better than 0.13mag per 2 minute observation, and that multiple observations can be averaged to arrive at smaller uncertainties. Results presented here are also compared, insofar as it is possible, with measures in the Hipparcos Catalogue and to previous studies using adaptive optics. No major systematic errors were identified.
- ID:
- ivo://CDS.VizieR/J/AJ/158/141
- Title:
- Differential photometry & RVs of HAT-P-69 & HAT-P-70
- Short Name:
- J/AJ/158/141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Wide-field surveys for transiting planets are well suited to searching diverse stellar populations, enabling a better understanding of the link between the properties of planets and their parent stars. We report the discovery of HAT-P-69 b (TOI 625.01) and HAT-P-70 b (TOI 624.01), two new hot Jupiters around A stars from the Hungarian-made Automated Telescope Network (HATNet) survey that have also been observed by the Transiting Exoplanet Survey Satellite. HAT-P-69 b has a mass of 3.58_-0.58_^+0.58^ M_Jup_ and a radius of 1.676_-0.033_^+0.051^ R_Jup_ and resides in a prograde 4.79 day orbit. HAT-P-70 b has a radius of 1.87_-0.10_^+0.15^ R_Jup_ and a mass constraint of <6.78 (3{sigma}) M_Jup_ and resides in a retrograde 2.74 day orbit. We use the confirmation of these planets around relatively massive stars as an opportunity to explore the occurrence rate of hot Jupiters as a function of stellar mass. We define a sample of 47126 main-sequence stars brighter than T_mag_=10 that yields 31 giant planet candidates, including 18 confirmed planets, 3 candidates, and 10 false positives. We find a net hot Jupiter occurrence rate of 0.41+/-0.10% within this sample, consistent with the rate measured by Kepler for FGK stars. When divided into stellar mass bins, we find the occurrence rate to be 0.71+/-0.31% for G stars, 0.43+/-0.15% for F stars, and 0.26+/-0.11% for A stars. Thus, at this point, we cannot discern any statistically significant trend in the occurrence of hot Jupiters with stellar mass.
- ID:
- ivo://CDS.VizieR/J/AJ/143/70
- Title:
- Differential reddening in Milky Way globulars
- Short Name:
- J/AJ/143/70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Extensive photometric studies of the globular clusters located toward the center of the Milky Way have been historically neglected. The presence of patchy differential reddening in front of these clusters has proven to be a significant obstacle to their detailed study. We present here a well defined and reasonably homogeneous photometric database for 25 of the brightest Galactic globular clusters located in the direction of the inner Galaxy. These data were obtained in the B, V, and I bands using the Magellan 6.5m Telescope and the Hubble Space Telescope. A new technique is extensively used in this paper to map the differential reddening in the individual cluster fields, and to produce cleaner, dereddened color-magnitude diagrams for all the clusters in the database. Subsequent papers will detail the astrophysical analysis of the cluster populations, and the properties of the obscuring material along the clusters' lines of sight.
- ID:
- ivo://CDS.VizieR/J/A+A/591/A43
- Title:
- Differential rotation in solar-like stars
- Short Name:
- J/A+A/591/A43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Surface differential rotation (SDR) plays a key role in dynamo models and determines a lower limit on the accuracy of stellar rotation period measurements. SDR estimates are therefore essential to constrain theoretical models and infer realistic rotation period uncertainties. We measure a lower limit to SDR in a sample of solar-like stars belonging to young loose stellar associations with the aim of investigating how SDR depends on global stellar parameters in the age range (4-95Myr). The rotation period of a solar-like star can be recovered by analyzing the flux modulation caused by dark spots and stellar rotation. The SDR and the latitude migration of dark-spots induce a modulation of the detected rotation period. We employed long-term photometry to measure the amplitude of such a modulation and to compute the quantity {Delta}{Omega}_phot_=2{pi}/P_min_-2{pi}/P_max_ that is a lower limit to SDR. We find that {Delta}{Omega}_phot_ increases with the stellar effective temperature and with the global convective turn-over timescale tau_c_, which is the characteristic time for the rise of a convective element through the stellar convection zone. We find that {Delta}{Omega}_phot_ is proportional to T_eff_^2.18+/-0.65^ in stars recently settled on the ZAMS. This power law is less steep than those found by previous authors, but closest to recent theoretical models. We investigate how {Delta}{Omega}_phot_ changes in time in a 1M_{sun}_ star. We find that {Delta}{Omega}_phot_ steeply increases between 4 and 30Myr and that it is almost constant between 30 and 95Myr. We find also that the relative shear increases with the Rossby number Ro. Although our results are qualitatively in agreement with hydrodynamical mean-field models, our measurements are systematically higher than the values predicted by these models. The discrepancy between {Delta}{Omega}_phot_ measurements and theoretical models is particularly large in stars with periods between 0.7 and 2d. Such a discrepancy, together with the anomalous SDR measured by other authors for HD 171488 (rotating in 1.31d), suggests that the rotation period could influence SDR more than predicted by the models.
- ID:
- ivo://CDS.VizieR/J/AJ/132/663
- Title:
- Differential Velocities of very low mass SBs
- Short Name:
- J/AJ/132/663
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the results of a survey for radial velocity variability in a heterogeneous sample of very low mass stars and brown dwarfs. One distinguishing characteristic of the survey is its time span, which allows an overlap between spectroscopic binaries and those that can be found by high angular resolution imaging. Despite our relatively low velocity precision, we are able to place a new constraint on the total binary fraction in these objects, which suggests that they are more likely the result of extending the same processes at work at higher masses into this mass range, rather than a distinct mode of formation.
- ID:
- ivo://CDS.VizieR/J/A+A/423/579
- Title:
- Diffuse emissions in Carina nebula
- Short Name:
- J/A+A/423/579
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of mapping observations with ISO of [OI]63{mu}m, 145{mu}m, [NII]122{mu}m, [CII]158{mu}m, [SiII]35{mu}m, and H_2_9.66{mu}m line emissions for the Carina nebula, an active star-forming region in the Galactic plane. The observations were made for the central 40'x20' area of the nebula, including the optically bright HII region and molecular cloud lying in front of the ionized gas. Around the center of the observed area is the interface between the HII region and the molecular cloud which creates a typical photodissociation region (PDR).
- ID:
- ivo://CDS.VizieR/J/ApJ/733/91
- Title:
- Diffuse interstellar band equivalent widths
- Short Name:
- J/ApJ/733/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The diffuse interstellar bands (DIBs) are ubiquitous absorption spectral features arising from the tenuous material in the space between stars -the interstellar medium (ISM). Since their first detection nearly nine decades ago, over 400 DIBs have been observed in the visible and near-infrared wavelength range in both the Milky Way and external galaxies, both nearby and distant. However, the identity of the species responsible for these bands remains as one of the most enigmatic mysteries in astrophysics. An equally mysterious interstellar spectral signature is the 2175{AA} extinction bump, the strongest absorption feature observed in the ISM. Its carrier also remains unclear since its first detection 46 years ago. Polycyclic aromatic hydrocarbon (PAH) molecules have long been proposed as a candidate for DIBs as their electronic transitions occur in the wavelength range where DIBs are often found. In recent years, the 2175{AA} extinction bump is also often attributed to the {pi}-{pi}* transition in PAHs. If PAHs are indeed responsible for both the 2175{AA} extinction feature and DIBs, their strengths may correlate. We perform an extensive literature search for lines of sight for which both the 2175{AA} extinction feature and DIBs have been measured. Unfortunately, we found no correlation between the strength of the 2175{AA} feature and the equivalent widths of the strongest DIBs. A possible explanation might be that DIBs are produced by small free gas-phase PAH molecules and ions, while the 2175{AA} bump is mainly from large PAHs or PAH clusters in condensed phase so that there is no tight correlation between DIBs and the 2175{AA} bump.
- ID:
- ivo://CDS.VizieR/II/149
- Title:
- Diffuse Interstellar Band Measurements
- Short Name:
- II/149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog contains diffuse band data collected from an exhaustive search of the literature and reduced to a common measurement system. The authors have adopted Herbig (1975ApJ...196..129H) as a standard data set for DIB measurements.
- ID:
- ivo://CDS.VizieR/J/MNRAS/358/563
- Title:
- Diffuse Interstellar Bands in 49 stars
- Short Name:
- J/MNRAS/358/563
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We relate the equivalent widths of 11 diffuse interstellar bands, measured in the spectra of 49 stars, to different colour excesses in the ultraviolet. We find that most of the observed bands correlate positively with the extinction in the neighbourhood of the 2175{AA} bump. Correlation with colour excesses in other parts of the extinction curve is more variable from one diffuse interstellar band to another; we find that some diffuse bands (5797, 5850 and 6376{AA}) correlate positively with the overall slope of the extinction curve, while others (5780 and 6284{AA}) exhibit negative correlation. We discuss the implications of these results on the links between the diffuse interstellar band carriers and the properties of the interstellar grains.