- ID:
- ivo://CDS.VizieR/J/A+A/620/A163
- Title:
- Cores in California molecular cloud
- Short Name:
- J/A+A/620/A163
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We extracted 300 cores, of which 33 are protostellar and 267 are starless cores. About 51% (137 of 267) of the starless cores are prestellar cores. Three cores have the potential to evolve into high-mass stars. The prestellar core mass function (CMF) can be well fit by a log-normal form. The high-mass end of the prestellar CMF shows a power-law form with an index {alpha}=-0.9+/-0.1 that is shallower than that of the Galactic field stellar mass function. Combining the mass transformation efficiency ({epsilon}) from the prestellar core to the star of 15+/-1% and the core formation efficiency (CFE) of 5.5%, we suggest an overall star formation efficiency of about 1% in the CMC. In the single-pointing observations with the IRAM 30m telescope, we find that 6 cores show blue-skewed profile, while 4 cores show red-skewed profile. [HCO^+^]/[HNC] and [HCO^+^]/[N_2_H^+^] in protostellar cores are higher than those in prestellar cores; this can be used as chemical clocks. The best-fit chemical age of the cores with line observations is ~50000 years.
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- ID:
- ivo://CDS.VizieR/J/A+A/564/A119
- Title:
- CoRoT red giants abundances
- Short Name:
- J/A+A/564/A119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A precise characterisation of the red giants in the seismology fields of the CoRoT satellite is a prerequisite for further in-depth seismic modelling. High-resolution FEROS and HARPS spectra were obtained as part of the ground-based follow-up campaigns for 19 targets holding great asteroseismic potential. These data are used to accurately estimate in a self-consistent manner their fundamental parameters and the abundances of 16 chemical species. Some powerful probes of mixing are investigated (the Li and CNO abundances, as well as the carbon isotopic ratio in a few cases). The information provided by the spectroscopic and seismic data is combined to provide more accurate physical parameters and abundances. The stars in our sample follow the general trends between various abundance ratios and the metallicity observed in stars of the Galactic disk. After allowance is made for the chemical evolution of the interstellar medium, the observational signature of internal mixing phenomena is revealed through the detection at the stellar surface of the products of the CN and, in the case of the most massive stars, NeNa cycles. Together with the asteroseismic constraints, these data will pave the way for a detailed theoretical investigation of the physical processes responsible for the transport of chemical elements in evolved, low- and intermediate-mass stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/752/72
- Title:
- Correlation metallicity / eclipse depth
- Short Name:
- J/ApJ/752/72
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Previous studies of the interior structure of transiting exoplanets have shown that the heavy-element content of gas giants increases with host star metallicity. Since metal-poor planets are less dense and have larger radii than metal-rich planets of the same mass, one might expect that metal-poor stars host a higher proportion of gas giants with large radii than metal-rich stars. Here I present evidence for a negative correlation at the 2.3{sigma} level between eclipse depth and stellar metallicity in the Kepler gas giant candidates. Based on Kendall's {tau} statistics, the probability that eclipse depth depends on star metallicity is 0.981. The correlation is consistent with planets orbiting low-metallicity stars being, on average, larger in comparison with their host stars than planets orbiting metal-rich stars. Furthermore, since metal-rich stars have smaller radii than metal-poor stars of the same mass and age, a uniform population of planets should show a rise in median eclipse depth with [M/H]. The fact that I find the opposite trend indicates that substantial changes in the gas giant interior structure must accompany increasing [M/H]. I investigate whether the known scarcity of giant planets orbiting low-mass stars could masquerade as an eclipse depth-metallicity correlation, given the degeneracy between metallicity and temperature for cool stars in the Kepler Input Catalog. While the eclipse depth-metallicity correlation is not yet on firm statistical footing and will require spectroscopic [Fe/H] measurements for validation, it is an intriguing window into how the interior structure of planets and even the planet formation mechanism may be changing with Galactic chemical evolution.
- ID:
- ivo://CDS.VizieR/J/A+A/566/A66
- Title:
- Correlation of logR'HK with logIH{alpha}
- Short Name:
- J/A+A/566/A66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The re-emission in the cores of the CaII H & K and H{alpha} lines are well known proxies of stellar activity. However, these activity indices probe different activity phenomena: the first is more sensitive to plage variation, while the other is more sensitive to filaments. In this paper, we study the long-term correlation between logR'_HK_ and logI_H{alpha}_, two indices based on the CaII H & K and H{alpha} lines, respectively, for a sample of 271 FGK stars using measurements obtained over a ~9-year time span. Because stellar activity is one of the main obstacles to the detection of low-mass and long-period planets, understanding this activity index correlation further can give us some hints about the optimal target to focus on ways to correct for these activity effects. We found a great variety of long-term correlations between logR'_HK_ and logI_H{alpha}_. Around 20% of our sample has a strong positive correlation between the indices while about 3% show strong negative correlation. These fractions are compatible with those found for the case of early-M dwarfs. Stars exhibiting a positive correlation have a tendency to be more active when compared to the median of the sample, while stars showing a negative correlation are more present among higher metallicity stars. There is also a tendency for the positively correlated stars to be more present among the coolest stars, a result which is probably due to the activity level effect on the correlation. Activity level and metallicity therefore seem to be playing a role on the correlation between logR'_HK_ and logI_H{alpha}_. Possible explanations based on the influence of filaments for the diversity in the correlations between these indices are discussed in this paper. As a parallel result, we show a way to estimate the effective temperature of FGK dwarfs that exhibit a low activity level by using the H{alpha} index.
- ID:
- ivo://CDS.VizieR/J/ApJ/887/5
- Title:
- COS CGM compendium (CCC). III. z<=1 Ly{alpha} syst.
- Short Name:
- J/ApJ/887/5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We characterize the metallicities and physical properties of cool, photoionized gas in a sample of 152 z<=1 strong Ly{alpha} forest systems (SLFSs, absorbers with 15<logN_HI_<16.2). The sample is drawn from our Cosmic Origins Spectrograph (COS) circumgalactic medium compendium (CCC), an ultraviolet survey of HI-selected circumgalactic gas around z<=1 galaxies that targets 261 absorbers with 15<logN_HI_<19. We show that the metallicity probability distribution function of the SLFSs at z<=1 is unimodal, skewed to low metallicities with a mean and median of [X/H]=-1.47 and -1.18dex. Very metal-poor gas with [X/H]{<}-1.4 represents about half of the population of absorbers with 15<logN_HI_<=18, while it is rare at higher N_HI_. Thus, there are important reservoirs of primitive (though not pristine) diffuse ionized gas around z<=1 galaxies. The photoionized gas around z<=1 galaxies is highly inhomogeneous based on the wide range of metallicities observed (-3<=[X/H]<=+0.4) and the fact that there are large metallicity variations (factors of 2 to 25) for most of the closely spaced absorbers ({Delta}v<=300km/s) along the same sightlines. These absorbers show a complex evolution with redshift and HI column density, and we identify subtle cosmic evolution effects that affect the interpretation of metallicity distributions and comparison with other absorber samples. We discuss the physical conditions and cosmic baryon and metal budgets of the CCC absorbers. Finally, we compare the CCC results to recent cosmological zoom simulations and explore the origins of the 15<logN_HI_<19 absorbers within the Evolution and Assembly of GaLaxies and their Environments (EAGLE) high-resolution simulations.
- ID:
- ivo://CDS.VizieR/J/MNRAS/459/1170
- Title:
- Coulour-Period relation for Cepheids
- Short Name:
- J/MNRAS/459/1170
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We compare mid-infrared (IR) 3.6 and 4.5{mu}m Warm Spitzer observations for Cepheids in the Milky Way and the Large and Small Magellanic Clouds. Using models, we explore in detail the effect of the CO rotation-vibration band-head at 4.6{mu}m on the mid-IR photometry. We confirm the temperature sensitivity of the CO band-head at 4.6{mu}m and find no evidence for an effect at 3.6{mu}m. We compare the ([3.6]-[4.5]) period-colour relations in the MW, LMC and SMC. The slopes of the period-colour relations for the three galaxies are in good agreement, but there is a trend in zero-point with metallicity, with the lowest metallicity Cepheids having redder mid-IR colours. Finally, we present a colour-[Fe/H] relation based on published spectroscopic metallicities. This empirical relation, calibrated to the metallicity system of Genovali et al., demonstrates that the ([3.6]-[4.5]) colour provides a reliable metallicity indicator for Cepheids, with a precision comparable to current spectroscopic determinations.
- ID:
- ivo://CDS.VizieR/J/ApJ/725/2349
- Title:
- C/O vs Mg/Si of planetary systems
- Short Name:
- J/ApJ/725/2349
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Theoretical studies suggest that C/O and Mg/Si are the most important elemental ratios in determining the mineralogy of terrestrial planets. The C/O ratio controls the distribution of Si among carbide and oxide species, while Mg/Si gives information about the silicate mineralogy. We present a detailed and uniform study of C, O, Mg, and Si abundances for 61 stars with detected planets and 270 stars without detected planets from the homogeneous high-quality unbiased HARPS GTO sample, together with 39 more planet-host stars from other surveys. We determine these important mineralogical ratios and investigate the nature of the possible terrestrial planets that could have formed in those planetary systems. We find mineralogical ratios quite different from those of the Sun, showing that there is a wide variety of planetary systems which are not similar to our solar system. Many planetary host stars present an Mg/Si value lower than 1, so their planets will have a high Si content to form species such as MgSiO_3_. This type of composition can have important implications for planetary processes such as plate tectonics, atmospheric composition, or volcanism.
- ID:
- ivo://CDS.VizieR/J/A+A/614/A84
- Title:
- C/O vs Mg/Si ratios in solar type stars
- Short Name:
- J/A+A/614/A84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We aim to present a detailed study of the magnesium-to-silicon and carbon-to-oxygen ratios (Mg/Si and C/O) and their importance in determining the mineralogy of planetary companions. Using 499 solar-like stars from the HARPS sample, we determined C/O and Mg/Si elemental abundance ratios to study the nature of the possible planets formed. We separated the planetary population in low-mass planets (<30M_{sun}_) and high-mass planets (>30M_{sun}_) to test for a possible relation with the mass. We find a diversity of mineralogical ratios that reveal the different kinds of planetary systems that can be formed, most of them dissimilar to our solar system. The different values of the Mg/Si and C/O can determine different composition of planets formed. {We found that 100% of our planetary sample present C/O<0.8. 86% of stars with high-mass companions present 0.8>C/O>0.4, while 14% present C/O values lower than 0.4. Regarding Mg/Si, all stars with low-mass planetary companion showed values between one and two, while 85% of the high-mass companion sample does. The other 15% showed Mg/Si values below one. No stars with planets were found with Mg/Si>2. Planet hosts with low-mass companions present C/O and Mg/Si similar to those found in the Sun, whereas stars with high-mass companions have lower C/O.
- ID:
- ivo://CDS.VizieR/J/MNRAS/487/5922
- Title:
- CP stars catalog (roAp, He-weak, He-rich)
- Short Name:
- J/MNRAS/487/5922
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To enlarge our data base of chemically peculiar stars, we compiled published data concerning the He-weak and He-rich stars observed by high-resolution spectroscopy techniques during last decades. Twenty He-weak and 28 He-rich stars have been added to the data base. We have also distinguished roAp stars from stars previously identified as Ap stars. To deepen our knowledge on statistical overview of the abundance anomalies versus the physical parameters of stars, we compared our data with previous compilations. We applied statistical tests on our data and found interesting correlations for effective temperature and surface gravity for all type of stars and a few correlations for projected rotation velocity only for He-rich stars. Because of the lack of the data, we could not check whether being a member of binary system is affecting on chemical peculiarities of those stars.
- ID:
- ivo://CDS.VizieR/J/ApJS/237/18
- Title:
- Cr, Co, and Ni abundances for metal-poor red giants
- Short Name:
- J/ApJS/237/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present measurements of the abundances of chromium, cobalt, and nickel in 4113 red giants, including 2277 stars in globular clusters (GCs), 1820 stars in the Milky Way's dwarf satellite galaxies, and 16 field stars. We measured the abundances from mostly archival Keck/DEIMOS medium-resolution spectroscopy with a resolving power of R~6500 and a wavelength range of approximately 6500-9000{AA}. The abundances were determined by fitting spectral regions that contain absorption lines of the elements under consideration. We used estimates of temperature, surface gravity, and metallicity that we previously determined from the same spectra. We estimated systematic error by examining the dispersion of abundances within mono- metallic GCs. The median uncertainties for [Cr/Fe], [Co/Fe], and [Ni/Fe] are 0.20, 0.20, and 0.13, respectively. Finally, we validated our estimations of uncertainty through duplicate measurements, and we evaluated the accuracy and precision of our measurements through comparison to high-resolution spectroscopic measurements of the same stars.
