- ID:
- ivo://CDS.VizieR/J/ApJ/697/544
- Title:
- Planets orbiting metal-poor dwarfs. II.
- Short Name:
- J/ApJ/697/544
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of three years of precision radial velocity (RV) measurements of 160 metal-poor stars observed with HIRES on the Keck 1 telescope. We report on variability and long-term velocity trends for each star in our sample. We identify several long-term, low-amplitude RV variables worthy of followup with direct imaging techniques. We place lower limits on the detectable companion mass as a function of orbital period. Our survey would have detected, with a 99.5% confidence level, over 95% of all companions on low-eccentricity orbits with velocity semiamplitude K>~100m/s, or M_p_sini>~3.0M_J_(P/yr)^(1/3)^, for orbital periods P<~3yr. None of the stars in our sample exhibits RV variations compatible with the presence of Jovian planets with periods shorter than the survey duration.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/855/107
- Title:
- PMAS Integral-field SN hosts COmpilation (PISCO)
- Short Name:
- J/ApJ/855/107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the PMAS/PPak Integral-field Supernova hosts COmpilation (PISCO), which comprises integral field spectroscopy (IFS) of 232 supernova (SN) host galaxies that hosted 272 SNe, observed over several semesters with the 3.5m telescope at the Calar Alto Observatory (CAHA). PISCO is the largest collection of SN host galaxies observed with wide-field IFS, totaling 466347 individual spectra covering a typical spatial resolution of ~380pc. Focused studies regarding specific SN Ia-related topics will be published elsewhere; this paper aims to present the properties of the SN environments, using stellar population (SP) synthesis, and the gas-phase interstellar medium, providing additional results separating stripped-envelope SNe into their subtypes. With 11270 HII regions detected in all galaxies, we present for the first time a statistical analysis of HII regions, which puts HII regions that have hosted SNe in context with all other star-forming clumps within their galaxies. SNe Ic are associated with environments that are more metal-rich and have higher EW(H{alpha}) and higher star formation rate within their host galaxies than the mean of all HII regions detected within each host. This in contrast to SNe IIb, which occur in environments that are very different compared to other core-collapse SNe types. We find two clear components of young and old SPs at SNe IIn locations. We find that SNe II fast decliners tend to explode at locations where the {Sigma}SFR is more intense. Finally, we outline how a future dedicated IFS survey of galaxies in parallel to an untargeted SN search would overcome the biases in current environmental studies.
1363. PN abundances
- ID:
- ivo://CDS.VizieR/J/A+AS/126/297
- Title:
- PN abundances
- Short Name:
- J/A+AS/126/297
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Abundance determinations of about 110 planetary nebulae, which are likely to be in the Galactic Bulge are presented. Plasma diagnostics have been performed by making use of the available forbidden line ratios combined with radio continuum measurements. Chemical abundances of He, O, N, Ne, S, Ar, and Cl are then derived by employing theoretical nebular models as interpolation devices in establishing the ionization correction factors (ICFs) used to estimate the distribution of atoms among unobserved ionization stages. The overall agreement between the results derived by using the model-ICFs and those obtained from the theoretical models is reasonably good. The uncertainties related to the total abundances show a clear dependence on the level of excitation. In most cases, the abundances of chlorine can be derived only in objects with a relatively high Cl-abundance. Contrary to the conclusion previously drawn by Webster (1988MNRAS.230..377W), we found the excitation classes are not uniformly distributed. A clear peak at about classes 5 and 6 is noticed. The distribution is shifted toward a lower excitation range with respect to that of the nearby nebulae, reflecting the difference in the central star temperature distribution between the two samples.
- ID:
- ivo://CDS.VizieR/J/A+A/336/667
- Title:
- PN abundances in five galaxies
- Short Name:
- J/A+A/336/667
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have collected photometric and spectroscopic data on planetary nebulae (PNe) in 5 galaxies: the Milky Way (bulge), M31 (bulge), M 32, the LMC and the SMC. We have computed the abundances of O, Ne and N and compared them from one galaxy to another. In each Galaxy, the distribution of oxygen abundances has a large dispersion. The average O/H ratio is larger in the M31 and the Galactic bulge PNe than in those in the Magellanic Clouds. In a given galaxy, it is also larger for PNe with [OIII] luminosities greater than 100L_{sun}_, which are likely to probe more recent epochs in the galaxy history. We find that the M31 and the Galactic bulge PNe extend the very tight Ne/H-O/H correlation observed in the Galactic disk and Magellanic Clouds PNe towards higher metallicities. We note that the anticorrelation between N/O and O/H that was known to occur in the Magellanic Clouds and in the disk PNe is also marginally found in the PNe of the Galactic bulge. Furthermore, we find that high N/O ratios are higher for less luminous PNe. In M 32, all PNe have a large N/O ratio, indicating that the stellar nitrogen abundance is enhanced in this galaxy. We have also compared the PN evolution in the different galactic systems by constructing diagrams that are independent of abundances, and have found strikingly different behaviours of the various samples. In order to help in the interpretation of these data, we have constructed a grid of expanding, PN photoionization models in which the central stars evolve according to the evolutionary tracks of Bloecker (1995A&A...299..755B). These models show that the apparent spectroscopic properties of PNe are extremely dependent, not only on the central stars, but also on the masses and expansion velocities of the nebular envelopes. The main conclusion of the confrontation of the observed samples with the model grids is that the PN populations are indeed not the same in the various parent galaxies. Both stars and nebulae are different. In particular, the central stars of the Magellanic Clouds PNe are shown to evolve differently from the hydrogen burning stellar evolutionary models of Bloecker (1995). In the Galactic bulge, on the other hand, the behaviour of the observed PNe is roughly compatible with the theoretical stellar evolutionary tracks. The case of M31 is not quite clear, and additional observations are necessary. It seems that the central star mass distribution is narrower for the M31 PNe than for the Galactic bulge PNe. We show that spectroscopy of complete samples of PNe down to a factor 100 below the maximum luminosity would help to better characterize the PN central star mass distribution.
- ID:
- ivo://CDS.VizieR/J/ApJ/419/596
- Title:
- Pop I UV radiation models
- Short Name:
- J/ApJ/419/596
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This series of papers comprises a systematic exploration of the hypothesis that the far-ultraviolet radiation from star clusters and elliptical galaxies originates from extremely hot horizontal-branch (HB) stars and their post-HB progeny. This first paper presents an extensive grid of calculations of stellar models from the zero-age horizontal branch (ZAHB) through to a point late in post-HB evolution or a point on the white dwarf cooling track. The grid will be used to produce synthesized UV fluxes for the interpretation of existing and future short-wavelength (900-3000A) observations. Our sequences have been computed for a range of masses which concentrates on models that begin their HB evolution very close to the hot end of the ZAHB. We have calculated tracks for three metal-poor compositions ([Fe/H]=-2.26, -1.48, -0.47 with [O/Fe]>0), for use with globular cluster observations. We have also chosen three metal rich compositions (Z=0.017=Z_{sun}_, Z=0.04, 0.06) for use in the study of elliptical galaxy populations. For each of the two super-metal-rich compositions, for which the helium abundance is unconstrained by observation, we have computed two sets of sequences: one assuming no additional helium, and a second with a large enhancement (Y(HB)=0.29 and 0.36 for Z=0.04), and (Y(HB)=0.29 and 0.46 for Z=0.06). For each set of sequences, our lowest ZAHB envelope masses (M^0^_env_) are in the range 0.002M_{sun}_<M^0^_env_<0.006M_{sun}_. We use the term extreme horizontal branch (EHB) to refer to HB sequences of constant mass that do not reach the thermally pulsing stage on the AGB. These models evolve after core helium exhaustion into post-early asymptotic giant branch (AGB) stars, which leave the AGB before thermal pulsing, and AGB-manque stars, which never reach the AGB. We describe various features of the evolution of post-HB stars, discussing the correspondence between slow phases of evolution at high temperature and the early-AGB evolution. We note that the relationship between core mass and luminosity for stars on the upper AGB is not straightforward, because stars arrive on the ZAHB with a range of masses and subsequently burn different amounts of fuel. We determine from our models an upper bound to the masses of EHB stars, finding that it varies little for [Fe/H]<0, but that it is sensitive to the helium abundance. We show that for each composition there is a range of M^0^_env_ (at least a few hundredths M_{sun}) in which the models have a slow phase of evolution at high temperature. The duration of this phase is found to increase with the metallicity, but its luminosity is lower, so that total UV energy output is not significantly different from metal-poor sequences. The properties of very metal rich stars are, however, made uncertain by our lack of knowledge of the helium abundance for [Fe/H]>0; the range of stellar masses in which high temperatures are attained for significant periods of time increases with Y. There is no intrinsic composition dependence of the peak UV output from evolved stars; the output from a stellar population depends most directly on the mass distribution of stars arriving on the ZAHB. This is determined mainly by the mass loss that occurs on the red giant branch.
- ID:
- ivo://CDS.VizieR/J/MNRAS/403/2012
- Title:
- PopStar II. Giant HII regions models
- Short Name:
- J/MNRAS/403/2012
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the second paper of a series reporting the results from the popstar evolutionary synthesis models. Here, we present synthetic emission-line spectra of HII regions photoionized by young star clusters, for seven values of cluster masses and for ages between 0.1 and 5.2Myr. The ionizing spectral energy distributions (SEDs) are those obtained by the popstar code for six different metallicities, with a very low-metallicity set, Z=0.0001 , not included in previous similar works. We assume that the radius of the HII region is the distance at which the ionized gas is deposited by the action of the mechanical energy of the winds and supernovae from the central ionizing young cluster.
- ID:
- ivo://CDS.VizieR/J/ApJS/171/146
- Title:
- Population synthesis in the blue. IV
- Short Name:
- J/ApJS/171/146
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new set of model predictions for 16 Lick absorption line indices from H{delta} through Fe5335 and UBV colors for single stellar populations with ages ranging between 1 and 15Gyr, [Fe/H] ranging from -1.3 to +0.3, and variable abundance ratios. The models are based on accurate stellar parameters for the Jones library stars and a new set of fitting functions describing the behavior of line indices as a function of effective temperature, surface gravity, and iron abundance. The abundances of several key elements in the library stars have been obtained from the literature in order to characterize the abundance pattern of the stellar library, thus allowing us to produce model predictions for any set of abundance ratios desired. We develop a method to estimate mean ages and abundances of iron, carbon, nitrogen, magnesium, and calcium that explores the sensitivity of the various indices modeled to those parameters. The models are compared to high-S/N data for Galactic clusters spanning the range of ages, metallicities, and abundance patterns of interest. Essentially all line indices are matched when the known cluster parameters are adopted as input. Comparing the models to high-quality data for galaxies in the nearby universe, we reproduce previous results regarding the enhancement of light elements and the spread in the mean luminosity-weighted ages of early-type galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/737/L7
- Title:
- Post-AGB star SAO 40039 equivalent widths
- Short Name:
- J/ApJ/737/L7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have conducted an LTE abundance analysis for SAO 40039, a warm post-AGB star whose spectrum is known to show surprisingly strong HeI lines for its effective temperature and has been suspected of being H-deficient and He-rich. High-resolution optical spectra are analyzed using a family of model atmospheres with different He/H ratios. Atmospheric parameters are estimated from the ionization equilibrium set by neutral and singly ionized species of Fe and Mg, the excitation of FeI and FeII lines, and the wings of the Paschen lines. On the assumption that the HeI lines are of photospheric and not chromospheric origin, a He/H ratio of approximately unity is found by imposing the condition that the adopted He/H ratio of the model atmosphere must equal the ratio derived from the observed HeI triplet lines at 5876, 4471, and 4713{AA}, and singlet lines at 4922 and 5015{AA}. Using the model with the best-fitting atmospheric parameters for this He/H ratio, SAO 40039 is confirmed to exhibit mild dust-gas depletion, i.e., the star has an atmosphere deficient in elements of high condensation temperature. The star appears to be moderately metal-deficient with [Fe/H]=-0.4dex. But the star's intrinsic metallicity as estimated from Na, S, and Zn, elements of a low condensation temperature, is [Fe/H]_o_~-0.2 ([Fe/H]_o_ refers to the star's intrinsic metallicity). The star is enriched in N and perhaps O as well, changes reflecting the star's AGB past and the event that led to He enrichment.
- ID:
- ivo://CDS.VizieR/J/A+A/600/A104
- Title:
- Potassium abundance in 3 globular clusters
- Short Name:
- J/A+A/600/A104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derived Potassium abundances in red giant branch stars in the Galactic globular clusters NGC 104 (144 stars), NGC 6752 (134 stars) and NGC 6809 (151 stars) using high-resolution spectra collected with FLAMES at the ESO - Very Large Telescope. In the considered samples we do not find significant intrinsic spreads in [K/Fe] (confirming the previous findings by Carretta et al.), at variance with the cases of the massive clusters NGC 2419 and NGC 2808. Additionally, marginally significant [K/Fe]-[O/Fe] anti-correlations are found in NGC 104 and NGC 6809, and [K/Fe]-[Na/Fe] correlations are found in NGC 104 and NGC 6752. No evidence of [K/Fe]-[Mg/Fe] anti-correlation are found. The results of our analysis are consistent with a scenario in which the process leading to the multi-populations in globular clusters implies also enrichment in the K abundance, the amplitude of the associated [K/Fe] enhancement becoming measurable only in stars showing the most extreme effects of O and Mg depletion. Stars enhanced in [K/Fe] have been found so far only in clusters harbouring some Mg-poor stars, while the other globulars, without a Mg-poor sub-population, show small or null [K/Fe] spreads.
- ID:
- ivo://CDS.VizieR/J/ApJ/769/40
- Title:
- Potassium abundance in red giants of GCs
- Short Name:
- J/ApJ/769/40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Two independent studies recently uncovered two distinct populations among giants in the distant, massive globular cluster (GC) NGC 2419. One of these populations has normal magnesium (Mg) and potassium (K) abundances for halo stars: enhanced Mg and roughly solar K. The other population has extremely depleted Mg and very enhanced K. To better anchor the peculiar NGC 2419 chemical composition, we have investigated the behavior of K in a few red giant branch stars in NGC 6752, NGC 6121, NGC 1904, and {omega} Cen. To verify that the high K abundances are intrinsic and not due to some atmospheric features in giants, we also derived K abundances in less evolved turn-off and subgiant stars of clusters 47 Tuc, NGC 6752, NGC 6397, and NGC 7099. We normalized the K abundance as a function of the cluster metallicity using 21 field stars analyzed in a homogeneous manner. For all GCs of our sample, the stars lie in the K-Mg abundance plane on the same locus occupied by the Mg-normal population in NGC 2419 and by field stars. This holds for both giants and less-evolved stars. At present, NGC 2419 seems unique among GCs.