- ID:
- ivo://CDS.VizieR/J/ApJ/497/330
- Title:
- Candidate main-sequence stars
- Short Name:
- J/ApJ/497/330
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Vega-like sources are main-sequence stars that exhibit IR fluxes in excess of expectations for stellar photospheres, most likely due to reradiation of stellar emission intercepted by orbiting dust grains. We have identified a large sample of main-sequence stars with possible excess IR radiation by cross-correlating the Michigan Catalog of Two-dimensional Spectral Types for the HD Stars with the IRAS Faint Source Survey Catalog. Some 60 of these Vega-like sources were not found during previous surveys of the IRAS database, the majority of which employed the lower sensitivity Point Source Catalog. Here, we provide details of our search strategy, together with a preliminary examination of the full sample of Vega-like sources.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/379/90
- Title:
- Candidate Planetary Nebulae in M81
- Short Name:
- J/A+A/379/90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- File table1.dat contains the identification number, the coordinates (2000), the [OIII]5007 and the H{alpha}+[NII] flux of the candidate PNe detected in Messier 81, using the Isaac Newton Telescope (INT) (La Palma, Spain) in 2000, December and 2001, January. The accuracy on position is approximately 0.5 arcsec.
- ID:
- ivo://CDS.VizieR/J/A+A/367/498
- Title:
- Candidate Planetary Nebulae in M 33
- Short Name:
- J/A+A/367/498
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- File table1.dat contains the identification number, the coordinates (2000), the H{alpha}+[NII] flux and the [OIII]5007 flux of the PNe detected in Messier 33, with the Isaac Newton Telescope (INT) (La Palma, Spain) in 1998, November. File table2.dat contains the identification number, the coordinates (2000), the H{alpha} flux, the [OIII]5007 flux and the continuum flux (at lambda 5550{AA} in Stroemgrem filter) of emission lines objects with non-negligible continuum emission detected in Messier 33, with the INT (La Palma, Spain) in 1998, November.
- ID:
- ivo://CDS.VizieR/J/ApJ/872/199
- Title:
- Candidate spectrophotometric standard DA WDs
- Short Name:
- J/ApJ/872/199
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present precise photometry and spectroscopy for 23 candidate spectrophotometric standard white dwarfs. The selected stars are distributed in the Northern hemisphere and around the celestial equator, and are all fainter than r~16.5mag. This network of stars, when established as standards and together with the three Hubble Space Telescope primary CALSPEC white dwarfs, will provide a set of spectrophotometric standards to directly calibrate data products to better than 1%. In future deep photometric surveys and facilities, these new faint standard white dwarfs will have enough signal-to-noise ratio to be measured accurately while still avoiding saturation. They will also fall within the dynamic range of large telescopes and their instruments for the foreseeable future. This paper discusses the provenance of the observational data for our candidate standard stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/735/41
- Title:
- Carbon and oxygen abundances in FGK stars
- Short Name:
- J/ApJ/735/41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present carbon and oxygen abundances for 941 FGK stars -the largest such catalog to date. We find that planet-bearing systems are enriched in these elements. We self-consistently measure N_C_/N_O_, which is thought to play a key role in planet formation. We identify 46 stars with N_C_/N_O_>=1.00 as potential hosts of carbon-dominated exoplanets. We measure a downward trend in [O/Fe] versus [Fe/H] and find distinct trends in the thin and thick disks, supporting the work of Bensby et al. Finally, we measure sub-solar N_C_/N_O_=0.40^+0.11^_-0.07_, for WASP-12, a surprising result as this star is host to a transiting hot Jupiter whose dayside atmosphere was recently reported to have N_C_/N_O_>=1 by Madhusudhan et al. Our measurements are based on 15,000 high signal-to-noise spectra taken with the Keck 1 telescope as part of the California Planet Search. We derive abundances from the [OI] and CI absorption lines at {lambda}=6300 and 6587{AA} using the SME spectral synthesizer.
- ID:
- ivo://CDS.VizieR/J/ApJ/825/38
- Title:
- Carbon and oxygen isotopic ratios for nearby Miras
- Short Name:
- J/ApJ/825/38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Carbon and oxygen isotopic ratios are reported for a sample of 46 Mira and SRa-type variable asymptotic giant branch (AGB) stars. Vibration-rotation first and second-overtone CO lines in 1.5-2.5{mu}m spectra were measured to derive isotopic ratios for ^12^C/^13^C, ^16^O/^17^O, and ^16^O/^18^O. Comparisons with previous measurements for individual stars and with various samples of evolved stars, as available in the extant literature, are discussed. Models for solar composition AGB stars of different initial masses are used to interpret our results. We find that the majority of M-stars have main sequence masses <=2M_{sun}_ and have not experienced sizable third dredge-up (TDU) episodes. The progenitors of the four S-type stars in our sample are slightly more massive. Of the six C-stars in the sample three have clear evidence relating their origin to the occurrence of TDU. Comparisons with O-rich presolar grains from AGB stars that lived before the formation of the solar system reveal variations in the interstellar medium chemical composition. The present generation of low-mass AGB stars, as represented by our sample of long period variables (LPVs), shows a large spread of ^16^O/^17^O ratios, similar to that of group 1 presolar grains and in agreement with theoretical expectations for the composition of mass 1.2-2M_{sun}_ stars after the first dredge-up. In contrast, the ^16^O/^18^O ratios of present-day LPVs are definitely smaller than those of group 1 grains. This is most probably a consequence of the the decrease with time of the ^16^O/^18^O ratio in the interstellar medium due to the chemical evolution of the Milky Way. One star in our sample has an O composition similar to that of group 2 presolar grains originating in an AGB star undergoing extra-mixing. This may indicate that the extra-mixing process is hampered at high metallicity, or, equivalently, favored at low metallicity. Similarly to O-rich grains, no star in our sample shows evidence of hot bottom burning, which is expected for massive AGB stars.
- ID:
- ivo://CDS.VizieR/J/A+A/632/A32
- Title:
- Carbon depletion observed inside T Tauri inner rims
- Short Name:
- J/A+A/632/A32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The carbon content of protoplanetary disks is an important parameter to characterize planets formed at different disk radii. There is some evidence from far-infrared and submillimeter observations that gas in the outer disk is depleted in carbon, with a corresponding enhancement of carbon-rich ices at the disk midplane. Observations of the carbon content inside of the inner sublimation rim could confirm how much cpc on remains locked in kilometer size bodies in the disk. I aim to determine the density, temperature, and carbon abundance inside the disk dust sublimation rim in a set of T Tauri stars with full protoplanetary disks. Using medium-resolution, near-infrared (0.8 to 2.5um) spectra and the new GAIA DR2 distances, I self-consistently determine the stellar, extinction, veiling, and accretion properties of the 26 stars in my sample. From these values, and non-accreting T Tauri spectral templates, I extract the inner disk excess of the target stars from their observed spectra. Then I identify a series of C0 recombination lines in 18 of these disks and use the CHIANTI atomic line database with an optically thin slab model to constrain the average ne, Te, and nC for these lines in the five disks with a complete set of lines. By comparing these values with other slab models of the inner disk using the Cloudy photoionization code, I also constrain nH and the carbon abundance, XC, and hence the amount of carbon 'missing' from the slab. For one disk, DR Tau, I use relative abundances for the accretion stream from the literature to also determine XSi and XN . The inner disks modeled here are extremely dense (nH~10^16^cm^-3^), warm (Te~4500K), and moderately ionized (logXe~3.3). Three of the five modeled disks show robust carbon depletion up to a factor of 42 relative to the solar value. I discuss multiple ways in which the 'missing' carbon could be locked out of the accreting gas. Given the high-density inner disk gas, evidence for radial drift, and lack of obvious gaps in these three systems, their carbon depletion is most consistent with the 'missing' carbon being sequestered in kilometer size bodies. For DR Tau, nitrogen and silicon are also depleted by factors of 45 and 4, respectively, suggesting that the kilometer size bodies into which the grains are locked were formed beyond the N_2_ snowline. I explore briefly what improvements in the models and observations are needed to better address this topic in the future.
- ID:
- ivo://CDS.VizieR/J/ApJ/824/L19
- Title:
- Carbon-enhanced metal-poor star BD+44493 EWs
- Short Name:
- J/ApJ/824/L19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The carbon-enhanced metal-poor star BD+44{deg}493 ([Fe/H]=-3.9) has been proposed as a candidate second-generation star enriched by metals from a single Pop III star. We report the first detections of P and S and the second detection of Zn in any extremely metal-poor carbon-enhanced star, using new spectra of BD+44493 collected by the Cosmic Origins Spectrograph on the Hubble Space Telescope. We derive [P/Fe]=-0.34+/-0.21, [S/Fe]=+0.07+/-0.41, and [Zn/Fe]=-0.10+/-0.24. We increase by 10-fold the number of SiI lines detected in BD+44493, yielding [Si/Fe]=+0.15+/-0.22. The [S/Fe] and [Zn/Fe] ratios exclude the hypothesis that the abundance pattern in BD+44493 results from depletion of refractory elements onto dust grains. Comparison with zero-metallicity supernova (SN) models suggests that the stellar progenitor that enriched BD+44493 was massive and ejected much less than 0.07M_{sun}_ of ^56^Ni, characteristic of a faint SN.
- ID:
- ivo://CDS.VizieR/J/ApJ/801/125
- Title:
- Carbon in red giants in GCs and dSph galaxies
- Short Name:
- J/ApJ/801/125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present carbon abundances of red giants in Milky Way (MW) globular clusters and dwarf spheroidal galaxies (dSphs). Our sample includes measurements of carbon abundances for 154 giants in the clusters NGC2419, M68, and M15 and 398 giants in the dSphs Sculptor, Fornax, Ursa Minor, and Draco. This sample doubles the number of dSph stars with measurements of [C/Fe]. The [C/Fe] ratio in the clusters decreases with increasing luminosity above (L/L_{sun}_)~=1.6, which can be explained by deep mixing in evolved giants. The same decrease is observed in dSphs, but the initial [C/Fe] of the dSph giants is not uniform. Stars in dSphs at lower metallicities have larger [C/Fe] ratios. We hypothesize that [C/Fe] (corrected to the initial carbon abundance) declines with increasing [Fe/H] due to the metallicity dependence of the carbon yield of asymptotic giant branch stars and due to the increasing importance of SNe Ia at higher metallicities. We also identified 11 very carbon-rich giants (eight previously known) in three dSphs. However, our selection biases preclude a detailed comparison to the carbon-enhanced fraction of the MW stellar halo. Nonetheless, the stars with [C/Fe]<+1 in dSphs follow a different [C/Fe] track with [Fe/H] than the halo stars. Specifically, [C/Fe] in dSphs begins to decline at lower [Fe/H] than in the halo. The difference in the metallicity of the [C/Fe] "knee" adds to the evidence from [{alpha}/Fe] distributions that the progenitors of the halo had a shorter timescale for chemical enrichment than the surviving dSphs.
- ID:
- ivo://CDS.VizieR/J/ApJS/226/1
- Title:
- Carbon stars from LAMOST DR2 data
- Short Name:
- J/ApJS/226/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this work, we present the new catalog of carbon stars from the LAMOST DR2 catalog. In total, 894 carbon stars are identified from multiple line indices measured from the stellar spectra. We are able to identify the carbon stars by combining the CN bands in the red end with C_2_ and other lines. Moreover, we also classify the carbon stars into spectral sub-types of C-H, C-R, and C-N. These sub-types show distinct features in the multi-dimensional line indices, implying that in the future they can be used to identify carbon stars from larger spectroscopic data sets. While the C-N stars are clearly separated from the others in the line index space, we find no clear separation between the C-R and C-H sub-types. The C-R and C-H stars seem to smoothly transition from one to another. This may hint that the C-R and C-H stars may not be different in their origins, instead their spectra look different because of different metallicities. Due to the relatively low spectral resolution and lower signal-to-noise ratio, the ratio of ^12^C/^13^C is not measured and thus the C-J stars are not identified.
