- ID:
- ivo://CDS.VizieR/J/MNRAS/414/418
- Title:
- Chromospheric Mg II h+k flux of evolved stars
- Short Name:
- J/MNRAS/414/418
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Of a total of 177 cool G, K and M giants and supergiants, we measured the MgII h+k line emission of extended chromospheres in high-resolution (LWR) International Ultraviolet Explorer (IUE) spectra by using the IUE final data archive at the Space Telescope Science Institute (STScI) and derived the respective stellar surface fluxes. They represent the chromospheric radiative energy losses presumably related to basal heating by the dissipation of acoustic waves, plus a highly variable contribution due to magnetic activity.
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- ID:
- ivo://CDS.VizieR/J/A+A/579/A20
- Title:
- Circumstellar debris discs
- Short Name:
- J/A+A/579/A20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Tentative correlations between the presence of dusty circumstellar debris discs and low-mass planets have recently been presented. In parallel, detailed chemical abundance studies have reported different trends between samples of planet and non-planet hosts. Whether these chemical differences are indeed related to the presence of planets is still strongly debated. We aim to test whether solar-type stars with debris discs show any chemical peculiarity that could be related to the planet formation process. We determine in a homogeneous way the metallicity, [Fe/H], and abundances of individual elements of a sample of 251 stars including stars with known debris discs, stars harbouring simultaneously debris discs and planets, stars hosting exclusively planets, and a comparison sample of stars without known discs or planets. High-resolution echelle spectra (R~57000) from 2-3m class telescopes are used. Our methodology includes the calculation of the fundamental stellar parameters (T_eff_, logg, microturbulent velocity, and metallicity) by applying the iron ionisation and equilibrium conditions to several isolated Fe i and Fe ii lines, as well as individual abundances of C, O, Na, Mg, Al, Si, S, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, and Zn.
- ID:
- ivo://CDS.VizieR/J/A+A/606/A67
- Title:
- Circumstellar envelopes CO photodissociation
- Short Name:
- J/A+A/606/A67
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Carbon monoxide is the most abundant molecule after H_2_ and is important for chemistry in circumstellar envelopes around late-type stars. The size of the envelope is important when modelling low-J transition lines and deriving mass-loss rates from such lines. Now that ALMA is coming to full power the extent of the CO emitting region can be measured directly for nearby asymptotic giant branch (AGB) stars. In parallel, it has become obvious in the past few years that the strength of the interstellar radiation field (ISRF) can have a significant impact on the interpretation of the emission lines. In this paper an update and extension of the classical Mamon et al. (1988ApJ...328..797M) paper is presented; these authors provided the CO abundance profile, described by two parameters, as a function of mass-loss rate and expansion velocity. Following recent work an improved numerical method and updated H_2_ and CO shielding functions are used and a larger grid is calculated that covers more parameter space, including the strength of the ISRF. The effect of changing the photodissociation radius on the low-J CO line intensities is illustrated in two cases.
- ID:
- ivo://CDS.VizieR/J/A+A/600/A71
- Title:
- C17O and C18O spectra of nine AGB stars
- Short Name:
- J/A+A/600/A71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We seek to investigate the ^17^O/^18^O ratio for a sample of AGB stars containing M-, S-, and C-type stars. These ratios are evaluated in relation to fundamental stellar evolution parameters: the stellar initial mass and pulsation period. Circumstellar ^13^C^16^O, ^12^C^17^O, and ^12^C^18^O line observations were obtained for a sample of nine stars with various singledish long-wavelength facilities. Line intensity ratios are shown to relate directly to the surface ^17^O/^18^O abundance ratio. Stellar evolution models predict the ^17^O/^18^O ratio to be a sensitive function of initial mass and to remain constant throughout the entire TP-AGB phase for stars initially less massive than 5 solar masses. This makes the measured ratio a probe of the initial stellar mass. Observed ^17^O/^18^O ratios are found to be well in the range predicted by stellar evolution models that do not consider convective overshooting. From this, accurate initial mass estimates are calculated for seven sources. For the remaining two sources, there are two mass solutions, although there is a larger probability that the low-mass solution is correct. Finally, we present hints at a possible separation between M/S- and C-type stars when comparing the ^17^O/^18^O ratio to the stellar pulsation period.
- ID:
- ivo://CDS.VizieR/J/A+AS/99/291
- Title:
- CO and HCN observations of circumstellar envelopes
- Short Name:
- J/A+AS/99/291
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have searched the literature for all observations of the ^12^CO(1-0), ^12^CO(2-1), and HCN(1-0) lines in circumstellar envelopes of late type stars published between January 1985 and September 1992. We report data for 1361 observations (stellar velocity, expansion velocity, peak intensity, integrated area, noise level). This CO-HCN sample now contains 444 sources. 184 are identified as oxygen-rich, 205 as carbon-rich, and there are 9 S stars. About 85% of the sources are AGB stars. There are 32 planetary nebulae and about thirty post-AGB stars candidates. Besides results of millimeter observations, we also list identifications, coordinates, IRAS data, chemical and spectral types for every source. For AGB stars, we have estimated (or compiled) bolometric fluxes and distances for 349 sources, and mass loss rates deduced from CO results for 324 sources, taking into account the influence of the CO photodissociation radius. We also list mass loss rates derived from detailed models of CO emission which we could find in the literature.
- ID:
- ivo://CDS.VizieR/J/A+AS/93/121
- Title:
- CO emission from a sample of IRAS sources
- Short Name:
- J/A+AS/93/121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The first results from a survey of circumstellar CO(1-0) emission are presented. The sources were selected from the IRAS point source catalog according to the IRAS color criteria described in van der Veen and Habing (1988A&A...194..125V). The sources have good quality fluxes at 12, 25, and 60 microns, flux densities larger than 20Jy at 25{mu}m, and are situated more than 5{deg} away from the Galactic plane. The survey is undertaken to study the relationship between mass loss rates, dust properties, and the evolution along the AGB. The sample consists of 787 sources and contains both oxygen and carbon-rich stars, including Mira variables, OH/IR objects, protoplanetary nebulae, planetary nebulae, and 60-micron excess sources. So far, 519 objects, situated on both the northern and the southern sky, have been observed; 163 sources were found to have circumstellar CO emission, and in 58 of these CO emission has not previously been detected.
- ID:
- ivo://CDS.VizieR/J/AJ/139/1808
- Title:
- Colors and kinematics of SDSS L dwarfs
- Short Name:
- J/AJ/139/1808
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of 484 L dwarfs, 210 of which are newly discovered from the Sloan Digital Sky Survey (SDSS) Data Release 7 spectroscopic database. We combine this sample with known L dwarfs to investigate their izJHKS colors. We present photometric distance relations based on i-z and i-J colors and derive distances to our L dwarf sample. We combine the distances with SDSS/2MASS proper motions in order to examine the tangential velocities.
- ID:
- ivo://CDS.VizieR/J/A+A/551/A46
- Title:
- Compiled photometry for Cham I and II members
- Short Name:
- J/A+A/551/A46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a proper motion study aiming at providing further evidence on the origin of the proposed stellar members of the Chamaeleon I and II clouds and to identify interlopers from the foreground young clusters {epsilon} Cha and {eta} Cha. We compiled lists of spectroscopically confirmed members of the four associations, and of background objects in the same line of sight. Using Virtual Observatory tools, we cross-matched these lists with the UCAC3 (Cat. I/315) catalogue to get proper motions for the objects. In the vector point diagram, we identified the different moving groups, and used this information to study the membership of proposed candidate members of the associations from the literature. For those objects with available radial velocities, we computed their Galactic space velocities. We compiled photometry from public data archives and from the literature for the Cha I and II objects. We looked for correlations between the properties of the objects and their proper motions.
- ID:
- ivo://CDS.VizieR/J/A+A/557/A104
- Title:
- CO observations of post-AGB stars
- Short Name:
- J/A+A/557/A104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- There is a group of binary post-AGB stars that show conspicuous near infrared (NIR) excess, which is usually assumed to arise from hot dust in very compact possibly rotating disks. These stars are surrounded by significantly fainter nebulae than the standard, well studied protoplanetary and planetary nebulae (PPNe, PNe). We aim to identify and study extended rotating disks around these stars and shed light on the role of disks in the formation and shaping of planetary nebulae. We present high-sensitivity mm-wave observations of CO lines in 24 objects of this type. The resulting CO lines are compared with profiles expected to arise from rotating disks, from both theoretical and observational grounds. We derive simple formulae that allow us to determine the mass of the CO-emitting gas and estimate its extent. The reliability and uncertainty of the methods are also widely discussed. CO emission is detected in most observed sources, and the line profiles show that the emissions very probably come from disks in rotation. We derive typical values of the disk mass between 10^-3^ and 10^-2^M_{sun}_, about two orders of magnitude lower than the (total) masses of standard PPNe. The high-detection rate (upper limits being not very significant) clearly confirm that the NIR excess of these stars arises from compact disks in rotation, which are likely the inner parts of those found here. Low-velocity outflows are also found in about eight objects with moderate expansion velocities of ~10km/s, to be compared with the velocities of about 100km/s often found in standard PPNe. Except for two sources with complex profiles, the outflowing gas in our objects represents a minor nebular component. Our simple estimates of the typical disk sizes yields values ~0.5-1arcsec, which is between 5x10^15^ and 3x10^16^cm. Estimates of the linear momenta carried by the outflows, which can only be performed in a few well studied objects, also yield moderate values when compared to the linear momenta that can be released by the stellar radiation pressure (contrary, again, to the case of the very massive and fast bipolar outflows in $standard$ PPNe that are strongly overluminous). The mass and dynamics of nebulae around various classes of post-AGB stars differ very significantly, and we can expect the formation of PNe with very different properties.
- ID:
- ivo://CDS.VizieR/J/PASP/106/452
- Title:
- Cool Dwarfs - Temperatures
- Short Name:
- J/PASP/106/452
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The file contains values of Cousins R-I and theta [= 5040/T(eff)] for 417 F-K stars which are on or near the main sequence.
