- ID:
- ivo://CDS.VizieR/J/A+A/624/A107
- Title:
- IK Tau & IRC+10011 interferometric observations
- Short Name:
- J/A+A/624/A107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- AGB stars go through a process of strong mass-loss that involves pulsations of the atmosphere, which extends to a region where the conditions are adequate for dust grains to form. Radiation pressure acts on these grains which, coupled to the gas, drive a massive outflow. The details of this process are not clear, including which molecules are involved in the condensation of dust grains. To study the role of the SiO molecule in the process of dust formation and mass-loss in M-type AGB stars. Using the IRAM NOEMA interferometer we observed the ^28^SiO and ^29^SiO J=3-2, v=0 emission from the inner circumstellar envelope of the evolved stars IK Tau and IRC+10011. We computed azimuthally averaged emission profiles to compare the observations to models using a molecular excitation and ray-tracing code for SiO thermal emission. We observed circular symmetry in the emission distribution. We also found that the source diameter varies only marginally with radial velocity, which is not the expected behavior for envelopes expanding at an almost constant velocity. The adopted density, velocity, and abundance laws, together with the mass-loss rate, which best fit the observations, give us information on the chemical behavior of the SiO molecule and its role in the dust formation process. The results indicate that there is a strong coupling between the depletion of gas phase SiO and gas acceleration in the inner envelope. This could be explained by the condensation of SiO into dust grains.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/131/612
- Title:
- Infrared-optical phase lags in AGB stars
- Short Name:
- J/AJ/131/612
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To search for phase lags in the optical-infrared light curves of asymptotic giant branch stars, we have compared infrared data from the COBE DIRBE satellite with optical light curves from the AAVSO and other sources. We found 17 examples of phase lags between the times of infrared and optical maximum, and 4 stars with no observed lags.
- ID:
- ivo://CDS.VizieR/J/AJ/144/148
- Title:
- Infrared photometry of brown dwarf and Hyper-LIRG
- Short Name:
- J/AJ/144/148
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Spitzer 3.6 and 4.5{mu}m photometry and positions for a sample of 1510 brown dwarf candidates identified by the Wide-field Infrared Survey Explorer (WISE) all-sky survey. Of these, 166 have been spectroscopically classified as objects with spectral types M(1), L(7), T(146), and Y(12). Sixteen other objects are non-(sub)stellar in nature. The remainder are most likely distant L and T dwarfs lacking spectroscopic verification, other Y dwarf candidates still awaiting follow-up, and assorted other objects whose Spitzer photometry reveals them to be background sources. We present a catalog of Spitzer photometry for all astrophysical sources identified in these fields and use this catalog to identify seven fainter (4.5{mu}m~17.0mag) brown dwarf candidates, which are possibly wide-field companions to the original WISE sources. To test this hypothesis, we use a sample of 919 Spitzer observations around WISE-selected high-redshift hyper-luminous infrared galaxy candidates. For this control sample, we find another six brown dwarf candidates, suggesting that the seven companion candidates are not physically associated. In fact, only one of these seven Spitzer brown dwarf candidates has a photometric distance estimate consistent with being a companion to the WISE brown dwarf candidate. Other than this, there is no evidence for any widely separated (>20AU) ultra-cool binaries. As an adjunct to this paper, we make available a source catalog of ~7.33x10^5^ objects detected in all of these Spitzer follow-up fields for use by the astronomical community. The complete catalog includes the Spitzer 3.6 and 4.5{mu}m photometry, along with positionally matched B and R photometry from USNO-B; J, H, and K_s_ photometry from Two Micron All-Sky Survey; and W1, W2, W3, and W4 photometry from the WISE all-sky catalog.
- ID:
- ivo://CDS.VizieR/J/AJ/160/253
- Title:
- Infrared photometry of late-type dwarfs in Kepler Field
- Short Name:
- J/AJ/160/253
- Date:
- 08 Dec 2021
- Publisher:
- CDS
- Description:
- While it is well-established that giant-planet occurrence rises rapidly with host star metallicity, it is not yet clear if small-planet occurrence around late-type dwarf stars depends on host star metallicity. Using the Kepler Data Release 25 planet candidate list and its completeness data products, we explore planet occurrence as a function of metallicity in the Kepler field's late-type dwarf stellar population. We find that planet occurrence increases with metallicity for all planet radii Rp down to at least Rp~2R{Earth}, and that in the range 2R{Earth}<~Rp<~5R{Earth}, planet occurrence scales linearly with metallicity Z. Extrapolating our results, we predict that short-period planets with Rp<~2R{Earth} should be rare around early-M dwarf stars with [M/H]<~-0.5 or late-M dwarf stars with [M/H]<~+0.0. This dependence of planet occurrence on metallicity observed in the Kepler field emphasizes the need to control for metallicity in estimates of planet occurrence for late-type dwarf stars like those targeted by Kepler's K2 extension and the Transiting Exoplanet Survey Satellite. We confirm the theoretical expectation that the small-planet occurrence-host star metallicity relation is stronger for low-mass stars than for solar-type stars. We establish that the expected solid mass in planets around late-type dwarfs in the Kepler field is comparable to the total amount of planet-making solids in their protoplanetary disks. We argue that this high efficiency of planet formation favors planetesimal accretion over pebble accretion as the origin of the small planets observed by Kepler around late-type dwarf stars.
- ID:
- ivo://CDS.VizieR/J/A+A/372/245
- Title:
- Infrared properties of barium stars
- Short Name:
- J/A+A/372/245
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a systematic survey for IRAS associations of barium stars. A total of 155 associations were detected, and IRAS low-resolution spectra exist for 50 barium stars. We use different color-color diagrams from the visual band to 60{mu}m, relations between these colors and the spectral type, the barium intensity, and the IRAS low-resolution spectra to discuss physical properties of barium stars in the infrared. It is confirmed that most barium stars have infrared excesses in the near infrared. However, a new result of this work is that most barium stars have no excesses in the far infrared. This fact may imply that infrared excesses of barium stars are mainly due to the re-emission of energy lost from the Bond-Neff depression. It is also shown that the spectral type and the barium intensity of barium stars are not correlated with infrared colors, but may be correlated with V-K color.
- ID:
- ivo://CDS.VizieR/J/A+A/505/L5
- Title:
- Infrared radial velocities of vB10
- Short Name:
- J/A+A/505/L5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present radial velocities of the M8V-type, very low-mass star vB 10 obtained at four different epochs between 2001 and 2008. We use high-resolution (R~20000) near-infrared (J-band) spectra taken with the NIRSPEC instrument on the Keck II telescope. Our data suggest that vB 10 shows radial velocity variability with an amplitude of ~1km/s, a result that is consistent with the recent finding of a massive planet companion around the star. More velocity measurements and a better sampling of the orbital phase are required to precisely constrain the orbital parameters and the individual masses of the pair.
- ID:
- ivo://CDS.VizieR/J/MNRAS/446/1584
- Title:
- IRAC point sources for M32
- Short Name:
- J/MNRAS/446/1584
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the population of cool, evolved stars in the Local Group dwarf elliptical galaxy M32, using Infrared Array Camera observations from the Spitzer Space Telescope. We construct deep mid-infrared colour-magnitude diagrams for the resolved stellar populations within 3.5 arcmin of M32's centre, and identify those stars that exhibit infrared excess. Our data are dominated by a population of luminous, dust-producing stars on the asymptotic giant branch (AGB) and extend to approximately 3 mag below the AGB tip. We detect for the first time a sizeable population of `extreme' AGB stars, highly enshrouded by circumstellar dust and likely completely obscured at optical wavelengths. The total dust-injection rate from the extreme AGB candidates is measured to be 7.5x10^-7^M_{sun}_/yr, corresponding to a gas mass-loss rate of 1.5x10^-4^M_{sun}_/yr. These extreme stars may be indicative of an extended star formation epoch between 0.2 and 5Gyr ago.
- ID:
- ivo://CDS.VizieR/III/170B
- Title:
- IRAS Point Source Identifications
- Short Name:
- III/170B
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The file "ps_class.dat" is an ASCII text file containing the classifications of 14,192 IRAS Point Sources with the flux at 12{mu}m greater than the flux at 25{mu}m and falling within about 7{deg} of the galactic plane. The aim has been to provide classifications of IRAS-PS with no previous associations, so most bright stars such as in the BSC, SAO, and HD which have associations and good spectral types are not included. Also, many known carbon stars from the catalogue of Stephenson known to be associated with PS are not included.
- ID:
- ivo://CDS.VizieR/J/A+A/387/129
- Title:
- IR observations of S stars
- Short Name:
- J/A+A/387/129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometric observations in the near infrared for 161 S stars, including 18 Tc-rich (intrinsic) stars, 19 Tc-deficient (extrinsic) ones and 124 candidates for Tc-deficient S stars, are presented in this paper. Based on some further investigations into the infrared properties of both Tc-rich and Tc-deficient S stars, 104 candidates are identified as very likely Tc-deficient S stars. The large number of infrared-selected Tc-deficient S stars provides a convenient way to study the physical properties and the evolutionary status of this species of S stars.
- ID:
- ivo://CDS.VizieR/J/AJ/162/187
- Title:
- IRTF spectral indices for giant stars
- Short Name:
- J/AJ/162/187
- Date:
- 15 Mar 2022
- Publisher:
- CDS
- Description:
- We present infrared spectral indices (1.0-2.3{mu}m) of Galactic late-type giants and red supergiants (RSGs). We used existing and new spectra obtained at resolution power R=2000 with SpeX on the IRTF telescope. While a large CO equivalent width (EW), at 2.29{mu}m ([CO,2.29]>~45{AA}) is a typical signature of RSGs later than spectral type M0, [CO] of K-type RSGs and giants are similar. In the [CO,2.29] versus [MgI,1.71] diagram, RSGs of all spectral types can be distinguished from red giants because the MgI line weakens with increasing temperature and decreasing gravity. We find several lines that vary with luminosity, but not temperature: SiI (1.59{mu}m), Sr (1.033{mu}m), Fe+Cr+Si+CN (1.16{mu}m), Fe+Ti (1.185{mu}m), Fe+Ti (1.196{mu}m), Ti+Ca (1.28{mu}m), and Mn (1.29{mu}m). Good markers of CN enhancement are the Fe+Si+CN line at 1.087{mu}m and CN line at 1.093{mu}m. Using these lines, at the resolution of SpeX, it is possible to separate RSGs and giants. Contaminant O-rich Mira and S-type AGBs are recognized by strong molecular features due to water vapor features, TiO band heads, and/or ZrO absorption. Among the 42 candidate RSGs that we observed, all but one were found to be late types. Twenty-one have EWs consistent with those of RSGs, 16 with those of O-rich Mira AGBs, and one with an S-type AGB. These infrared results open new, unexplored, potential for searches at low resolution of RSGs in the highly obscured innermost regions of the Milky Way.
