- ID:
- ivo://CDS.VizieR/J/A+A/390/501
- Title:
- Millimetre observations of carbon stars. I.
- Short Name:
- J/A+A/390/501
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Millimetre observations of IRAS selected red carbon stars are presented. About 260 stars have been observed with SEST and IRAM in the CO (1-0) and CO (2-1) lines and partially in HCN (1-0) and SiO (3-2). An overall detection rate, in at least one line, of about 80% is achieved. The survey represents the second largest survey for AGB stars, and the largest ever for carbon stars. Two new detections in SiO (3-2) in carbon stars are reported. When available, the SiO/HCN and HCN/CO(1-0) line ratios are consistent with the ratios expected for carbon stars.
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- ID:
- ivo://CDS.VizieR/J/A+A/390/511
- Title:
- Millimetre observations of carbon stars. II.
- Short Name:
- J/A+A/390/511
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Dust- and gas mass loss rates and distances are determined for a sample of about 330 infra-red carbon stars that probe a distance up to about 5.5kpc. The dependence of the dust- and gas mass loss rates, and the expansion velocity upon galactic longitude (l) are studied. It is found that the expansion velocity significantly depends on l, but that the absolute bolometric magnitude, the dust mass loss rate and the gas-to-dust ratio depend on l marginally, if at all, and the gas mass loss rate does not depend on l. Beyond the solar circle, the expansion velocity (as well as the luminosity, dust-to-gas ratio, dust mass loss rate) is lower than inside the solar circle, as expected from the overall gradient in metallicity content of the Galaxy. Combining the average expansion velocity inside and beyond the solar circle with the theoretically predicted relation between expansion velocity and gas-to-dust ratio, we find that the metallicity gradient in the solar neighbourhood is about -0.034dex/kpc, well within the quoted range of values in the literature.
- ID:
- ivo://CDS.VizieR/J/ApJ/818/106
- Title:
- MILO. I. HD 7449 radial velocities
- Short Name:
- J/ApJ/818/106
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high-contrast Magellan adaptive optics images of HD 7449, a Sun-like star with one planet and a long-term radial velocity (RV) trend. We unambiguously detect the source of the long-term trend from 0.6-2.15{mu}m at a separation of ~0.54". We use the object's colors and spectral energy distribution to show that it is most likely an M4-M5 dwarf (mass ~0.1-0.2M_{sun}_) at the same distance as the primary and is therefore likely bound. We also present new RVs measured with the Magellan/MIKE and Planet Finder Spectrograph (PFS) spectrometers and compile these with archival data from CORALIE and HARPS. We use a new Markov chain Monte Carlo procedure to constrain both the mass (>0.17M_{sun}_ at 99% confidence) and semimajor axis (~18 AU) of the M dwarf companion (HD 7449B). We also refine the parameters of the known massive planet (HD 7449Ab), finding that its minimum mass is 1.09_-0.19_^+0.52^M_J_, its semimajor axis is 2.33_-0.02_^+0.01^AU, and its eccentricity is 0.8_-0.06_^+0.08^. We use N-body simulations to constrain the eccentricity of HD 7449B to <~0.5. The M dwarf may be inducing Kozai oscillations on the planet, explaining its high eccentricity. If this is the case and its orbit was initially circular, the mass of the planet would need to be <~1.5M_J_. This demonstrates that strong constraints on known planets can be made using direct observations of otherwise undetectable long-period companions.
- ID:
- ivo://CDS.VizieR/J/AJ/162/137
- Title:
- Minerva-Australis radial velocity of AU Mic
- Short Name:
- J/AJ/162/137
- Date:
- 14 Mar 2022 08:18:00
- Publisher:
- CDS
- Description:
- We report measurements of the sky-projected spin-orbit angle for AU Mic b, a Neptune-size planet orbiting a very young (~20Myr) nearby pre-main-sequence M-dwarf star, which also hosts a bright, edge-on, debris disk. The planet was recently discovered from preliminary analysis of radial-velocity observations and confirmed to be transiting its host star from photometric data from the NASA's TESS mission. We obtained radial-velocity measurements of AU Mic over the course of two partially observable transits and one full transit of planet b from high-resolution spectroscopic observations made with the MINERVA-Australis telescope array. Only a marginal detection of the Rossiter-McLaughlin effect signal was obtained from the radial velocities, in part due to AU Mic being an extremely active star and the lack of full transit coverage plus sufficient out-of-transit baseline. As such, a precise determination of the obliquity for AU Mic b is not possible in this study and we find a sky-projected spin-orbit angle of {lambda}=47_-54_^+26^deg . This result is consistent with both the planet's orbit being aligned or highly misaligned with the spin axis of its host star. Our measurement independently agrees with, but is far less precise than observations carried out on other instruments around the same time that measure a low-obliquity orbit for the planet. AU Mic is the youngest exoplanetary system for which the projected spin-orbit angle has been measured, making it a key data point in the study of the formation and migration of exoplanets-particularly given that the system is also host to a bright debris disk.
- ID:
- ivo://CDS.VizieR/J/A+A/416/507
- Title:
- Minor-axis velocity gradients in disk galaxies
- Short Name:
- J/A+A/416/507
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the ionized-gas kinematics and photometry of a sample of 4 spiral galaxies which are characterized by a zero-velocity plateau along the major axis and a velocity gradient along the minor axis, respectively. By combining these new kinematical data with those available in the literature for the ionized-gas component of the S0s and spirals listed in the Revised Shapley-Ames Catalog of Bright Galaxies we realized that about 50% of unbarred galaxies show a remarkable gas velocity gradient along the optical minor axis. This fraction rises to about 60% if we include unbarred galaxies with an irregular velocity profile along the minor axis. This phenomenon is observed all along the Hubble sequence of disk galaxies, and it is particularly frequent in early-type spirals. Since minor-axis velocity gradients are unexpected if the gas is moving onto circular orbits in a disk coplanar to the stellar one, we conclude that non-circular and off-plane gas motions are not rare in the inner regions of disk galaxies.
- ID:
- ivo://CDS.VizieR/J/AJ/110/2131
- Title:
- M/L for Draco and UMi. I.
- Short Name:
- J/AJ/110/2131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have measured 206 radial velocities for 94 probable members in the Ursa Minor dwarf spheroidal galaxy and 167 velocities for 91 probable members in the Draco dwarf spheroidal galaxy. These velocities were obtained using the KPNO 4m telescope with the Hydra multifiber positioner and bench spectrograph in 1992, 1993, and 1994. Both simulations and repeated measurements show that the median uncertainty in these velocities is 4.0km/s. Our velocities are compared with the other major datasets for Draco and Ursa Minor. Aside from a small zero-point difference, there is excellent agreement between the Hydra velocities and the Olszewski et al. MMT echelle velocities. Comparison with the Hargreaves et al. Ursa Minor velocities reveals inconsistencies which we ascribe to underestimated errors in the Hargreaves et al. data. After correcting for zero-point differences, we combine the three major sets of velocities. Our spectra recovered all of the known Carbon (C) stars in Draco and Ursa Minor and revealed one new C star in Draco and two in Ursa Minor. In addition, one star whose velocity is consistent with membership in Ursa Minor has a deep and wide HBeta absorption line in its spectrum. An initial discussion of the kinematics of the two galaxies is presented. The systemic velocities of Draco and Ursa Minor are -293.3+/-1.0 and -274+/-1.0km/s, respectively. Ursa Minor shows apparent rotation about a position angle of 75deg with an amplitude of about 3km/s; the morphological major axis is 53+/-5deg. No such rotation is found in Draco. We find a velocity dispersion of 10.4+/-0.9km/s for Ursa Minor including all stars and 8.8+/-0.8km/s excluding the star with the most extreme velocity. In Draco we find 10.7+/-0.9km/s including all stars and 8.5+/-0.7km/s excluding the three stars with the most extreme velocities. These dispersions are consistent with the dispersions measured in the other two studies and confirm that Draco and Ursa Minor have the largest mass-to-light ratios of any of the dwarf spheroidals.
- ID:
- ivo://CDS.VizieR/J/AJ/157/231
- Title:
- MLSDSS-GaiaDR2 sample of M and L dwarfs
- Short Name:
- J/AJ/157/231
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of 74216 M and L dwarfs constructed from two existing catalogs of cool dwarfs spectroscopically identified in the Sloan Digital Sky Survey (SDSS). We cross-matched the SDSS catalog with Gaia DR2 (Cat. I/345) to obtain parallaxes and proper motions and modified the quality cuts suggested by the Gaia Collaboration to make them suitable for late-M and L dwarfs. We also provide relations between Gaia colors and absolute magnitudes with spectral type and conclude that (G-G_RP_) has the tightest relation to spectral type for M and L dwarfs. In addition, we study magnetic activity as a function of position on the color-magnitude diagram, finding that H{alpha} magnetically active stars have, on average, redder colors and/or brighter magnitudes than inactive stars. This effect cannot be explained by youth alone and might indicate that active stars are magnetically inflated, binaries, and/or high metallicity. Moreover, we find that vertical velocity and vertical action dispersion are correlated with H{alpha} emission, confirming that these two parameters are age indicators. We also find that stars below the main sequence have high tangential velocity, which is consistent with a low metallicity and old population of stars that belong to the halo or thick disk.
- ID:
- ivo://CDS.VizieR/J/ApJ/751/55
- Title:
- MMT hypervelocity star survey. II.
- Short Name:
- J/ApJ/751/55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discovery of five new unbound hypervelocity stars (HVSs) in the outer Milky Way halo. Using a conservative estimate of Galactic escape velocity, our targeted spectroscopic survey has now identified 16 unbound HVSs as well as a comparable number of HVSs ejected on bound trajectories. A Galactic center origin for the HVSs is supported by their unbound velocities, the observed number of unbound stars, their stellar nature, their ejection time distribution, and their Galactic latitude and longitude distribution. Other proposed origins for the unbound HVSs, such as runaway ejections from the disk or dwarf galaxy tidal debris, cannot be reconciled with the observations. An intriguing result is the spatial anisotropy of HVSs on the sky, which possibly reflects an anisotropic potential in the central 10-100pc region of the Galaxy. Further progress requires measurement of the spatial distribution of HVSs over the southern sky. Our survey also identifies seven B supergiants associated with known star-forming galaxies; the absence of B supergiants elsewhere in the survey implies there are no new star-forming galaxies in our survey footprint to a depth of 1-2Mpc.
- ID:
- ivo://CDS.VizieR/J/ApJ/813/97
- Title:
- M62 (NGC 6266) giant branch stars abundances
- Short Name:
- J/ApJ/813/97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have collected UVES-FLAMES high-resolution spectra for a sample of 6 asymptotic giant branch (AGB) and 13 red giant branch (RGB) stars in the Galactic globular cluster (GC) M62 (NGC 6266). Here we present the detailed abundance analysis of iron, titanium, and light elements (O, Na, Mg, and Al). For the majority (five out of six) of the AGB targets, we find that the abundances of both iron and titanium determined from neutral lines are significantly underestimated with respect to those obtained from ionized features, the latter being, instead, in agreement with those measured for the RGB targets. This is similar to recent findings in other clusters and may suggest the presence of nonlocal thermodynamic equilibrium (NLTE) effects. In the O-Na, Al-Mg, and Na-Al planes, the RGB stars show the typical correlations observed for GC stars. Instead, all the AGB targets are clumped in the regions where first-generation stars are expected to lie, similar to what was recently found for the AGB population of NGC6752. While the sodium and aluminum abundances could be underestimated as a consequence of the NLTE bias affecting iron and titanium, the oxygen line used does not suffer from the same effects, and the lack of O-poor AGB stars therefore is a solid result. We can thus conclude that none of the investigated AGB stars belongs to the second stellar generation of M62. We also find an RGB star with extremely high sodium abundance ([Na/Fe]=+1.08dex).
- ID:
- ivo://CDS.VizieR/J/A+A/550/A103
- Title:
- Model 1D (LHD) and 3D (CO5BOLD) spectra
- Short Name:
- J/A+A/550/A103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To derive space velocities of stars along the line of sight from wavelength shifts in stellar spectra requires accounting for a number of second-order effects. For most stars, gravitational redshifts, convective blueshifts, and transverse stellar motion are the dominant contributors. We provide theoretical corrections for the net velocity shifts due to convection expected for the measurements from the Gaia Radial Velocity Spectrometer (RVS). We used a set of three-dimensional time-dependent simulations of stellar surface convection computed with CO5BOLD to calculate spectra of late-type stars in the Gaia RVS range and to infer the net velocity offset that convective motions will induce in radial velocities derived by cross-correlation. The net velocity shifts derived by cross-correlation depend both on the wavelength range and spectral resolution of the observations. Convective shifts for Gaia RVS observations are less than 0.1km/s for late-K-type stars, and they increase with stellar mass, reaching about 0.3km/s or more for early F-type dwarfs. This tendency is the result of an increase with effective temperature in both temperature and velocity fluctuations in the line-forming region. Our simulations also indicate that the net RVS convective shifts can be positive (i.e. redshifts) in some cases. Overall, the blueshifts weaken slightly with increasing surface gravity, and are enhanced at low metallicity. Gravitational redshifts amount up to 0.7km/s and dominate convective blueshifts for dwarfs, but become much weaker for giants.
