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- ID:
- ivo://CDS.VizieR/J/ApJ/877/104
- Title:
- High-res. spectroscopy of LAMOST Li-rich giants
- Short Name:
- J/ApJ/877/104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The discovery of Li-rich giants has introduced a new challenge for standard stellar evolution models. To resolve this issue, the number of this type of object has been rapidly increased through the development of worldwide surveys. Taking advantage of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope survey, 44 new Li-rich giants are reported, which are confirmed with high-resolution observations. Based on the high-resolution and high signal-to-noise spectra, we derived the atmospheric parameters and elemental abundances with the spectral synthesis method. We performed a detailed analysis of their evolutionary stages, infrared excess, projected rotational velocity (vsini), and stellar population. We find that (1) the Li-rich giants concentrate at the evolutionary status of the red giant branch bump, red clump, and asymptotic giant branch; (2) three of them are fast rotators and none exhibit infrared excess. Our results imply that the origins of Li enrichment are most likely to be associated with the extra mixing in the stellar interior, and the external sources might only make a minor contribution. Moreover, various Li-rich episodes take place at different evolutionary stages.
6283. High Speed Photometer
- ID:
- ivo://archive.stsci.edu/hst/hsp
- Title:
- High Speed Photometer
- Short Name:
- HST.HSP
- Date:
- 23 Jul 2020 19:49:53
- Publisher:
- Space Telescope Science Institute Archive
- Description:
- The High Speed Photometer (HSP) was one of the four original axial instruments on the Hubble Space Telescope (HST). The HSP was designed to make very rapid photometric observations of astrophysical sources in a variety of filters and passbands from the near ultraviolet to the visible. The HSP was removed from HST during the First Servicing Mission in December, 1993.
- ID:
- ivo://CDS.VizieR/J/A+A/638/A122
- Title:
- High-speed stars. Galactic hitchhikers
- Short Name:
- J/A+A/638/A122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The search for stars born in the very early stages of the Milky Way star formation history is of paramount importance in the study of the early Universe since their chemistry carries irreplaceable information on the conditions in which early star formation and galaxy buildup took place. The search for these objects has generally taken the form of expensive surveys for faint extremely metal-poor stars, the most obvious but not the only candidates to a very early formation. Thanks to Gaia DR2 radial velocities and proper motions, we identified 72 bright cool stars displaying heliocentric transverse velocities in excess of 500km/s. These objects are most likely members of extreme outer-halo populations, either formed in the early Milky Way build-up or accreted from since-destroyed self-gravitating stellar systems. We analysed low-resolution FORS spectra of the 72 stars in the sample and derived the abundances of a few elements. Despite the large uncertainties on the radial velocity determination, we derived reliable orbital parameters for these objects. The stars analysed are mainly slightly metal poor, with a few very metal-poor stars. Their chemical composition is much more homogeneous than expected. All the stars have very eccentric halo orbits, some extending well beyond the expected dimension of the Milky Way. These stars can be the result of a disrupted small galaxy or they could have been globular cluster members. Age estimates suggest that some of them are evolved blue stragglers, now on the subgiant or asymptotic giant branches.
- ID:
- ivo://CDS.VizieR/J/ApJS/209/12
- Title:
- High-velocity clouds from GASS. I.
- Short Name:
- J/ApJS/209/12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of high-velocity clouds (HVCs) from the Galactic All Sky Survey (GASS) of southern sky neutral hydrogen, which has 57mK sensitivity and 1 km/s velocity resolution and was obtained with the Parkes Telescope. Our catalog has been derived from the stray-radiation-corrected second release of GASS. We describe the data and our method of identifying HVCs and analyze the overall properties of the GASS population. We catalog a total of 1693 HVCs at declinations <0{deg}, including 1111 positive velocity HVCs and 582 negative velocity HVCs. Our catalog also includes 295 anomalous velocity clouds (AVCs). The cloud line-widths of our HVC population have a median FWHM of ~19 km/s, which is lower than that found in previous surveys. The completeness of our catalog is above 95% based on comparison with the HIPASS catalog of HVCs upon which we improve by an order of magnitude in spectral resolution. We find 758 new HVCs and AVCs with no HIPASS counterpart. The GASS catalog will shed unprecedented light on the distribution and kinematic structure of southern sky HVCs, as well as delve further into the cloud populations that make up the anomalous velocity gas of the Milky Way.
- ID:
- ivo://CDS.VizieR/J/ApJS/140/331
- Title:
- High-velocity HI observations at 21cm
- Short Name:
- J/ApJS/140/331
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Very sensitive HI 21cm observations have been made in 860 directions at {delta}>=-43{deg} in search of weak, Galactic, high-velocity HI emission lines at moderate and high Galactic latitudes.
- ID:
- ivo://CDS.VizieR/J/A+AS/142/25
- Title:
- High velocity HI Southern Survey
- Short Name:
- J/A+AS/142/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new high-sensitivity HI survey of the southern sky was made south of Declination -25{deg}, at the Instituto Argentino de Radioastronomia (IAR), on a half-degree grid in galactic coordinates. A total of 50980 positions were observed. One of the goals of this survey was to search for high velocity clouds (HVCs). The HI profiles have been smoothed to a velocity resolution of 8km/s. The resulting rms noise falls in the range 0.015 to 0.020K. We have detected 6848 high velocity (HV) components.
- ID:
- ivo://CDS.VizieR/J/ApJS/252/3
- Title:
- High-velocity stars in the Gal. halo from LAMOST & Gaia
- Short Name:
- J/ApJS/252/3
- Date:
- 03 Mar 2022 11:59:54
- Publisher:
- CDS
- Description:
- In this paper, we report 591 high-velocity star candidates (HiVelSCs) selected from over 10 million spectra of Data Release 7 (DR7) of the Large Sky Area Multi-object Fiber Spectroscopic Telescope and the second Gaia data release, with three-dimensional velocities in the Galactic rest frame larger than 445km/s. We show that at least 43 HiVelSCs are unbound to the Galaxy with escape probabilities larger than 50%, and this number decreases to eight if the possible parallax zero-point error is corrected. Most of these HiVelSCs are metal-poor and slightly {alpha}-enhanced inner halo stars. Only 14% of them have [Fe/H]>-1, which may be the metal-rich "in situ" stars in the halo formed in the initial collapse of the Milky Way or metal-rich stars formed in the disk or bulge but kinematically heated. The low ratio of 14% implies that the bulk of the stellar halo was formed from the accretion and tidal disruption of satellite galaxies. In addition, HiVelSCs on retrograde orbits have slightly lower metallicities on average compared with those on prograde orbits; meanwhile, metal-poor HiVelSCs with [Fe/H]{<}-1 have an even faster mean retrograde velocity compared with metal-rich HiVelSCs. To investigate the origins of HiVelSCs, we perform orbit integrations and divide them into four types, i.e., hypervelocity stars, hyper-runaway stars, runaway stars and fast halo stars.
- ID:
- ivo://CDS.VizieR/J/PASP/110/1434
- Title:
- High-velocity stars radial velocities
- Short Name:
- J/PASP/110/1434
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe methods for extracting quantitative spectra and astrometric positions from objective prism plates. In particular, we have studied 7161 stars in eight fields along the south Galactic meridian using the 6{deg}+4{deg} objective prisms on the Curtis Schmidt telescope at Cerro Tololo Inter-American Observatory. In this paper we concentrate on techniques for deriving radial velocities and astrometric positions from opposed dispersion plate pairs. For our data the typical accuracy in radial velocity is ~8km/s. A catalog of 108 stars with high radial velocities is presented, which is complete (and unbiased in either kinematics or metallicity) to a limiting B magnitude of 12.5 in the eight fields studied. Only two of this sample of 108 stars have previously reported radial velocities.
- ID:
- ivo://CDS.VizieR/J/AJ/103/514
- Title:
- High-velocity stars toward South Galactic Cap
- Short Name:
- J/AJ/103/514
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present spectroscopic observations of stars identified in Murray's (1986) astrometric survey of the South Galactic Cap