- ID:
- ivo://CDS.VizieR/J/AJ/130/2677
- Title:
- Stars in the Carina dSph galaxy field
- Short Name:
- J/AJ/130/2677
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The question of the existence of active and prominent tidal disruption around various Galactic dwarf spheroidal (dSph) galaxies remains controversial. That debate often centers on the nature (bound vs. unbound) of extended populations of stars claimed to lie outside the bounds of single King profiles fitted to the density distributions of dSph centers. However, the more fundamental issue of the very existence of the previously reported extended populations is still contentious. We present a critical evaluation of the debate centering on one particular dSph, Carina, for which claims both for and against the existence of stars beyond the King limiting radius have been made.
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- ID:
- ivo://CDS.VizieR/J/ApJS/251/29
- Title:
- Stellar bow shock nebulae spectroscopic obs.
- Short Name:
- J/ApJS/251/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Arcuate mid-infrared nebulae known as stellar bow shock nebulae (SBNe) have been previously hypothesized to be supported by the strong stellar winds and/or luminosity of massive early-type stars. We present an optical spectroscopic survey of 84 stars identified from mid-infrared images as candidate SBN-supporting stars. Eighty-one of 84 sources, 96%, are O or early-B spectral types. K-band luminosities for a larger sample of 289 stars at the centers of bow shock nebulae are overwhelmingly consistent with OB stars. This affirms both that SBNe are supported by massive stars and that arcuate mid-infrared nebulae are reliable indicators of the presence of a massive star. The radial velocity dispersions of these systems and detections of double-lined systems indicate that at least 27 of the 74 systems with multiple observations (>36%) are candidate multiple-star systems. This rate is consistent with observed multiplicity rates of field OB stars detected with similar radial velocity surveys and lower than, but not inconsistent with, the multiplicity rates of OB stars in clusters and associations.
- ID:
- ivo://CDS.VizieR/J/AJ/103/1205
- Title:
- Stellar Content of LH 9 and 10 in the LMC
- Short Name:
- J/AJ/103/1205
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CCD photometry and spectroscopy for stars in Lucke-Hodge 9 and 10, two adjacent OB association in the northwest corner of the LMC. Our catalog contains UBV photometry (complete to ~18mag in all three filters) for 795 stars and BV-only photometry (complete to ~19mag in both filters) for an additional 434 stars.
- ID:
- ivo://CDS.VizieR/J/AJ/105/980
- Title:
- Stellar content of Tr 14 and Tr 16
- Short Name:
- J/AJ/105/980
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The stellar content of the region around {eta} Car is investigated using CCD photometry and spectroscopy.
- ID:
- ivo://CDS.VizieR/J/ApJ/596/437
- Title:
- Stellar-mass black holes in the SDSS
- Short Name:
- J/ApJ/596/437
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We search for nearby, isolated, accreting, "stellar-mass" (3-100M_{sun}_) black holes. Models suggest a synchrotron spectrum in visible wavelengths and some emission in X-ray wavelengths. Of 3.7 million objects in the Sloan Digital Sky Survey Early Data Release, Cat. <J/AJ/123/567>, about 150,000 objects have colors and properties consistent with such a spectrum, and 87 of these objects are X-ray sources from the ROSAT All-Sky Survey (Cat. <IX/10> and <IX/29>). Thirty-two of these have been confirmed not to be black holes using optical spectra. We give the positions and colors of these 55 black hole candidates and quantitatively rank them on their likelihood to be black holes. We discuss uncertainties in the expected number of sources and the contribution of black holes to local dark matter.
- ID:
- ivo://CDS.VizieR/J/A+A/589/A61
- Title:
- Stellar parameters and abundances for M30
- Short Name:
- J/A+A/589/A61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The prediction of the PLANCK-constrained primordial lithium abundance in the Universe is in discordance with the observed Li abundances in warm Population II dwarf and subgiant stars. Among the physically best motivated ideas, it has been suggested that this discrepancy can be alleviated if the stars observed today had undergone photospheric depletion of lithium. The cause of this depletion is investigated by accurately tracing the behaviour of the lithium abundances as a function of effective temperature. Globular clusters are ideal laboratories for such an abundance analysis as the relative stellar parameters of their stars can be precisely determined. We performed a homogeneous chemical abundance analysis of 144 stars in the metal-poor globular cluster M30, ranging from the cluster turnoff point to the tip of the red giant branch. Non-local thermal equilibrium (NLTE) abundances for Li, Ca, and Fe were derived where possible by fitting spectra obtained with VLT/FLAMES-GIRAFFE using the quantitative-spectroscopy package SME. Stellar parameters were derived by matching isochrones to the observed V vs V-I colour-magnitude diagram. Independent effective temperatures were obtained from automated profile fitting of the Balmer lines and by applying colour-Teff calibrations to the broadband photometry.
- ID:
- ivo://CDS.VizieR/J/A+A/567/A72
- Title:
- Stellar parameters and abundances in NGC 6752
- Short Name:
- J/A+A/567/A72
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Abundance trends in heavier elements with evolutionary phase have been shown to exist in the globular cluster NGC 6752. These trends are a result of atomic diffusion and additional (non-convective) mixing. Studying such trends can provide us with important constraints on the extent to which diffusion modifies the internal structure and surface abundances of solar-type, metal-poor stars. Taking advantage of a larger data sample, we investigate the reality and the size of these abundance trends and address questions and potential biases associated with the various stellar populations that make up NGC 6752. We perform an abundance analysis by combining photometric and spectroscopic data of 194 stars located between the turnoff point and the base of the red giant branch. Stellar parameters are derived from uvby Stromgren photometry. Using the quantitative-spectroscopy package SME, stellar surface abundances for light elements such as Li, Na, Mg, Al, and Si as well as heavier elements such as Ca, Ti, and Fe are derived in an automated way by fitting synthetic spectra to individual lines in the stellar spectra, obtained with the VLT/FLAMES-GIRAFFE spectrograph. Based on uvby Stromgren photometry, we are able to separate three stellar populations in NGC 6752 along the evolutionary sequence from the base of the red giant branch down to the turnoff point. We find weak systematic abundance trends with evolutionary phase for Ca, Ti, and Fe which are best explained by stellar-structure models including atomic diffusion with efficient additional mixing. We derive a new value for the initial lithium abundance of NGC 6752 after correcting for the effect of atomic diffusion and additional mixing which falls slightly below the predicted standard BBN value. We find three stellar populations by combining photometric and spectroscopic data of 194 stars in the globular cluster NGC 6752. Abundance trends for groups of elements, differently affected by atomic diffusion and additional mixing, are identified. Although the statistical significance of the individual trends is weak, they all support the notion that atomic diffusion is operational along the evolutionary sequence of NGC 6752.
- ID:
- ivo://CDS.VizieR/J/A+A/517/A3
- Title:
- Stellar parameters of Kepler early-type targets
- Short Name:
- J/A+A/517/A3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar pulsation offers a unique opportunity to constrain the intrinsic parameters of stars and to unveil their inner structure. Kepler satellite is collecting a huge amount of data of unprecedent photometric precision, that will allow us to test theory and obtain a very precise tomography of stellar interiors. Aiming at providing the stars' fundamental parameters (Teff, logg, vsini, and luminosity) which are needed for computing asteroseismic models and interpreting Kepler data, we report spectroscopic observations of 23 early-type Kepler asteroseismic targets and 13 other stars in the Kepler field, but not selected to be observed. The cross-correlation with template spectra was used for measuring the radial velocity with the aim of identifying non-single stars. Spectral synthesis has been performed in order to derive the stellar parameters for our target stars. State-of-art LTE atmospheric models have been computed. For all the stars of our sample, we derive the radial velocity, Teff, logg, vsini, and luminosities. Further, for 12 stars, we perform a detailed abundance analysis of 20 species; for 16, we could derive only the [Fe/H] ratio. A spectral classification has been also performed for 17 stars in the sample. We found two double-lined spectroscopic binaries, HIP96299 and HIP98551, the former of which is an already known eclipsing binary, and two single-lined spectroscopic binaries, HIP97254 and HIP97724. We also report two suspected spectroscopic binaries, HIP92637 and HIP96762, and the detection of a possible variability of the radial velocity of HIP96277. Two of our program stars turn out to be chemically peculiar, namely HIP93941, which we classify as B2 He-weak, and HIP96210, which we classify as B6Mn. Finally, we find that HIP93522, HIP93941, HIP93943, HIP96210 and HIP96762, are very slow rotators (vsini<20km/s) which makes them very interesting and promising targets for an asteroseismic modeling.
- ID:
- ivo://CDS.VizieR/J/MNRAS/409/1455
- Title:
- Stellar populations of early-type galaxies
- Short Name:
- J/MNRAS/409/1455
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The influence of environment on the formation and evolution of early-type galaxies is, as yet, an unresolved issue. Constraints can be placed on models of early-type galaxy formation and evolution by examining their stellar populations as a function of environment. We present a catalogue of galaxies well suited to such an investigation. The magnitude-limited (b_J_<=19.45) sample was drawn from four clusters (Coma, A1139, A3558 and A930 at <z>=0.04) and their surrounds. The catalogue contains luminosities, redshifts, velocity dispersions and Lick line strengths for 416 galaxies, of which 245 are classified as early types. Luminosity-weighted ages, metallicities and {alpha}-element abundance ratios have been estimated for 219 of these early types. We also outline the steps necessary for measuring fully calibrated Lick indices and estimating the associated stellar population parameters using up-to-date methods and stellar population models. In a subsequent paper we perform a detailed study of the stellar populations of early-type galaxies in clusters and investigate the effects of environment.
- ID:
- ivo://CDS.VizieR/J/MNRAS/390/1437
- Title:
- Stellar streams in Andromeda (M31)
- Short Name:
- J/MNRAS/390/1437
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopic analysis of five stellar streams ("A", "B", "Cr", "Cp" and "D") as well as the extended star cluster, EC4, which lies within Stream "C", all discovered in the halo of M31 from our Canada-France-Hawaii Telescope/MegaCam survey. These spectroscopic results were initially serendipitous, making use of our existing observations from the DEep Imaging Multi-Object Spectrograph mounted on the Keck II telescope, and thereby emphasizing the ubiquity of tidal streams that account for ~70 per cent of the M31 halo stars in the targeted fields. Subsequent spectroscopy was then procured in Stream "C" and Stream "D" to trace the velocity gradient along the streams. Nine metal-rich ([Fe/H]~-0.7) stars at v_hel_=-349.5km/s, {sigma}_v,corr_~5.1+/-2.5km/s are proposed as a serendipitous detection of Stream "Cr", with follow-up kinematic identification at a further point along the stream. Seven metal-poor ([Fe/H]~-1.3) stars confined to a narrow, 15km/s velocity bin centred at v_hel_=-285.6, {sigma}_v,corr_=4.3^+1.7^_-1.4_km/s represent a kinematic detection of Stream "Cp", again with follow-up kinematic identification further along the stream. For the cluster EC4, candidate member stars with average [Fe/H]~-1.4, are found at v_hel_=-282 suggesting it could be related to Stream "Cp". No similarly obvious cold kinematic candidate is found for Stream "D", although candidates are proposed in both of two spectroscopic pointings along the stream (both at ~-400km/s). Spectroscopy near the edge of Stream "B" suggests a likely kinematic detection at v_hel_~-330, {sigma}_v,corr_~6.9km/s, while a candidate kinematic detection of Stream "A" is found (plausibly associated to M33 rather than M31) with v_hel_~-170, {sigma}_v,corr_=12.5km/s. The low dispersion of the streams in kinematics, physical thickness and metallicity makes it hard to reconcile with a scenario whereby these stream structures as an ensemble are related to the giant southern stream. We conclude that the M31 stellar halo is largely made up of multiple kinematically cold streams.