- ID:
- ivo://CDS.VizieR/J/A+A/495/379
- Title:
- Optical radial velocities in A85
- Short Name:
- J/A+A/495/379
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this series of papers we explore the evolution of late-type galaxies in the rich cluster Abell 85. In this first paper we revisit the complex dynamical state of A 85 by using independent methods. First, we analyze the galaxy redshift distribution towards A 85 in the whole range 0-40000km/s, and determine the mean redshifts of the background clusters A 87 and A 89, very close in projection to A 85. Then we search for substructures in A 85 by considering the 2D galaxy distribution of its members (13000-20000km/s) and by applying the kinematical 3D {Delta}-test to both projected positions and radial velocities.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/860/49
- Title:
- Optical spectroscopy of young {alpha}-rich stars
- Short Name:
- J/ApJ/860/49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report chemical abundances of 14 young {alpha}-rich stars including neutron-capture elements based on high-quality optical spectra from HIRES/Keck I and differential line-by-line analysis. From a comparison of the abundance patterns of young {alpha}-rich stars to those of nearby bright red giants with a similar metallicity range (-0.7<[Fe/H]{<}-0.2), we confirm their high {alpha}-element abundances reported by previous studies based on near-infrared spectroscopy. We reveal for the first time low abundances of s-process elements and high abundances of r-process elements. All the abundances are consistent with those seen in the typical {alpha}-rich population of the Galactic disk, and no abundance anomalies are found except for Li-enhancement in one object previously reported and mild enhancement of Na in two stars. In particular, the lack of s-process enhancement excludes the hypothesis that mass transfer from asymptotic giant branch stars plays an important role in the formation of young {alpha}-rich stars. The high frequency of radial velocity variation (more than 50%) is also confirmed. We argue that mass transfer from low-mass red giants is the likely dominant formation mechanism for young {alpha}-rich stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/844/138
- Title:
- Optical spectroscopy toward Orion B fields
- Short Name:
- J/ApJ/844/138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from high-resolution optical spectra toward 66 young stars in the Orion B molecular cloud to study their kinematics and other properties. Observations of the H{alpha} and Li I 6707{AA} lines are used to check membership and accretion properties. While the stellar radial velocities of NGC 2068 and L1622 are in good agreement with that of the molecular gas, many of the stars in NGC 2024 show a considerable offset. This could be a signature of either the expansion of the cluster, the high degree of the ejection of the stars from the cluster through dynamical interaction, or the acceleration of the gas due to stellar feedback.
- ID:
- ivo://CDS.VizieR/J/AZh/81/1104
- Title:
- Optical spectrum of Cyg OB2 No. 12
- Short Name:
- J/AZh/81/1104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained the first high spectral-resolution (R=15000 and 60000) optical spectra for the extremely luminous star No.12, identified with the IR-source IRAS 20308+4104 in the Cyg OB2 association. We have identified about 200 spectral features at 4552-7939{AA}, including interstellar NaI, KI and numerous DIBs, which are in the strongest absorptions in the spectrum, along with the HeI, CII, SiII lines. A two-dimensional spectral classification indicates that the star's spectral type is B5+/-0.5 Ia^+^. Our analyses of the radial velocities pattern shows the presence of a radial velocity gradient in the stellar atmosphere due to the infall of matter onto the star. The strong H(alpha) emission line displays broad Thompson wings and time-variable core absorption, providing evidence that the stellar wind is inhomogeneous and slightly blue-shifted P Cygni absorption profile. We conclude that the wind is time-variable.
- ID:
- ivo://CDS.VizieR/J/ApJ/854/145
- Title:
- Opt. photometry & NIR spectroscopy of Wolf 1130
- Short Name:
- J/ApJ/854/145
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Following the discovery of the T8 subdwarf WISE J200520.38+542433.9 (Wolf 1130C), which has a proper motion in common with a binary (Wolf 1130AB) consisting of an M subdwarf and a white dwarf, we set out to learn more about the old binary in the system. We find that the A and B components of Wolf 1130 are tidally locked, which is revealed by the coherence of more than a year of V-band photometry phase-folded to the derived orbital period of 0.4967 days. Forty new high-resolution, near-infrared spectra obtained with the Immersion Grating Infrared Spectrometer (IGRINS) provide radial velocities and a projected rotational velocity (vsini) of 14.7+/-0.7km/s for the M subdwarf. In tandem with a Gaia parallax-derived radius and verified tidal locking, we calculate an inclination of i=29{deg}+/-2{deg}. From the single-lined orbital solution and the inclination we derive an absolute mass for the unseen primary (1.24_-0.15_^+0.19^M_{sun}_). Its non-detection between 0.2 and 2.5{mu}m implies that it is an old (>3.7Gyr) and cool (T_eff_<7000K) ONe white dwarf. This is the first ultramassive white dwarf within 25pc. The evolution of Wolf 1130AB into a cataclysmic variable is inevitable, making it a potential SN Ia progenitor. The formation of a triple system with a primary mass >100 times the tertiary mass and the survival of the system through the common-envelope phase, where ~80% of the system mass was lost, is remarkable. Our analysis of Wolf 1130 allows us to infer its formation and evolutionary history, which has unique implications for understanding low-mass star and brown dwarf formation around intermediate-mass stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/872/42
- Title:
- Opt. spectroscopy of redback ms pulsar binaries
- Short Name:
- J/ApJ/872/42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first optical spectroscopy of five confirmed (or strong candidate) redback millisecond pulsar binaries, obtaining complete radial velocity curves for each companion star. The properties of these millisecond pulsar binaries with low-mass, hydrogen-rich companions are discussed in the context of the 14 confirmed and 10 candidate field redbacks. We find that the neutron stars in redbacks have a median mass of 1.78+/-0.09M_{sun}_ with a dispersion of {sigma}=0.21+/-0.09. Neutron stars with masses in excess of 2M_{sun}_ are consistent with, but not firmly demanded by, current observations. Redback companions have median masses of 0.36+/-0.04M_{sun}_ with a scatter of {sigma}=0.15+/-0.04M_{sun}_, and a tail possibly extending up to 0.7-0.9M_{sun}_. Candidate redbacks tend to have higher companion masses than confirmed redbacks, suggesting a possible selection bias against the detection of radio pulsations in these more massive candidate systems. The distribution of companion masses between redbacks and the less massive black widows continues to be strongly bimodal, which is an important constraint on evolutionary models for these systems. Among redbacks, the median efficiency of converting the pulsar spin-down energy to {gamma}-ray luminosity is ~10%.
- ID:
- ivo://CDS.VizieR/J/ApJ/725/L186
- Title:
- Orbital eccentricities of 31535 G-dwarfs
- Short Name:
- J/ApJ/725/L186
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We test four competing models that aim to explain the nature of stars in spiral galaxies that are well away (>1kpc) from the midplane, the so-called thick disk: the stars may have gotten there through orbital migration, through satellite mergers and accretion, or through heating of pre-existing thin disk stars. The eccentricity distribution of thick disk stars has recently been proposed as a diagnostic to differentiate between these mechanisms. Drawing on SDSS-DR7, we have assembled a sample of 31535 G-dwarfs with six-dimensional phase-space information and metallicities and have derived the orbital eccentricities for them.
- ID:
- ivo://CDS.VizieR/J/A+A/473/829
- Title:
- Orbital elements of 156 spectroscopic binaries
- Short Name:
- J/A+A/473/829
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on a comprehensive, long-term monitoring programme aiming to improve our knowledge of such binary systems. We monitored the radial velocities of 1309 red giants in 187 open clusters with the Coravel spectrometers for 20 years, with a typical accuracy of 0.4km/s per observation. In total, 289 spectroscopic binaries were detected in the sample. We present first orbits for 67 systems and improved elements for another 64 previously published orbits, based on additional observations. For completeness, 25 published orbits are listed as well. The orbits are based on a total of 4039 observations, an average of 26 per system. Orbital periods range from 41.5 to 14722-days (40yrs), eccentricities from 0.00 to 0.81. The remaining systems have too long periods and/or inadequate phase coverage for an orbit determination at this time or too few observations.
- ID:
- ivo://CDS.VizieR/J/ApJ/835/209
- Title:
- Orbital nature of 81 ellipsoidal red giant binaries
- Short Name:
- J/ApJ/835/209
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we collect a sample of 81 ellipsoidal red giant binaries in the Large Magellanic Cloud (LMC), and we study their orbital natures individually and statistically. The sample contains 59 systems with circular orbits and 22 systems with eccentric orbits. We derive orbital solutions using the 2010 version of the Wilson-Devinney code (Wilson & Devinney 1971ApJ...166..605W ; Wilson 1979ApJ...234.1054W, 1990ApJ...356..613W ; Wilson+ 2009, J/ApJ/702/403). The sample is selection-bias corrected, and the orbital parameter distributions are compared to model predictions for the LMC and to observations in the solar vicinity. The masses of the red giant primaries are found to range from about 0.6 to 9M_{sun}_ with a peak at around 1.5M_{sun}_, in agreement with studies of the star formation history of the LMC, which find a burst of star formation beginning around 4 Gyr ago. The observed distribution of mass ratios q=m_2_/m_1_ is more consistent with the flat q distribution derived for the solar vicinity by Raghavan+ (2010, J/ApJS/190/1) than it is with the solar vicinity q distribution derived by Duquennoy & Mayor (1991A&A...248..485D). There is no evidence for an excess number of systems with equal mass components. We find that about 20% of the ellipsoidal binaries have eccentric orbits, twice the fraction estimated by Soszynski+ (2004, J/AcA/54/347). Our eccentricity evolution test shows that the existence of eccentric ellipsoidal red giant binaries on the upper parts of the red giant branch (RGB) can only be explained if tidal circularization rates are ~1/100 the rates given by the usual theory of tidal dissipation in convective stars.
- ID:
- ivo://CDS.VizieR/J/A+A/562/A95
- Title:
- Orbital solutions of eight close sdB binaries
- Short Name:
- J/A+A/562/A95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The project Massive Unseen Companions to Hot Faint Underluminous Stars from SDSS (MUCHFUSS) aims at finding hot subdwarf stars (sdBs) with massive compact companions such as white dwarfs, neutron stars, or stellar-mass black holes. In a supplementary programme we obtained time-resolved spectroscopy of known hot subdwarf binary candidates. Here we present orbital solutions of eight close sdB binaries with orbital periods ranging from 0.1 to 10 days, which allow us to derive lower limits on the masses of their companions. Additionally, a dedicated photometric follow-up campaign was conducted to obtain light curves of the reflection-effect binary HS 2043+0615. We are able to constrain the most likely nature of the companions in all cases but one, making use of information derived from photometry and spectroscopy. Four sdBs have white dwarf companions, while another three are orbited by low-mass main sequence stars of spectral type M.
