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- ID:
- ivo://CDS.VizieR/J/ApJ/821/8
- Title:
- Spectroscopic binary population of ONC and NGC2264
- Short Name:
- J/ApJ/821/8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We examine the spectroscopic binary population for two massive nearby regions of clustered star formation, the Orion Nebula Cluster (ONC) and NGC 2264, supplementing the data presented by Tobin et al. (2009, J/ApJ/697/1103) with more recent observations and more extensive analysis. The inferred multiplicity fraction up to 10 au based on these observations is 5.3+/-1.2% for NGC 2264 and 5.8+/-1.1% for the ONC; these values are consistent with the distribution of binaries in the field in the relevant parameter range. Eight of the multiple systems in the sample have enough epochs to perform an initial fit for the orbital parameters. Two of these sources are double-lined spectroscopic binaries; for them, we determine the mass ratio. Our reanalysis of the distribution of stellar radial velocities toward these clusters presents a significantly better agreement between stellar and gas kinematics than was previously thought.
- ID:
- ivo://CDS.VizieR/J/A+A/328/551
- Title:
- Spectroscopic data of 4 Herculis
- Short Name:
- J/A+A/328/551
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A collection of spectroscopic data of 4 Her at our disposal (RV and spectrophotometric measurements) consist of spectra obtained at the Ondrejov and Haute Provence Observatories. Table 1 summarizes the measurements of radial velocities and line intensities carried out in the red spectra. In Table 2 a list of the spectra and RV measurements for the violet-blue region is given.
- ID:
- ivo://CDS.VizieR/J/A+A/622/A110
- Title:
- Spectroscopic membership for NGC 3532
- Short Name:
- J/A+A/622/A110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 3532 is an extremely rich open cluster embedded in the Galactic disc, hitherto lacking a comprehensive, documented membership list. We provide membership probabilities from new radial velocity observations of solar-type and low-mass stars in NGC 3532, in part as a prelude to a subsequent study of stellar rotation in the cluster. Using extant optical and infra-red photometry we constructed a preliminary photometric membership catalogue, consisting of 2230 dwarf and turn-off stars. We selected 1060 of these for observation with the AAOmega spectrograph at the 3.9m Anglo-Australian Telescope and 391 stars for observations with the Hydra-South spectrograph at the 4m Victor Blanco Telescope, obtaining spectroscopic observations over a decade for 145 stars. We measured radial velocities for our targets through cross-correlation with model spectra and standard stars, and supplemented them with radial velocities for 433 additional stars from the literature. We also measured logg, Teff, and [Fe/H] from the AAOmega spectra. The radial velocity distribution emerging from the observations is centred at 5.43+/-0.04km/s and has a width (standard deviation) of 1.46km/s. Together with proper motions from Gaia DR2 we find 660 exclusive members, of which five are likely binary members. The members are distributed across the whole cluster sequence, from giant stars to M dwarfs, making NGC~3532 one of the richest Galactic open clusters known to date, on par with the Pleiades. From further spectroscopic analysis of 153 dwarf members we find the metallicity to be marginally sub-solar, with [Fe/H]=-0.07+/-0.10. We confirm the extremely low reddening of the cluster, E_B-V_=0.034+/-0.012mag, despite its location near the Galactic plane. Exploiting trigonometric parallax measurements from Gaia DR2 we find a distance of 484^+35^_-30_pc [(m-M)_0_=8.42+/-0.14mag]. Based on the membership we provide an empirical cluster sequence in multiple photometric passbands. A comparison of the photometry of the measured cluster members with several recent model isochrones enables us to confirm the 300Myr cluster age. However, all of the models evince departures from the cluster sequence in particular regions, especially in the lower mass range.
- ID:
- ivo://CDS.VizieR/J/ApJ/770/16
- Title:
- Spectroscopic members of Segue 2 galaxy
- Short Name:
- J/ApJ/770/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Segue 2, discovered by Belokurov et al. (2009, Cat. J/MNRAS/397/1748), is a galaxy with a luminosity of only 900L_{sun}_. We present Keck/DEIMOS spectroscopy of 25 members of Segue 2 - a threefold increase in spectroscopic sample size. The velocity dispersion is too small to be measured with our data. The upper limit with 90% (95%) confidence is {sigma}_v_<2.2(2.6)km/s, the most stringent limit for any galaxy. The corresponding limit on the mass within the three-dimensional half-light radius (46pc) is M_1/2_<1.5(2.1)x10^5^M_{sun}_. Segue 2 is the least massive galaxy known. We identify Segue 2 as a galaxy rather than a star cluster based on the wide dispersion in [Fe/H] (from -2.85 to -1.33) among the member stars. The stars' [{alpha}/Fe] ratios decline with increasing [Fe/H], indicating that Segue 2 retained Type Ia supernova ejecta despite its presently small mass and that star formation lasted for at least 100 Myr. The mean metallicity, <[Fe/H]>=-2.22+/-0.13 (about the same as the Ursa Minor galaxy, 330 times more luminous than Segue 2), is higher than expected from the luminosity-metallicity relation defined by more luminous dwarf galaxy satellites of the Milky Way. Segue 2 may be the barest remnant of a tidally stripped, Ursa Minor-sized galaxy. If so, it is the best example of an ultra-faint dwarf galaxy that came to be ultra-faint through tidal stripping. Alternatively, Segue 2 could have been born in a very low mass dark matter subhalo (v_max_<10km/s), below the atomic hydrogen cooling limit.
- ID:
- ivo://CDS.VizieR/J/A+A/473/523
- Title:
- Spectroscopic monitoring of 3 neutron stars
- Short Name:
- J/A+A/473/523
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a spectroscopic monitoring campaign of the OB-star companions to the eclipsing X-ray pulsars SMC X-1, LMC X-4 and Cen X-3. High-resolution optical spectra obtained with UVES on the ESO Very Large Telescope are used to determine the radial-velocity orbit of the OB (super)giants with high precision. The excellent quality of the spectra provides the opportunity to measure the radial-velocity curve based on individual lines, and to study the effect of possible distortions of the line profiles due to e.g. X-ray heating on the derived radial-velocity amplitude.
- ID:
- ivo://CDS.VizieR/J/ApJ/751/46
- Title:
- Spectroscopic observations in VV124 (UGC 4879)
- Short Name:
- J/ApJ/751/46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- VV124 (UGC 4879) is an isolated, dwarf irregular/dwarf spheroidal (dIrr/dSph) transition-type galaxy at a distance of 1.36 Mpc. Previous low-resolution spectroscopy yielded inconsistent radial velocities for different components of the galaxy, and photometry hinted at the presence of a stellar disk. In order to quantify the stellar dynamics, we observed individual red giants in VV124 with the Keck/Deep Extragalactic Imaging Multi-Object Spectrograph (DEIMOS). We validated members based on their positions in the color-magnitude diagram, radial velocities, and spectral features. Our sample contains 67 members. The average radial velocity is <v_r_>=-29.1+/-1.3km/s in agreement with the previous radio measurements of H I gas. The velocity distribution is Gaussian, indicating that VV124 is supported primarily by velocity dispersion inside a radius of 1.5 kpc. Outside that radius, our measurements provide only an upper limit of 8.6km/s on any rotation in the photometric disk-like feature. The velocity dispersion is {sigma}_v_=9.4+/-1.0km/s, from which we inferred a mass of M_1/2_=(2.1 +/-0.2)x10^7^M_{sun}_ and a mass-to-light ratio of (M/L_V_)_1/2_=5.2+/-1.1M_{sun}_/L_{sun}_, both measured within the half-light radius. Thus, VV124 contains dark matter. We also measured the metallicity distribution from neutral iron lines. The average metallicity, <[Fe/H]>=-1.14+/-0.06, is consistent with the mass-metallicity relation defined by dSph galaxies. The dynamics and metallicity distribution of VV124 appear similar to dSphs of similar stellar mass.
- ID:
- ivo://CDS.VizieR/J/A+AS/101/475
- Title:
- Spectroscopic observations of A3571
- Short Name:
- J/A+AS/101/475
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectroscopic data and density counts are presented for this southern cluster, which seems to belong to the outskirts of the Shapley 8 concentration (= A 3558 = SC 1326-311). Using telescopes at the Cerro Tololo Interamerican Observatory and La Silla Observatory a total of 72 galaxy velocities were measured giving a mean redshift of 0.0384 and a global velocity dispersion of 1022 (+99, -77) km/s. A preliminary analysis of velocity and density data suggests the presence of various subgroups. The central core of the cluster is dominated by a very elongated, distorded and diffuse cD galaxy. This cluster may be an example where the cD was formed early in the collapse process of a cluster which has not reached overall virialization yet. The derived X-ray luminosity of ~2x10^44^erg/s in the 2-6keV band places this cluster in the group of strong X-ray cluster sources.
- ID:
- ivo://CDS.VizieR/J/A+A/501/291
- Title:
- Spectroscopic observations of HD 152219
- Short Name:
- J/A+A/501/291
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- HD 152219 is a massive binary system with O9.5 III + B1-2 V/III components and a short orbital period of 4.2d. Its primary component further displays clear line profile variability (LPV). The primary component being located within the pulsational instability domain predicted for high-luminosity stars, we previously suggested that the observed LPV could be associated with non-radial pulsations. The aim of the present work is to determine the nature of the observed LPV in the spectrum of the primary component of HD 152219. During a 4-night FEROS monitoring campaign, we collected a new set of 134 high signal-to-noise spectra. These new observations were then used to re-investigate the variability of different line profiles in the spectrum of HD~152219. Based on the present analysis, we discard the non-radial pulsations and point out the Rossiter-McLaughlin effect as the cause of the LPV in HD 152219. The upper limit on the amplitude of possible weak pulsations is set at a few parts per thousand of the continuum level.
- ID:
- ivo://CDS.VizieR/J/ApJ/842/97
- Title:
- Spectroscopic obs. of 413 HII regions in M33
- Short Name:
- J/ApJ/842/97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The spectra of 413 star-forming (or H II) regions in M33 (NGC 598) were observed using the multifiber spectrograph of Hectospec at the 6.5m Multiple Mirror Telescope. Using this homogeneous spectra sample, we measured the intensities of emission lines and some physical parameters, such as electron temperatures, electron densities, and metallicities. Oxygen abundances were derived via the direct method (when available) and two empirical strong-line methods, namely, O3N2 and N2. At the high-metallicity end, oxygen abundances derived from the O3N2 calibration were higher than those derived from the N2 index, indicating an inconsistency between O3N2 and N2 calibrations. We present a detailed analysis of the spatial distribution of gas-phase oxygen abundances in M33 and confirm the existence of the axisymmetric global metallicity distribution that is widely assumed in the literature. Local variations were also observed and subsequently associated with spiral structures to provide evidence of radial migration driven by arms. Our O/H gradient fitted out to 1.1 R_25_ resulted in slopes of -0.17+/-0.03, -0.19+/-0.01, and -0.16+/-0.17dex R_25_^-1^, utilizing abundances from O3N2, N2 diagnostics, and a direct method, respectively.
