- ID:
- ivo://CDS.VizieR/J/A+A/577/L2
- Title:
- Barnard 1b-N and 1b-S nascent bipolar outflows
- Short Name:
- J/A+A/577/L2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the theory of star formation, the first hydrostatic core (FHSC) phase is a critical step in which a condensed object emerges from a prestellar core. This step lasts about one thousand years, a very short time compared with the lifetime of prestellar cores, and therefore is hard to detect unambiguously. We present IRAM Plateau de Bure observations of the Barnard 1b dense molecular core, combining detections of H2CO and CH3OH spectral lines and dust continuum at 2.3" resolution (~500AU). The two compact cores B1b-N and B1b-S are detected in the dust continuum at 2mm, with fluxes that agree with their spectral energy distribution. Molecular outflows associated with both cores are detected. They are inclined relative to the direction of the magnetic field, in agreement with predictions of collapse in turbulent and magnetized gas with a ratio of mass to magnetic flux somewhat higher than the critical value, {mu}~2-7. The outflow associated with B1b-S presents sharp spatial structures, with ejection velocities of up to ~7km/s from the mean velocity. Its dynamical age is estimated to be ~2000yr. The B1b-N outflow is smaller and slower, with a short dynamical age of ~1000yr. The B1b-N outflow mass, mass-loss rate, and mechanical luminosity agree well with theoretical predictions of FHSC. These observations confirm the early evolutionary stage of B1b-N and the slightly more evolved stage of B1b-S.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/559/A17
- Title:
- Barycentric radial velocities of Gl 586A
- Short Name:
- J/A+A/559/A17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The visual A component of the Gliese 586AB system is a double-lined spectroscopic binary consisting of two cool stars with the exceptional orbital eccentricity of 0.976. Such an extremely eccentric system may be important for our understanding of low-mass binary formation. Precise stellar masses, ages, orbital elements, and rotational periods are a prerequisite for comparing stellar observations to angular-momentum evolution models.
- ID:
- ivo://CDS.VizieR/J/ApJS/220/18
- Title:
- BDKP IV. RVs of late-M and L dwarfs with MagE
- Short Name:
- J/ApJS/220/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Radial velocity measurements are presented for 85 late M- and L-type very low-mass stars and brown dwarfs obtained with the Magellan Echellette spectrograph. Targets primarily have distances within 20pc of the Sun, with more distant sources selected for their unusual spectral energy distributions. We achieved precisions of 2-3km/s, and combined these with astrometric and spectrophotometric data to calculate UVW velocities. Most are members of the thin disk of the Galaxy, and velocity dispersions indicate a mean age of 5.2+/-0.2Gyr for sources within 20pc. We find significantly different kinematic ages between late-M dwarfs (4.0+/-0.2Gyr) and L dwarfs (6.5+/-0.4Gyr) in our sample that are contrary to predictions from prior simulations. This difference appears to be driven by a dispersed population of unusually blue L dwarfs which may be more prevalent in our local volume-limited sample than in deeper magnitude-limited surveys. The L dwarfs exhibit an asymmetric U velocity distribution with a net inward flow, similar to gradients recently detected in local stellar samples. Simulations incorporating brown dwarf evolution and Galactic orbital dynamics are unable to reproduce the velocity asymmetry, suggesting non-axisymmetric perturbations or two distinct L dwarf populations. We also find the L dwarfs to have a kinematic age-activity correlation similar to more massive stars. We identify several sources with low surface gravities, and two new substellar candidate members of nearby young moving groups: the astrometric binary DENIS J08230313-4912012AB, a low-probability member of the {beta} Pictoris Moving Group; and 2MASS J15104786-2818174, a moderate-probability member of the 30-50Myr Argus Association.
- ID:
- ivo://CDS.VizieR/J/A+A/576/A66
- Title:
- BD+20 1790 radial velocities and photometry
- Short Name:
- J/A+A/576/A66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In a previous paper we reported a planetary companion to the young and very active K5Ve star BD+20 1790. This paper aims to more rigorously assess the nature of the radial velocity measurements with an expanded data set and new methods of analysis. We have employed Bayesian methods to simultaneously analyse the radial velocity and activity measurements based on a combined data set that includes new and previously published observations.
- ID:
- ivo://CDS.VizieR/J/A+A/513/L8
- Title:
- BD+20 1790 radial velocity curve
- Short Name:
- J/A+A/513/L8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The young active star BD +20 1790 has been inferred to host a substellar companion from radial-velocity measurements that detected the reflex motion induced on the parent star. We attempt to completely characterize the radial-velocity signal in order to assess its nature.
- ID:
- ivo://CDS.VizieR/J/MNRAS/368/471
- Title:
- Berkeley 32 BVI photometry and spectroscopy
- Short Name:
- J/MNRAS/368/471
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained medium- and low-resolution spectroscopy and BVI CCD imaging of Berkeley 32, an old open cluster which lies in the anticentre direction. From the radial velocities of 48 stars in the cluster direction, we found that 31 of them, in crucial evolutionary phases, are probable cluster members, with an average radial velocity of +106.7(sigma=8.5)km/s . From isochrone fitting to the colour-magnitude diagrams of Berkeley 32, we have obtained an age of 6.3Gyr, (m-M)0=12.48 and E(B-V)=0.10. The best fit is obtained with Z=0.008. A consistent distance, (m-M)_0_~=12.6+/-0.1, has been derived from the mean magnitude of red clump stars with confirmed membership; we may assume (m-M)_0_~=12.55+/-0.1. The colour-magnitude diagram of the nearby field observed to check for field stars contamination looks intriguingly similar to that of the Canis Major overdensity.
- ID:
- ivo://CDS.VizieR/J/MNRAS/469/4175
- Title:
- Be star candidates in Magellanic Clouds
- Short Name:
- J/MNRAS/469/4175
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a proper motion investigation of a sample of Be star candidates towards the Magellanic Clouds, which has resulted in the identification of separate populations, in the Galactic foreground and in the Magellanic background. Be stars are broadly speaking B-type stars that have shown emission lines in their spectra. In this work, we studied a sample of 2446 and 1019 Be star candidates towards the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC), respectively, taken from the literature and proposed as possible Be stars due to their variability behaviour in the OGLE-II I band. JHKs magnitudes from the InfraRed Survey Facility catalogue and proper motions from the Southern Proper Motion 4 catalogue were obtained for 1188 and 619 LMC and SMC Be stars candidates, respectively. Colour-colour and vector-point diagrams were used to identify different populations amongst the Be star candidates. In the LMC sample, two populations with distinctive infrared colours and kinematics were found, the bluer sample is consistent with being in the LMC and the redder one with belonging to the Milky Way disc. This settles the nature of the redder sample that had been described in previous publications as a possible unknown subclass of stars amongst the Be candidates in the LMC. In the SMC sample, a similar but less evident result was obtained, since this apparent unknown subclass was not seen in this galaxy. We confirm that in the selection of Be stars by their variability, although generally successful, there is a higher risk of contamination by Milky Way objects towards redder B-V and V-I colours.
- ID:
- ivo://CDS.VizieR/J/ApJ/885/160
- Title:
- Best-fit emission-line properties in NGC 5775
- Short Name:
- J/ApJ/885/160
- Date:
- 08 Mar 2022
- Publisher:
- CDS
- Description:
- The structure and kinematics of gaseous, disk-halo interfaces are imprinted with the processes that transfer mass, metals, and energy between galactic disks and their environments. We study the extraplanar diffuse ionized gas (eDIG) layer in the interacting, star-forming galaxy NGC5775 to better understand the consequences of star formation feedback on the dynamical state of the thick-disk interstellar medium. Combining emission-line spectroscopy from the Robert Stobie Spectrograph on the Southern African Large Telescope with radio continuum observations from Continuum Halos in Nearby Galaxies-an EVLA Survey, we ask whether thermal, turbulent, magnetic field, and cosmic-ray pressure gradients can stably support the eDIG layer in dynamical equilibrium. This model fails to reproduce the observed exponential electron scale heights of the eDIG thick disk and halo on the northeast (h_z,e_=0.6,7.5kpc) and southwest (h_z,e_=0.8,3.6kpc) sides of the galaxy at R<11kpc. We report the first definitive detection of an increasing eDIG velocity dispersion as a function of height above the disk. Blueshifted gas along the minor axis at large distances from the midplane hints at a disk-halo circulation and/or ram pressure effects caused by the ongoing interaction with NGC5774. This work motivates further integral field unit and/or Fabry-Perot spectroscopy of galaxies with a range of star formation rates to develop a spatially resolved understanding of the role of star formation feedback in shaping the kinematics of the disk-halo interface.
- ID:
- ivo://CDS.VizieR/J/A+A/543/A98
- Title:
- {beta} Gem radial velocity and photometric data
- Short Name:
- J/A+A/543/A98
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our aim is to use precise radial velocity measurements and photometric data to derive the frequency spacing of the p-mode oscillation spectrum of the planet-hosting star beta Gem. This spacing along with the interferometric radius for this star can then be used to derive an accurate stellar mass.
- ID:
- ivo://CDS.VizieR/J/A+A/312/879
- Title:
- Beta Lyr radial velocities and UBV data
- Short Name:
- J/A+A/312/879
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A preliminary analysis of an extensive collection of interferometric, spectroscopic and photometric observations of the bright Be star {beta} Lyr lead to the following main conclusions: (1) The bulk of the H{alpha} and He I 6678 emission seems to originate in jets of material perpendicular to the orbital plane of the binary. The jets are associated with the more massive component of the binary (star 1) and probably emanate from the `hot spot' in the disk, i.e. the region of interaction of the gas stream flowing from the Roche-lobe filling B6-8II component (star 2) toward star 1. Some contribution to the emission also comes from a region located between the two stars (the gas stream and the `hot spot') and from the `pseudoatmosphere' of the accretion disk around star 1. (2) The 282-d cyclic variation of the light curve of {beta} Lyr is confirmed on the basis of 2852 homogenized V-band observations covering an interval of 36yrs. We find, however, that the amplitude and phase of these variations vary with the orbital phase: the long-term modulation of the light curve almost disappears near orbital phases 0.25P and 0.50P (elongation and secondary eclipse). (3) Pronounced line-profile variations of the H{alpha} and He I 6678 lines on a time scale shorter than one orbital period were clearly detected. They may be periodic, with a period near 4.70-4.75d, and this periodicity may be related to the 282-d change via the orbital period.