- ID:
- ivo://CDS.VizieR/J/A+A/642/A21
- Title:
- Astrometric parameters for 135 OB stars
- Short Name:
- J/A+A/642/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our goal is to better understand the origin and the star-formation history of regions NGC 6334 and NGC 6357. We focus our study on the young stars (young stellar objects and OB stars) kinematics in both regions using mainly Gaia-DR2 data. For both regions we compiled OB stars and young stellar objects catalogues from literature and we complemented them using VPHAS+ DR2 and Spitzer IRAC/GLIMPSE photometry catalogues. A cross-match is performed with the Gaia-DR2 catalogue in order to obtain the parallax and transverse motion information. We confirm that NGC 6334 and NGC 6357 are in the far side of the Saggitarius-Carina arm at a distance of 1.76kpc. For NGC 6357, OB stars show strong clustering and ordered star motion with Vlon~-10.7km/s and Vlat ~3.7km/s while for NGC 6334, no significant systemic motion is observed. The OB stars motions and distribution in NGC 6334 suggest to classify it as an association. Ten and two runaway candidates can be related to NGC 6357 and NGC 6334, respectively. The spatial distributions of the runaway candidates in and around NGC 6357 favor a dynamical (and early) ejection during the cluster(s) formation. Because such stars are likely to be ejected during cluster's formation the fact of not observing as many of such stars towards NGC 6334 suggest different formation conditions than for NGC 6357.
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- ID:
- ivo://CDS.VizieR/J/AJ/136/452
- Title:
- Astrometric studies of GAT stars
- Short Name:
- J/AJ/136/452
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of astrometric studies in the regions of Groombridge 34A, the Hyades, Aldebaran, Ross 47, BD+5 1668, 81 Cancri, BD+15 2620, Arcturus, Vega, and Ross 248 are presented. Estimates of the absolute parallax of each star are presented and a mass estimate is present for 81 Cancri. Comments include the discussion of the apparent motions of a few previously suggested planetary systems.
- ID:
- ivo://CDS.VizieR/J/AJ/145/136
- Title:
- Astrometry and photometry of nearby white dwarfs
- Short Name:
- J/AJ/145/136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the preliminary results of a survey aimed at significantly increasing the range and completeness of the local census of spectroscopically confirmed white dwarfs. The current census of nearby white dwarfs is reasonably complete only to about 20pc of the Sun, a volume that includes around 130 white dwarfs, a sample too small for detailed statistical analyses. This census is largely based on follow-up investigations of stars with very large proper motions. We describe here the basis of a method that will lead to a catalog of white dwarfs within 40pc of the Sun and north of the celestial equator, thus increasing by a factor of eight the extent of the northern sky census. White dwarf candidates are identified from the SUPERBLINK proper motion database, allowing us to investigate stars down to a proper motion limit {mu}>40mas/yr, while minimizing the kinematic bias for nearby objects. The selection criteria and distance estimates are based on a combination of color-magnitude and reduced proper motion diagrams. Our follow-up spectroscopic observation campaign has so far uncovered 193 new white dwarfs, among which we identify 127 DA (including 9 DA+dM and 4 magnetic), 1 DB, 56 DC, 3 DQ, and 6 DZ stars. We perform a spectroscopic analysis on a subsample of 84 DAs, and provide their atmospheric parameters. In particular, we identify 11 new white dwarfs with spectroscopic distances within 25pc of the Sun, including five candidates to the D<20pc subset.
- ID:
- ivo://CDS.VizieR/J/AJ/154/147
- Title:
- Astrometry&photometry for late-type dwarfs&subdwarfs
- Short Name:
- J/AJ/154/147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New, updated, and/or revised CCD parallaxes determined with the Strand Astrometric Reflector at the Naval Observatory Flagstaff Station are presented. Included are results for 309 late-type dwarf and subdwarf stars observed over the 30+ years that the program operated. For 124 of the stars, parallax determinations from other investigators have already appeared in the literature and we compare the different results. Also included here are new or updated VI photometry on the Johnson-Kron-Cousins system for all but a few of the faintest targets. Together with 2MASS JHK_s_ near-infrared photometry, a sample of absolute magnitude versus color and color versus color diagrams are constructed. Because large proper motion was a prime criterion for targeting the stars, the majority turn out to be either M-type subdwarfs or late M-type dwarfs. The sample also includes 50 dwarf or subdwarf L-type stars, and four T dwarfs. Possible halo subdwarfs are identified in the sample based on tangential velocity, subluminosity, and spectral type. Residuals from the solutions for parallax and proper motion for several stars show evidence of astrometric perturbations.
- ID:
- ivo://CDS.VizieR/J/AJ/155/252
- Title:
- Astrometry & photometry of dwarf carbon stars
- Short Name:
- J/AJ/155/252
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Parallaxes are presented for a sample of 20 nearby dwarf carbon stars. The inferred luminosities cover almost two orders of magnitude. Their absolute magnitudes and tangential velocities confirm prior expectations that some originate in the Galactic disk, although more than half of this sample are halo stars. Three stars are found to be astrometric binaries, and orbital elements are determined; their semimajor axes are 1-3 au, consistent with the size of an AGB mass-transfer donor star.
- ID:
- ivo://CDS.VizieR/J/AJ/162/14
- Title:
- Astrometry & radial velocity, Alpha Centauri system
- Short Name:
- J/AJ/162/14
- Date:
- 14 Mar 2022 06:46:54
- Publisher:
- CDS
- Description:
- Alpha Centauri A is the closest solar-type star to the Sun and offers the best opportunity to find and ultimately to characterize an Earth-sized planet located in its habitable zone. Here, we describe initial results from an Atacama Large Millimeter/submillimeter Array (ALMA) program to search for planets in the {alpha} Cen AB system using differential astrometry at millimeter wavelengths. Our initial results include new absolute astrometric measurements of the proper motion, orbital motion and parallax of the {alpha} Cen system. These lead to an improved knowledge of the physical properties of both {alpha} Cen A and B. Our estimates of ALMA's relative astrometric precision suggest that we will ultimately be sensitive to planets of a few tens of Earth mass in orbits from 1 to 3au, where stable orbits are thought to exist.
- ID:
- ivo://CDS.VizieR/J/AN/325/740
- Title:
- Astrophysical supplements to ASCC-2.5
- Short Name:
- J/AN/325/740
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The catalogue of stars in the Galactic open cluster areas (CSOCA) is the result of the kinematic (proper motion), photometric and spatial member selection of stars listed in the homogeneous All-sky Compiled Catalogue of 2.5 Million Stars (ASCC-2.5, Cat. <I/280>) within 520 areas with open clusters selected from an on-line release 2.0 of catalogue by Dias et al. (2004, http://www.astro.iag.usp.br/~wilton, Cat. VII/229). The areas represent quadratic fields centered at adopted cluster centers with side lengths of a_cl_[deg]=2*(r_cl_+0.1), where r_cl_ is the determined angular radius of the cluster. For clusters with r_cl_<0.4{deg}, a_cl_=1{deg}. In every cluster area the CSOCA contains the complete list of the ASCC-2.5 stars. The catalog includes accurate J2000 equatorial coordinates, proper motions in the Hipparcos system, BV photometric data in the Johnson system, proper motion, photometric and spatial membership probabilities, and angular distances from the cluster centers for all included stars. If available, trigonometric parallaxes, multiplicity and variability flags from the ASCC-2.5, spectral types (from the ASCC-2.5 or the Tycho-2 Spectral Type Catalog <III/231>), and radial velocities with their errors from the Catalogue of Radial Velocities of Galactic Stars with high precision Astrometric Data (CRVAD, <III/239>) are also given. Since some cluster areas overlap each other some stars are included in the CSOCA several times. The catalogue contains 171319 entries for 149849 stars. Entries are sorted in right ascension J2000 order.
- ID:
- ivo://CDS.VizieR/J/AJ/156/61
- Title:
- A study of the H{alpha} variability of Be stars
- Short Name:
- J/AJ/156/61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents the results of 4 years of high-resolution spectral observations of 69 emission-line stars, 54 of them being newly discovered sources. We classified the stars on the basis of their position in the two-color IR diagram and some additional criteria: shape and width of the H{alpha} profile, presence of He lines, proper motion and parallax, membership to open cluster and associations. Sixty of our targets turned out to be Be stars. We also found four late giants, four pre-MS stars, and one late dwarf. The H{alpha} emission profiles of our Be stars range from single peaked to typical shell profiles that can also be highly asymmetric or single-peaked profiles with a narrow absorption core. The emission profiles appear almost constant with time or highly variable in intensity and in their V/R ratio. The detected long-term variability of the H{alpha} emission is important for investigating the on/off switch phenomenon of Be stars. Our study led to an increase of the number of the emission-line stars of 16 open clusters.
- ID:
- ivo://CDS.VizieR/J/PAZh/25/115
- Title:
- A study of the open cluster NGC 6811
- Short Name:
- J/PAZh/25/115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 191 individual measurements of radial velocities made with CORAVEL-type spectrometer are presented for 60 stars in the large region of NGC 6811 open cluster. Photoelectric UBVR magnitudes are given for 117 stars - members of the cluster by proper motions. Spectral classification of these stars is taken from Straizys and Kazlauskas (1993BaltA...2....1S).
- ID:
- ivo://CDS.VizieR/J/ApJ/784/154
- Title:
- A survey for H{alpha} pulsar bow shocks
- Short Name:
- J/ApJ/784/154
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on a survey for H{alpha} bow shock emission around nearby {gamma}-detected energetic pulsars. This survey adds three Balmer-dominated neutron star bow shocks to the six previously confirmed examples. In addition to the shock around Fermi pulsar PSR J1741-2054, we now report H{alpha} structures around two additional {gamma}-ray pulsars, PSR J2030+4415 and PSR J1509-5850. These are the first known examples of H{alpha} nebulae with pre-ionization halos. With new measurements, we show that a simple analytic model can account for the angular size and flux of the bow shocks' apices. The latter, in particular, provides a new pulsar probe and indicates large moments of inertia and smaller distances than previously assumed in several cases. In particular, we show that the re-measured PSR J0437-4715 shock flux implies I=(1.7+/-0.2)x10^45^/(f_H I_sin i)g cm^2^. We also derive a distance d~0.72 kpc for the {gamma}-ray only pulsar PSR J2030+4415 and revised distances for PSRs J1959+2048 (1.4 kpc) and J2555+6535 (~1 kpc), smaller than the conventional DM-estimated values. Finally, we report upper limits for 94 additional LAT pulsars. An estimate of the survey sensitivity indicates that for a warm neutral medium filling factor {phi}_WNM_~0.3 there should be a total of approximately nine H{alpha} bow shocks in our LAT-targeted survey; given that seven such objects are now known, a much larger {phi}_WNM_ seems problematic.