Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/692/973
- Title:
- Protostars in Perseus, Serpens and Ophiuchus
- Short Name:
- J/ApJ/692/973
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an unbiased census of deeply embedded protostars in Perseus, Serpens, and Ophiuchus, assembled by combining large-scale 1.1mm Bolocam continuum and Spitzer Legacy surveys. We identify protostellar candidates based on their mid-infrared (mid-IR) properties, correlate their positions with 1.1mm core positions from Enoch et al. in 2006 (Cat. J/ApJ/638/293) and 2007ApJ...666..982E, and Young et al. in 2006ApJ...644..326Y, and construct well-sampled spectral energy distributions using our extensive wavelength coverage ({lambda}=1.25-1100um). Source classification based on the bolometric temperature yields a total of 39 Class 0 and 89 Class I sources in the three-cloud sample. We compare to protostellar evolutionary models using the bolometric temperature-luminosity diagram, finding a population of low-luminosity Class I sources that are inconsistent with constant or monotonically decreasing mass accretion rates.
- ID:
- ivo://CDS.VizieR/J/AJ/150/97
- Title:
- Radial velocities in M67. I. 1278 candidate members
- Short Name:
- J/AJ/150/97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from 13776 radial-velocity (RV) measurements of 1278 candidate members of the old (4Gyr) open cluster M67 (NGC 2682). The measurements are the results of a long-term survey that includes data from seven telescopes with observations for some stars spanning over 40years. For narrow-lined stars, RVs are measured with precisions ranging from about 0.1 to 0.8km/s. The combined stellar sample reaches from the brightest giants in the cluster down to about 4mag below the main-sequence turnoff (V=16.5), covering a mass range of about 1.34M_{sun}_ to 0.76M_{sun}_. Spatially, the sample extends to a radius of 30arcmin (7.4pc in projection at a distance of 850pc or 6-7 core radii). We find M67 to have a mean radial velocity of +33.64km/s (with an internal precision of +/-0.03km/s) well separated from the mean velocity of the field. For stars with >=3 measurements, we derive RV membership probabilities and identify RV variables, finding 562 cluster members, 142 of which show significant RV variability. We use these cluster members to construct a color-magnitude diagram and identify a rich sample of stars that lie far from the standard single star isochrone, including the well-known blue stragglers, sub-subgiants and yellow giants. These exotic stars have a binary frequency of (at least) 80%, more than three times that detected for stars in the remainder of the sample. We confirm that the cluster is mass segregated, finding the binaries to be more centrally concentrated than the single stars in our sample at the 99.8% confidence level (and at the 98.7% confidence level when only considering main-sequence stars). The blue stragglers are centrally concentrated as compared to the solar-type main-sequence single stars in the cluster at the 99.7% confidence level. Accounting for measurement precision, we derive an RV dispersion in M67 of 0.80+/-0.04km/s for our sample of single main-sequence stars, subgiants and giants with V{<=}15.5. When corrected for undetected binaries, this sample yields a true RV dispersion of 0.59_-0.06_^+0.07^km/s. The radial distribution of the velocity dispersion is consistent with an isothermal distribution within our stellar sample. Using the cluster RV dispersion, we estimate a virial mass for the cluster of 2100_-550_^+610^M_{sun}_.
- ID:
- ivo://CDS.VizieR/III/239
- Title:
- Radial Velocities with Astrometric Data
- Short Name:
- III/239
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The catalogue of radial velocities of Galactic stars with high precision astrometric data (CRVAD) is the result of a merging of star lists from the General Catalog of Mean Radial Velocities (GCRV, Cat. III/213) and from the All-sky Compiled Catalogue of 2.5 Million Stars (ASCC-2.5, Cat. I/280). The cross identification of GCRV and ASCC-2.5 objects was carried out with help of coordinate, magnitude, colour and/or spectral type criteria. Data from the Catalogue of Components of Double and Multiple Stars (CCDM, Cat. I/274) were taken into account for the identification of multiple system components. 34553 stars of the ASCC-2.5 were identified with 33509 stars of the GCRV, i.e. 33509 stars of the GCRV have one entry in the ASCC-2.5, and 1044 objects have two entries. The catalogue includes accurate equatorial coordinates J2000, proper motions and trigonometric parallaxes in the Hipparcos system, B and V magnitudes in Johnson system, spectral classes, multiplicity and variability flags from the ASCC-2.5, and radial velocities, stellar magnitudes and spectra from the GCRV. Stars are sorted in right ascension J2000 order. 3967 stars were selected as radial velocity standard candidates (file rv_std.dat). These stars: - do not have any multiplicity and/or variability flags both in the GCRV and ASCC-2.5; - have standard errors of equatorial coordinates e <= 40 mas; - have standard errors of proper motions e_pm <= 4 mas/yr; - have standard errors of V magnitude e_V <= 0.05 mag and (B-V) colour e_(B-V) <= 0.07 mag; - have standard errors of radial velocity e_RV <= 2 km/s or quality index A or B, which corresponds to e_RV 0.74 and 1.78 km/s; - have at least four RV observations N_RV.
- ID:
- ivo://CDS.VizieR/J/ApJS/249/22
- Title:
- Radial velocity variable stars from LAMOST DR4
- Short Name:
- J/ApJS/249/22
- Date:
- 25 Oct 2021 00:46:50
- Publisher:
- CDS
- Description:
- Radial velocity (RV) variable stars are important in astrophysics. The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) spectroscopic survey has provided ~6.5 million stellar spectra in its Data Release 4 (DR4). During the survey ~4.7 million unique sources were targeted and ~1 million stars observed repeatedly. The probabilities of stars being RV variables are estimated by comparing the observed RV variations with simulated ones. We build a catalog of 80702 RV variable candidates with probability greater than 0.60 by analyzing the multi-epoch sources covered by LAMOST DR4. Simulations and cross-identifications show that the purity of the catalog is higher than 80%. The catalog consists of 77% binary systems and 7% pulsating stars as well as 16% pollution by single stars. 3138 RV variables are classified through cross-identifications with published results in literatures. By using the 3138 sources common in both LAMOST and a collection of published RV variable catalogs, we are able to analyze LAMOST's RV variable detection rate. The efficiency of the method adopted in this work relies not only on the sampling frequency of observations but also periods and amplitudes of RV variables. With the progress of LAMOST, Gaia, and other surveys, more and more RV variables will be confirmed and classified.
- ID:
- ivo://CDS.VizieR/J/ApJ/703/285
- Title:
- Radio and IR counterparts of BLAST sources in CDFS
- Short Name:
- J/ApJ/703/285
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have identified radio and/or mid-infrared counterparts to 198 out of 350 sources detected at >=5{sigma} over ~9deg^2^ centered on the Chandra Deep Field South by the Balloon-borne Large Aperture Submillimeter Telescope (BLAST) at 250, 350, and 500um. We have matched 114 of these counterparts to optical sources with previously derived photometric redshifts and fitted spectral energy distributions to the BLAST fluxes and fluxes at 70 and 160um acquired with the Spitzer Space Telescope. In this way, we have constrained dust temperatures, total far-infrared/submillimeter luminosities, and star formation rates for each source. Our findings show that, on average, the BLAST sources lie at significantly lower redshifts and have significantly lower rest-frame dust temperatures compared to submillimeter sources detected in surveys conducted at 850um. We demonstrate that an apparent increase in dust temperature with redshift in our sample arises as a result of selection effects. Finally, we provide the full multiwavelength catalog of >=5{sigma} BLAST sources contained within the complete ~9deg^2^ survey area.
- ID:
- ivo://CDS.VizieR/J/ApJ/838/139
- Title:
- Radio follow-up on 3FGL unassociated sources
- Short Name:
- J/ApJ/838/139
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The third Fermi Large Area Telescope {gamma}-ray source catalog (3FGL) contains over 1000 objects for which there is no known counterpart at other wavelengths. The physical origin of the {gamma}-ray emission from those objects is unknown. Such objects are commonly referred to as unassociated and mostly do not exhibit significant {gamma}-ray flux variability. We performed a survey of all unassociated {gamma}-ray sources found in 3FGL using the Australia Telescope Compact Array and Very Large Array in the range 4.0-10.0 GHz. We found 2097 radio candidates for association with {gamma}-ray sources. The follow-up with very long baseline interferometry for a subset of those candidates yielded 142 new associations with active galactic nuclei that are {gamma}-ray sources, provided alternative associations for seven objects, and improved positions for another 144 known associations to the milliarcsecond level of accuracy. In addition, for 245 unassociated {gamma}-ray sources we did not find a single compact radio source above 2 mJy within 3{sigma} of their {gamma}-ray localization. A significant fraction of these empty fields, 39%, are located away from the Galactic plane. We also found 36 extended radio sources that are candidates for association with a corresponding {gamma}-ray object, 19 of which are most likely supernova remnants or H II regions, whereas 17 could be radio galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/741/30
- Title:
- Radio/{gamma}-ray correlation in AGN
- Short Name:
- J/ApJ/741/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed statistical analysis of the correlation between radio and gamma-ray emission of the active galactic nuclei (AGNs) detected by Fermi during its first year of operation, with the largest data sets ever used for this purpose. We use both archival interferometric 8.4GHz data (from the Very Large Array and ATCA, for the full sample of 599 sources) and concurrent single-dish 15GHz measurements from the Owens Valley Radio Observatory (OVRO, for a sub sample of 199 objects). Our unprecedentedly large sample permits us to assess with high accuracy the statistical significance of the correlation, using a surrogate data method designed to simultaneously account for common-distance bias and the effect of a limited dynamical range in the observed quantities.
- ID:
- ivo://CDS.VizieR/J/ApJS/135/155
- Title:
- Radio identification of 3EG EGRET sources
- Short Name:
- J/ApJS/135/155
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The method of Mattox et al. (1996ApJ...461..396M) for identifying EGRET sources with 5GHz radio sources has been applied to the 3EG EGRET catalog of Hartman et al. (1999, Cat. <J/ApJS/123/79>). Complete results are tabulated. We tabulate separately 46 EGRET sources with radio identifications which we expect to have a high probability of being correct. We suggest that these sources are appropriate for most studies of the properties of {gamma}-ray blazars as a class. All but one of these 46 sources were classified by Hartman et al. (1999, Cat. <J/ApJS/123/79>) as high-confidence identifications; and the additional source was classified by Hartman et al. (1999, Cat. <J/ApJS/123/79>) as a plausible identification. We also tabulate separately 37 additional "plausible identifications of EGRET sources with radio sources." These less secure possibilities include the remaining 21 "high-confidence identifications" of Hartman et al. (1999, Cat. <J/ApJS/123/79>), three of the 27 "lower confidence potential blazar identifications" of Hartman et al. (1999, Cat. <J/ApJS/123/79>), and an additional 15 plausible identifications which have not been suggested previously. Many of these sources require new radio and optical observations to establish them as blazars. We suggest that the 23 "lower-confidence potential blazar identifications" of Hartman et al. (1999, Cat. <J/ApJS/123/79>) which we do not find plausible should not be used in studies of the properties of the EGRET blazars. For this analysis, we have made elliptical fits to the 95% confidence contours of the position uncertainty regions of the 3EG sources.
- ID:
- ivo://CDS.VizieR/J/ApJ/481/95
- Title:
- Radio identification of EGRET sources
- Short Name:
- J/ApJ/481/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a method to assess the reliability of the identification of EGRET sources with extragalactic radio sources. We verify that EGRET is detecting the blazar class of active galactic nuclei (AGNs). However many published identifications are found to be questionable. We provide a table of 42 blazars that we expect to be robust identifications of EGRET sources. This includes one previously unidentified EGRET source, the lensed AGN PKS 1830-210, near the direction of the Galactic center. We provide the best available positions for 16 more radio sources that are also potential identifications for previously unidentified EGRET sources. All high Galactic latitude EGRET sources (|b|>3) that demonstrate significant variability can be identified with flat-spectrum radio sources. This suggests that EGRET is not detecting any type of AGN other than blazars. This identification method has been used to establish with 99.998% confidence that the peak gamma-ray flux of a blazar is correlated with its average 5GHz radio flux. An even better correlation is seen between gamma-ray flux and the 2.29GHz flux density measured with VLBI at the base of the radio jet. Also, using high-confidence identifications, we find that the radio sources identified with EGRET sources have greater correlated VLBI flux densities than the parent population of flat radio spectrum sources.
