- ID:
- ivo://CDS.VizieR/J/MNRAS/467/4565
- Title:
- Bimodal radio variability in OVRO blazars
- Short Name:
- J/MNRAS/467/4565
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Blazars are known to show periods of quiescence followed by outbursts visible throughout the electromagnetic spectrum. We present a novel maximum likelihood approach to capturing this bimodal behavior by examining blazar radio variability in the flux-density domain. We separate quiescent and flaring components of a source's light curve by modeling its flux-density distribution as a series of "off" and "on" states. Our modeling allows us to extract information regarding the flaring ratio, duty cycle, and the modulation index in the "off"-state, in the "on"-state, as well as throughout the monitoring period of each blazar. We apply our method to a flux-density-limited subsample from the Owens Valley Radio observatory's 15 GHz blazar monitoring program, and explore differences in the variability characteristics between BL Lacs and FSRQs as well as between {gamma}-ray detected and non-detected sources. We find that: (1) BL Lacs are more variable and have relatively larger outbursts than the FSRQs; (2) unclassified blazar candidates in our sample show similar variability characteristics as the FSRQs; and (3) {gamma}-ray detected differ from the {gamma}-ray non-detected sources in all their variability properties, suggesting a link between the production of {gamma}-rays and the mechanism responsible for the radio variability. Finally, we fit distributions for blazar flaring ratios, duty cycles, and on- and off- modulation indices that can be used in population studies of variability-dependent blazar properties.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/745/147
- Title:
- Binaries among debris disk stars
- Short Name:
- J/ApJ/745/147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have gathered a sample of 112 main-sequence stars with known debris disks. We collected published information and performed adaptive optics observations at Lick Observatory to determine if these debris disks are associated with binary or multiple stars. We discovered a previously unknown M-star companion to HD 1051 at a projected separation of 628 AU. We found that 25%+/-4% of our debris disk systems are binary or triple star systems, substantially less than the expected ~50%. The period distribution for these suggests a relative lack of systems with 1-100 AU separations. Only a few systems have blackbody disk radii comparable to the binary/triple separation. Together, these two characteristics suggest that binaries with intermediate separations of 1-100 AU readily clear out their disks. We find that the fractional disk luminosity, as a proxy for disk mass, is generally lower for multiple systems than for single stars at any given age. Hence, for a binary to possess a disk (or form planets) it must either be a very widely separated binary with disk particles orbiting a single star or it must be a small separation binary with a circumbinary disk.
- ID:
- ivo://CDS.VizieR/J/AJ/132/891
- Title:
- Binaries among nearby L dwarfs
- Short Name:
- J/AJ/132/891
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used the Near-Infrared Camera and Multi-Object Spectrometer NIC1 camera on the Hubble Space Telescope to obtain high angular resolution images of 52 ultracool dwarfs in the immediate solar neighborhood. Nine systems are resolved as binary, with component separations from 1.5 to 15AU. Based on current theoretical models and empirical bolometric corrections, all systems have components with similar luminosities and, consequently, high mass ratios, q>0.8. Limiting analysis to L dwarfs within 20pc, the observed binary fraction is 12%(9-19%). Applying Bayesian analysis to our data set, we derive a mass-ratio distribution that peaks strongly at unity. Modeling the semimajor axis distribution as a logarithmic Gaussian, the best fit is centered at log(a_0_)=0.8AU (a_0_~6.3AU), with a (logarithmic) width of +/-0.3. The current data are consistent with an overall binary frequency of ~24%.
- ID:
- ivo://CDS.VizieR/J/A+A/583/A85
- Title:
- Binaries in beta Pic moving group
- Short Name:
- J/A+A/583/A85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We look for common proper motion companions to stars of the nearby young {beta} Pictoris moving group. First, we compiled a list of 185 {beta} Pictoris members and candidate members from 35 representative works. Next, we used the Aladin and STILTS virtual observatory tools and the PPMXL proper motion and Washington Double Star catalogues to look for companion candidates. The resulting potential companions were subjects of a dedicated astro-photometric follow-up using public data from all-sky surveys. After discarding 67 sources by proper motion and 31 by colour-magnitude diagrams, we obtained a final list of 36 common proper motion systems. The binding energy of two of them is perhaps too small to be considered physically bound. Of the 36 pairs and multiple systems, eight are new, 16 have only one stellar component previously classified as a {beta} Pictoris member, and three have secondaries at or below the hydrogen-burning limit. Sixteen stars are reported here for the first time as moving group members. The unexpected large number of high-order multiple systems, 12 triples and two quadruples among 36 systems, may suggest a biased list of members towards close binaries or an increment of the high-order-multiple fraction for very wide systems.
1685. Binaries in NGC 3201
- ID:
- ivo://CDS.VizieR/J/ApJS/90/83
- Title:
- Binaries in NGC 3201
- Short Name:
- J/ApJS/90/83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present BV CCD and APM photometry, accurate astrometry and 1859 radial velocities for 1318 stars within ~36deg of the Galactic globular cluster NGC 3201. The field and cluster populations separate unambiguously in two distinct samples since the systemic radial velocity of NGC 3201 is 494.2km/s. After removal of the 19 known NGC 3201 photometric variables in our sample, we have a database of 930 radial velocities for 420 member giants (276 of which have multiple velocity measurements) with which to identify spectroscopic binaries on the basis of radial velocity variations. The mean time span of the observations is 1.7yr, with coverage up to ~6yr for our best-studied stars. Monte Carlo simulations of the observed velocity variations have provided _upper_limits_ to the cluster binary fraction (for binaries with 0.1<=P<=5-10yr and mass ratios in the range 0.1-1) of 0.06-0.10 (circular orbits) and 0.15-0.18 (eccentric orbits). These results suggest an incidence of binarism for NGC 3201 consistent with the corresponding incidence among nearby solar-type stars having similar periods and mass ratios (0.04-0.08) and that for a small sample of other globular clusters (0.05-0.12) studied by Hut et al. (1992PASP..104..981H). The detailed analysis of the cluster dynamics, based on the data given here, are presented by Cote et al. (1995ApJ...454..788C).
- ID:
- ivo://CDS.VizieR/J/ApJ/521/682
- Title:
- Binaries in the Praesepe and Coma clusters
- Short Name:
- J/ApJ/521/682
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This completes a study of the evolution of binary systems in five open clusters of various ages. Among 21 stars observed in Praesepe, eight are found or confirmed to be spectroscopic binaries and orbital elements are derived, while one more shows long-term binary motion. Among 18 stars observed in the Coma Berenices cluster, five are found or confirmed to be spectroscopic binaries and orbital elements are derived, while a sixth has tentative elements.
- ID:
- ivo://CDS.VizieR/J/other/PNAOJ/2.561
- Title:
- Binaries speckle observations. IV.
- Short Name:
- J/other/PNAOJ/2.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the fourth paper of this series giving results of speckle observations for 22 visual and 161 spectroscopic binaries. The observation was carried out by using the 212 cm telescope of San Pedro Martir Observatory in Mexico at 7 nights from July 20 to July 26, 1991. We obtained fringes in power spectra of i 19 visual and 11 spectroscopic binaries (6 newly resolved ones) with angular separation larger than 0.06". We introduced a new ICCD TV camera in this observation, and were able to achieve the diffraction-limit resolution of the 212 cm telescope.
- ID:
- ivo://CDS.VizieR/J/MNRAS/479/1332
- Title:
- Binaries with F, G or K primaries and M dwarfs
- Short Name:
- J/MNRAS/479/1332
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigated almost 500 stars distributed among 193 binary or multiple systems made of late-F, G-, or early-K primaries and late-K or M dwarf companion candidates. For all of them, we compiled or measured coordinates, J-band magnitudes, spectral types, distances, and proper motions. With these data, we established a sample of 192 physically bound systems. In parallel, we carried out observations with HERMES/Mercator and obtained high-resolution spectra for the 192 primaries and five secondaries. We used these spectra and the automatic STEPAR code for deriving precise stellar atmospheric parameters: Teff, logg, {xi}, and chemical abundances for 13 atomic species, including [Fe/H]. After computing Galactocentric space velocities for all the primary stars, we performed a kinematic analysis and classified them in different Galactic populations and stellar kinematic groups of very different ages, which match our own metallicity determinations and isochronal age estimations. In particular, we identified three systems in the halo and 33 systems in the young Local Association, Ursa Major and Castor moving groups, and IC 2391 and Hyades Superclusters. We finally studied the exoplanet-metallicity relation in our 193 primaries and made a list 13 M-dwarf companions with very high metallicity that can be the targets of new dedicated exoplanet surveys. All in all, our dataset will be of great help for future works on the accurate determination of metallicity of M dwarfs.
- ID:
- ivo://CDS.VizieR/J/A+A/379/162
- Title:
- Binaries with post-T Tauri secondaries
- Short Name:
- J/A+A/379/162
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- File table2 contains the values of the color indices: (b-y), m1, c1, H{beta}, from the Stroemgren photometry and the observational errors on these indices as given by the Hauck and Mermiliod (1998, Cat. <II/215>). The values of Teff and logg are obtained from the Moon & Dworetsky (1985MNRAS.217..305M) calibration to which we have implemented the corrections by Castelli (1991A&A...251..106C). The errors on the parameters Teff and logg, as explained in section 3.3, are the consequence of the observational error on the photometric indices; SigmaTeff is the total error, on Teff, computed as explained in section 3.3. File table5 contains the values of the parallax, the error on the parallax, the Teff and the luminosity for the early-type star and late type star of each visual binary system. The errors on the Teff and on the luminosity are taken into account to compute for each of these parameters its minimum and maximum value. File table7 gives the values of the ages and masses computed for the early-type stars from the Schaller et al. (1993, Cat. <J/A+AS/96/269>) isochrones and Meynet at al. (1993A&AS...98..477M) models and from the Girardi et al. (2000, Cat. <J/A+AS/141/371>) models. The errors on the Teff and the luminosity are used to compute the minimum and the maximum values for the age and the mass. The last two columns concern only the primary stars with a Teff greater than 15000K for which we also compute the age and the mass using as Teff value: (Teff-500K); 500K corresponds to the systematic shift between Teff derived by using different photometric system (see Sect. 3.3). File table9 gives the values of the ages and masses computed for the late-type components from the isochrones and evolutionary tracks by D'Antona et al. (1998, web page, http://www.mporzio.astro.it/~dantona/ ) Palla and Stahler (1999ApJ...525..772P), Siess et al. (2000A&A...358..593S) and Tout et al. (1999MNRAS.310..360T). When possible, the minimum and the maximum values of these parameters are given by taking into account the errors on the Teff and on the luminosity.
- ID:
- ivo://CDS.VizieR/J/AJ/134/26
- Title:
- Binaries with white dwarf in 2MASS
- Short Name:
- J/AJ/134/26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the culmination of our near-infrared survey of the optically spectroscopically identified white dwarf stars from the McCook and Sion (1999ApJS..121....1M, see Cat. <III/235>) catalog, conducted using photometric data from the Two Micron All Sky Survey final All Sky Data Release. The color selection technique, which identifies candidate binaries containing a white dwarf and a low-mass stellar (or substellar) companion via their distinctive locus in the near-infrared color-color diagram, is demonstrated to be simple to apply and to yield candidates with a high rate of subsequent confirmation. We recover 105 confirmed binaries, and identify 27 firm candidates (19 of which are new to this work) and 21 tentative candidates (17 of which are new to this work) from the 2MASS data.
