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- ID:
- ivo://CDS.VizieR/J/ApJS/224/37
- Title:
- White-light flares on close binaries from Kepler
- Short Name:
- J/ApJS/224/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on Kepler data, we present the results of a search for white light flares on 1049 close binaries. We identify 234 flare binaries, of which 6818 flares are detected. We compare the flare-binary fraction in different binary morphologies ("detachedness"). The result shows that the fractions in over-contact and ellipsoidal binaries are approximately 10%-20% lower than those in detached and semi-detached systems. We calculate the binary flare activity level (AL) of all the flare binaries, and discuss its variations along the orbital period (P_orb_) and rotation period (P_rot_, calculated for only detached binaries). We find that the AL increases with decreasing P_orb_ or P_rot_, up to the critical values at P_orb_~3 days or P_rot_~1.5 days, and thereafter the AL starts decreasing no matter how fast the stars rotate. We examine the flaring rate as a function of orbital phase in two eclipsing binaries on which a large number of flares are detected. It appears that there is no correlation between flaring rate and orbital phase in these two binaries. In contrast, when we examine the function with 203 flares on 20 non-eclipse ellipsoidal binaries, bimodal distribution of amplitude-weighted flare numbers shows up at orbital phases 0.25 and 0.75. Such variation could be larger than what is expected from the cross section modification.
- ID:
- ivo://CDS.VizieR/J/AJ/141/50
- Title:
- White-light flares on cool stars from Kepler
- Short Name:
- J/AJ/141/50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a search for white-light flares on ~23000 cool dwarfs in the Kepler Quarter 1 long cadence data. We have identified 373 flaring stars, some of which flare multiple times during the observation period. We calculate relative flare energies, flare rates, and durations and compare these with the quiescent photometric variability of our sample.
- ID:
- ivo://CDS.VizieR/J/A+A/618/A46
- Title:
- W3(H2O/OH) continuum & line data cubes at 1.3mm
- Short Name:
- J/A+A/618/A46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The fragmentation mode of high-mass molecular clumps and the properties of the central rotating structures surrounding the most luminous objects have yet to be comprehensively characterised. We study the fragmentation and kinematics of the high-mass star-forming region W3(H_2_O), as part of the IRAM NOrthern Extended Millimeter Array (NOEMA) large programme CORE. Using the IRAM NOEMA and the IRAM 30m telescope, the CORE survey has obtained high-resolution observations of 20 well-known highly luminous star-forming regions in the 1.37 mm wavelength regime in both line and dust continuum emission. We present the spectral line set-up of the CORE survey and a case study for W3(H_2_O). At ~0.35" (700AU at 2.0kpc) resolution, the W3(H_2_O) clump fragments into two cores (west and east), separated by ~2300AU. Velocity shifts of a few km/s are observed in the dense-gas tracer, CH_3_CN, across both cores, consistent with rotation and perpendicular to the directions of two bipolar outflows, one emanating from each core. The kinematics of the rotating structure about W3(H_2_O) W shows signs of differential rotation of material, possibly in a disk-like object. The observed rotational signature around W3(H_2_O) E may be due to a disk-like object, an unresolved binary (or multiple) system, or a combination of both. We fit the emission of CH_3_CN (12K-11K) K=4-6 and derive a gas temperature map with a median temperature of ~165K across W3(H_2_O). We create a Toomre Q map to study the stability of the rotating structures against gravitational instability. The rotating structures appear to be Toomre unstable close to their outer boundaries, with a possibility of further fragmentation in the differentially rotating core, W3(H_2_O) W. Rapid cooling in the Toomre unstable regions supports the fragmentation scenario. Combining millimetre dust continuum and spectral line data toward the famous high-mass star-forming region W3(H_2_O), we identify core fragmentation on large scales, and indications for possible disk fragmentation on smaller spatial scales.
- ID:
- ivo://CDS.VizieR/J/A+A/579/A34
- Title:
- 1WHSP: VHE {gamma}-ray blazar candidates
- Short Name:
- J/A+A/579/A34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Blazars are the dominant type of extragalactic sources at microwave and at {gamma}-ray energies. In the most energetic part of the electromagnetic spectrum (E>~100GeV) a high fraction of high Galactic latitude sources are blazars of the high synchrotron peaked (HSP) type, that is BL Lac objects with synchrotron power peaking in the UV or in the X-ray band. Building new large samples of HSP blazars is key to understand the properties of jets under extreme conditions, and to study the demographics and the peculiar cosmological evolution of these sources. High synchrotron peaked blazars are remarkably rare, with only a few hundreds of them expected to be above the sensitivity limits of currently available surveys, some of which include hundreds of millions of sources. To find these very uncommon objects, we have devised a method that combines ALLWISE survey data with multi-frequency selection criteria. The sample was defined starting from a primary list of infrared colour-colour selected sources from the ALLWISE all sky survey database, and applying further restrictions on IR-radio and IR-X-ray flux ratios. Using a polynomial fit to the multi-frequency data (radio to X-ray), we estimated synchrotron peak frequencies and fluxes of each object.
- ID:
- ivo://CDS.VizieR/J/AJ/120/2269
- Title:
- Wide-Angle-Tailed radio galaxies redshifts
- Short Name:
- J/AJ/120/2269
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new redshifts and positions for 635 galaxies in nine rich clusters containing wide-angle tailed (WAT) radio galaxies. Combined with existing data, we now have a sample of 18 WAT-containing clusters with more than 10 redshifts. This sample contains a substantial portion of the WAT clusters in the VLA 20 cm survey of Abell clusters, including 75% of WAT clusters in the complete survey (z<=0.09), and 20% of WAT clusters with z>0.09. It is a representative sample, which should not contain biases other than selection by radio morphology. We graphically present the new data using histograms and sky maps. A semiautomated procedure is used to search for emission lines in the spectra in order to add and verify galaxy redshifts. We find that the average apparent fraction of emission-line galaxies is about 9% in both the clusters and the field. We investigate the magnitude completeness of our redshift surveys with CCD data for a test case, Abell 690. This case indicates that our galaxy target lists are deeper than the detection limit of a typical MX exposure, and they are 82% complete down to R=19.0. The importance of the uniformity of the placement of fibers on targets is posited, and we evaluate this in our data sets. We find some cases of nonuniformities which may influence dynamical analyses. A second paper will use this database to look for correlations between the WAT radio morphology and the cluster's dynamical state.
- ID:
- ivo://CDS.VizieR/J/ApJ/703/1511
- Title:
- Wide binaries in Taurus and Upper Sco
- Short Name:
- J/ApJ/703/1511
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe an astrometric and spectroscopic campaign to confirm the youth and association of a complete sample of candidate wide companions in Taurus and Upper Sco. Our survey found 15 new binary systems (three in Taurus and 12 in Upper Sco) with separations of 3"-30" (500-5000AU) among all of the known members with masses of 2.5-0.012M_{sun}_. The total sample of 49 wide systems in these two regions conforms to only some expectations from field multiplicity surveys. Higher mass stars have a higher frequency of wide binary companions, and there is a marked paucity of wide binary systems near the substellar regime. However, the separation distribution appears to be log-flat, rather than declining as in the field, and the mass ratio distribution is more biased toward similar-mass companions than the initial mass function or the field G-dwarf distribution. The maximum separation also shows no evidence of a limit at <~5000AU until the abrupt cessation of any wide binary formation at system masses of ~0.3M_{sun}_. We attribute this result to the post-natal dynamical sculpting that occurs for most field systems; our binary systems will escape to the field intact, but most field stars are formed in denser clusters and undergo significant dynamical evolution. In summary, only wide binary systems with total masses <~0.3M_{sun}_ appear to be "unusually wide."
- ID:
- ivo://CDS.VizieR/J/MNRAS/472/675
- Title:
- Wide binaries in Tycho-Gaia: search method
- Short Name:
- J/MNRAS/472/675
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We mine the Tycho-Gaia astrometric solution (TGAS) catalogue for wide stellar binaries by matching positions, proper motions and astrometric parallaxes. We separate genuine binaries from unassociated stellar pairs through a Bayesian formulation that includes correlated uncertainties in the proper motions and parallaxes. Rather than relying on assumptions about the structure of the Galaxy, we calculate Bayesian priors and likelihoods based on the nature of Keplerian orbits and the TGAS catalogue itself. We calibrate our method using radial velocity measurements and obtain 7108 high-confidence candidate wide binaries with projected separations s<~1pc. The normalization of this distribution suggests that at least 0.7 per cent of TGAS stars have an associated, distant TGAS companion in a wide binary. We demonstrate that Gaia's astrometry is precise enough that it can detect projected orbital velocities in wide binaries with orbital periods as large as 10^6^yr. For pairs with s<~4x10^4^au, characterization of random alignments indicates our contamination to be 5-10 per cent. For s<~5x10^3^au, our distribution is consistent with Opik's law. At larger separations, the distribution is steeper and consistent with a power-law P(s){propto}s^-1.6^; there is no evidence in our data of any bimodality in this distribution for s<~1pc. Using radial velocities, we demonstrate that at large separations, i.e. of order s~1pc and beyond, any potential sample of genuine wide binaries in TGAS cannot be easily distinguished from ionized former wide binaries, moving groups or contamination from randomly aligned stars.
- ID:
- ivo://CDS.VizieR/J/AJ/133/971
- Title:
- Wide companions of low-mass stars and brown dwarfs
- Short Name:
- J/AJ/133/971
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a deep-imaging search for wide companions to low-mass stars and brown dwarfs using NSFCam on the Infrared Telescope Facility. We searched a sample of 132 M7-L8 dwarfs to magnitude limits of J~20.5 and K~18.5, corresponding to secondary-to-primary mass ratios of ~0.5. No companions were found with separations between 2" and 31" (~40 to ~1000AU). This null result implies a wide companion frequency below 2.3% at the 95% confidence level within the sensitivity limits of the survey. Preliminary modeling efforts indicate that we could have detected 85% of companions more massive than 0.05M_{sun}_ and 50% above 0.03M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/A+A/650/A190
- Title:
- Wide companions to M and L subdwarfs
- Short Name:
- J/A+A/650/A190
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The aim of the project is to identify wide common proper motion companions to a sample of spectroscopically confirmed M and L metal-poor dwarfs (also known as subdwarfs) to investigate the impact of metallicity on the binary fraction of low-mass metal-poor binaries and to improve the determination of their metallicity from the higher-mass binary. We made use of Virtual Observatory tools and large-scale public surveys to look in Gaia for common proper motion companions to a well-defined sample of ultracool subdwarfs with spectral types later than M5 and metallicities below or equal to ~0.5dex. We collected low-resolution optical spectroscopy for our best system, which is a binary composed of one sdM1.5 subdwarf and one sdM5.5 subdwarf located at ~1360au, and for another two likely systems separated by more than 115000au. We confirm one wide companion to an M subdwarf, and infer a multiplicity for M subdwarfs (sdMs) of 1.0_-1.0_^+2.0^% for projected physical separations of up to 743000au. We also find four M-L systems, three of which are new detections. No colder companion was identified in any of the 219 M and L subdwarfs of the sample, mainly because of limitations on the detection of faint sources with Gaia. We infer a frequency of wide systems for sdM5-9.5 of 0.60_-0.60_^+1.17^% for projected physical separations larger than 1360au (up to 142400au). This study shows a multiplicity rate of 1.0_-1.0_^+2.0^% in sdMs, and 1.9_-1.9_^+3.7^% in extreme M subdwarfs. We did not find any companion for the ultra M subdwarfs of our sample, establishing an upper limit of 5.3% on binarity for these objects.
