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17361. White dwarfs in SDSS Stripe 82
ID:
ivo://CDS.VizieR/J/MNRAS/473/3241
Title:
White dwarfs in SDSS Stripe 82
Short Name:
J/MNRAS/473/3241
Date:
21 Oct 2021
Publisher:
CDS
Description:
Binary evolution theory predicts that accreting white dwarfs with substellar companions dominate the Galactic population of cataclysmic variables (CVs). In order to test these predictions, it is necessary to identify these systems, which may be difficult if the signatures of accretion become too weak to be detected. The only chance to identify such 'dead' CVs is by exploiting their close binary nature. We have therefore searched the Sloan Digital Sky Survey (SDSS) Stripe 82 area for apparently isolated white dwarfs that undergo eclipses by a dark companion. We found no such eclipses in either the SDSS or Palomar Transient Factory data sets among our sample of 2264 photometrically selected white dwarf candidates within Stripe 82. This null result allows us to set a firm upper limit on the space density, {rho}0, of dead CVs. In order to determine this limit, we have used Monte Carlo simulations to fold our selection criteria through a simple model of the Galactic CV distribution. Assuming a T_WD_=7500K, the resulting 2{sigma} limit on the space density of dead CVs is {rho}0<~2x10^-5^pc^-3^, where TWD is the typical effective temperature of the white dwarf in such systems.
17362. White Dwarfs in the SDSS
ID:
ivo://CDS.VizieR/J/AJ/126/1023
Title:
White Dwarfs in the SDSS
Short Name:
J/AJ/126/1023
Date:
21 Oct 2021
Publisher:
CDS
Description:
An initial assessment is made of white dwarf and hot subdwarf stars observed in the Sloan Digital Sky Survey. In a small area of sky (190 square degrees), observed much like the full survey will be, 269 white dwarfs (WDs) and 56 hot subdwarfs are identified spectroscopically where only 44 white dwarfs and five hot subdwarfs were known previously. Most are ordinary DA (hydrogen atmosphere) and DB (helium) types. In addition, in the full survey to date, a number of WDs have been found with uncommon spectral types. Among these are blue DQ stars displaying lines of atomic carbon; red DQ stars showing molecular bands of C2 with a wide variety of strengths; DZ stars where Ca and occasionally Mg, Na, and/or Fe lines are detected; and magnetic WDs with a wide range of magnetic field strengths in DA, DB, DQ, and (probably) DZ spectral types. Photometry alone allows identification of stars hotter than 12000K, and the density of these stars for magnitude g 15<g<20 is found to be ~2.2deg^-2^ at Galactic latitudes of 29{deg}-62{deg}. Spectra are obtained for roughly half of these hot stars. The spectra show that for 15<g<17, 40% of hot stars are WDs, and the fraction of WDs rises to ~90% at g=20. The remainder are hot sdB and sdO stars.
17363. White dwarfs in 47 Tuc (NGC 104) with HST
ID:
ivo://CDS.VizieR/J/AJ/143/50
Title:
White dwarfs in 47 Tuc (NGC 104) with HST
Short Name:
J/AJ/143/50
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a new distance determination to the Galactic globular cluster 47 Tucanae (47 Tuc, NGC 104) by fitting the spectral energy distributions of its white dwarfs (WDs) to pure hydrogen atmosphere WD models. Our photometric data set is obtained from a 121-orbit Hubble Space Telescope program using the Wide Field Camera 3 UVIS/IR channels, capturing F390W, F606W, F110W, and F160W images. These images cover more than 60 arcmin^2^ and extend over a radial range of 5-13.7arcmin (6.5-17.9pc) within the globular cluster. Using a likelihood analysis, we obtain a best-fitting unreddened distance modulus of (m-M)_o_=13.36+/-0.02+/-0.06 corresponding to a distance of 4.69+/-0.04+/-0.13kpc, where the first error is random and the second is systematic. We also search the WD photometry for infrared excess in the F160W filter, indicative of low-mass companions, and find no convincing cases within our sample.
17364. White dwarfs with cool companions
ID:
ivo://CDS.VizieR/J/ApJ/586/1356
Title:
White dwarfs with cool companions
Short Name:
J/ApJ/586/1356
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present near-infrared (IR) magnitudes for all white dwarfs (selected from the catalog of McCook & Sion, 1999, See Cat. <III/235>) contained in the Two Micron All-Sky Survey second incremental data release (2MASS 2IDR, Cat. <II/241>). We show that the near-IR color-color diagram is an effective means of identifying candidate binary stars containing a WD and a low-mass, main-sequence star. The loci of single WDs and WD+red dwarf binaries occupy distinct regions of the near-IR color-color diagram. We recovered all known unresolved WD+red dwarf binaries located in the 2IDR sky coverage and also identified as many new candidate binaries (47 new candidates out of 95 total). Using observational near-IR data for WDs and M-L dwarfs, we have compared a sample of simulated WD+red dwarf binaries with our 2MASS data. The colors of the simulated binaries are dominated by the low-mass companion through the late M to early L spectral types. As the spectral type of the companion becomes progressively later, however, the colors of unresolved binaries become progressively bluer. Binaries containing the lowest mass companions will be difficult to distinguish from single WDs solely on the basis of their near-IR colors.
17365. White dwarfs within 25pc of the Sun
ID:
ivo://CDS.VizieR/J/AJ/147/129
Title:
White dwarfs within 25pc of the Sun
Short Name:
J/AJ/147/129
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the fractional distribution of spectroscopic subtypes, range and distribution of surface temperatures, and kinematical properties of the white dwarfs (WDs) within 25pc of the Sun. There is no convincing evidence of halo WDs in the total 25pc sample of 224 WDs. There is also little to suggest the presence of genuine thick disk subcomponent members within 25pc. It appears that the entire 25pc sample likely belongs to the thin disk. We also find no significant kinematic differences with respect to spectroscopic subtypes. The total DA to non-DA ratio of the 25pc sample is 1.8, a manifestation of deepening envelope convection, which transforms DA stars with sufficiently thin H surface layers into non-DAs. We compare this ratio with the results of other studies. We find that at least 11% of the WDs within 25pc of the Sun (the DAZ and DZ stars) have photospheric metals that likely originate from accretion of circumstellar material (debris disks) around them. If this interpretation is correct, then it suggests the possibility that a similar percentage have planets, asteroid-like bodies, or debris disks orbiting them. Our volume-limited sample reveals a pileup of DC WDs at the well-known cutoff in DQ WDs at T_eff_~6000K. Mindful of small number statistics, we speculate on its possible evolutionary significance. We find that the incidence of magnetic WDs in the 25pc sample is at least 8% in our volume-limited sample, dominated by cool WDs. We derive approximate formation rates of DB and DQ degenerates and present a preliminary test of the evolutionary scenario that all cooling DB stars become DQ WDs via helium convective dredge-up with the diffusion tail of carbon extending upward from their cores.
17366. White-light flares on close binaries from Kepler
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.
17367. White-light flares on cool stars from Kepler
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.
17368. W3(H2O/OH) continuum & line data cubes at 1.3mm
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.
17369. 1WHSP blazar candidates catalog
ID:
ivo://bsdc.icranet.org/whsp/q/cone
Title:
1WHSP blazar candidates catalog
Short Name:
whsp cone
Date:
21 Dec 2016 00:42:39
Publisher:
BSDC
Description:
The catalog 1WHSP is the result of a multi-frequency selection for blazars like SED, further filtered using IR-radio and IR-X-ray flux-ratios. The sample assembled contains almost 992 sources of HSP blazars, of which 425 are previously known blazars, 151 new identifications and 416 blazar candidates. On the very high energy trend, 299 are confirmed GeV gamma-ray photons emitters and 36 have already been detected in the TeV band.
17370. 2WHSP Catalog of High Synchrotron Peaked Blazars and Candidates
ID:
ivo://nasa.heasarc/wisehspcat
Title:
2WHSP Catalog of High Synchrotron Peaked Blazars and Candidates
Short Name:
WISEHSPCAT
Date:
01 Nov 2024
Publisher:
NASA/GSFC HEASARC
Description:
High Synchrotron Peaked blazars (HSPs) dominate the gamma-ray sky at energies larger than a few GeV, however only a few hundred blazars of this type have been catalogued so far. In this paper, the authors present the 2WHSP sample, the largest and most complete list of HSP blazars available to date, which is an expansion of the 1WHSP catalog (Arsioli et al. 2015, A&amp;A, 579, A34) of gamma-ray source candidates away from the Galactic Plane. They cross-matched a number of multi-wavelength surveys (in the radio, infrared and X-ray bands) and applied selection criteria based on the radio to IR, and IR to X-ray spectral slopes. To ensure the selection of genuine HSPs, the authors examined the spectral energy distribution (SED) of each candidate and estimated the peak frequency of its synchrotron emission (nu&lt;sub&gt;peak&lt;/sub&gt;) using the Agenzia Spaziale Italiana Science Data Center (ASDC) SED tool, including only sources with nu&lt;sub&gt;peak&lt;/sub&gt; &gt; 10&lt;sup&gt;15&lt;/sup&gt; Hz (equivalent to nu&lt;sub&gt;peak&lt;/sub&gt; &gt; 4 eV). The authors have assembled the largest and most complete catalog of HSP blazars to date, which includes 1691 sources. A number of population properties, such as infrared colors, synchrotron peak, redshift distributions, and gamma-ray spectral properties, have been used to characterize the sample and maximize completeness. The authors also derived the radio log N - log S distribution. This catalog has already been used to provide seeds to discover new very high energy objects within Fermi-LAT data and to look for the counterparts of neutrino and ultra-high energy cosmic ray sources, showing its potential for the identification of promising high-energy gamma-ray sources and multi-messenger targets. This table comprises the 2WHSP catalog, a multi-frequency catalog of HSP. It contains 1691 sources, 288 of which are newly identified HSPs, 540 are previously known HSPs, 814 are HSP candidates, 45 are HSP blazars taken from the 2FHL catalog, and 4 from TeVCat (&lt;a href="http://tevcat.uchicago.edu"&gt;http://tevcat.uchicago.edu&lt;/a&gt;). This table was created by the HEASARC in February 2017 based on &lt;a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/598/A17"&gt;CDS Catalog J/A+A/598/A17&lt;/a&gt; file 2whsp.dat. This is a service provided by NASA HEASARC .

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