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15421. The 2E Catalogue
ID:
ivo://CDS.VizieR/IX/13
Title:
The 2E Catalogue
Short Name:
IX/13
Date:
21 Oct 2021
Publisher:
CDS
Description:
This catalog contains sources from EINSTEIN IPC (Imaging Proportional counter aboard the EINSTEIN (HEAO 2) satellite, in orbit between November 1978 and April 1981) detected during pointed observations. Note that a single source may have more than one entry in the catalog.
15422. The edge of the young Galactic disk
ID:
ivo://CDS.VizieR/J/ApJ/718/683
Title:
The edge of the young Galactic disk
Short Name:
J/ApJ/718/683
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this work, we report and discuss the detection of two distant diffuse stellar groups in the third Galactic quadrant. They are composed of young stars, with spectral types ranging from late O to late B, and lie at galactocentric distances between 15 and 20kpc. These groups are located in the area of two cataloged open clusters (VdB-Hagen 04 and Ruprecht 30), projected toward the Vela-Puppis constellations, and within the core of the Canis Major overdensity. Their reddening and distances have been estimated by analyzing their color-color and color-magnitude diagrams, derived from deep UBV photometry. The existence of young star aggregates at such extreme distances from the Galactic center challenges the commonly accepted scenario in which the Galactic disk has a sharp cutoff at about 14kpc from the Galactic center and indicates that it extends to much greater distances (as also supported by the recent detection of CO molecular complexes well beyond this distance). While the groups we find in the area of Ruprecht 30 are compatible with the Orion and Norma-Cygnus spiral arms, respectively, the distant group we identify in the region of VdB-Hagen 04 lies in the external regions of the Norma-Cygnus arm, at a galactocentric distance (~20kpc) where no young stars have been detected so far in the optical.
15423. The Einstein@Home gamma-ray pulsar survey. II.
ID:
ivo://CDS.VizieR/J/ApJ/854/99
Title:
The Einstein@Home gamma-ray pulsar survey. II.
Short Name:
J/ApJ/854/99
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report on the analysis of 13 gamma-ray pulsars discovered in the Einstein@Home blind search survey using Fermi Large Area Telescope (LAT) Pass 8 data. The 13 new gamma-ray pulsars were discovered by searching 118 unassociated LAT sources from the third LAT source catalog (3FGL), selected using the Gaussian Mixture Model machine-learning algorithm on the basis of their gamma-ray emission properties being suggestive of pulsar magnetospheric emission. The new gamma-ray pulsars have pulse profiles and spectral properties similar to those of previously detected young gamma-ray pulsars. Follow-up radio observations have revealed faint radio pulsations from two of the newly discovered pulsars and enabled us to derive upper limits on the radio emission from the others, demonstrating that they are likely radio-quiet gamma-ray pulsars. We also present results from modeling the gamma-ray pulse profiles and radio profiles, if available, using different geometric emission models of pulsars. The high discovery rate of this survey, despite the increasing difficulty of blind pulsar searches in gamma rays, suggests that new systematic surveys such as presented in this article should be continued when new LAT source catalogs become available.
15424. The Einstein Observatory HRI Source List
ID:
ivo://CDS.VizieR/IX/24
Title:
The Einstein Observatory HRI Source List
Short Name:
IX/24
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Einstein Observatory is the second of NASA's three High Energy Astrophysical Observatories, HEAO-2, renamed Einstein after launch, and was the first fully imaging X-ray telescope put into space. It observed in the energy range 0.2-20keV. It was launched on 12 November 1978, and remained in operation until April 1981. The High Resolution Imager (HRI) is one fo the four instruments aboard the Einstein Observatory, operating in the 0.2-3.0keV energy range, with a spatial resolution of a few arcseconds, and a field of view of 25arcmin. Field and source parameters observed with this instrument are given here.
15425. The Einstein Two-Sigma Catalog
ID:
ivo://CDS.VizieR/J/ApJ/461/127
Title:
The Einstein Two-Sigma Catalog
Short Name:
J/ApJ/461/127
Date:
21 Oct 2021
Publisher:
CDS
Description:
The X-ray sources from the observations with the Einstein Observatory (HEAO-2) with intensities of 2-sigma above the background are compiled in this catalog. This catalog covers more sky at fainter flux levels than the Einstein Medium Sensitivity Survey. Fields with diffuse emission sources were excluded. Thus data within 10 degrees of the galactic plane as well as fields within the boundaries of the Magellanic Clouds were excluded. The catalog covers 1850 sq. degrees of the sky. The generation of the Einstein Two-Sigma Catalog was described in detail by Moran et al. (1996). Read this article carefully to ensure responsible use of the Catalog. Address any questions to Ed Moran (edhed@igpp.llnl.gov). In particular it should be noted that only 28%, or about 13,000 sources in the 2-sigma catalog are real sources. The authors show that cross-correlations with other catalogs is an effective way to select sources in this catalog that are probably real.
15426. The ELM survey. I. Low-mass white dwarfs
ID:
ivo://CDS.VizieR/J/ApJ/723/1072
Title:
The ELM survey. I. Low-mass white dwarfs
Short Name:
J/ApJ/723/1072
Date:
21 Oct 2021
Publisher:
CDS
Description:
We analyze radial velocity observations of the 12 extremely low-mass (ELM), with <=0.25M_{sun}_, white dwarfs (WDs) in the MMT Hypervelocity Star Survey. Eleven of the twelve WDs are binaries with orbital periods shorter than 14hr; the one non-variable WD is possibly a pole-on system among our non-kinematically selected targets. Our sample is unique: it is complete in a well-defined range of apparent magnitude and color. The orbital mass functions imply that the unseen companions are most likely other WDs, although neutron star companions cannot be excluded. Six of the eleven systems with orbital solutions will merge within a Hubble time due to the loss of angular momentum through gravitational wave radiation. The quickest merger is J0923+3028, a g=15.7 ELM WD binary with a 1.08hr orbital period and a <=130Myr merger time. The chance of a supernova Ia event among our ELM WDs is only 1%-7%, however. Three binary systems (J0755+4906, J1233+1602, and J2119-0018) have extreme mass ratios and will most likely form stable mass-transfer AM CVn systems. Two of these objects, SDSS J1233+1602 and J2119-0018, are the lowest surface gravity WDs ever found; both show CaII absorption likely from accretion of circumbinary material. We predict that at least one of our WDs is an eclipsing detached double WD system, important for constraining helium core WD models.
15427. The ELM Survey. VIII. Final double WD binaries
ID:
ivo://CDS.VizieR/J/ApJ/889/49
Title:
The ELM Survey. VIII. Final double WD binaries
Short Name:
J/ApJ/889/49
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the final sample of 98 detached double white dwarf (WD) binaries found in the Extremely Low Mass (ELM) Survey, a spectroscopic survey targeting <0.3M_{sun}_ He-core WDs completed in the Sloan Digital Sky Survey footprint. Over the course of the survey we observed ancillary low-mass WD candidates like GD 278, which we show is a P=0.19d double WD binary, as well as candidates that turn out to be field blue straggler/subdwarf A-type stars with luminosities too high to be WDs given their Gaia parallaxes. Here, we define a clean sample of ELM WDs that is complete within our target selection and magnitude range 15<g_0_<20mag. The measurements are consistent with 100% of ELM WDs being 0.0089<P<1.5d double WD binaries, 35% of which belong to the Galactic halo. We infer that these are mostly He+CO WD binaries given the measurement constraints. The merger rate of the observed He+CO WD binaries exceeds the formation rate of stable mass-transfer AM CVn binaries by a factor of 25, and so the majority of He+CO WD binaries must experience unstable mass transfer and merge. The systems with the shortest periods, such as J0651+2844, are signature LISA verification binaries that can be studied with gravitational waves and light.
15428. The ELM survey. VII. 15 new ELM white dwarf cand.
ID:
ivo://CDS.VizieR/J/ApJ/818/155
Title:
The ELM survey. VII. 15 new ELM white dwarf cand.
Short Name:
J/ApJ/818/155
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the discovery of 15 extremely low-mass (5<logg<7) white dwarf (WD) candidates, 9 of which are in ultra-compact double-degenerate binaries. Our targeted extremely low-mass Survey sample now includes 76 binaries. The sample has a lognormal distribution of orbital periods with a median period of 5.4hr. The velocity amplitudes imply that the binary companions have a normal distribution of mass with 0.76 M_{sun}_ mean and 0.25M_{sun}_ dispersion. Thus extremely low-mass WDs are found in binaries with a typical mass ratio of 1:4. Statistically speaking, 95% of the WD binaries have a total mass below the Chandrasekhar mass, and thus are not type Ia supernova progenitors. Yet half of the observed binaries will merge in less than 6Gyr due to gravitational wave radiation; probable outcomes include single massive WDs and stable mass transfer AM CVn binaries.
15429. The ELM survey. VI. 11 new ELM WD binaries
ID:
ivo://CDS.VizieR/J/ApJ/812/167
Title:
The ELM survey. VI. 11 new ELM WD binaries
Short Name:
J/ApJ/812/167
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the discovery of 11 new double degenerate systems containing extremely low-mass white dwarfs (ELM WDs). Our radial velocity observations confirm that all of the targets have orbital periods <=1 day. We perform spectroscopic fits and provide a complete set of physical and binary parameters. We review and compare recent evolutionary calculations and estimate that the systematic uncertainty in our mass determinations due to differences in the evolutionary models is small (~0.01M_{sun}_). Five of the new systems will merge due to gravitational wave radiation within a Hubble time, bringing the total number of merger systems found in the ELM Survey to 38. We examine the ensemble properties of the current sample of ELM WD binaries, including the period distribution as a function of effective temperature, and the implications for the future evolution of these systems. We also revisit the empirical boundaries of instability strip of ELM WDs and identify new pulsating ELM WD candidates. Finally, we consider the kinematic properties of our sample of ELM WDs and estimate that a significant fraction of the WDs from the ELM Survey are members of the Galactic halo.
15430. The ELM survey. V. White dwarf binaries
ID:
ivo://CDS.VizieR/J/ApJ/769/66
Title:
The ELM survey. V. White dwarf binaries
Short Name:
J/ApJ/769/66
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the discovery of 17 low-mass white dwarfs (WDs) in short-period (P<=1 day) binaries. Our sample includes four objects with remarkable logg=~5 surface gravities and orbital solutions that require them to be double degenerate binaries. All of the lowest surface gravity WDs have metal lines in their spectra implying long gravitational settling times or ongoing accretion. Notably, six of the WDs in our sample have binary merger times <10Gyr. Four have >~0.9M_{sun}_ companions. If the companions are massive WDs, these four binaries will evolve into stable mass transfer AM CVn systems and possibly explode as underluminous supernovae. If the companions are neutron stars, then these may be millisecond pulsar binaries. These discoveries increase the number of detached, double degenerate binaries in the Extremely low mass (ELM) Survey to 54; 31 of these binaries will merge within a Hubble time.

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