TeVCat (<a href="http://tevcat.uchicago.edu/">http://tevcat.uchicago.edu/</a>) is an online, interactive catalog for very-high-energy (VHE: energies, E >~ 50 GeV) gamma-ray astronomy. As VHE astronomy continues to grow, the usefulness of a one-stop clearing house for information on new sources is increasingly evident. TeVCat is intended to be such a resource. With sky maps, scientific information, visibility plotters and linked references available at the website, it will help the wider gamma-ray community stay up-to-date and informed on this exciting and rapidly developing field. This HEASARC database table provides the TeVCat list of VHE sources as well as links to the TeV source resource pages on the TeVCat website. The catalog and <a href="http://tevcat.uchicago.edu/">the website at the University of Chicago</a> are maintained by Scott Wakely and Deirdre Horan. This table was first ingested by the HEASARC in July 2017 based on the catalog of VHE gamma-ray sources available at <a href="http://tevcat.uchicago.edu/">http://tevcat.uchicago.edu/</a>. It is updated automatically within a few days of the catalog being updated on the University of Chicago website. This is a service provided by NASA HEASARC .
We have collected the most complete multi-wavelength (6.0-6.0E^-18^cm) dataset of very high energy (VHE) gamma-ray emitting (TeV) BL Lacs, which are the most numerous extragalactic VHE sources. Using significant correlations between different bands, we aim to identify the best TeV BL Lac candidates that can be discovered by the current and next generation of imaging air Cherenkovtelescopes. We formed five datasets from lower energy data, i.e. radio, mid-infrared, optical, X-rays, and GeV gamma-ray, and five VHE gamma-ray datasets to perform a correlation study between different bands and to construct the prediction method. The low energy datasets were averaged for individual sources, while the VHE gamma-ray data were divided into subsets according to the flux state of the source. We then looked for significant correlations and determined their best-fit parameters. Using the best-fit parameters we predicted the level of VHE gamma-ray flux for a sample of 182 BL Lacs, which have not been detected at TeV energies. We identified the most promising TeV BL Lac candidates based on the predicted VHE gamma-ray flux for each source. We found 14 significant correlations between radio, mid-infrared, optical, gamma-ray, and VHE gamma-ray bands. The correlation between optical and VHE gamma-ray luminosity is established for the first time. We attribute this to the more complete sample and more accurate handling of host galaxy flux in our work. We found nine BL Lac candidates whose predicted VHE gamma-ray flux is high enough for detection in less than 25 hours with current imaging air Cherenkov telescopes.
We present a clustering analysis of the Texas-Oxford NVSS Structure (TONS) radio galaxy redshift survey. This complete flux-limited survey consists of 268 radio galaxies with spectroscopic redshifts in three separate regions of the sky covering a total of 165{deg}^2^. By going to faint radio flux densities (S_1.4_>=3mJy) but imposing relatively bright optical limits (E~R~19.5), the TONS sample is optimized for looking at the clustering properties of low-luminosity radio galaxies in a region of moderate (0<=z<=0.5) redshifts. Description:
We present the Texas Survey of discrete radio sources between -35.5deg and 71.5deg declination (B1950), which was carried out at 365MHz with the Texas Interferometer during 1974-1983. The Survey lists accurate positions with internal errors of about an arcsecond, flux densities which for strong point sources have internal errors of about 1% and total errors of about 5%, simple structure models and indications of spectrum and variability for 66841 sources. Results of comparisons with other data are presented, and show that the Survey is 90% complete at 0.4Jy and 80% complete at 0.25Jy, is nearly free from spurious sources, and has a lobeshift incidence which is reasonably described by quality flags associated with each source.
This catalog is from the Texas Survey of discrete radio sources between -35.5 degrees and +71.5 degrees declination (B1950), which was carried out at a frequency of 365 MHz (82 cm wavelength) with the Texas Interferometer during the period from 1974 to 1983. The Survey lists accurate positions with internal errors of about an arcsecond, flux densities (which for strong point sources have internal errors of about 1% and total errors of about 5%), simple structure models and indications of spectrum and variability for 66841 sources. Results of comparisons with other data show that the Survey is 90% complete at 0.4 Jy and 80% complete at 0.25 Jy, is nearly free from spurious sources, and has a lobeshift incidence which is reasonably described by quality flags associated with each source. The University of Texas Radio Astronomy Observatory (UTRAO) carried out, with the Texas Interferometer, this 365 MHz survey of the sky, which was intended to be complete to a flux density level of 0.25 Jy, to provide positions with an accuracy of about 1 arcsec in both coordinates, to give accurate flux densities and indication of source variability, and to give rough structure models for each source. The observations began in 1974 and were completed in 1983. A preliminary version of one declination strip was published (Douglas et al., Publ. Dept. Astron. Univ. Texas, No. 17, Oct. 1980), and a number of intermediate versions of the survey were privately circulated for various purposes, pending completion of the final analysis and adjustment of the data. This database was created by the HEASARC in February 2001, based on CDS/ADC catalog VIII/42. This is a service provided by NASA HEASARC .
The abundance of deuterium in giant planet atmospheres provides constraints on the reservoirs of ices incorporated into these worlds during their formation and evolution. Motivated by discrepancies in the measured deuterium-hydrogen ratio (D/H) on Jupiter and Saturn, we present a new measurement of the D/H ratio in methane for Saturn from ground-based measurements. We analysed a spectral cube (covering 1151-1160cm^-1^ from 6 February 2013) from the Texas Echelon Cross Echelle Spectrograph (TEXES) on NASA's Infrared Telescope Facility (IRTF) where emission lines from both methane and deuterated methane are well resolved. Our estimate of the D/H ratio in stratospheric methane, 1.65(-0.21/+0.27)*10^-5^ is in agreement with results derived from Cassini CIRS and ISO/SWS observations, confirming the unexpectedly low CH3D abundance. Assuming a fractionation factor of 1.34(+/-0.19) we derive a hydrogen D/H of 1.23(-0.23/+0.27)*10^-5^. This value remains lower than previous tropospheric hydrogen D/H measurements of (i) Saturn 2.10(+/-0.13)*10^-5^, (ii) Jupiter 2.6(+/-0.7)*10^-5^ and (iii) the proto-solar hydrogen D/H of 2.1(+/-0.5)*10^-5^, suggesting that the fractionation factor may not be appropriate for stratospheric methane, or that the D/H ratio in Saturn's stratosphere is not representative of the bulk of the planet.
This table is a subset of GaiaSource comprising those stars in the
Hipparcos and Tycho-2 Catalogues for which a full 5-parameter
astrometric solution has been possible in Gaia Data Release 1. This is
possible because the early Hipparcos epoch positions break some
degeneracies due to the limited Gaia time coverage. This table
contains a substantial fraction of the around 2.5 million stars in the
Hipparcos and Tycho-2 catalogue. Many stars have been excluded due to
several reasons, such as saturation, cross-match errors or bad
astrometric solution. All rows have Gaia solution id
1635378410781933568.
Parallaxes for 331 classical Cepheids, 31 Type II Cepheids and 364 RR Lyrae stars in common between Gaia and the Hipparcos and Tycho-2 catalogues are published in Gaia Data Release 1 (DR1) as part of the Tycho-Gaia Astrometric Solution (TGAS). In order to test these first parallax measurements of the primary standard candles of the cosmological distance ladder, that involve astrometry collected by Gaia during the initial 14 months of science operation, we compared them with literature estimates and derived new period-luminosity (PL), period-Wesenheit (PW) relations for classical and Type II Cepheids and infrared PL, PL-metallicity (PLZ) and optical luminosity-metallicity (MV-[Fe/H]) relations for the RR Lyrae stars, with zero points based on TGAS. The new relations were computed using multi-band (V, I, J, Ks, W1) photometry and spectroscopic metal abundances available in the literature, and applying three alternative approaches: (i) by linear least squares fitting the absolute magnitudes inferred from direct transformation of the TGAS parallaxes, (ii) by adopting astrometric-based luminosities, and (iii) using a Bayesian fitting approach. TGAS parallaxes bring a significant added value to the previous Hipparcos estimates. The relations presented in this paper represent first Gaia-calibrated relations and form a "work-in-progress" milestone report in the wait for Gaia-only parallaxes of which a first solution will become available with Gaia's Data Release 2 (DR2) in 2018.
We derive unbiased distance estimates for the Gaia-TGAS data set by correcting for the bias due to the distance dependence of the selection function, which we measure directly from the data. From these distances and proper motions, we estimate the vertical and azimuthal velocities, W and V_{phi}_, and angular momentum L_z_ for stars in the Galactic centre and anticentre directions. The resulting mean vertical motion W^-^ hows a linear increase with both V_{phi}_ and L_z_ at 10{sigma} significance. Such a trend is expected from and consistent with the known Galactic warp. This signal extends to stars with guiding centre radii R_g_<R_0_, placing the onset of the warp at R<=7kpc. At equally high significance, we detect a previously unknown wave-like pattern of W^-^ over guiding centre R_g_ with an amplitude ~1km/s and a wavelength ~2.5kpc. This pattern is present in both the centre and anticentre directions, consistent with a winding (corrugated) warp or bending wave, likely related to known features in the outer disc (TriAnd and Monoceros overdensities), and may be caused by the interaction with the Sgr dwarf galaxy ~1Gyr ago. The only significant deviation from this simple fit is a stream-like feature near R_g_~9kpc (|L_z_|~2150kpc.km/s).
The Tycho-Gaia Astrometric Solution (TGAS) subset of the first Gaia catalogue contains an unprecedented sample of proper motions and parallaxes for two million stars brighter than G~12 mag. We take advantage of the full astrometric solution available for those stars to identify the members of known open clusters and compute mean cluster parameters using either TGAS or UCAC4 proper motions, and TGAS parallaxes. We apply an unsupervised membership assignment procedure to select high probability cluster members, we use a Bayesian/MCMC technique to fit stellar isochrones to the observed 2MASS JHK magnitudes of the member stars and derive cluster parameters (age, metallicity, extinction, distance modulus), and we combine TGAS data with spectroscopic radial velocities to compute full Galactic orbits. We obtain mean astrometric parameters (proper motions and parallaxes) for 128 clusters closer than about 2kpc, and cluster parameters from isochrone fitting for 26 of them located inside 1kpc from us. We show the orbital parameters obtained from integrating 36 orbits in a Galactic potential.