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- ID:
- ivo://CDS.VizieR/J/A+A/612/A110
- Title:
- Cas A LOFAR and VLA images
- Short Name:
- J/A+A/612/A110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Cassiopeia A is one of the best-studied supernova remnants. Its bright radio and X-ray emission is due to shocked ejecta. Cas A is rather unique in that the unshocked ejecta can also be studied: through emission in the infrared, the radio-active decay of ^44^Ti, and the low-frequency free-free absorption caused by cold ionised gas, which is the topic of this paper. Free-free absorption processes are acted by the mass, geometry, temperature, and ionisation conditions in the absorbing gas. Observations at the lowest radio frequencies can constrain a combination of these properties. We used Low Frequency Array (LOFAR) Low Band Antenna observations at 30-77MHz and Very Large Array (VLA) L-band observations at 1-2GHz to fit for internal absorption as parametrised by the emission measure. We simultaneously fit multiple UV-matched images with a common resolution of 17" (this corresponds to 0.25pc for a source at the distance of Cas A). The ample frequency coverage allows us separate the relative contributions from the absorbing gas, the unabsorbed front of the shell, and the absorbed back of the shell to the emission spectrum. We explored the effects that a temperature lower than the ~100-500K proposed from infrared observations and a high degree of clumping can have on the derived physical properties of the unshocked material, such as its mass and density. We also compiled integrated radio flux density measurements, fit for the absorption processes that occur in the radio band, and considered their ect on the secular decline of the source. We find a mass in the unshocked ejecta of M=2.95+/-0.48M_{sun}_ for an assumed gas temperature of T=100K. This estimate is reduced for colder gas temperatures and, most significantly, if the ejecta are clumped.We measure the reverse shock to have a radius of 114+/-6" and be centred at 23:23:26, +58:48:54 (J2000).We also find that a decrease in the amount of mass in the unshocked ejecta (as more and more material meets the reverse shock and heats up) cannot account for the observed low-frequency behaviour of the secular decline rate. To reconcile our low-frequency absorption measurements with models that reproduce much of the observed behaviour in Cas A and predict little mass in the unshocked ejecta, the ejecta need to be very clumped or the temperature in the cold gas needs to be low (~10K). Both of these options are plausible and can together contribute to the high absorption value that we find.
- ID:
- ivo://CDS.VizieR/J/A+A/657/A87
- Title:
- CASCADES I. Sample definition and first results
- Short Name:
- J/A+A/657/A87
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Following the first discovery of a planet orbiting a giant star in 2002, we started the CORALIE radial-velocity search for companions around evolved stars (CASCADES). We present the observations of three stars conducted at the 1.2m Leonard Euler Swiss telescope at La Silla Observatory, Chile, using the CORALIE spectrograph. We aim to detect planetary companions to intermediate-mass G- and K- type evolved stars and perform a statistical analysis of this population. We searched for new planetary systems around the stars HD22532 (TIC200851704), HD64121 (TIC264770836), and HD69123 (TIC146264536). We have followed a volume-limited sample of 641 red giants since 2006 to obtain high-precision radial-velocity measurements. We used the Data & Analysis Center for Exoplanets (DACE) platform to perform a radial-velocity analysis to search for periodic signals in the line profile and activity indices, to distinguish between planetary-induced radial-velocity variations and stellar photospheric jitter, and to search for significant signals in the radial-velocity time series to fit a corresponding Keplerian model. In this paper, we present the survey in detail, and we report on the discovery of the first three planets of the sample around the giant stars HD22532, HD64121, and HD69123.
- ID:
- ivo://CDS.VizieR/J/AJ/109/2376
- Title:
- Case blue/emission-line galaxies
- Short Name:
- J/AJ/109/2376
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CCD imaging and spectroscopic data for 176 blue and/or emission-line galaxies from Lists I and II of the Case Northern Sky Survey. Our sample consists of all Case galaxies which lie in the region which overlaps the original Slice of the Universe survey. We use the observational data to investigate the physical properties of the galaxies selected by the surveys to compare with various parameters published in the survey lists, and to investigate the selection characteristics and completeness limit of the survey. The majority of the Case galaxies are energized by regions of active star formation; only 5% of the sample are Seyfert galaxies. The dual selection techniques used (both UV-excess and emission lines) allow the survey to detect star-forming galaxies with a wide range of properties and evolutionary states. In particular, the Case survey selects galaxies with lower levels of activity than most previous surveys. The survey also includes a larger fraction of intermediate and low-luminosity galaxies than would be present in a purely magnitude-limited sample. Although galaxies as faint as m_B_=19 are present in the sample, the completeness limit of the UV-excess selected portion of the survey is closer to m_B_=16. The luminosity function of the Case galaxies is derived and compared with that of the "normal" field galaxies in the same volume of space. The shape of the Case luminosity function is similar to that for the field sample. A surprising result is that 31% of the field galaxy population can be accounted for by galaxies of the type selected in the Case survey.
- ID:
- ivo://CDS.VizieR/J/ApJS/66/309
- Title:
- Case low-dispersion Survey VI
- Short Name:
- J/ApJS/66/309
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Positions, estimated magnitudes, and finding charts (when needed) are provided for 183 A-F stars (including both Population I and horizontal-branch stars) contained within the region 12h00m <R.A> <13h00m and +29.0 <decl. <+34.0. These stars, whose blue magnitudes range from 5.5 to 17.5, were identified on low-dispersion, objective-prism plates taken with the Burrell Schmidt telescope.
- ID:
- ivo://CDS.VizieR/J/ApJS/66/387
- Title:
- Case low-dispersion Survey VII.
- Short Name:
- J/ApJS/66/387
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observational data on 132 faint (R magnitude = 9-17) red stars with carbon-star or late M-type spectra are presented in tables and briefly characterized. The data were collected in a survey of a 1000-sq deg region at high northern Galactic latitude (right ascension 8h15 to 17h30 and declination +29 to +38 deg) on low-dispersion 330-535-nm objective-prism plates obtained with the 61/91-cm Burrell Schmidt telescope at Kitt Peak Observatory.
- ID:
- ivo://CDS.VizieR/J/ApJS/71/549
- Title:
- Case low-dispersion Survey X.
- Short Name:
- J/ApJS/71/549
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Position, estimated magnitudes, and finding charts are provided for 540 A-F stars in the region 8h00m <R.A< 11h10m and +29.0 <Decl.<+43.0 (1950). The Galactic latitudes lie within the range +27 and +68. The A-F stars, with blue magnitudes between 14 and 17, were identified on low-dispersion objective-prism plates taken with the Burell Schmidt telescope. A large fraction of these A-F stars are expected to belong to Population II.
- ID:
- ivo://CDS.VizieR/J/ApJ/742/54
- Title:
- CASH project II. 14 extremely metal-poor stars
- Short Name:
- J/ApJ/742/54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive abundance analysis of 20 elements for 16 new low-metallicity stars from the Chemical Abundances of Stars in the Halo (CASH) project. The abundances have been derived from both Hobby-Eberly Telescope High Resolution Spectrograph snapshot spectra (R~15000) and corresponding high-resolution (R~35000) Magellan Inamori Kyocera Echelle spectra. The stars span a metallicity range from [Fe/H] from -2.9 to -3.9, including four new stars with [Fe/H]<-3.7. We find four stars to be carbon-enhanced metal-poor (CEMP) stars, confirming the trend of increasing [C/Fe] abundance ratios with decreasing metallicity. Two of these objects can be classified as CEMP-no stars, adding to the growing number of these objects at [Fe/H]<-3. We also find four neutron-capture-enhanced stars in the sample, one of which has [Eu/Fe] of 0.8 with clear r-process signatures. These pilot sample stars are the most metal-poor ([Fe/H]<~-3.0) of the brightest stars included in CASH and are used to calibrate a newly developed, automated stellar parameter and abundance determination pipeline. This code will be used for the entire ~500 star CASH snapshot sample. We find that the pipeline results are statistically identical for snapshot spectra when compared to a traditional, manual analysis from a high-resolution spectrum.
- ID:
- ivo://CDS.VizieR/J/ApJ/659/162
- Title:
- CAS parameters of 199 nearby galaxies
- Short Name:
- J/ApJ/659/162
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a quantitative analysis of the morphologies for 199 nearby galaxies as parameterized with measurements of the concentration, asymmetry, and clumpiness (CAS) parameters at wavelengths from 0.15 to 0.85um. We find that these CAS parameters depend on both galaxy type and the wavelength of observation. As such, we use them to obtain a quantitative measure of the "morphological k-correction", i.e., the change in appearance of a galaxy with rest-frame wavelength.
- ID:
- ivo://CDS.VizieR/J/A+A/620/A127
- Title:
- Cassification of RR Lyrae and Cepheid
- Short Name:
- J/A+A/620/A127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The second data release of the Gaia mission (DR2) includes an advance catalogue of variable stars. The classifications of these stars are based on sparse photometry from the first 22 months of the mission. We set out to investigate the purity and completeness of the all-sky Gaia classification results with the help of the continuous light curves of the observed targets from the Kepler and K2 missions, focusing specifically on RR Lyrae and Cepheid pulsators, outside the Galactic bulge region. We cross-matched the Gaia identifications with the observations collected by the Kepler space telescope. We inspected the light curves visually, then calculated the relative Fourier coefficients and period ratios for the single- and double-mode K2 RR Lyrae stars to further classify them. We identified 1443 and 41 stars classified as RR Lyrae or Cepheid variables in Gaia DR2 in the targeted observations of the two missions and 263 more RR Lyre targets in the full-frame images (FFI) of the original mission. We provide the cross-match of these sources. We conclude that the RR Lyrae catalogue has a completeness between 70-78%, and provide a purity estimate of between 92-98% (targeted observations) with lower limits of 75% (FFI stars) and 51% (K2 worst-case scenario). The low number of Cepheids prevents us from drawing detailed conclusions, but the purity of the DR2 sample is estimated to be about 66%.