- ID:
- ivo://CDS.VizieR/J/ApJS/248/23
- Title:
- 4FGL sources with IR/Rad associations
- Short Name:
- J/ApJS/248/23
- Date:
- 09 Nov 2021 09:30:22
- Publisher:
- CDS
- Description:
- Associating {gamma}-ray sources to their low-energy counterparts is one of the major challenges of modern {gamma}-ray astronomy. In the context of the Fourth Fermi Large Area Telescope Source Catalog (4FGL), the associations rely mainly on parameters such as apparent magnitude, integrated flux, and angular separation between the {gamma}-ray source and its low-energy candidate counterpart. In this work, we propose a new use of the likelihood ratio (LR) and a complementary supervised learning technique to associate {gamma}-ray blazars in 4FGL, based only on spectral parameters such as the {gamma}-ray photon index, mid-infrared colors, and radio-loudness. In the LR approach, we crossmatch the Wide-field Infrared Survey Explorer Blazar-Like Radio-Loud Sources catalog with 4FGL and compare the resulting candidate counterparts with the sources listed in the {gamma}-ray blazar locus to compute an association probability (AP) for 1138 counterparts. In the supervised learning approach, we train a random forest algorithm with 869 high-confidence blazar associations and 711 fake associations and then compute an AP for 1311 candidate counterparts. A list with all 4FGL blazar candidates of uncertain type associated by our method is provided to guide future optical spectroscopic follow-up observations.
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- ID:
- ivo://CDS.VizieR/J/AJ/161/154
- Title:
- 3FGL X-ray Analysis and ML
- Short Name:
- J/AJ/161/154
- Date:
- 07 Mar 2022 07:09:03
- Publisher:
- CDS
- Description:
- We conduct X-ray spectral fits on 184 likely counterparts to Fermi-LAT 3FGL unassociated sources. Characterization and classification of these sources allows for more complete population studies of the high-energy sky. Most of these X-ray spectra are well fit by an absorbed power law model, as expected for a population dominated by blazars and pulsars. A small subset of 7 X-ray sources have spectra unlike the power law expected from a blazar or pulsar and may be linked to coincident stars or background emission. We develop a multiwavelength machine learning classifier to categorize unassociated sources into pulsars and blazars using gamma- and X-ray observations. Training a random forest procedure with known pulsars and blazars, we achieve a cross-validated classification accuracy of 98.6%. Applying the random forest routine to the unassociated sources returned 126 likely blazar candidates (defined as P_bzr_>90%) and 5 likely pulsar candidates (P_bzr_<10%). Our new X-ray spectral analysis does not drastically alter the random forest classifications of these sources compared to previous works, but it builds a more robust classification scheme and highlights the importance of X-ray spectral fitting. Our procedure can be further expanded with UV, visual, or radio spectral parameters or by measuring flux variability.
- ID:
- ivo://CDS.VizieR/III/9A
- Title:
- F2-G5 Stars in a North Galactic Pole Region
- Short Name:
- III/9A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The catalog is an objective-prism survey for stars of spectral classes F2 to G5 in a region of high galactic latitude. The catalog contains 1127 stars and is complete to a limiting photographic magnitude of 12.5. The photographic plates used permit a separation of the stars into narrow and well-defined spectral classes. The spectral classification of the stars in the catalog is based on the Yerkes MK system. The catalog is subdivided into one-degree declination zones as are the DM catalogs. The degree zones are based on 1855 coordinates. The catalog includes sequence numbers of the stars, BD and HD numbers, positions (B1950), B magnitudes, spectral types, and remarks.
- ID:
- ivo://CDS.VizieR/J/MNRAS/393/1467
- Title:
- Field early-type galaxies at 0.2<z<0.8
- Short Name:
- J/MNRAS/393/1467
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore the properties of 24 field early-type galaxies in the redshift range 0.20<z<0.75 down to M_B<=-19.30 in a sample extracted from the FORS Deep Field and the William Herschel Deep Field. Target galaxies were selected on the basis of a combination of luminosity, spectrophotometric type, morphology and photometric redshift or broad-band colours. High signal-to-noise intermediate-resolution spectroscopy has been acquired at the Very Large Telescope, complemented by deep high-resolution imaging with the Advanced Camera for Surveys onboard the HST and additional ground-based multi-band photometry. All galaxy spectra were observed under sub-arcsecond conditions and allow to derive accurate kinematics and stellar population properties of the galaxies. To clarify the low level of star formation detected in some galaxies, we identify the amount of active galactic nuclei (AGN) activity in our sample using archive data of Chandra and XMM-Newton X-ray surveys. None of the galaxies in our sample were identified as secure AGN sources based on their X-ray emission. The rest-frame B and K-band scaling relations of the Faber-Jackson relation and the Fundamental Plane display a moderate evolution for the field early-type galaxies. Lenticular (S0) galaxies feature on average a stronger luminosity evolution and bluer rest-frame colours which can be explained that they comprise more diverse stellar populations compared to elliptical galaxies. The evolution of the FP can be interpreted as an average change in the dynamical (effective) mass-to-light ratio of our galaxies as <{Delta}log(M/L_B_)/z>=-0.74+/-0.08. The M/L evolution of these field galaxies suggests a continuous mass assembly of field early-type galaxies during the last 5Gyr, that gets support by recent studies of field galaxies up to z~1. Independent evidence for recent star formation activity is provided by spectroscopic (OII emission, Hdelta) and photometric (rest-frame broad-band colors) diagnostics. Based on the Hdelta absorption feature we detect a weak residual star formation for galaxies that accounts for 5%-10% in the total stellar mass of these galaxies. The co-evolution in the luminosity and mass of our galaxies favours a downsizing formation process. We find some evidence that our galaxies experienced a period of star formation quenching, possible triggered by AGN activity that is in good agreement with recent results on both observational and theoretical side.
- ID:
- ivo://CDS.VizieR/J/MNRAS/448/2749
- Title:
- 257 field giant stars spectroscopic parameters
- Short Name:
- J/MNRAS/448/2749
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The study of stellar parameters of planet-hosting stars, such as metallicity and chemical abundances, help us to understand the theory of planet formation and stellar evolution. Here, we present a catalogue of accurate stellar atmospheric parameters and iron abundances for a sample of 257 K and G field evolved stars that are being surveyed for planets using precise radial-velocity measurements as part of the Coralie programme to search for planets around giants. The analysis was done using a set of high-resolution and high-signal-to-noise Ultraviolet and Visible Echelle Spectrograph spectra. The stellar parameters were derived using Fe I and II ionization and excitation equilibrium methods. To take into account possible effects related to the choice of the lines on the derived parameters, we used three different iron line-list sets in our analysis, and the results differ among themselves by a small factor for most of stars. For those stars with previous literature parameter estimates, we found very good agreement with our own values. In the present catalogue, we are providing new precise spectroscopic measurements of effective temperature, surface gravity, microturbulence, and metallicity for 190 stars for which it has not been found or published in previous articles.
- ID:
- ivo://CDS.VizieR/J/A+A/431/143
- Title:
- Field horizontal-branch stars in the Galaxy
- Short Name:
- J/A+A/431/143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of 8321 candidate Field Horizontal-Branch (FHB) stars selected by automatic spectral classification in the digital data base of the Hamburg/ESO objective-prism survey. The stars are distributed over 8225 square degrees of the southern sky, at |b|>~30{deg}. The average distance of the sample, assuming that they are all FHB stars, is 9.8kpc, and distances of up to ~30kpc are reached. Moderate-resolution spectroscopic follow-up observations and $UBV$ photometry of 125 test sample stars demonstrate that the contamination of the full candidate sample with main-sequence A-type stars is <16%, while it would be up to 50% in a flux-limited sample at high galactic latitudes. Hence more than ~6800 of our FHB candidates are expected to be genuine FHB stars. The candidates are being used as distance probes for high-velocity clouds and for studies of the structure and kinematics of the Galactic halo.
- ID:
- ivo://CDS.VizieR/J/A+A/304/347
- Title:
- 40 field red supergiants in the SMC
- Short Name:
- J/A+A/304/347
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Low-resolution spectra (~5A) for 40 red supergiants in the Small Magellanic Cloud were compared with synthetic spectra, and their metallicities were derived. A mean metallicity of [Fe/He]=-0.71 is found for 38 stars cooler than T_eff_<4500K. Using the stellar parameters derived, the carbon abundances were determined by comparing synthetic spectra at the G-band region to the observed spectra. A mean {epsilon}(C)=7.85 is found, clearly higher than the low values suggested in the literature for the H II regions.
4678. Field RR Lyrae stars
- ID:
- ivo://CDS.VizieR/J/MNRAS/459/4360
- Title:
- Field RR Lyrae stars
- Short Name:
- J/MNRAS/459/4360
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents an extensive overview of known and proposed RR Lyrae stars in binaries. The aim is to revise and extend the list with new Galactic field systems. We utilized maxima timings for 11 RRab type stars with suspicious behaviour from the GEOS database, and determined maxima timings from data of sky surveys and our own observations. This significantly extended the number of suitable maxima timings. We modelled the proposed Light Time Effect (LiTE) in O-C diagrams to determine orbital parameters for these systems. In contrast to recent studies, our analysis focused on decades-long periods instead of periods in the order of years. Secondary components were found to be predominantly low-mass objects. However, for two of the stars, RZ Cet and AT Ser, the mass of the suspected companion of more than one solar mass suggests that it is a massive white dwarf, a neutron star or even a black hole. We found that the semi-major axes of the proposed orbits are between 1 and 20au. Because the studied stars belong to the closest RR Lyraes, maximal angular distances between components during orbit should at least be between 1 and 13mas and this improves the chance to detect both stars using current telescopes and interferometers. However, our interpretation of the O-C diagrams as a consequence of the LiTE should be considered as preliminary without reliable spectroscopic measurements. On the other hand, our models give a prediction of the period and radial velocity evolution which should be sufficient for plausible proof of binarity.
- ID:
- ivo://CDS.VizieR/I/175
- Title:
- Fifth Fundamental Catalogue (FK5) - Extension
- Short Name:
- I/175
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The FK5 Extension provides improved mean positions and proper motions for the 3117 new fundamental stars. The machine version of the catalog contains the positions and proper motions of the Extension stars for the epochs and equinoxes J2000.0 and B1950.0, the mean epochs of individual observed right ascensions and declinations used to determine the final positions, the mean errors of the final positions and proper motions for the reported epochs, and ancillary data such as magnitudes, spectral types, parallaxes, and radial velocities. Cross identifications to the numbering systems of the AGK3R, SRS, HD, DM, and GC catalogs are also included.
- ID:
- ivo://CDS.VizieR/I/149A
- Title:
- Fifth Fundamental Catalogue (FK5) Part I
- Short Name:
- I/149A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Basic Fifth Fundamental Catalogue (FK5) Part I provides improved mean positions and proper motions for the 1535 classical fundamental stars that had been included in the FK3 and FK4 catalogs. The machine version of the catalog contains the positions and proper motions of the Basic FK5 stars for the epochs and equinoxes J2000.0 and B1950.0, the mean epochs of individual observed right ascensions and declinations used to determine the final positions, the mean errors of the final positions and proper motions for the reported epochs, and ancillary data such as magnitudes, spectral types, parallaxes, radial velocities, and cross identifications to other catalog designations.