- ID:
- ivo://CDS.VizieR/J/ApJ/771/57
- Title:
- Fermi-LAT flaring gamma-ray sources from FAVA
- Short Name:
- J/ApJ/771/57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we present the Fermi All-sky Variability Analysis (FAVA), a tool to systematically study the variability of the gamma-ray sky measured by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. For each direction on the sky, FAVA compares the number of gamma-rays observed in a given time window to the number of gamma-rays expected for the average emission detected from that direction. This method is used in weekly time intervals to derive a list of 215 flaring gamma-ray sources. We proceed to discuss the 27 sources found at Galactic latitudes smaller than 10{deg} and show that, despite their low latitudes, most of them are likely of extragalactic origin.
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- 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.
- ID:
- ivo://CDS.VizieR/J/ApJ/682/985
- Title:
- FIREWORKS photometry of GOODS CDF-S
- Short Name:
- J/ApJ/682/985
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a Ks-selected catalog, dubbed FIREWORKS, for the Chandra Deep Field-South (CDF-S) containing photometry in the U_38_, B_435_, B, V, V_606_, R, i_775_, I, z_850_, J, H, Ks, [3.6um], [4.5um], [5.8um], [8.0um], and MIPS [24um] bands. The imaging has a typical K^tot^_s,AB_ limit of 24.3mag (5{sigma}) and coverage over 113arcmin^2^ in all bands and 138arcmin^2^ in all bands but H. We cross-correlate our catalog with the 1Ms X-ray catalog by Giacconi et al. (2002, Cat. J/ApJS/139/369) and with all available spectroscopic redshifts to date. We find and explain systematic differences in a comparison with the "z_850_+Ks"-selected GOODS-MUSIC catalog (Cat. J/A+A/449/951) that covers ~90% of the field. We exploit the U_38_-to-24um photometry to determine which Ks-selected galaxies at 1.5<z<2.5 have the brightest total IR luminosities and which galaxies contribute most to the integrated total IR emission. The answer to both questions is that red galaxies are dominating in the IR. This is true no matter whether color is defined in the rest-frame UV, optical, or optical-near-IR. We do find, however, that among the reddest galaxies in the rest-frame optical, there is a population of sources with only little mid-IR emission, suggesting a quiescent nature.
- ID:
- ivo://CDS.VizieR/J/ApJS/143/1
- Title:
- FIRST-APM Source Catalog
- Short Name:
- J/ApJS/143/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe a program to identify optical counterparts to radio sources from the VLA FIRST survey using the Cambridge APM scans of the POSS-I plates. We use radio observations covering 4150deg^2^ of the north Galactic cap to a 20cm flux density threshold of 1.0mJy; the 382,892 sources detected all have positional uncertainties of <1" (radius of 90% confidence). Our description of the APM catalog, derived from the 148 POSS-I O and E plates covering this region, includes an assessment of its astrometric and photometric accuracy, a photometric recalibration using the Minnesota APS catalog, a discussion of the classification algorithm, and quantitative tests of the catalog's reliability and completeness. We go on to show how the use of FIRST sources as astrometric standards allows us to improve the absolute astrometry of the POSS plates by nearly an order of magnitude to ~0.15" rms. Matching the radio and optical catalogs yields counterparts for over 70,000 radio sources; we include detailed discussions of the reliability and completeness of these identifications as a function of optical and radio morphology, optical magnitude and color, and radio flux density. An analysis of the problem of radio sources with complex morphologies (e.g., double-lobed radio galaxies) is included. We conclude with a brief discussion of the source classes represented among the radio sources with identified counterparts.
- ID:
- ivo://CDS.VizieR/IV/22
- Title:
- FK5 - SAO - HD - Common Name Cross Index
- Short Name:
- IV/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The author has combined data from various catalogs to produce a cross index of the numbers in the FK5 (I/149, I/175), SAO (I/131), and HD (III/135) catalogs. He has also added the Bayer or Flamsteed designations and the common or variable star names.
- ID:
- ivo://CDS.VizieR/J/other/PZ/23.141
- Title:
- Flare stars in the Pleiades
- Short Name:
- J/other/PZ/23.14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A brief account is given of the problems in identifying newly discovered variable stars with already known ones. These problems are most acute in dense stellar fields, for instance, in the Pleiades. To arrive to a homogeneous coordinates system for variable stars in the Pleiades, the author has measured the coordinates for nearly 550 stars in the region centered on Alcyone. This has made it possible to obtain for the first time accurate coordinates for 165 flare stars; then, for 46 stars we have round significant errors in the published coordinates. A cross-identification table between the GCVS (Cat. <II/139>) and the catalogue of Haro et al. (1982, Cat. <II/131>) has been compiled.
- ID:
- ivo://CDS.VizieR/J/ApJ/846/34
- Title:
- Flaring gamma-ray sources; LAT 7.4yr (2FAV)
- Short Name:
- J/ApJ/846/34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the second catalog of flaring gamma-ray sources (2FAV) detected with the Fermi All-sky Variability Analysis (FAVA), a tool that blindly searches for transients over the entire sky observed by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. With respect to the first FAVA catalog, this catalog benefits from a larger data set, the latest LAT data release (Pass 8), as well as from an improved analysis that includes likelihood techniques for a more precise localization of the transients. Applying this analysis to the first 7.4 years of Fermi observations, and in two separate energy bands 0.1-0.8GeV and 0.8-300GeV, a total of 4547 flares were detected with significance greater than 6{sigma} (before trials), on the timescale of one week. Through spatial clustering of these flares, 518 variable gamma-ray sources were identified. Based on positional coincidence, likely counterparts have been found for 441 sources, mostly among the blazar class of active galactic nuclei. For 77 2FAV sources, no likely gamma-ray counterpart has been found. For each source in the catalog, we provide the time, location, and spectrum of each flaring episode. Studying the spectra of the flares, we observe a harder-when-brighter behavior for flares associated with blazars, with the exception of BL Lac flares detected in the low-energy band. The photon indexes of the flares are never significantly smaller than 1.5. For a leptonic model, and under the assumption of isotropy, this limit suggests that the spectrum of freshly accelerated electrons is never harder than p~2.
- ID:
- ivo://CDS.VizieR/J/ApJ/892/105
- Title:
- Fourth catalog of Fermi LAT-detected AGNs (4LAC)
- Short Name:
- J/ApJ/892/105
- Date:
- 17 Jan 2022 00:31:09
- Publisher:
- CDS
- Description:
- The fourth catalog of active galactic nuclei (AGNs) detected by the Fermi Gamma-ray Space Telescope Large Area Telescope (4LAC) between 2008 August 4 and 2016 August 2 contains 2863 objects located at high Galactic latitudes (|b|>10{deg}). It includes 85% more sources than the previous 3LAC catalog based on 4yr of data. AGNs represent at least 79% of the high-latitude sources in the fourth Fermi-Large Area Telescope Source Catalog (4FGL), which covers the energy range from 50MeV to 1TeV. In addition, 344 gamma-ray AGNs are found at low Galactic latitudes. Most of the 4LAC AGNs are blazars (98%), while the remainder are other types of AGNs. The blazar population consists of 24% Flat Spectrum Radio Quasars (FSRQs), 38% BL Lac-type objects, and 38% blazar candidates of unknown types (BCUs). On average, FSRQs display softer spectra and stronger variability in the gamma-ray band than BL Lacs do, confirming previous findings. All AGNs detected by ground-based atmospheric Cerenkov telescopes are also found in the 4LAC.
119. Gaia DR2
- ID:
- ivo://CDS.VizieR/I/345
- Title:
- Gaia DR2
- Short Name:
- I/345
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Gaia Data Release 2. Summary of the contents and survey properties: We present the second Gaia data release, Gaia DR2, consisting of astrometry, photometry, radial velocities, and information on as- trophysical parameters and variability, for sources brighter than magnitude 21. In addition epoch astrometry and photometry are provided for a modest sample of minor planets in the solar system. A summary of the contents of Gaia DR2 is presented, accompanied by a discussion on the differences with respect to Gaia DR1 and an overview of the main limitations which are still present in the survey. Recommendations are made on the responsible use of Gaia DR2 results. Methods. The raw data collected with the Gaia instruments during the first 22 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into this second data release, which represents a major advance with respect to Gaia DR1 in terms of completeness, performance, and richness of the data products. Gaia DR2 contains celestial positions and the apparent brightness in G for approximately 1.7 billion sources. For 1.3 billion of those sources, parallaxes and proper motions are in addition available. The sample of sources for which variability information is provided is expanded to 0.5 million stars. This data release contains four new elements: broad-band colour information in the form of the apparent brightness in the G_BP_ (330-680nm) and G_RP_ (630-1050nm) bands is available for 1.4 billion sources; median radial velocities for some 7 million sources are presented; for between 77 and 161 million sources estimates are provided of the stellar effective temperature, extinction, reddening, and radius and luminosity; and for a pre-selected list of 14000 minor planets in the solar system epoch astrometry and photometry are presented. Finally, Gaia DR2 also represents a new materialisation of the celestial reference frame in the optical, the Gaia-CRF2, which is the first optical reference frame based solely on extragalactic sources. There are notable changes in the photometric system and the catalogue source list with respect to Gaia DR1, and we stress the need to consider the two data releases as independent. Gaia DR2 represents a major achievement for the Gaia mission, delivering on the long standing promise to provide parallaxes and proper motions for over 1 billion stars, and representing a first step in the availability of complementary radial velocity and source astrophysical information for a sample of stars in the Gaia survey which covers a very substantial fraction of the volume of our galaxy. The catalogue of radial velocity standard stars (Soubiran et al., 2018A&A...616A...7S) The Radial Velocity Spectrometer (RVS) on board of Gaia having no calibration device, the zero point of radial velocities needs to be calibrated with stars proved to be stable at the level of 300m/s during the Gaia observations. A dataset of about 71000 ground-based radial velocity measurements from five high resolution spectrographs has been compiled. A catalogue of 4813 stars was built by combining these individual measurements. The zero point has been established using asteroids. The resulting catalogue has 7 observations per star on average on a typical time baseline of 6 years, with a median standard deviation of 15m/s. A subset of the most stable stars fulfilling the RVS requirements has been used to establish the zero point of the radial velocities provided in Gaia DR2. The stars not used for calibration are used for the RVS data validation.
- ID:
- ivo://CDS.VizieR/J/AcA/66/433
- Title:
- Gaia DR1 and OGLE variable stars
- Short Name:
- J/AcA/66/433
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comparison of the Gaia DR1 samples of pulsating variable stars - Cepheids and RR Lyr type - with the OGLE Collection of Variable Stars aiming at the characterization of the Gaia mission performance in the stellar variability domain. Out of 575 Cepheids and 2322 RR Lyr candidates from the Gaia DR1 samples located in the OGLE footprint in the sky, 559 Cepheids and 2302 RR Lyr stars are genuine pulsators of these types. The number of misclassified stars is low indicating reliable performance of the Gaia data pipeline. The completeness of the Gaia DR1 samples of Cepheids and RR Lyr stars is at the level of 60-75% as compared to the OGLE Collection dataset. This level of completeness is moderate and may limit the applicability of the Gaia data in many projects.
