- ID:
- ivo://CDS.VizieR/J/ApJ/722/520
- Title:
- Gamma-ray light curves of Fermi blazars
- Short Name:
- J/ApJ/722/520
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents light curves as well as the first systematic characterization of variability of the 106 objects in the high-confidence Fermi Large Area Telescope Bright AGN Sample (LBAS). Weekly light curves of this sample, obtained during the first 11 months of the Fermi survey (2008 August 4-2009 July 4), are tested for variability and their properties are quantified through autocorrelation function and structure function analysis. For the brightest sources, 3 or 4 day binned light curves are extracted in order to determine power density spectra (PDSs) and to fit the temporal structure of major flares. More than 50% of the sources are found to be variable with high significance, where high states do not exceed 1/4 of the total observation range. Variation amplitudes are larger for flat spectrum radio quasars and low/intermediate synchrotron frequency peaked BL Lac objects. Autocorrelation timescales derived from weekly light curves vary from four to a dozen of weeks.
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5322. {gamma}-ray loud blazars
- ID:
- ivo://CDS.VizieR/J/ApJ/726/16
- Title:
- {gamma}-ray loud blazars
- Short Name:
- J/ApJ/726/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The radio properties of blazars detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope have been observed as part of the VLBA Imaging and Polarimetry Survey. This large, flux-limited sample of active galactic nuclei (AGNs) provides insights into the mechanism that produces strong {gamma}-ray emission. At lower flux levels, radio flux density does not directly correlate with {gamma}-ray flux. We find that the LAT-detected BL Lac objects tend to be similar to the non-LAT BL Lac objects, but that the LAT-detected FSRQs are often significantly different from the non-LAT FSRQs. The differences between the {gamma}-ray loud and quiet FSRQs can be explained by Doppler boosting; these objects appear to require larger Doppler factors than those of the BL Lac objects. It is possible that the {gamma}-ray loud FSRQs are fundamentally different from the {gamma}-ray quiet FSRQs. Strong polarization at the base of the jet appears to be a signature for {gamma}-ray loud AGNs.
- ID:
- ivo://CDS.VizieR/J/MNRAS/442/1693
- Title:
- Gamma-ray-loud blazars optical polarization
- Short Name:
- J/MNRAS/442/1693
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present first results from RoboPol, a novel-design optical polarimeter operating at the Skinakas Observatory in Crete. The data, taken during the 2013 May-June commissioning of the instrument, constitute a single-epoch linear polarization survey of a sample of gamma-ray-loud blazars, defined according to unbiased and objective selection criteria, easily reproducible in simulations, as well as a comparison sample of, otherwise similar, gamma-ray-quiet blazars. As such, the results of this survey are appropriate for both phenomenological population studies and for tests of theoretical population models. We have measured polarization fractions as low as 0.015 down to Rmag of 17 and as low as 0.035 down to 18mag. The hypothesis that the polarization fractions of gamma-ray-loud and gamma-ray-quiet blazars are drawn from the same distribution is rejected at the 3{sigma} level. We therefore conclude that gamma-ray-loud and gamma-ray-quiet sources have different optical polarization properties. This is the first time this statistical difference is demonstrated in optical wavelengths. The polarization fraction distributions of both samples are well described by exponential distributions with averages of <p>=6.4^+0.9^_-0.8_x10^-2^ for gamma-ray-loud blazars, and <p>=3.2^+2.0^_-1.1_x10^-2^ for gamma-ray-quiet blazars. The most probable value for the difference of the means is 3.4^+1.5^_-2.0_x10^-2^. The distribution of polarization angles is statistically consistent with being uniform.
- ID:
- ivo://CDS.VizieR/J/A+A/598/A134
- Title:
- {gamma}-ray signature in WHSP blazars (1BIGB)
- Short Name:
- J/A+A/598/A134
- Date:
- 04 Feb 2022 00:00:12
- Publisher:
- CDS
- Description:
- A direct search of {gamma}-ray emission centered on multifrequency selected candidates is a valuable complementary approach to the standard search adopted in current {gamma}-ray Fermi-LAT catalogs. Our sources are part of the 2WHSP sample that was assembled with the aim of providing targets for Imaging Atmospheric Cherenkov Telescopes (IACT). A likelihood analysis based on their known position enabled us to detect 150 {gamma}-ray excess signals that have not yet been reported in previous {gamma}-ray catalogs (1FGL, 2FGL, 3FGL). By identifying new sources, we solve a fraction of the extragalactic isotropic {gamma}-ray background (IGRB) composition, improving the description of the {gamma}-ray sky. We perform data reduction with the Fermi Science Tools using positions from 400 high synchrotron peaked (HSP) blazars as seeds of tentative {gamma}-ray sources; none of them have counterparts from previous 1FGL, 2FGL and 3FGL catalogs. Our candidates are part of the 2WHSP sample (currently the largest set of HSP blazars). We focus on HSPs characterized by bright synchrotron component with peak flux {nu}f_({nu})_>=10^-12.1^erg/cm^2^/s, testing the hypothesis of having a {gamma}-ray source in correspondence to the WHSP positions. Our likelihood analysis considers the 0.3-500GeV energy band, integrating over 7.2yr of Fermi-LAT observation and making use of the Pass 8 data release. From the 400 candidates tested, a total of 150 2WHSPs showed excess {gamma}-ray signature: 85 high-significance detections with test statistic (TS)>25, and 65 lower-significance detections with TS between 10 to 25. We assume a power law spectrum in the 0.3-500GeV band and list the spectrum parameters describing all 150 new {gamma}-ray sources. We study the {gamma}-ray photon spectral index distribution, the likelihood of detection according to the synchrotron peak brightness (figure of merit parameter), and plot the measured {gamma}-ray LogN-LogS of HSP blazars, also discussing the portion of the IGRB that has been resolved by the present work. We also report on four cases where we could resolve source confusion and find counterparts for unassociated 3FGL sources with the help of high-energy TS maps together with multifrequency data. The 150 new {gamma}-ray sources are named with the acronym 1BIGB for the first version of the Brazil ICRANet Gamma-ray Blazar catalog, in reference to the cooperation agreement supporting this work.
- ID:
- ivo://nasa.heasarc/mggammadet
- Title:
- Gamma-RaySourceDetailedCatalog(Macomb&Gehrels1999)
- Short Name:
- MGGAMMADET
- Date:
- 27 Sep 2024
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This database table contains the slightly revised contents of the detailed Tables 2A - 2G from the General Gamma-Ray Source Catalog of Macomb & Gehrels (1999). It lists details of all known gamma-ray observations within the energy range from 50 keV to ~1 TeV for 314 discrete gamma-ray sources that were listed in Tables 2A - 2G of the published version of this catalog, including all 310 sources listed in the published Summary Table 1, together with 4 sources (2CG 054+01, A0620-00, GX 340+0, and H1822-000) that were listed only in Table 2 of the published catalog but were (presumably accidentally) omitted from Table 1. The positions for the sources in the present database were taken from Table 1 of the General Gamma-Ray Source Catalog. Thus, this table is essentially a compilation of gamma-ray observations of discrete sources as known to the authors as of early 1999. There is another HEASARC database table called the Gamma-Ray Source Summary Catalog (Macomb & Gehrels 1999) or MGGAMMACAT that contains the summary information on these sources that was given in Table 1 of the General Gamma-Ray Source Catalog. As noted above, this is a slightly revised version compared to the published Tables 2A - 2G. The known differences between the HEASARC and published versions are discussed in the HEASARC_Version section of the help documentation. This database table was created by the HEASARC in March 2002 based upon machine-readable versions of Tables 2A-2G of the Macomb & Gehrels (1999) General Gamma-Ray Source Catalog that were supplied by the authors. One duplicate entry was removed from this table in June 2019. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/mggammacat
- Title:
- Gamma-RaySourceSummaryCatalog(Macomb&Gehrels1999&2001)
- Short Name:
- M&GGamma-ray
- Date:
- 27 Sep 2024
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This database table is a revised and updated version of the published General Gamma-Ray Source Catalog (Macomb & Gehrels 1999, ApJS, 120, 335). It contains all 309 gamma-ray point sources listed in Table 1 of the published version of this catalog; 4 gamma-ray point sources (2CG 054+01, A0620-00, GX 340+0, and H1822-000) added by the HEASARC that were listed in Table 2 of the published catalog but were (presumably accidentally) omitted from Table 1 of the published catalog; and 107 sources (106 sources from the 3rd Egret (3EG) catalog of Hartman et al. (1999, ApJS, 123, 79) and GEV J1732-3130) that were compiled by Macomb and Gehrels subsequent to their original publication (Macomb and Gehrels 2001, unpublished). Thus, the present database table is essentially a summary master list of all detected gamma-ray point sources as of circa 2000. There is another HEASARC database table called the Gamma-Ray Source Detailed Catalog (Macomb & Gehrels 1999 & 2001) or MGGAMMADET that contains detailed information on the gamma-ray properties of these sources such as fluxes and spectral indices and that is based on Tables 2A-2G of the Macomb & Gehrels paper. This database table was created by the HEASARC in March 2001 based on tables supplied to the HEASARC by the catalog authors which contained an updated version of Table 1 from the published paper. This is a service provided by NASA HEASARC .
- ID:
- ivo://CDS.VizieR/J/other/RAA/18.56
- Title:
- gamma-ray spectrum for Fermi blazars
- Short Name:
- J/other/RAA/18.5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The curvature of the {gamma}-ray spectrum in blazars may reflect the intrinsic distribution of emitting electrons, which will further give some information on the possible acceleration and cooling processes in the emitting region. The {gamma}-ray spectra of Fermi blazars are normally fitted either by a single power-law (PL) or a log-normal (call Logarithmic Parabola, LP) form. The possible reason for this difference is not clear. We statistically explore this issue based on the different observational properties of 1419 Fermi blazars in the 3LAC Clean Sample.We find that the {gamma}-ray flux (100MeV-100GeV) and variability index follow bimodal distributions for PL and LP blazars, where the {gamma}-ray flux and variability index show a positive correlation. However, the distributions of {gamma}-ray luminosity and redshift follow a unimodal distribution. Our results suggest that the bimodal distribution of {gamma}-ray fluxes for LP and PL blazars may not be intrinsic and all blazars may have an intrinsically curved {gamma}-ray spectrum, and the PL spectrum is just caused by the fitting effect due to less photons.
- ID:
- ivo://CDS.VizieR/J/A+A/589/A70
- Title:
- Gamma Vel cluster membership and IMF
- Short Name:
- J/A+A/589/A70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Understanding the properties of young open clusters, such as the Initial Mass Function (IMF), star formation history and dynamic evolution, is crucial to obtain reliable theoretical predictions of the mechanisms involved in the star formation process. We want to obtain a list, as complete as possible, of confirmed members of the young open cluster Gamma Velorum, with the aim of deriving general cluster properties such as the IMF. We used all available spectroscopic membership indicators within the Gaia-ESO public archive together with literature photometry and X-ray data and, for each method, we derived the most complete list of candidate cluster members. Then, we considered photometry, gravity and radial velocities as necessary conditions to select a subsample of candidates whose membership was confirmed by using the lithium and H{alpha} lines and X-rays as youth indicators. We found 242 confirmed and 4 possible cluster members for which we derived masses using very recent stellar evolutionary models. The cluster IMF in the mass range investigated in this study shows a slope of {alpha}=2.6+/-0.5 for 0.5<M/M_{sun}<1.3 and {alpha}=1.1+/-0.4 for 0.16<M/M_{sun}_<0.5 and is consistent with a standard IMF. The similarity of the IMF of the young population around gamma^2^ Vel to that in other star forming regions and the field suggests it may have formed through very similar processes.
- ID:
- ivo://CDS.VizieR/J/A+A/530/A118
- Title:
- G29.96-0.02 and G35.20-1.74 1mm and 3mm maps
- Short Name:
- J/A+A/530/A118
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Most work on high-mass star formation has focused on observations of young massive stars in protoclusters. Very little is known about the preceding stage. Here, we present a new high-resolution study of pre-protocluster regions in tracers exclusively probing the coldest and dense gas (NH_2_ D). The two target regions G29.96-0.02 and G35.20-1.74 (W48) are drawn from the SCAMPS project, which searches for pre-protoclusters near known ultracompact HII regions. We used our data to constrain the chemical, thermal, kinematic, and physical conditions (i.e., densities) in G29.96e and G35.20w. NH_3_, NH_2_ D, HCO^+^, and continuum emission were mapped using the VLA, PdBI, and BIMA.
- ID:
- ivo://CDS.VizieR/J/A+A/612/A36
- Title:
- G346.056-0.021 and G346.077-0.056 radio images
- Short Name:
- J/A+A/612/A36
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a multiwavelength study of two southern Galactic H II regions G346.056-0.021 and G346.077-0.056 which are located at a distance of 10.9kpc. The distribution of ionized gas, cold and warm dust, and the stellar population associated with the two H II regions are studied in detail using measurements at near-infrared, mid-infrared, far-infrared, submillimeter and radio wavelengths. The radio continuum maps at 1280 and 610MHz were obtained using the Giant Metrewave Radio Telescope to probe the ionized gas. The dust temperature, column density, and dust emissivity maps were generated using modified blackbody fits in the far-infrared wavelength range 160-500um. Various near- and mid-infrared color and magnitude criteria were adopted to identify candidate ionizing star(s) and the population of young stellar objects in the associated field. The radio maps reveal the presence of diffuse ionized emission displaying distinct cometary morphologies. The 1280MHz flux densities translate to ZAMS spectral types in the range O7.5V-O7V and O8.5V-O8V for the ionizing stars of G346.056-0.021 and G346.077-0.056, respectively. A few promising candidate ionizing star(s) are identified using near-infrared photometric data. The column density map shows the presence of a large, dense dust clump enveloping G346.077-0.056. The dust temperature map shows peaks towards the two HII regions. The submillimeter image shows the presence of two additional clumps, one being associated with G346.056-0.021. The masses of the clumps are estimated to range between ~1400 and 15250M_{sun}_. Based on simple analytic calculations and the correlation seen between the ionized gas distribution and the local density structure, the observed cometary morphology in the radio maps is better explained invoking the champagne-flow model.