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Start Over Subject gamma-ray astronomy Validation Level 2
241. Long & short GRBs with host galaxies data
ID:
ivo://CDS.VizieR/J/ApJS/227/7
Title:
Long & short GRBs with host galaxies data
Short Name:
J/ApJS/227/7
Date:
21 Oct 2021
Publisher:
CDS
Description:
Gamma-ray bursts (GRBs) are classified into long and short categories based on their durations. Broadband studies suggest that these two categories of objects roughly correspond to two different classes of progenitor systems, i.e., compact star mergers (Type I) versus massive star core collapse (Type II). However, the duration criterion sometimes leads to mis-identification of the progenitor systems. We perform a comprehensive multi-wavelength comparative study between duration-defined long GRBs and short GRBs as well as the so-called "consensus" long GRBs and short GRBs (which are believed to be more closely related to the two types of progenitor systems). The parameters we study include two parts: the prompt emission properties including duration (T_90_), spectral peak energy (E_p_), low energy photon index ({alpha}), isotropic {gamma}-ray energy (E_{gamma},iso_), isotropic peak luminosity (L_p,iso_), and the amplitude parameters (f and f_eff_); and the host galaxy properties including stellar mass (M_*_), star formation rate, metallicity ([X/H]), half light radius (R_50_), angular and physical (R_off_) offset of the afterglow from the center of the host galaxy, the normalized offset (r_off_=R_off_/R_50_), and the brightness fraction F_light_. For most parameters, we find interesting overlapping properties between the two populations in both one-dimensional (1D) and 2D distribution plots. The three best parameters for the purpose of classification are T_90_, f_eff_, and F_light_. However, no single parameter alone is good enough to place a particular burst into the right physical category, suggesting the need for multiple criteria for physical classification.
242. MAGIC map of 1E 2259+586
ID:
ivo://CDS.VizieR/J/A+A/549/A23
Title:
MAGIC map of 1E 2259+586
Short Name:
J/A+A/549/A23
Date:
21 Oct 2021
Publisher:
CDS
Description:
Magnetars are an extreme, highly magnetized class of isolated neutron stars whose large X-ray luminosity is believed to be driven by their high magnetic field. Study for the first time the possible very high energy {gamma}-ray emission above 100GeV from magnetars, observing the sources 4U 0142+61 and 1E 2259+586.
243. MeV-GeV counterparts of TeV sources
ID:
ivo://CDS.VizieR/J/A+A/587/A93
Title:
MeV-GeV counterparts of TeV sources
Short Name:
J/A+A/587/A93
Date:
21 Oct 2021
Publisher:
CDS
Description:
Known TeV sources detected by major,Cerenkov telescopes are investigated to identify possible MeV-GeV {gamma}-ray counterparts. A systematic study of the known sources in the web-based TeVCat catalog has been performed to search for possible {gamma}-ray counterparts on the AGILE data collected during the first period of operations in observing pointing mode. For each TeV source, a search for a possible {gamma}-ray counterpart that is based on a multi-source maximum likelihood algorithm is performed on the AGILE data taken with the GRID instrument from July 2007 to October 2009. In the case of high-significance detection, the average {gamma}-ray flux is estimated. For cases of low-significance detection the 95% confidence level (CL) flux upper limit is given. 52TeV sources out of 152 (corresponding to ~34% of the analysed sample) show a significant excess in the AGILE data covering the pointing observation period. This analysis found 26 new AGILE sources with respect to the AGILE reference catalogs, 15 of which are galactic, 7 are extragalactic and 4 are unidentified. Detailed tables with all available information on the analysed sources are presented.
244. MGGPOD Monte Carlo suite
ID:
ivo://CDS.VizieR/J/ApJS/156/69
Title:
MGGPOD Monte Carlo suite
Short Name:
J/ApJS/156/69
Date:
21 Oct 2021
Publisher:
CDS
Description:
Intense and complex instrumental backgrounds, against which the much smaller signals from celestial sources have to be discerned, are a notorious problem for low- and intermediate-energy {gamma}-ray astronomy (~50keV-10MeV). Therefore, a detailed qualitative and quantitative understanding of instrumental line and continuum backgrounds is crucial for most stages of {gamma}-ray astronomy missions, ranging from the design and development of new instrumentation through performance prediction to data reduction. We have developed MGGPOD, a user-friendly suite of Monte Carlo codes built around the widely used GEANT (ver. 3.21) package, to simulate ab initio the physical processes relevant for the production of instrumental backgrounds. These include the build-up and delayed decay of radioactive isotopes as well as the prompt de-excitation of excited nuclei, both of which give rise to a plethora of instrumental {gamma}-ray background lines in addition to continuum backgrounds. The MGGPOD package and documentation are publicly available online (http://sigma-2.cesr.fr/spi/MGGPOD/). We demonstrate the capabilities of the MGGPOD suite by modeling high-resolution {gamma}-ray spectra recorded by the Transient Gamma-Ray Spectrometer (TGRS) on board Wind during 1995. The TGRS is a Ge spectrometer operating in the 40keV-8MeV range. Because of its fine energy resolution, these spectra reveal the complex instrumental background in formidable detail, particularly the many prompt and delayed {gamma}-ray lines. We evaluate the successes and failures of the MGGPOD package in reproducing TGRS data and provide identifications for the numerous instrumental lines.
245. 115-155MHz radio survey of Fermi sources
ID:
ivo://CDS.VizieR/J/ApJ/846/L19
Title:
115-155MHz radio survey of Fermi sources
Short Name:
J/ApJ/846/L19
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using LOFAR, we have performed a very-low-frequency (115-155MHz) radio survey for millisecond pulsars (MSPs). The survey targeted 52 unidentified Fermi {gamma}-ray sources. Employing a combination of coherent and incoherent dedispersion, we have mitigated the dispersive effects of the interstellar medium while maintaining sensitivity to fast-spinning pulsars. Toward 3FGLJ1553.1+5437 we have found PSRJ1552+5437, the first MSP to be discovered (through its pulsations) at a radio frequency <200MHz. PSR J1552+5437 is an isolated MSP with a 2.43ms spin period and a dispersion measure of 22.9pc/cm^3^. The pulsar has a very steep radio spectral index ({alpha}-2.8+/-0.4). We obtain a phase-connected timing solution combining the 0.74yr of radio observations with {gamma}-ray photon arrival times covering 7.5yr of Fermi observations. We find that the radio and {gamma}-ray pulse profiles of PSR J1552+5437 appear to be nearly aligned. The very steep spectrum of PSR J1552+5437, along with other recent discoveries, hints at a population of radio MSPs that have been missed in surveys using higher observing frequencies. Detecting such steep spectrum sources is important for mapping the population of MSPs down to the shortest spin periods, understanding their emission in comparison to slow pulsars, and quantifying the prospects for future surveys with low-frequency radio telescopes like SKA-Low and its precursors.
246. 12mm line survey towards W28 SNR
ID:
ivo://CDS.VizieR/J/MNRAS/411/1367
Title:
12mm line survey towards W28 SNR
Short Name:
J/MNRAS/411/1367
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present 12mm Mopra observations of dense molecular gas towards the W28 supernova remnant (SNR) field. The focus is on the dense molecular gas towards the TeV gamma-ray sources detected by the HESS telescopes, which likely trace the cosmic rays from W28 and possibly other sources in the region. Using the NH_3_ inversion transitions we reveal several dense cores inside the molecular clouds,
247. Model predictions for GRB host galaxies
ID:
ivo://CDS.VizieR/J/ApJ/802/103
Title:
Model predictions for GRB host galaxies
Short Name:
J/ApJ/802/103
Date:
21 Oct 2021
Publisher:
CDS
Description:
Long-duration gamma-ray bursts (GRBs) are powerful probes of the star formation history of the universe, but the correlation between the two depends on the highly debated presence and strength of a metallicity bias. To investigate this correlation, we use a phenomenological model that successfully describes star formation rates, luminosities, and stellar masses of star-forming galaxies and apply it to GRB production. We predict the luminosities, stellar masses, and metallicities of host galaxies depending on the presence (or absence) of a metallicity bias. Our best-fitting model includes a moderate metallicity bias, broadly consistent with the large majority of the long-duration GRBs in metal-poor environments originating from a collapsar (probability ~83%, with [0.74;0.91] range at 90% confidence level), but with a secondary contribution (~17%) from a metal-independent production channel, such as binary evolution. Because of the mass-metallicity relation of galaxies, the maximum likelihood model predicts that the metal-independent channel becomes dominant at z~<2, where hosts have higher metallicities and collapsars are suppressed. This possibly explains why some studies find no clear evidence of a metal bias based on low-z samples. However, while metallicity predictions match observations well at high redshift (z>~2), there is tension with low-redshift observations, since a significant fraction of GRB hosts are predicted to have (near) solar metallicity. This is in contrast to observations, unless obscured, metal-rich hosts are preferentially missed in current data sets, and suggests that lower efficiencies of the metal-independent GRB channel might be preferred following a comprehensive fit that includes metallicity of GRB hosts from complete samples. Overall, we are able to clearly establish the presence of a metallicity bias for GRB production, but continued characterization of GRB host galaxies is needed to quantify its strength.
248. Mrk421 in March 2010
ID:
ivo://CDS.VizieR/J/A+A/578/A22
Title:
Mrk421 in March 2010
Short Name:
J/A+A/578/A22
Date:
21 Oct 2021
Publisher:
CDS
Description:
A flare from the TeV blazar Mrk 421, occurring in March 2010, was observed for 13 consecutive days from radio to very high energy (VHE; E>100GeV) gamma-rays with MAGIC, VERITAS, Whipple, FermiLAT, MAXI, RXTE, Swift, GASP-WEBT, and several optical and radio telescopes. We model the day-scale SEDs with one-zone and two-zone synchrotron self-Compton (SSC) models, investigate the physical parameters, and evaluate whether the observed broadband SED variability can be associated to variations in the relativistic particle population. Flux variability was remarkable in the X-ray and VHE bands while it was minor or not significant in the other bands. The one-zone SSC model can describe reasonably well the SED of each day for the 13 consecutive days. This flaring activity is also very well described by a two-zone SSC model, where one zone is responsible for the quiescent emission while the other smaller zone, which is spatially separated from the first one, contributes to the daily-variable emission occurring in X-rays and VHE gamma-rays. Both the one-zone SSC and the two-zone SSC models can describe the daily SEDs via the variation of only four or five model parameters, under the hypothesis that the variability is associated mostly to the underlying particle population. This shows that the particle acceleration and cooling mechanism producing the radiating particles could be the main one responsible for the broadband SED variations during the flaring episodes in blazars. The two-zone SSC model provides a better agreement to the observed SED at the narrow peaks of the low- and high-energy bumps during the highest activity, although the reported one-zone SSC model could be further improved by the variation of the parameters related to the emitting region itself ({delta}, B and R), in addition to the parameters related to the particle population.
249. Mrk 501 long-term multi-band photometry
ID:
ivo://CDS.VizieR/J/A+A/655/A93
Title:
Mrk 501 long-term multi-band photometry
Short Name:
J/A+A/655/A93
Date:
14 Mar 2022 07:47:04
Publisher:
CDS
Description:
Radio-to-TeV observations of the bright nearby (z=0.034) blazar Markarian 501 (Mrk 501), performed from December 2012 to April 2018, are used to study the emission mechanisms in its relativistic jet. We examined the multi-wavelength variability and the correlations of the light curves obtained by eight different instruments, including the First G-APD Cherenkov Telescope (FACT), observing Mrk 501 in very high-energy (VHE) gamma-rays at TeV energies. We identified individual TeV and X-ray flares and found a sub-day lag between variability in these two bands. The source was found to be variable on different timescales. Simultaneous TeV and X-ray variations with almost zero lag are consistent with synchrotron self-Compton (SSC) emission, where TeV photons are produced through inverse Compton scattering. The characteristic time interval of 5-25 days between TeV flares is consistent with them being driven by Lense-Thirring precession.
250. Mrk421 multi-instrument observations in 2017
ID:
ivo://CDS.VizieR/J/A+A/655/A89
Title:
Mrk421 multi-instrument observations in 2017
Short Name:
J/A+A/655/A89
Date:
21 Mar 2022 08:46:33
Publisher:
CDS
Description:
We present a detailed characterisation and theoretical interpretation of the broadband emission of the paradigmatic TeV blazar Mrk 421, with a special focus on the multi-band flux correlations. The dataset has been collected through an extensive multi-wavelength campaign organised between 2016 December and 2017 June. The instruments involved are MAGIC, FACT, Fermi-LAT, Swift, GASP-WEBT, OVRO, Medicina, and Metsahovi. Additionally, four deep exposures (several hours long) with simultaneous MAGIC and NuSTAR observations allowed a precise measurement of the falling segments of the two spectral components. The very-high-energy (VHE; E>100GeV) gamma rays and X-rays are positively correlated at zero time lag, but the strength and characteristics of the correlation change substantially across the various energy bands probed. The VHE versus X-ray fluxes follow different patterns, partly due to substantial changes in the Compton dominance for a few days without a simultaneous increase in the X-ray flux (i.e. orphan gamma-ray activity). Studying the broadband spectral energy distribution (SED) during the days including NuSTAR observations, we show that these changes can be explained within a one-zone leptonic model with a blob that increases its size over time. The peak frequency of the synchrotron bump varies by two orders of magnitude throughout the campaign. Our multi-band correlation study also hints at an anti-correlation between UV-optical and X-ray at a significance higher than 3{sigma}. A VHE flare observed on MJD~57788 (2017 February 4) shows gamma-ray variability on multi-hour timescales, with a factor ten increase in the TeV flux but only a moderate increase in the keV flux. The related broadband SED is better described by a two-zone leptonic scenario rather than by a one-zone scenario. We find that the flare can be produced by the appearance of a compact second blob populated by high energetic electrons spanning a narrow range of Lorentz factors, from {gamma}'_min_=2x10^4^ to {gamma}'_max_=6x10^5^.