- ID:
- ivo://CDS.VizieR/J/ApJ/831/102
- Title:
- Swift and NuSTAR obs. of the BL Lac Mrk 421
- Short Name:
- J/ApJ/831/102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of the Swift and NuSTAR observations of the nearby BL Lac object Mrk 421 during 2013 January-June. The source exhibited a strong long-term variability in the 0.3-10keV and 3-79keV bands with the maximum-to-minimum daily-binned flux ratios of 22 and 95, respectively, in about 3 months, mainly due to unprecedented strong X-ray outbursts by more than an order of magnitude in both bands within 2 weeks in 2013 April when the 0.3-10keV count rate exceeded the level of 200cts/s for the first time, and Mrk 421 became one of the brightest sources in the X-ray sky. The source was also very active on intra-day timescales, and it showed flux doubling and halving timescales of 1.16-7.20hr and 1.04-3.54hr, respectively. On some occasions, the flux varied by 4%-23% within 300-840s. During this period, the source also exhibited some of the most extreme X-ray spectral variability ever reported for BL Lacs-the location of the synchrotron spectral energy distribution peak shifted from a few eV to ~10keV, and the photon index at 1 keV and curvature parameter varied on timescales from a few weeks down to intervals shorter than 1ks. MAGIC and First G-APD Cherenkov Telescope observations also revealed a very strong very high energy (VHE) flare during April 11-17. The UV and HE {gamma}-ray flares were much weaker compared to their X-ray counterparts, and they generally showed significantly stronger correlation with each other than with the X-ray fluxes.
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- ID:
- ivo://CDS.VizieR/J/ApJ/850/74
- Title:
- Swift/BAT AGN Spectroscopic Survey. I.
- Short Name:
- J/ApJ/850/74
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first catalog and data release of the Swift-BAT AGN Spectroscopic Survey. We analyze optical spectra of the majority of the detected AGNs (77%, 642/836) based on their 14-195keV emission in the 70-month Swift-BAT all-sky catalog. This includes redshift determination, absorption and emission-line measurements, and black hole mass and accretion rate estimates for the majority of obscured and unobscured AGNs (74%, 473/642), with 340 measured for the first time. With ~90% of sources at z<0.2, the survey represents a significant advance in the census of hard X-ray-selected AGNs in the local universe. In this first catalog paper, we describe the spectroscopic observations and data sets, and our initial spectral analysis. The FWHMs of the emission lines show broad agreement with the X-ray obscuration (~94%), such that Sy 1-1.8 have N_H_<10^21.9^cm^-2^, and Seyfert 2 have N_H_>10^21.9^cm^-2^. Seyfert 1.9, however, show a range of column densities. Compared to narrow-line AGNs in the SDSS, the X-ray-selected AGNs have a larger fraction of dusty host galaxies (H{alpha}/H{beta}>5), suggesting that these types of AGN are missed in optical surveys. Using the [OIII]{lambda}5007/H{beta} and [NII]{lambda}6583/H{alpha} emission-line diagnostic, about half of the sources are classified as Seyferts; ~15% reside in dusty galaxies that lack an H{beta} detection, but for which the upper limits on line emission imply either a Seyfert or LINER, ~15% are in galaxies with weak or no emission lines despite high-quality spectra, and a few percent each are LINERS, composite galaxies, H II regions, or in known beamed AGNs.
- ID:
- ivo://CDS.VizieR/J/ApJS/233/17
- Title:
- Swift/BAT AGN spectroscopic survey. V. X-ray data
- Short Name:
- J/ApJS/233/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Hard X-ray (>=10keV) observations of active galactic nuclei (AGNs) can shed light on some of the most obscured episodes of accretion onto supermassive black holes. The 70-month Swift/BAT all-sky survey, which probes the 14-195keV energy range, has currently detected 838 AGNs. We report here on the broadband X-ray (0.3-150keV) characteristics of these AGNs, obtained by combining XMM-Newton, Swift/XRT, ASCA, Chandra, and Suzaku observations in the soft X-ray band (<=10keV) with 70-month averaged Swift/BAT data. The nonblazar AGNs of our sample are almost equally divided into unobscured (N_H_<10^22^cm^-2^) and obscured (N_H_>=10^22^cm^-2^) AGNs, and their Swift/BAT continuum is systematically steeper than the 0.3-10keV emission, which suggests that the presence of a high-energy cutoff is almost ubiquitous. We discuss the main X-ray spectral parameters obtained, such as the photon index, the reflection parameter, the energy of the cutoff, neutral and ionized absorbers, and the soft excess for both obscured and unobscured AGNs.
18444. SWIFT/BAT detections of AGN
- ID:
- ivo://CDS.VizieR/J/ApJ/633/L77
- Title:
- SWIFT/BAT detections of AGN
- Short Name:
- J/ApJ/633/L77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present preliminary results from the first 3 months of the Swift Burst Alert Telescope (BAT) high Galactic latitude survey in the 14-195keV band. The survey reaches a flux of ~10^-11^erg/cm^2^/s and has ~2.7' (90% confidence) positional uncertainties for the faintest sources. This represents the most sensitive survey to date in this energy band. These data confirm the conjectures that a high-energy-selected active galactic nucleus (AGN) sample would have very different properties from those selected in other bands and that it represents a "true" sample of the AGN population. We have identified 86% of the 66 high-latitude sources. Twelve are Galactic-type sources, and 44 can be identified with previously known AGNs.
- ID:
- ivo://CDS.VizieR/J/ApJ/896/L20
- Title:
- Swift BAT gamma-ray burst durations
- Short Name:
- J/ApJ/896/L20
- Date:
- 21 Mar 2022 07:00:25
- Publisher:
- CDS
- Description:
- The duration of a gamma-ray burst (GRB) is a key indicator of its physical origin, with long bursts perhaps associated with the collapse of massive stars and short bursts with mergers of neutron stars. However, there is substantial overlap in the properties of both short and long GRBs and neither duration nor any other parameter so far considered completely separates the two groups. Here we unambiguously classify every GRB using a machine-learning dimensionality reduction algorithm, t-distributed stochastic neighborhood embedding, providing a catalog separating all Swift GRBs into two groups. Although the classification takes place only using prompt emission light curves, every burst with an associated supernova is found in the longer group and bursts with kilonovae in the short, suggesting along with the duration distributions that these two groups are truly long and short GRBs. Two bursts with a clear absence of a supernova belong to the longer class, indicating that these might have been direct-collapse black holes, a proposed phenomenon that may occur in the deaths of more massive stars.
18446. Swift BAT survey of AGNs
- ID:
- ivo://CDS.VizieR/J/ApJ/681/113
- Title:
- Swift BAT survey of AGNs
- Short Name:
- J/ApJ/681/113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of the analysis of the first 9 months of data of the Swift BAT (Burst Alert Telescope) survey of AGNs in the 14-195keV band. Using archival X-ray data or follow-up Swift X-ray telescope (XRT) observations, we have identified 129 (103 AGNs) of 130 objects detected at |b|>15{deg} and with significance >4.8{sigma}. One source remains unidentified. These same X-ray data have allowed measurement of the X-ray properties of the objects.
18447. Swift-BAT survey of AGNs
- ID:
- ivo://CDS.VizieR/J/ApJ/728/58
- Title:
- Swift-BAT survey of AGNs
- Short Name:
- J/ApJ/728/58
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive and analyze the active galactic nuclei (AGNs) absorption distribution using a complete sample of AGNs detected by Swift-BAT in the first three years of the survey. The fraction of Compton-thick AGNs represents only 4.6% of the total AGN population detected by Swift-BAT. However, we show that once corrected for the bias against the detection of very absorbed sources the real intrinsic fraction of Compton-thick AGNs is 20^+9^_-6_%. We proved for the first time (also in the Burst Alert Telescope (BAT) band) that the anti-correlation of the fraction of absorbed AGNs and luminosity is tightly connected to the different behavior of the X-ray luminosity functions (XLFs) of absorbed and unabsorbed AGNs. This points toward a difference between the two subsamples of objects with absorbed AGNs being, on average, intrinsically less luminous than unobscured ones. Moreover, the XLFs show that the fraction of obscured AGNs might also decrease at very low luminosity.
- ID:
- ivo://CDS.VizieR/J/ApJ/721/1843
- Title:
- Swift-BAT survey of Galactic sources
- Short Name:
- J/ApJ/721/1843
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the populations of X-ray sources in the Milky Way in the 15-55keV band using a deep survey with the BAT instrument aboard the Swift observatory. We present the log N-log S distributions of the various source types and we analyze their variability and spectra. For the low-mass X-ray binaries (LMXBs) and the high-mass X-ray binaries (HMXBs), we derive the luminosity functions to a limiting luminosity of L_X_~7x10^34^erg/s. Our results confirm the previously found flattening of the LMXB luminosity function below a luminosity of L_X_~10^37^erg/s. The luminosity function of the HMXBs is found to be significantly flatter in the 15-55keV band than in the 2-10keV band. From the luminosity functions we estimate the ratios of the hard X-ray luminosity from HMXBs to the star formation rate, and the LMXB luminosity to the stellar mass. We use these to estimate the X-ray emissivity in the local universe from X-ray binaries and show that it constitutes only a small fraction of the hard X-ray background.
- ID:
- ivo://CDS.VizieR/J/ApJ/765/L26
- Title:
- Swift/BAT ultra-hard X-ray data from GOALS LIRGs
- Short Name:
- J/ApJ/765/L26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first analysis of the all-sky Swift Burst Alert Telescope (BAT) ultra-hard X-ray (14-195keV) data for a targeted list of objects. We find that the BAT data can be studied at three-times-fainter limits than in previous blind detection catalogs based on prior knowledge of source positions and using smaller energy ranges for source detection. We determine the active galactic nucleus (AGN) fraction in 134 nearby (z<0.05) luminous infrared galaxies (LIRGs) from the GOALS sample. We find that LIRGs have a higher detection frequency than galaxies matched in stellar mass and redshift at 14-195keV and 24-35keV. In agreement with work at other wavelengths, the AGN detection fraction increases strongly at high IR luminosity with half of the high-luminosity LIRGs (50%, 6/12, logL_IR_/L_{sun}_>11.8) detected. The BAT AGN classification shows 97% (37/38) agreement with Chandra and XMM-Newton AGN classification using hardness ratios or detection of an iron K{alpha} line. This confirms our statistical analysis and supports the use of the Swift/BAT all-sky survey to study fainter populations of any category of sources in the ultra-hard X-ray band. BAT AGNs in LIRGs tend to show higher column densities with 40%+/-9% showing 14-195 keV/2-10 keV hardness flux ratios suggestive of high or Compton-thick column densities (logN_H_>24/cm2), compared to only 12%+/-5% of non-LIRG BAT AGNs. We also find that using specific energy ranges of the BAT detector can yield additional sources over total band detections with 24% (5/21) of detections in LIRGs at 24-35keV not detected at 14-195keV.
- ID:
- ivo://CDS.VizieR/J/ApJ/864/84
- Title:
- Swift follow-up obs. of the TXS 0506+056 blazar
- Short Name:
- J/ApJ/864/84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Detection of the IceCube-170922A neutrino coincident with the flaring blazar TXS 0506+056, the first and only ~3{sigma} high-energy neutrino source association to date, offers a potential breakthrough in our understanding of high-energy cosmic particles and blazar physics. We present a comprehensive analysis of TXS 0506+056 during its flaring state, using newly collected Swift, NuSTAR, and X-shooter data with Fermi observations and numerical models to constrain the blazar's particle acceleration processes and multimessenger (electromagnetic (EM) and high-energy neutrino) emissions. Accounting properly for EM cascades in the emission region, we find a physically consistent picture only within a hybrid leptonic scenario, with {gamma}-rays produced by external inverse-Compton processes and high-energy neutrinos via a radiatively subdominant hadronic component. We derive robust constraints on the blazar's neutrino and cosmic-ray emissions and demonstrate that, because of cascade effects, the 0.1-100keV emissions of TXS 0506+056 serve as a better probe of its hadronic acceleration and high-energy neutrino production processes than its GeV-TeV emissions. If the IceCube neutrino association holds, physical conditions in the TXS 0506+056 jet must be close to optimal for high-energy neutrino production, and are not favorable for ultrahigh-energy cosmic-ray acceleration. Alternatively, the challenges we identify in generating a significant rate of IceCube neutrino detections from TXS 0506+056 may disfavor single-zone models, in which {gamma}-rays and high-energy neutrinos are produced in a single emission region. In concert with continued operations of the high-energy neutrino observatories, we advocate regular X-ray monitoring of TXS 0506+056 and other blazars in order to test single-zone blazar emission models, clarify the nature and extent of their hadronic acceleration processes, and carry out the most sensitive possible search for additional multimessenger sources.