(Abridged) We present simultaneous optical--to--X-ray spectral energy distributions (SEDs) from Swift's X-ray and UV--optical telescopes (XRT and UVOT) for a well-selected sample of 26 low-redshift (z<0.1) AGN from the Swift/BAT 9-month catalogue, the largest well-studied, hard X-ray selected survey of local AGN to date. Our subsample consists of AGN with low intrinsic X-ray absorption (N_H<10^22 cm^-2) and minimal spectral complexity, to more accurately recover the intrinsic accretion luminosity in these sources. We perform a correction for host galaxy contamination in all available UVOT filter images to recover the intrinsic AGN emission, and estimate intrinsic dust extinction from the resultant nuclear SEDs. Black hole mass estimates are determined from the host-galaxy 2MASS K-band bulge luminosity. Accretion rates determined from our SEDs are on average low (Eddington ratios <~ 0.1) and hard X-ray bolometric corrections cluster at ~10-20, in contrast with the higher values seen for quasars. An average SED for the 22 low accretion rate (Eddington ratio < 0.1) objects is presented, with and without correction for intrinsic extinction. We do not find a correlation of optical--to--X-ray spectral index with Eddington ratio, regardless of the optical reference wavelength chosen for defining the spectral index. The low accretion rates and bolometric corrections found for this representative low-redshift sample are of particular importance for studies of AGN accretion history.
The 70-month Swift/BAT catalogue provides a sensitive view of the extragalactic X-ray sky at hard energies (>10 keV) containing about 800 Active Galactic Nuclei. We explore its content in heavily obscured, Compton-thick AGN by combining the BAT (14-195 keV) with the lower energy XRT (0.3-10 keV) data. We apply a Bayesian methodology using Markov chains to estimate the exact probability distribution of the column density for each source. We find 53 possible Compton-thick sources (with probability 3 to 100%) translating to a ~7% fraction of the AGN in our sample. We derive the first parametric l…
We present a detailed X-ray spectral analysis of a complete sample of hard X-ray selected AGN in the Northern Galactic Cap of the 58-month Swift Burst Alert Telescope (Swift/BAT) catalog, consisting of 100 AGN with b>50deg. This region has excellent potential for further study due to the availability of a wide range of archival multi-wavelength data, and we propose it as a low-redshift analog to the `deep fields' work on AGN at higher redshifts. We present distributions of luminosity, absorption, and other key quantities, from fitting new and archival X-ray data gathered from XMM-Newton, Swift…
We present the catalog of sources detected in 70 months of observations of the BAT hard X-ray detector on the Swift gamma-ray burst observatory. The Swift-BAT 70 month survey has detected 1171 hard X-ray sources (more than twice as many sources as the previous 22 month survey) in the 14-195 keV band down to a significance level of 4.8 sigma, associated with 1210 counterparts. The 70 month Swift-BAT survey is the most sensitive and uniform hard X-ray all-sky survey and reaches a flux level of 1.03e-11 ergs/sec/cm2 over 50% of the sky and 1.34e-11 ergs/sec/cm2 over 90% of the sky. The majority o…
We present the joint NuSTAR and XMM-Newton spectral analysis in the 0.6-70 keV band of three candidate Compton thick (CT-) AGN selected in the 100-month Swift-BAT catalog. These objects were previously classified as CT-AGNs based on low quality Swift-XRT and Swift-BAT data, and had soft photon indices (Gamma>2.2) that suggested a potential overestimation of the line of sight column density. Thanks to the high-quality NuSTAR and XMM-Newton data we were able to determine that in all three objects the photon index was significantly overestimated, and two out of three sources are reclassified from…
We systematically investigate the near- (NIR) to far-infrared (FIR) photometric properties of a nearly complete sample of local active galactic nuclei (AGN) detected in the Swift/Burst Alert Telescope (BAT) all-sky ultra hard X-ray (14-195 keV) survey. Out of 606 non-blazar AGN in the Swift/BAT 70-month catalog at high galactic latitude of $|b|>10^{\circ}$, we obtain IR photometric data of 604 objects by cross-matching the AGN positions with catalogs from the WISE, AKARI, IRAS, and Herschel infrared observatories. We find a good correlation between the ultra-hard X-ray and mid-IR (MIR) luminos…
We present a catalog of hard X-ray sources detected in the first 105 months of observations with the Burst Alert Telescope (BAT) coded mask imager on board the Swift observatory. The 105 month Swift-BAT survey is a uniform hard X-ray all-sky survey with a sensitivity of $8.40\times 10^{-12}\ {\rm erg\ s^{-1}\ cm^{-2}}$ over 90% of the sky and $7.24\times 10^{-12}\ {\rm erg\ s^{-1}\ cm^{-2}}$ over 50% of the sky in the 14-195 keV band. The Swift-BAT 105 month catalog provides 1632 (422 new detections) hard X-ray sources in the 14-195 keV band above the 4.8σ significance level. Adding to the pre…
Source identification for the Swift-BAT 150-month hard X-ray catalog using soft X-ray observations
Clemson University（克莱姆森大学）；University of Virginia（弗吉尼亚大学）；Università di Bologna（博洛尼亚大学）；INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna（意大利国家天体物理研究所博洛尼亚天文与空间科学观测站）；European Southern Observatory（欧洲南方天文台）；University of Illinois at Urbana-Champaign（伊利诺伊大学厄巴纳-香槟分校）；California Institute of Technology（加州理工学院）
Hard X-ray ($\geq 10$ keV) observations of Active Galactic Nuclei (AGN) 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 14-195 keV energy range, has currently detected 838 AGN. We report here on the broad-band X-ray (0.3-150 keV) characteristics of these AGN, obtained by combining XMM-Newton, Swift/XRT, ASCA, Chandra, and Suzaku observations in the soft X-ray band ($\leq 10$ keV) with 70-month averaged Swift/BAT data. The non-blazar AGN of our sample are almost equally divided into unobscur…
The fraction of Compton thick sources is one of the main uncertainties left in understanding the AGN population. The Swift Burst Alert Telescope (BAT) all-sky survey, for the first time gives us an unbiased sample of AGN for all but the most heavily absorbed sources (log NH > 25). Still, the BAT spectra (14 - 195 keV) are time-averaged over months of observations and therefore hard to compare with softer spectra from the Swift XRT or other missions. This makes it difficult to distinguish between Compton-thin and Compton-thick models. With Suzaku, we have obtained simultaneous hard (> 15 keV) a…
We present a new X-ray luminosity function of flat-spectrum radio quasars (FSRQs) utilizing the latest {\it Swift}/BAT 105-month X-ray source catalog. Contrary to previous studies of FSRQs in the X-ray band, using the luminosity-dependent density evolution model, we find that FSRQs show evolutionary peaks at $z\sim1-2$ depending on luminosities. Our result is rather consistent with the evolution of FSRQs seen in the radio and GeV bands, although the number density is a factor of 5--10 smaller. We further explore the contribution of FSRQs to the cosmic MeV gamma-ray background radiation. We fin…
The nature of a substantial percentage (about one fifth) of hard X-ray sources discovered with the BAT instrument onboard the Neil Gehrels Swift Observatory (hereafter Swift) is unknown because of the lack of an identified longer-wavelength counterpart. Without such follow-up, an X-ray catalogue is of limited astrophysical value: we therefore embarked, since 2009, on a long-term project to uncover the optical properties of sources identified by Swift by using a large suite of ground-based telescopes and instruments. In this work, we continue our programme of characterization of unidentified or…
We present the combined Chandra and Swift-BAT spectral analysis of nine low-redshift (z <= 0.10), candidate heavily obscured active galactic nuclei (AGN) selected from the Swift-BAT 150-month catalog. We located soft (1-10 keV) X-ray counterparts to these BAT sources and joint fit their spectra with physically motivated models.The spectral analysis in the 1-150 keV energy band determined that all sources are obscured, with a line-of-sight column density NH >= 10^22 cm^-2 at a 90% confidence level. Four of these sources show significant obscuration with NH >= 10^23 cm^-2 and two additional sour…
We present the broadband (0.5-100 keV) spectra of three heavily obscured Active Galactic Nuclei (AGNs), NGC 1106, UGC 03752, and NGC 2788A, observed with Suzaku and Swift/Burst Alert Telescope (BAT). The targets are selected from the Swift/BAT 70-month catalog on the basis of high hardness ratio between above and below 10 keV, and their X-ray spectra are reported here for the first time. We apply three models, a conventional model utilizing an analytic reflection code and two Monte-Carlo based torus models with a doughnut-like geometry (MYTorus) and with a nearly spherical geometry (Ikeda toru…
While X-ray emission from active galactic nuclei (AGN) is common, the detailed physics behind this emission is not well understood. This is in part because high quality broadband spectra are required to precisely derive fundamental parameters of X-ray emission such as the photon index, folding energy, and reflection coefficient. Here we present values of such parameters for 33 AGN observed as part of the 105 month Swift/BAT campaign and with coordinated archival XMM-Newton and NuSTAR observations. We look for correlations between the various coronal parameters in addition to correlations betwe…
We present the first analysis of the all-sky Swift BAT ultra hard X-ray (14-195 keV) data for a targeted list of objects. We find the BAT data can be studied at 3x 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 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 14-195 keV and 24-35 keV. In agreement with work at other wave…
We report the results of a cross-match study between the hard X-ray and GeV gamma-ray catalogs, by making use of the latest 105-month Swift-BAT and 10-yr Fermi-LAT catalogs, respectively. The spatial cross-matching between the two catalogs results in the matching of 132 point-like sources, including ~5% of false-match sources. Additionally, 24 sources that have been identified as the same identifications are matched. Among the 75 extended sources in the Fermi-LAT catalog, 31 sources have spatial coincidences with at least one Swift-BAT source inside their extent. All the matched sources consis…
Compton-thick AGN Characterisation in a Multi-wavelength Context: Insights from the 70-Month \textit{SWIFT}/BAT Catalogue
Radio Cosmology Research Lab, Centre for Astronomy and Astrophysics Research, Faculty of Science, Universiti Malaya（马来亚大学理学院天体物理学与天文学研究中心射电宇宙学实验室）；Centre of Foundation, Language and Malaysian Studies, Universiti Malaya-Wales（马来亚-威尔士大学基础、语言与马来西亚研究中心）；National Centre for Particle Physics (NCPP), Universiti Malaya（马来亚大学国家粒子物理中心）；National Astronomical Observatory of Japan, National Institutes of Natural Sciences (NINS)（日本国立天文台，国立自然科学研究所）；Department of Astronomical Science, SOKENDAI (The Graduate University of Advanced Studies)（尖端研究大学院大学天体科学系）；Natural Science Laboratory, Toyo University（东洋大学自然科学实验室）；Department of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia（马来西亚国民科技大学理学院应用物理系）
The all-sky hard X-ray survey performed by Swift/BAT allowed the detection of many heavily obscured Compton-thick AGN. In our previous work, we have identified more than 50 candidate Compton-thick AGN in the local Universe, corresponding to an observed fraction of about 7% of the total AGN population. This number can be converted to the intrinsic Compton-thick AGN number density, only if we know the form of the Compton-thick AGN spectrum, that is the energy of their absorption turnover, photon-index and its cut-off energy at high energies, as well as the strength of the reflection component on…
Using Gaussian Mixture Model and Expectation Maximization algorithm, we have performed a density estimation in the framework of $T_{90}$ versus hardness ratio for 296 Swift/BAT GRBs with known redshift. Here, Bayesian Information Criterion has been taken to compare different models. Our investigations show that two instead of three or more Gaussian components are favoured in both the observer and rest frames. Our key findings are consistent with some previous results.
We study the populations of X-ray sources in the Milky Way in the 15-55 keV band using a deep survey with the BAT instrument aboard the Swift observatory. We present the logN-logS 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~7 times10^{34} erg s/s. Our results confirm the previously found flattening of the LMXB luminosity function below a luminosity of L_X~10^{37} erg s/s. The luminosity function of the HM…
We investigate the feasibility of implementing a system called 'Follow the BAT' that will coordinate ground-based robotic optical and near infrared (NIR) telescopes to monitor the Swift BAT field-of-view (FoV). The system will optimize the monitoring locations in the BAT FoV based on individual robotic telescopes' location, FoV, sensitivity and local weather conditions. The aim is to perform coordinated BAT FoV monitoring by professional as well as amateur astronomers around the world. The scientific goal of the proposed system is to facilitate detection of prompt optical and NIR emission from…
We have analyzed the Swift data relevant to the high mass X-ray binary Swift J1816.7-1613. The timing analysis of the BAT survey data unveiled a modulation at a period of P_0=118.5+/-0.8 days that we interpret as the orbital period of the X-ray binary system. The modulation is due to a sequence of bright flares, lasting ~30 d, separated by long quiescence intervals. This behavior is suggestive of a Be binary system, where periodic or quasi-periodic outbursts are the consequence of an enhancement of the accretion flow from the companion star at the periastron passage. The position of Swift J181…
Changing-look (CL) AGN are unique probes of accretion onto supermassive black holes (SMBHs), especially when simultaneous observations in complementary wavebands allow investigations into the properties of their accretion flows. We present the results of a search for CL behaviour in 412 Swift-BAT detected AGN with multiple epochs of optical spectroscopy from the BAT AGN Spectroscopic Survey (BASS). 125 of these AGN also have 14-195 keV ultra-hard X-ray light-curves from Swift-BAT which are contemporaneous with the epochs of optical spectroscopy. Eight CL events are presented for the first time…
We present the Palermo Swift-BAT hard X-ray catalogue obtained from the analysis of the the data relative to the first 39 months of the Swift mission. We have developed a dedicated software to perform data reduction, mosaicking and source detection on the BAT survey data. We analyzed the BAT dataset in three energy bands (14-150 keV, 14-30 keV, 14-70 keV), obtaining a list of 962 detections above a significance threshold of 4.8 standard deviations. The identification of the source counterparts was pursued using three strategies: cross-correlation with published hard X-ray catalogues, analysis …
The durations of 388 gamma-ray bursts, detected by the Swift satellite, are studied statistically in order to search for their subgroups. Then the results are compared with the results obtained earlier from the BATSE database. The standard chi^2 test is used. Similarly to the BATSE database, the short and long subgroups are well detected also in the Swift data. Also the intermediate subgroup is seen in the Swift database. The whole sample of 388 GRBs gives a support for three subgroups.
The Swift/BAT 9-month catalogue of active galactic nuclei (AGN) provides an unbiased census of local supermassive black hole accretion, and probes to all but the highest levels of absorption in AGN. We explore a method for characterising the bolometric output of both obscured and unobscured AGN by combining the hard X-ray data from Swift/BAT (14-195keV) with the reprocessed IR emission as seen with the IRAS all-sky surveys. This approach bypasses the complex modifications to the SED introduced by absorption in the optical, UV and 0.1-10 keV regimes and provides a long-term, average picture of …
Variability is one of the hallmarks of Active Galactic Nuclei. The Burst Alert Telescope onboard of Swift, with its homogeneous coverage of the sky is a formidable tool to study variability at hard X-rays. We present here the analysis of the 1-month binned Swift/BAT lightcurves of the 20 brightest Active Galactic Nuclei in the hard X-ray sky. The sample consists of 2 blazars, 3 radio galaxies, 6 Seyfert 1/1.5s, 8 Seyfert 2s and 1 Narrow Line Seyfert 1. We found that all the objects show variability, and most of them have a value of the fractional root mean squared variability amplitude of Fvar…
We study time-resolved spectra of the prompt emission of Swift Gamma-ray bursts (GRB). Our goal is to see if previous BATSE claims of the existence of a large amount of spectra with the low energy photon indices harder than 2/3 are consistent with Swift data. We perform a systematic search of the episodes of the spectral hardening down to the photon indices below 2/3 in the prompt emission spectra of Swift GRBs. We show that the data of the BAT instrument on board of Swift are consistent with BATSE data, if one takes into account differences between the two instruments. Much lower statistics o…
IGR J16493-4348 is a supergiant high mass X-ray binary discovered by INTEGRAL in 2004. The source is detected at a significance level of $\sim21$ standard deviations in the Swift-BAT survey data collected during the first 54 months of the Swift mission. The timing analysis reveals an orbital period of $\sim$6.78 days and the presence of a full eclipse of the compact ob\ ject. The dynamical range (variability up to a factor $\sim$20) observed during the BAT monitoring suggests that IGR J16493-4348 is a wind-fed system. The derived semi-major axis of the binary system is $\sim55 R_{\sun}$ with a…
Short and long bursts were identified by the BATSE team in the early 90s. A decade ago there were some suggestions about the intermediate duration type of bursts. We are going to summarize recent analyses of the duration distributions of the Beppo-Sax and Swift data. Our conclusion is all the three satellites (CGRO, Swift, Beppo-Sax) can see the third type of the GRBs. The properties of the group members are very similar in the different data sets.
The most recent all-sky surveys performed with the INTEGRAL and SWIFT satellites allowed the detection of more than 1500 sources in hard X-rays above 20 keV. About one quarter of them has no obvious counterpart at other wavelengths and therefore could not be associated with any known class of high-energy emitting objects. Although cross-correlation with catalogues or surveys at other wavelengths (especially soft X-rays) is of invaluable support in pinpointing the putative optical candidates, only accurate optical spectroscopy can reveal the true nature of these sources. With the aim of identif…
Through an optical campaign performed at 4 telescopes located in the northern and the southern hemispheres, we have obtained optical spectroscopy for 75 counterparts of unclassified or poorly studied hard X-ray emitting objects detected with Swift/BAT and listed in the 54 month Palermo BAT catalogue. All these objects have also observations taken with Swift/XRT, ROSAT or Chandra satellites which allowed us to reduce the high energy error box and pinpoint the most likely optical counterpart/s. We find that 69 sources in our sample are Active Galactic Nuclei (AGNs); of them, 35 are classified as…
We present the analysis of 2.1 years of Fermi/LAT data on 491 Seyfert galaxies detected by the Swift/BAT survey. Only the two nearest objects, NGC 1068 and NGC 4945, which were identified in the Fermi First-year Catalog, are detected. Using the Swift/BAT and radio 20 cm fluxes, we define a new radio-loudness parameter $R_{X, BAT}$ where radio loud objects have $\log R_{X, BAT} > - 4.7$. Based on this parameter, only radio loud sources are detected by Fermi/LAT. An upper limit to the flux of the undetected sources is derived to be $\sim 2 \times 10^{-11}$ photons cm$^{-2}$ s$^{-1}$, approximate…
Two classes of gamma-ray bursts were identified in the BATSE catalogs characterized by their durations. There were also some indications for the existence of a third type of gamma-ray bursts. Swift satellite detectors have different spectral sensitivity than pre-Swift ones for GRBs. Therefore in this paper we analyze the bursts' duration distribution and also the duration-hardness bivariate distribution, published in The First BAT Catalog. Similarly to the BATSE data, to explain the BAT GRBs' duration distribution three components are needed. Although, the relative frequencies of the groups ar…
We present the newly developed broadband transient monitor using the Swift Burst Alert Telescope (BAT) and the MAXI Gas Slit Camera (GSC) data. Our broadband transient monitor monitors high energy transient sources from 2 keV to 200 keV in seven energy bands by combining the BAT (15-200 keV) and the GSC (2-20 keV) data. Currently, the daily and the 90-minute (one orbit) averaged light curves are available for 106 high energy transient sources. Our broadband transient monitor is available to the public through our web server, http://yoshidalab.mydns.jp/bat_gsc_trans_mon/, for a wider use by the…
The Swift Burst Alert Telescope (BAT) hard X-ray transient monitor tracks more than 700 galactic and extragalactic sources on time scales ranging from a single Swift pointing (approximately 20 minutes) to one day. The monitored sources include all objects from the Fermi LAT bright source list which are either identified or which have a 95% error confidence radius of less than eight arc minutes. We report on the detection statistics of these sources in the BAT monitor both before and after the launch of Fermi.
Using the gamma-ray bursts simultaneously detected by Swift/BAT and Fermi/GBM we performed a joint spectral and temporal analysis of the prompt emission data and confirm the rough correlation between the BAT-band photon index Gamma_BAT and the peak spectral energy Epeak. With the redshift known sub-sample, we derived the isotropic gamma-ray energy E_gamma,iso and also confirm the E_gamma,iso - Epeak,rest relation, with a larger scatter than the Amati sample but consistent with GBM team analyses. We also compare the T_90 values derived in the GBM band with those derived in the BAT band and find…
Studies of \textit{BATSE} bursts \citep{kouveliotou:93} have resulted in the widespread adoption of a two-group categorization: long bursts (those with durations $\geq 2$ seconds) and short bursts (those with durations $\leq 2$ seconds). This categorization, one must recall, used the observed $T_{90}$ time durations for bursts (during which 90\% of a burst's fluence is measured). In this work, we have explored two ideas: 1) a statistical search for a possible third, intermediate category of bursts (between the "short" and the "long" ones) among 2041 \textit{BATSE} GRBs and 757 \textit{Swift/BA…
A sample of 286 gamma-ray bursts (GRBs) detected by the Swift satellite and 358 GRBs detected by the RHESSI satellite are studied statistically. Previously published articles, based on the BATSE GRB Catalog, claimed the existence of an intermediate subgroup of GRBs with respect to duration. We use the statistical chi^2 test and the F-test to compare the number of GRB subgroups in our databases with the earlier BATSE results. Similarly to the BATSE database, the short and long subgroups are well detected in the Swift and RHESSI data. However, contrary to the BATSE data, we have not found a stat…
We present the Second Palermo Swift-BAT hard X-ray catalogue obtained by analysing data acquired in the first 54 months of the Swift mission. Using our software dedicated to the analysis of data from coded mask telescopes, we analysed the BAT survey data in three energy bands (15-30 keV, 15-70 keV, 15-150 keV), obtaining a list of 1256 detections above a significance threshold of 4.8 standard deviations. The identification of the source counterparts is pursued using two strategies: the analysis of field observations of soft X-ray instruments and cross-correlation of our catalogue with source d…
Swift/BAT and RXTE/ASM observations have monitored the X-ray binary system Her X-1 for approximately 14.5 years each, and both were monitoring Her X-1 for a period of ~5.5 years. Here we study the 35-day cycle using these observations. Using a cross-correlation method we find the times of peaks of the 35-day cycles for ~150 cycles observed by Swift/BAT and ~150 cycles observed by RXTE/ASM. These cycles include ~60 observed with both instruments. The noise level of the RXTE/ASM measurements is larger than that of Swift/BAT, resulting in larger uncertainty in peak times. The distribution of 35-d…
The observed durations of prompt gamma-ray emission from gamma-ray bursts (GRBs) are often used to infer the progenitors and energetics of the sources. Inaccurate duration measurements will have a significant impact on constraining the processes powering the bursts. The "tip-of-the-iceberg" effect describes how the observed signal is lost into background noise; lower instrument sensitivity leads to higher measurement bias. In this study, we investigate how observing conditions, such as the number of enabled detectors, background level, and incident angle of the source relative to the detector …
The reflection hump is a prominent feature in the hard X-ray spectrum of active galactic nuclei (AGN). Its exact shape and its correlation to other quantities provide valuable information about the inner and outer regions of an AGN. Our main goal is to study the reflection hump in a large sample of nearby AGN. We aim to investigate the evolution of reflection with absorption and its correlation with the spectral index. We analysed archived NuSTAR observations of the 70-month BAT catalogue AGN. By performing a detailed spectral analysis, we were able to constrain the spectral parameters and to …
We quantify the luminosity contribution of active galactic nuclei (AGN) to the 12 $μ$m, mid-infrared (MIR; 5-38 $μ$m), and the total IR (5-1000 $μ$m) emission in the local AGN detected in the all-sky 70-month Swift/Burst Alert Telescope (BAT) ultra hard X-ray survey. We decompose the IR spectral energy distributions (SEDs) of 587 objects into AGN and starburst components using AGN torus and star-forming galaxy templates. This enables us to recover the AGN torus emission also for low-luminosity end, down to $\log (L_{14-150}/{\rm erg}~{\rm s}^{-1}) \simeq 41$, which typically have significant h…
In this paper we make an attempt to combine the two kinds of data from the Swift-XRT instrument (windowed timing and photon counting modes) and the from BAT. A thorough desription of the applied procedure will be given. We apply various binning techniques to the different data: Bayes blocks, exponential binning and signal-to-noise type of binning. We present a handful of lightcurves and some possible applications.
We report Swift/BAT survey observations of the Tycho's supernova remnant, performed over a period of 104 months since the mission's launch. The remnant is detected with high significance (>10 sigma) below 50 keV. We detect significant hard X-ray emission in the 60-85 keV band, above the continuum level predicted by a simple synchrotron model. The location of the observed excess is consistent with line emission from radioactive Titanium-44, so far reported only for Type II supernova explosions. We discuss the implications of these results in the context of the galactic supernova rate, and nucle…
The multi-messenger discovery of gravitational waves (GWs) and light from the binary neutron star (NS) merger GW170817, associated with Gamma-Ray Burst (GRB) 170817A and kilonova AT2017gfo, has marked the start of a new era in astrophysics. GW170817 has confirmed that binary NS mergers are progenitors of at least some short GRBs. The peculiar properties of the GRB 170817A radio afterglow, characterized by a delayed onset related to the off-axis geometry, have also demonstrated how some nearby short GRBs may not be identified as such with standard short-timescale electromagnetic follow-up obser…
A comprehensive study is given to short gamma-ray bursts (sGRBs) in the third Swift/BAT GRB Catalog from December 2004 to July 2019. We examine in details the temporal properties of the three components in the prompt gamma-ray emission phase, including precursors, main peaks and extended emissions (EE). We investigate the similarity of the main peaks between one-component and two-component sGRBs. It is found that there is no substantial difference among their main peaks. Importantly, comparisons are made between in the single-peaked sGRBs and the double-peaked sGRBs. It is found that our resul…
We present a re-analysis of the Swift Burst Alert Telescope (BAT) data around the radio detection of FRB 131104. Possible evidence of a gamma-ray counterpart was presented by DeLaunay et al. However, based on our analysis using all the available BAT data, no significant emission is found in either the temporal or the image domain. We place a 5~sigma fluence upper limit of 3.3 $\times$ 10$^{-6}$ erg cm$^{-2}$ and 2.7 $\times$ 10$^{-6}$ erg cm$^{-2}$ (15-150 keV) with an integration time of 300 s assuming a simple power-law spectrum with photon index of -1.2 and -2.0, respectively. Our result do…
Compact binary system mergers are expected to generate gravitational radiation detectable by ground-based interferometers. A subset of these, the merger of a neutron star with another neutron star or a black hole, are also the most popular model for the production of short gamma-ray bursts (GRBs). The Swift Burst Alert Telescope (BAT) and the Fermi Gamma-ray Burst Monitor (GBM) trigger on short GRBs (SGRBs) at rates that reflect their relative sky exposures, with the BAT detecting 10 per year compared to about 45 for GBM. We examine the SGRB populations detected by Swift BAT and Fermi GBM. We …
Using Gaussian Mixture Model (GMM) and Expectation Maximization Algorithm, we perform an analysis of time duration ($T_{90}$) for \textit{CGRO}/BATSE, \textit{Swift}/BAT and \textit{Fermi}/GBM Gamma-Ray Bursts. The $T_{90}$ distributions of 298 redshift-known \textit{Swift}/BAT GRBs have also been studied in both observer and rest frames. Bayesian Information Criterion has been used to compare between different GMM models. We find that two Gaussian components are better to describe the \textit{CGRO}/BATSE and \textit{Fermi}/GBM GRBs in the observer frame. Also, we caution that two groups are e…
We present the catalog of sources detected in the first 22 months of data from the hard X-ray survey (14--195 keV) conducted with the BAT coded mask imager on the \swift satellite. The catalog contains 461 sources detected above the 4.8 sigma level with BAT. High angular resolution X-ray data for every source from Swift XRT or archival data have allowed associations to be made with known counterparts in other wavelength bands for over 97% of the detections, including the discovery of ~30 galaxies previously unknown as AGN and several new Galactic sources. A total of 266 of the sources are asso…
Resonant absorption cyclotron features are a key diagnostic tool to directly measure the strength of the magnetic field of accreting neutron stars. However, typical values for cyclotron features lie in the high-energy part of the spectrum between 20 keV and 50 keV, where detection is often damped by the low statistics from single pointed observations. We show that long-term monitoring campaign performed with Swift-BAT of persistently, but faint, accreting high-mass X-ray binaries is able to reveal in their spectra the presence of cyclotron features. We extracted the average Swift-BAT 15-150 ke…
Context: Monitoring of pulse period variations in accreting binary pulsars is an important tool to study the interaction between the magnetosphere of the neutron star and the accretion disk. While the X-ray flux of the brightest X-ray pulsars have been successfully monitored over many years (e.g. with RXTE/ASM, CGRO/BATSE, Swift/BAT), the possibility to monitor their pulse timing properties continuously has so far been very limited. Aims: In our work we show that the Swift/BAT observations can be used to monitor coherent pulsations of bright X-ray sources and use the Swift archival data to stu…
We study the luminosity function of long gamma-ray bursts (LGRBs) using the peak flux obtained from three LGRB samples with known redshifts: (a) a sample of 251 LGRBs from the \textit{Swift/BAT} satellite/instrument; (b) a sample of 37 LGRBs from the \textit{Fermi/GBM} telescope; (c) a sample of 152 GRBs from the \textit{Konus-Wind} instrument. For the \textit{Swift/BAT} and \textit{Fermi/GBM} samples, we use data available on the Swift Burst Analyser websites (\url{http://www.swift.ac.uk/burst_analyser}; \citep{Evans:2010}) and (\url{http://swift.gsfc.nasa.gov/archive/grb/table/}) and on the …
We present the results of our study of the variability time scales of a sample of 27 long Swift Gamma-Ray Bursts (GRBs) with known redshifts. The variability time scale can help our understanding of fundamental GRB parameters such as the initial bulk Lorentz factor and the characteristic size associated with the emission region. Fast Fourier Transform (FFT) techniques were used to extract a noise threshold crossing frequency, which we associate with a variability time scale. The threshold frequency appears to show a correlation with the peak isotropic luminosity of GRBs.
We select 52 long gamma-ray bursts(GRBs) having the precursor activity in the third Swift-BAT catalog. Each episode shown in both the precursors and the main bursts is fitted by the Norris function. We systematically analyze the temporal properties for both the precursors and the main bursts. We do not find any significant difference between the temporal profile of the precursor and that of the main burst. The photon count of the precursor is related to that of the main burst. It is indicated that the precursor and the main burst might have the same physical origin, as the precursor and the ma…
Monitoring of pulse period variations in accreting binary pulsars is an important tool to study the interaction between the magnetosphere of the neutron star and the accretion disk. While the X-ray flux of the brightest X-ray pulsars have been successfully monitored over many years (e.g. with RXTE/ASM, CGRO/BATSE, Swift/BAT), the possibility to monitor their pulse timing properties continuously has so far been very limited. In our work we use Swift/BAT observations to study one of the most enigmatic X-ray pulsars, Hercules X-1. For the first time, a quasi-continuous monitoring of the pulse per…
