The engines that produce extragalactic fast radio bursts (FRBs), and the mechanism by which the emission is generated, remain unknown. Many FRB models predict prompt multi-wavelength counterparts, which can be used to refine our knowledge of these fundamentals of the FRB phenomenon. However, several previous targeted searches for prompt FRB counterparts have yielded no detections, and have additionally not reached sufficient sensitivity with respect to the predictions. In this work, we demonstrate a technique to estimate the ratio, $η$, between the energy outputs of FRB counterparts at various wavelengths and the radio-wavelength emission. Our technique combines the fluence distribution of the FRB population with results from several wide-field blind surveys for fast transients from the optical to the TeV bands. We present constraints on $η$ that improve upon previous observations even in the case that all unclassified transient events in existing surveys are FRB counterparts. In some scenarios for the FRB engine and emission mechanism, we find that FRB counterparts should have already been detected, thus demonstrating that our technique can successfully test predictions for $η$. However, it is possible that FRB counterparts are lurking amongst catalogs of unclassified transient events. Although our technique is robust to the present uncertainty in the FRB fluence distribution, its ultimate application to accurately estimate or bound $η$ will require the careful analysis of all candidate fast-transient events in multi-wavelength survey data sets.
Aims: Drawing an analogy with Active Galactic Nuclei, we investigate the one-zone SSC model of Gamma Ray Bursts afterglows in the presence of electron injection and cooling both by synchrotron and SSC losses. Methods: We solve the spatially averaged kinetic equations which describe the simultaneous evolution of particles and photons, obtaining the multi-wavelength spectrum as a function of time. We back up our numerical calculations with analytical solutions of the equations using various profiles of the magnetic field evolution under certain simplifying assumptions. Results: We apply the mode…
This article presents the early results of synchronous multiwavelength observations of one of the brightest gamma-ray bursts (GRBs) GRB 160625B with the detailed continuous fast optical photometry of its optical counterpart obtained by MASTER and with hard X-ray and gamma-ray emission, obtained by the Lomonosov and Konus-Wind spacecraft. The detailed photometry led us to detect the quasi-periodical emission components in the intrinsic optical emission. As a result of our analysis of synchronous multiwavelength observations, we propose a three-stage collapse scenario for this long and bright GR…
We present the results of a multiwavelength campaign of FRB 20201124A, the third closest repeating fast radio burst recently localized in a nearby (z=0.0978) galaxy. Deep VLA observations led to the detection of quiescent radio emission, also marginally visible in X-rays with Chandra. Imaging at 22 GHz allowed us to resolve the source on a scale of $\gtrsim$ 1 arcsec and locate it at the position of the FRB, within an error of 0.2 arcsec. EVN and e-MERLIN observations sampled small angular scales, from 2 to 100 mas, providing tight upper limits on the presence of a compact source and evidence …
PSR J2032+4127 has recently been identified as being in a long period (45-50 years) binary in a highly eccentric orbit with the Be star MT91 213. Periastron is due to occur in November 2017 and this rare occurrence has prompted a multiwavelength monitoring campaign to determine if the system is a gamma-ray binary, and, if so, to study what would be only the second gamma-ray binary with a known compact object. In the same direction as TeV J2032+4130, gamma-ray emission from this binary system could be related to the extended very high energy gamma-ray emission from that region. As part of this …
The spectra of fast radio bursts (FRBs) encode valuable information about the source's local environment, underlying emission mechanism(s), and the intervening media along the line of sight. We present results from a long-term multiwavelength radio monitoring campaign of two repeating FRB sources, FRB 121102 and FRB 180916.J0158+65, with the NASA Deep Space Network (DSN) 70-m radio telescopes (DSS-63 and DSS-14). The observations of FRB 121102 were performed simultaneously at 2.3 and 8.4 GHz, and spanned a total of 27.3 hr between 2019 September 19 and 2020 February 11. We detected 2 radio bur…
The Fermi-LAT unassociated sources represent some of the most enigmatic gamma-ray sources in the sky. Observations with the Swift-XRT and -UVOT telescopes have identified hundreds of likely X-ray and UV/optical counterparts in the uncertainty ellipses of the unassociated sources. In this work we present spectral fitting results for 205 possible X-ray/UV/optical counterparts to 4FGL unassociated targets. Assuming that the unassociated sources contain mostly pulsars and blazars, we develop a neural network classifier approach that applies gamma-ray, X-ray, and UV/optical spectral parameters to y…
We use high-resolution relativistic MHD simulations coupled with a radiative transfer code to compute multiwavelength afterglow light curves of magnetized ejecta of gamma-ray bursts interacting with a uniform circumburst medium. The aim of our study is to determine how the magnetization of the ejecta at large distance from the central engine influences the afterglow emission, and to assess whether observations can be reliably used to infer the strength of the magnetic field. We find that, for typical parameters of the ejecta, the emission from the reverse shock peaks for magnetization $σ_0 \si…
GRB 110721A was detected by the Gamma-ray Burst Monitor and the Large Area Telescope (LAT) onboard the Fermi satellite and the Gamma-ray Burst Polarimeter onboard the IKAROS solar mission. Previous analysis done of this burst showed: i) a linear polarization signal with position angle stable ($ϕ_p= 160^\circ\pm11$) and high degree of $Π=84^{+16}_{-28}$, ii) an extreme peak energy of a record-breaking at 15$\pm$2 MeV, and iii) a subdominant prompt thermal component observed right after the onset of this burst. In this paper, the LAT data around the reported position of GRB 110721A are analysed …
The origin and phenomenology of the Fast Radio Burst (FRB) remains unknown despite more than a decade of efforts. Though several models have been proposed to explain the observed data, none is able to explain alone the variety of events so far recorded. The leading models consider magnetars as potential FRB sources. The recent detection of FRBs from the galactic magnetar SGR J1935+2154 seems to support them. Still, emission duration and energetic budget challenge all these models. Like for other classes of objects initially detected in a single band, it appeared clear that any solution to the …
Fast radio bursts (FRBs) are one of the most tantalizing mysteries of the radio sky; their progenitors and origins remain unknown and until now no rapid multiwavelength follow-up of an FRB has been possible. New instrumentation has decreased the time between observation and discovery from years to seconds, and enables polarimetry to be performed on FRBs for the first time. We have discovered an FRB (FRB 140514) in real-time on 14 May, 2014 at 17:14:11.06 UTC at the Parkes radio telescope and triggered follow-up at other wavelengths within hours of the event. FRB 140514 was found with a dispers…
We conduct X-ray spectral fits on 184 likely counterparts to Fermi-LAT 3FGL unassociated sources. Characterization and classification of these sources allows for more complete population studies of the high-energy sky. Most of these X-ray spectra are well fit by an absorbed power law model, as expected for a population dominated by blazars and pulsars. A small subset of 7 X-ray sources have spectra unlike the power law expected from a blazar or pulsar and may be linked to coincident stars or background emission. We develop a multiwavelength machine learning classifier to categorize unassociate…
Stellar sources of gamma rays are one of the front lines in modern astrophysics whose understanding can benefit from observational tools not originally designed for their study. We take advantage of the high precision photometric capabilities of present-day space facilities to obtain a new perspective on the optical behavior of the X-ray and gamma-ray binary LS I +61 303. Previously unknown phenomena whose effects manifest with amplitudes below 0.01 magnitude can now be clearly observed and studied. Our work is mainly based on the analysis of optical and gamma-ray archival data and uses the to…
We investigate the long GRB140629A through multiwavelength observations, which cover optical, infrared and X-rays between 40s and 3yr after the burst, to derive the properties of the dominant jet and its host galaxy. Polarisation observations by the MASTER telescope indicate that this burst is weakly polarised. The optical spectrum contains absorption features, from which we confirm the redshift of the GRB as originating at z=2.276. We performed spectral fitting of the X-rays to optical afterglow data and find there is no strong spectral evolution. We determine the hydrogen column density to b…
Predicting Multiwavelength Emission Associated with X-Ray Flares and Extended Emission of Gamma-Ray Bursts
Astronomical Institute, Graduate School of Science, Tohoku University（东北大学理学研究科天文学研究所）；Department of Earth Science and Astronomy, Graduate School of Arts and Sciences, The University of Tokyo（东京大学大学院综合文化研究科地球惑星科学专攻）；Frontier Research Institute for Interdisciplinary Sciences, Tohoku University（东北大学跨学科前沿研究院）；Department of Astronomy and Astrophysics, The Pennsylvania State University（宾夕法尼亚州立大学天文与天体物理系）；Institute for Gravitation and the Cosmos, The Pennsylvania State University（宾夕法尼亚州立大学引力与宇宙学研究所）；Center for Gravitational Physics and Quantum Information, Yukawa Institute for Theoretical Physics, Kyoto University（京都大学汤川理论物理研究所引力物理学与量子信息研究中心）；Key Laboratory of Particle Astrophysics and Experimental Physics Division and Computing Center, Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所粒子天体物理重点实验室及计算中心）；TIANFU Cosmic Ray Research Center（天府宇宙线研究中心）
A review is given on the various aspects of gamma-ray burst afterglow observations, and the inferences derived from the data. After a short history of optical transient search and the BeppoSAX discoveries, the main topics included are prompt multiwavelength emission, dark bursts, spectral lines line and continuum variability, the early light curve behaviour, jet breaks, X-ray flares, late afterglow features, polarization, and orphan afterglows.
Multiwavelength properties of short gamma ray bursts with extended emission observed by Swift
Università degli Studi di Milano（米兰大学）；INAF – Osservatorio Astronomico di Brera（意大利国家天体物理研究所布雷拉天文台）；Ioffe Institute（约费研究所）；INFN Sezione di Milano（意大利国家核物理研究所米兰分部）
The X-ray binary system 4U 2206+54 hides many mysteries. Among them, the surprising behavior of both of its components: the O9.5 dwarf star BD+53$^\circ$2790 and a slowly rotating neutron star. BD+53$^\circ$2790 misled the astronomers showing itself very likely as a Be star. However, a deeper spectral analysis and more intense monitoring, revealed that the real picture was a bit more complicated: a) Although it shows evidence of a circumstellar envelope, its observable properties differ from those typical envelopes in Be stars. b) Comparison with spectral standards and models indicates a possi…
We report on the multiwavelength observations of the bright, long gamma-ray burst \GRB, by the \Fermi and \Swift observatories, and by the MOA and GROND optical telescopes. The analysis of the prompt phase reveals that \GRB shares many features with bright Large Area Telescope bursts observed by \Fermi during the first 3 years on-orbit: a light curve with short time variability across the whole energy range during the prompt phase, delayed onset of the emission above 100 MeV, extra power law component and temporally extended high-energy emission. In addition, this the first GRB for which simul…
The candidate PeVatron MGRO J1908+06, which shows a hard spectrum beyond 100 TeV, is one of the most peculiar $γ$-ray sources in the Galactic plane. Its complex morphology and some possible counterparts spatially related with the VHE emission region, preclude to distinguish between a hadronic or leptonic nature of the $γ$-ray emission. In this paper we illustrate a new multiwavelength analysis of MGRO J1908+06, with the aim to shed light on its nature and the origin of its ultra high-energy emission. We performed an analysis of the $^{12}$CO and $^{13}$CO molecular line emission demonstrating …
Context. Multi-wavelength observations of gamma-ray burst (GRB) afterglows provide important information about the activity of their central engines and their environments. In particular, the short timescale variability, such as bumps and/or rebrightening features visible in the multi-wavelength light curves, is still poorly understood. Aims. We analyze the multi-wavelength observations of the GRB100219A afterglow at redshift 4.7. In particular, we attempt to identify the physical origin of the late achromatic flares/bumps detected in the X-ray and optical bands. Methods. We present ground-bas…
We propose an explanation for the far-infrared/radio correlation of galaxies in terms of the energy balance of the interstellar medium and determine the flux from high-energy photons and neutrinos from starburst galaxies. We present a catalog of the 127 brightest starburst galaxies with redshifts of z<0.03. In order to investigate the correlation between radio- and far-infrared emission, we apply the leaky box approximation. Further, we derive photon- and neutrino spectra from proton-proton interactions in supernova remnants (SNRs). Here, we assume that a fraction of the SNR's energy is transf…
A rare group of high mass X-ray binaries (HMXBs) are known that also exhibit MeV, GeV, and/or TeV emission ("gamma-ray binaries"). Expanding the sample of gamma-ray binaries and identifying unknown Fermi sources are currently of great interest to the community. Based upon their positional coincidence with the unidentified Fermi sources 1FGL J1127.7-6244c and 1FGL J1808.5-1954c, the Be stars HD 99771 and HD 165783 have been proposed as gamma-ray binary candidates. During Fermi Cycle 4, we have performed multiwavelength observations of these sources using XMM-Newton and the CTIO 1.5m telescope. …
We report on a search for high-energy counterparts to fast radio bursts (FRBs) with the Fermi Gamma-ray Burst Monitor (GBM), Fermi Large Area Telescope (LAT), and the Neil Gehrels Swift Observatory Burst Alert Telescope (BAT). We find no significant associations for any of the 23 FRBs in our sample, but report upper limits to the high-energy fluence for each on timescales of 0.1, 1, 10, and 100 s. We report lower limits on the ratio of the radio to high-energy fluence, $\frac{f_{r}}{f_γ}$, for timescales of 0.1 and 100 s. We discuss the implications of our non-detections on various proposed pr…
There is significant interest in the models for production of short gamma-ray bursts. Until now, the number of known short gamma-ray bursts with multi-wavelength afterglows has been small. While the {\it Fermi} Gamma-Ray Burst Monitor detects many gamma-ray bursts relative to the Neil Gehrels {\it Swift} Observatory, the large localization regions makes the search for counterparts difficult. With the Zwicky Transient Facility recently achieving first light, it is now fruitful to use its combination of depth ($m_\textrm{AB} \sim 20.6$), field of view ($\approx$ 47 square degrees), and survey ca…
We searched optical/UV/IR counterparts of seven supersoft X-ray sources (SSS) in M31 in the Hubble Space Telescope (HST) "Panchromatic Hubble Andromeda Treasury" (PHAT) archival images and photometric catalog. Three of the SSS were transient, the other four are persistent sources. The PHAT offers the opportunity to identify SSS hosting very massive white dwarfs that may explode as type Ia supernovae in single degenerate binaries, with magnitudes and color indexes typical of symbiotic stars, high mass close binaries, or systems with optically luminous accretion disks. We find evidence that the …
We discuss identification of possible counterparts and persistent sources related to Fast Radio Bursts (FRBs) in the framework of the model of supergiant pulses from young neutron stars with large spin-down luminosities. In particular, we demonstrate that at least some of sources of FRBs can be observed as ultraluminous X-ray sources (ULXs). At the moment no ULXs are known to be coincident with localization areas of FRBs. We searched for a correlation of FRB positions with galaxies in the 2MASS Redshift survey catalogue. Our analysis produced statistically insignificant overabundance ($p$-valu…
The discovery of a luminous radio burst, FRB 200428, with properties similar to those of fast radio bursts (FRB), in coincidence with an X-ray flare from the Galactic magnetar SGR 1935+2154, supports magnetar models for cosmological FRBs. The burst's X-ray to radio fluence ratio, as well as the X-ray spectral shape and peak energy, are consistent with FRB 200428 being the result of an ultra-relativistic shock (powered, e.g., by an ejected plasmoid) propagating into a magnetized baryon-rich external medium; the shock simultaneously generates X-ray/gamma-rays via thermal synchrotron emission fro…
HESS J1809-193 is an extended TeV gamma-ray source in the Galactic Plane. Multiwavelength observations of the HESS J1809-193 field reveal a complex picture. We present results from three CXO and two Suzaku observations of a region in the northeastern outskirts of HESS J1809-193, where enhanced TeV emission has been reported. Our analysis also includes GeV gamma-ray and radio data. One of the X-ray sources in the field is the X-ray binary XTE J1810-189, for which we present the outburst history from multiple observatories and confirm that XTE J1810-189 is a strongly variable type I X-ray burste…
This work extends a contemporaneous effort (Panaitescu & Vestrand 2022) to study the properties of the lower-energy counterpart synchrotron emission produced by the cooling of relativistic Gamma-Ray Burst (GRB) electrons through radiation (synchrotron and self-Compton) emission and adiabatic losses. We derive the major characteristics (pulse duration, lag-time after burst, brightness relative to the burst) of the Prompt Optical Counterpart (POC) accompanying GRBs. Depending on the magnetic field life-time, duration of electron injection, and electron transit-time Dto from hard X-ray (GRB) to o…
Fast radio bursts are bright, millisecond-scale radio flashes of yet unknown physical origin. Recently, their extragalactic nature has been demonstrated and an increasing number of the sources have been found to repeat. Young, highly magnetized, isolated neutron stars - magnetars - have been suggested as the most promising candidates for fast radio burst progenitors owing to their energetics and high X-ray flaring activity. Here we report the detection with the Konus-Wind of a hard X-ray event of April 28, 2020, temporarily coincident with a bright, two-peak radio burst from the Galactic magne…
The three gravitational wave events detected by LIGO are opening a new era for high- energy astrophysics. Nevertheless, location of such events remain unknown. A promising solution to the localization problem is to find an electromagnetic (EM) counterpart of GW- generating events, such as binary neutron star mergers (BNS). Indeed, their GW emission will be above sensitivity threshold in the near future. BNS are also considered as short Gamma Ray Bursts (sGRB) progenitors. However, sGRB are highly beamed. In this study, we will therefore focus on another EM counterpart candidate: the cocoon aft…
Fast radio bursts (FRBs) are millisecond-scale radio pulses, which originate in distant galaxies and are produced by unknown sources. The mystery remains partially because of the typical difficulty in localising FRBs to host galaxies. Accurate localisations delivered by the Commensal Real-time ASKAP Fast Transients (CRAFT) survey now provide an opportunity to study the host galaxies and potential transient counterparts of FRBs at a large range of wavelengths. In this work, we investigate whether the first three FRBs accurately localised by CRAFT have supernova-like transient counterparts. We o…
One of the most powerful gamma-ray bursts, GRB 130427A was swiftly detected from GeV $γ$-rays to optical wavelengths. In the GeV band, the Large Area Telescope (LAT) on board the Fermi Gamma-Ray Space Telescope observed the highest-energy photon ever recorded of 95 GeV, and a bright peak in the early phase followed by emission temporally extended for more than 20 hours. In the optical band, a bright flash with a magnitude of $7.03\pm 0.03$ in the time interval from 9.31 s to 19.31 s after the trigger was reported by RAPTOR in r-band. We study the origin of the GeV $γ$-ray emission, using the m…
The non-repeating fast radio bursts (FRBs) could arise from catastrophic stellar explosions or magnetar giant flares, so relativistic blast waves might be produced in these events. Motivated by this, we here search for GeV counterparts to all non-repeating FRBs with Fermi Large Area Telescope (LAT), including FRB 131104 that is claimed to be possibly associated with a gamma-ray transient candidate detected by Swift Burst Alert Telescope (BAT). FRB 131104 enters the field of view (FoV) of LAT ~5000s after the burst time, so we are only able to search for the GeV afterglow emission during this p…
SAX J2224.9+5421 is an extraordinary neutron star low-mass X-ray binary. Albeit discovered when it exhibited a ~10-s long thermonuclear X-ray burst, it had faded to a 0.5-10 keV luminosity of Lx<8E32 (D/7.1 kpc)^2 erg/s only ~8 hr later. It is generally assumed that neutron stars are quiescent (i.e., not accreting) at such an intensity, raising questions about the trigger conditions of the X-ray burst and the origin of the faint persistent emission. We report on a ~51 ks XMM-Newton observation aimed to find clues explaining the unusual behavior of SAX J2224.9+5421. We identify a likely counter…
The recent discovery of a Galactic fast radio burst (FRB) occurring simultaneously with an X-ray burst (XRB) from the Galactic magnetar SGR J1935+2154 implies that at least some FRBs arise from magnetar activities. We propose that FRBs are triggered by crust fracturing of magnetars, with the burst event rate depending on the magnetic field strength in the crust. Since the crust fracturing rate is relatively higher in polar regions, FRBs are preferred to be triggered near the directions of multipolar magnetic poles. Crust fracturing produces Alfvén waves, forming a charge starved region in the …
The supermassive black hole Sgr A* is located at the Milky Way center. We studied its flaring activity close to the DSO/G2 pericenter passage to constrain the physical properties and origin of the flares. Simultaneous/coordinated observations were made in 2014 Feb-Apr with XMM-Newton, HST/WFC3, VLT/SINFONI, VLA and CARMA. We detected 2 X-ray and 3 NIR flares on Mar. 10 and Apr. 2 with XMM-Newton and HST and 2 NIR flares on Apr. 3 and 4 with VLT. The Mar. 10 X-ray flare has a long rise and a rapid decay. Its NIR counterpart peaked 4320s before the X-ray peak implying a variation in the X-ray-to…
We present a multi-band search for X-ray, optical and $γ$-ray emission of the radio binary millisecond pulsar J1836-2354A, hosted in the globular cluster M22. X-ray emission is significantly detected in two Chandra observations, performed in 2005 and 2014, at a luminosity of $\sim$2-3$\times$10$^{30}$ erg s$^{-1}$, in the 0.5-8 keV energy range. The radio and the X-ray source positions are found consistent within 1$σ$ error box. No detection is found in archival XMM-Newton and Swift/XRT observations, compatible with the Chandra flux level. The low statistics prevents us to assess if the X-ray …
The shock system that produces the afterglow to GRBs consists of a forward- and a reverse-shock. For short GRBs, observational evidence for a reverse-shock has been sparse, however, the afterglow to GRB 160821B requires a reverse-shock at early times to explain the radio observations. GRB 160821B is additionally accompanied by the best-sampled macronova without a gravitational-wave detection, and an interesting late-time X-ray afterglow behaviour indicative of a refreshed-shock. The presence of an observed reverse-shock in an on-axis short GRB means that the reverse-shock should be considered …
The soft gamma-ray repeater candidate SGR 0755$-$2933 was discovered in 2016 by Swift/BAT, which detected a short ($\sim$30 ms) powerful burst typical of magnetars. To understand the nature of the source, we present here an analysis of follow-up observations of the tentative soft X-ray counterpart of the source obtained with Swift/XRT, NuSTAR and Chandra. From our analysis we conclude that, based on the observed counterpart position and properties, it is actually not a soft gamma ray repeater but rather a new high mass X-ray binary. We suggest to refer to it as 2SXPS J075542.5$-$293353. We con…
HESS J1534-571 is a very high energy gamma-ray source that was discovered by the H.E.S.S. observatory and reported as one of several new sources with a shell-like morphology at TeV energies, matching in size and location with the supernova remnant G323.7-1.0 discovered in radio observations by the Molonglo Galactic Plane Survey. Many known TeV shells also show X-ray emission, however, no X-ray counterpart has been seen for HESS J1534-571. The detection of a new GeV source using data from the \emph{Fermi} satellite that is compatible in extension with the radio supernova remnant and shows a ver…
