Multi-messenger astronomy with INTEGRAL Ferrigno, Carlo; Savchenko, Volodymyr; Coleiro, Alexis ...
New astronomy reviews,
06/2021, Volume:
92
Journal Article
Peer reviewed
Open access
At the time of defining the science objectives of the INTernational Gamma-Ray Astrophysics Laboratory (INTEGRAL), such a rapid and spectacular development of multi-messenger astronomy could not have ...been predicted, with new impulsive phenomena becoming accessible through different channels. Neutrino telescopes have routinely detected energetic neutrino events coming from unknown cosmic sources since 2013. Gravitational wave detectors opened a novel window on the sky in 2015 with the detection of the merging of two black holes and in 2017 with the merging of two neutron stars, followed by signals in the full electromagnetic range. Finally, since 2007, radio telescopes detected extremely intense and short burst of radio waves, known as Fast Radio Bursts (FRBs) whose origin is for most cases extragalactic, but enigmatic. The exceptionally robust and versatile design of the INTEGRAL mission has allowed researchers to exploit data collected not only with the pointed instruments, but also with the active cosmic-ray shields of the main instruments to detect impulses of gamma-rays in coincidence with unpredictable phenomena. The full-sky coverage, mostly unocculted by the Earth, the large effective area, the stable background, and the high duty cycle (85%) put INTEGRAL in a privileged position to give a major contribution to multi-messenger astronomy. In this review, we describe how INTEGRAL has provided upper limits on the gamma-ray emission from black-hole binary mergers, detected a short gamma-ray burst in coincidence with a binary neutron star merger, contributed to define the spectral energy distribution of a blazar associated with a neutrino event, set upper limits on impulsive and steady gamma-ray emission from cosmological FRBs, and detected a magnetar flare associated with fast radio bursting emission.
The gamma-ray burst (GRB) 221009A, with its extreme brightness, has provided the opportunity to explore GRB prompt and afterglow emission behavior on short time scales with high statistics. In ...conjunction with detection up to very high-energy gamma-rays, studies of this event shed light on the emission processes at work in the initial phases of GRBs emission. Using INTEGRAL/IBIS's soft gamma-ray detector, PICsIT (200-2600 keV), we studied the temporal and spectral evolution during the prompt phase and the early afterglow period. We found a "flux-tracking" behavior with the source spectrum "softer" when brighter. However the relationship between the spectral index and the flux changes during the burst. The PICsIT light curve shows afterglow emission begins to dominate at ~ T0 + 630s and decays with a slope of 1.6 +/- 0.2, consistent with the slopes reported at soft X-rays.
The Gamma-ray Burst Monitor (GBM) on board Fermi has been providing continuous data to the astronomical community since 2008 August 12. In this paper, we present the results of the analysis of the ...first three years of these continuous data using the Earth occultation technique to monitor a catalog of 209 sources. From this catalog, we detect 99 sources, including 40 low-mass X-ray binary/neutron star systems, 31 high-mass X-ray binary/neutron star systems, 12 black hole binaries, 12 active galaxies, and 2 other sources, plus the Crab Nebula, and the Sun. Nine of these sources are detected in the 100-300 keV band, including seven black hole binaries, the active galaxy Cen A, and the Crab. The Crab and Cyg X-1 are also detected in the 300-500 keV band. GBM provides complementary data to other sky-monitors below 100 keV and is the only all-sky monitor above 100 keV. Up-to-date light curves for all of the catalog sources can be found online.
On 2 September 2017 MAXI J1535-571 went into outburst and peaked at ~5 Crab in the 2-20 keV energy range. Early in the flare INTEGRAL performed Target of Opportunity pointings and monitored the ...source as it transitioned from the hard state to the soft state. Using quasi-simultaneous observations from MAXI/GSC and INTEGRAL/SPI, we studied the temporal and spectral evolution of MAXI J1535-571 in the 2-500 keV range. Early spectra show a Comptonized spectrum and a high-energy component dominant above ~150 keV. CompTT fits to the SPI data found electron temperatures (kTe) evolves from ~31 keV to 18 keV with a tied optical depth (tau ~ 0.85) or tau evolving from ~1.2-0.65 with a tied kTe (~24 keV). To investigate the nature of the high-energy component, we performed a spectral decomposition of the 100-400 keV energy band. The CompTT flux varies significantly during the hard state while the high-energy component flux is consistent with a constant flux. This result suggests that the two components originate from different locations, which favors a jet origin interpretation for the high-energy component over a hybrid corona interpretation. Lastly, two short rebrightenings during the hard-to-soft transition are compared to similar events reported in MAXI J1820+070.
The question of the origin of the hard X-ray/soft gamma-ray emission in Centaurus A (Cen A) persists despite decades of observations. Results from X-ray instruments suggest a jet origin since the ...implied electron temperature (kT_e) would cause pair production runaway in the corona. In contrast, instruments sensitive to soft gamma-rays report electron temperatures indicating a corona origin may be possible. In this context, we analyzed archival INTEGRAL/IBIS-ISGRI and SPI data and observations from a 2022 Cen A monitoring program. Our analysis did not find any spectral variability. Thus we combined all observations for long-term average spectra, which were fit with a NuSTAR observation to study the 3.5 keV - 2.2 MeV spectrum. Spectral fits using a CompTT model found kT_e ~ 550 keV, near pair-production runaway. The spectrum was also well described by a log-parabola to model synchrotron self-Compton emission from the jet. Additionally, a spectral fit with the 12-year catalog Fermi/LAT spectrum using a log-parabola can explain the data up to ~ 3 GeV. Above ~ 3 GeV, a power-law excess is present, which has been previously reported in LAT/H.E.S.S. analysis. However, including a corona spectral component can also describe the data well. In this scenario, the hard X-rays/soft gamma-rays are due the corona and the MeV to GeV emission is due to the jet.
The hard X-ray/soft gamma-ray sky is highly variable as source intensities can vary on timescales from fractions of a second to years. The type of sources emitting at these energies often include ...compact objects such as white dwarfs, neutron stars, and black holes interacting with the surrounding environment, which enables the study of the properties and characteristics of these exotic objects. Because the interactions with the environment is often through accretion, most of the emission is in X-rays and gamma-rays Frank et al. 1992 making this energy range critical to understanding the relevant physical processes and mechanisms.Hard X-ray/soft gamma-ray (10 keV - 1 MeV) photons are difficult to focus requiring alternative observing techniques to monitor sources in this energy range. One method is the Earth Occultation Technique (EOT) that uses the rapid change in count rate (~sim 10 sec) due to a source passing behind (or out from behind) the Earth to measure source intensity. The EOT has been applied to the Gamma-ray Burst Monitor (GBM) on board the NASA Fermi satellite since its launch in 2008 and has been performing all-sky monitoring of a predetermined catalog of ~200 hard X-ray/soft gamma-ray sources.Because the EOT requires prior knowledge of a source's position for monitoring, I have developed a tomographic imaging method Imaging with a Differential filter using the Earth Occultation Method (IDEOM) to generate all-sky images in search of sources absent from the input catalog to construct a catalog as complete as possible. A complete catalog is important for reducing a source of systematic error as the flux from an unaccounted-for source can be attributed to a known source thus biasing its flux measurement. Approximately 4 years of GBM data have been analyzed to produce all-sky images covering the 12-50 keV, 50-100 keV, and 100-300 keV energy bands with 16 sources being added to the GBM catalog. All-sky images are shown for each energy range along with a table listing the sources detected by IDEOM. Also, the list of sources detected by IDEOM has been compared to those detected by EOT in each energy band.In addition, spectral analysis was performed in the four persistent sources detected by GBM and the Fermi/Large Area Telescope (LAT) (NGC 1275, 3C 273, Cen A, and the Crab) thus providing energy coverage from ~10 keV to ~100 GeV to study the high energy emission processes of these sources. Spectral results from GBM and LAT are presented and shown to be in agreement with previously proposed models in the literature.Finally, I have also developed a transient search algorithm to search for flares and outbursts in the light curves of GBM sources. This algorithm was applied to the ~200 sources in the GBM catalog to search for transient events during the first four years of the mission in four energy bands covering 12-500 keV. The search resulted in 168 transient events found from 65 sources with 7 events detected above 50 keV and 1 event detected above 100 keV (XTE J1752-223). A table of start and stop times are listed for each event and energy band, and example light curves are shown for GK Per, GX 339-4, and XTE J1752-223.
WHEN A STANDARD CANDLE FLICKERS WILSON-HODGE, Colleen A; CHERRY, Michael L; FINGER, Mark H ...
The Astrophysical journal,
2011, Volume:
727, Issue:
2
Journal Article
During its strong outburst of 2015 June/July, the X-ray transient V404 Cygni (= GS2023+338) was observed up to a level of 50 Crab in the hard X-ray domain. We focus here on a particularly intense ...episode preceeding a definitive decline of the source activity. We benefit from large signal-to-noise ratios to investigate the source spectral variability on a timescale of 5 minutes. A Hardness-Intensity study of three broad bands reveals clearly different behaviors at low and high energy (below and above around 100 keV). In particular, on two occasions, the source intensity varies by a factor of 3-4 in amplitude while keeping the same spectral shape. On the other hand, at the end of the major flare, the emission presents a clear anticorrelation between flux and hardness. These behaviors strongly suggest the presence of two spectral components related to emission processes varying in a largely independent way. The first component (E < 100-150 keV) is classically identified with a Comptonizing thermal electron population and requires either an unusual seed photon population or a specific geometry with strong absorbing/reflecting material. The second component is modeled by a cutoff power-law, which could correspond to a second hotter Comptonizing population or another mechanism (synchrotron, non-thermal Comptonization...). In the framework of such a model, Hardness-Intensity and Flux-Flux diagrams clearly demonstrate that the source evolution follows a well organized underlying scheme. They reveal unique information about the Hard X-ray emission processes and connections between them.
Giant flares, short explosive events releasing up to 10\(^{47}\) erg of energy in the gamma-ray band in less than one second, are the most spectacular manifestation of magnetars, young neutron stars ...powered by a very strong magnetic field, 10\(^{14-15}\) G in the magnetosphere and possibly higher in the star interior. The rate of occurrence of these rare flares is poorly constrained, as only three have been seen from three different magnetars in the Milky Way and in the Large Magellanic Cloud in about 50 years since the beginning of gamma-ray astronomy. This sample can be enlarged by the discovery of extragalactic events, since for a fraction of a second giant flares reach peak luminosities above 10\(^{46}\) erg/s, which makes them visible by current instruments up to a few tens of Mpc. However, at these distances they appear similar to, and difficult to distinguish from, regular short gamma-ray bursts (GRBs). The latter are much more energetic events, 10\(^{50-53}\) erg, produced by compact binary mergers and originating at much larger distances. Indeed, only a few short GRBs have been proposed, with different levels of confidence, as magnetar giant flare candidates in nearby galaxies. Here we report the discovery of a short GRB positionally coincident with the central region of the starburst galaxy M82. Its spectral and timing properties, together with the limits on its X-ray and optical counterparts obtained a few hours after the event and the lack of an associated gravitational wave signal, qualify with high confidence this event as a giant flare from a magnetar in M82.
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