Browsing by Author "Baring, M.G."

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    Conservation laws and conversion efficiency in ultraintense laser-overdense plasma interactions
    (AIP Publishing LLC, 2013) Levy, M.C.; Wilks, S.C.; Tabak, M.; Baring, M.G.
    Particle coupling to the oscillatory and steady-state nonlinear force of an ultraintense laser is studied through analytic modeling and particle-in-cell simulations. The complex interplay between these absorption mechanisms—corresponding, respectively, to “hot” electrons and “hole punching” ions—is central to the viability of many ultraintense laser applications. Yet, analytic work to date has focused only on limiting cases of this key problem. In this paper, we develop a fully relativistic model in 1-D treating both modes of ponderomotive light absorption on equitable theoretical footing for the first time. Using this framework, analytic expressions for the conversion efficiencies into hole punching ions and into hot electrons are derived. Solutions for the relativistically correct hole punching velocity and the hot electron Lorentz factor are also calculated. Excellent agreement between analytic predictions and particle-in-cell simulations is demonstrated, and astrophysical analogies are highlighted.
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    CONSTRAINING THE HIGH-ENERGY EMISSION FROM GAMMA-RAY BURSTS WITH FERMI
    (The American Astronomical Society, 2012) Baring, M.G.; The Fermi Large Area Telescope Team
    We examine 288 gamma-ray bursts (GRBs) detected by the Fermi Gamma-ray Space Telescope’s Gamma-ray Burst Monitor (GBM) that fell within the field of view of Fermi’s Large Area Telescope (LAT) during the first 2.5 years of observations, which showed no evidence for emission above 100 MeV.We report the photon flux upper limits in the 0.1–10 GeV range during the prompt emission phase as well as for fixed 30 s and 100 s integrations starting from the trigger time for each burst.We compare these limits with the fluxes that would be expected from extrapolations of spectral fits presented in the first GBM spectral catalog and infer that roughly half of the GBM-detected bursts either require spectral breaks between the GBM and LAT energy bands or have intrinsically steeper spectra above the peak of the νFν spectra (Epk). In order to distinguish between these two scenarios, we perform joint GBM and LAT spectral fits to the 30 brightest GBM-detected bursts and find that a majority of these bursts are indeed softer above Epk than would be inferred from fitting the GBM data alone. Approximately 20% of this spectroscopic subsample show statistically significant evidence for a cutoff in their high-energy spectra, which if assumed to be due to γγ attenuation, places limits on the maximum Lorentz factor associated with the relativistic outflow producing this emission. All of these latter bursts have maximum Lorentz factor estimates that are well below the minimum Lorentz factors calculated for LAT-detected GRBs, revealing a wide distribution in the bulk Lorentz factor of GRB outflows and indicating that LAT-detected bursts may represent the high end of this distribution.
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    Development of an interpretive simulation tool for the proton radiography technique
    (AIP Publishing LLC., 2015) Levy, M.C.; Ryutov, D.D.; Wilks, S.C.; Ross, J.S.; Huntington, C.M.; Fiuza, F.; Martinez, D.A.; Kugland, N.L.; Baring, M.G.; Park, H.-S.
    Proton radiography is a useful diagnostic of high energy density (HED) plasmas under active theoretical and experimental development. In this paper, we describe a new simulation tool that interacts realistic laser-driven point-like proton sources with three dimensional electromagnetic fields of arbitrary strength and structure and synthesizes the associated high resolution protonradiograph. The present tool’s numerical approach captures all relevant physics effects, including effects related to the formation of caustics. Electromagnetic fields can be imported from particle-in-cell or hydrodynamic codes in a streamlined fashion, and a library of electromagnetic field “primitives” is also provided. This latter capability allows users to add a primitive, modify the field strength, rotate a primitive, and so on, while quickly generating a high resolution radiograph at each step. In this way, our tool enables the user to deconstruct features in a radiograph and interpret them in connection to specific underlying electromagnetic field elements. We show an example application of the tool in connection to experimental observations of the Weibel instability in counterstreaming plasmas, using ∼108 particles generated from a realistic laser-driven point-like proton source, imaging fields which cover volumes of ∼10 mm3. Insights derived from this application show that the tool can support understanding of HED plasmas.
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    Fermi-LAT Observations of LIGO/Virgo Event GW170817
    (IOP Publishing, 2018) Ajello, M.; Allafort, A.; Axelsson, M.; Baldini, L.; Barbiellini, G.; Baring, M.G.; Bastieri, D.; Bellazzini, R.; Berenji, B.; Bissaldi, E.; Blandford, R.D.; Bloom, E.D.; Bonino, R.; Bottacini, E.; Brandt, T.J.; Bregeon, J.; Bruel, P.; Buehler, R.; Burnett, T.H.; Buson, S.; Cameron, R.A.; Caputo, R.; Caraveo, P.A.; Casandjian, J.M.; Cavazzuti, E.; Chekhtman, A.; Cheung, C.C.; Chiang, J.; Chiaro, G.; Ciprini, S.; Cohen-Tanugi, J.; Cominsky, L.R.; Costantin, D.; Cuoco, A.; Cutini, S.; D’Ammando, F.; de Palma, F.; Di Lalla, N.; Di Mauro, M.; Di Venere, L.; Dubois, R.; Dumora, D.; Favuzzi, C.; Ferrara, E.C.; Franckowiak, A.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Giglietto, N.; Gill, R.; Giordano, F.; Giroletti, M.; Glanzman, T.; Granot, J.; Green, D.; Grenier, I.A.; Grondin, M.-H.; Guillemot, L.; Guiriec, S.; Harding, A.K.; Hays, E.; Horan, D.; Imazato, F.; Jóhannesson, G.; Kamae, T.; Kensei, S.; Kocevski, D.; Kuss, M.; La Mura, G.; Larsson, S.; Latronico, L.; Li, J.; Longo, F.; Loparco, F.; Lovellette, M.N.; Lubrano, P.; Magill, J.D.; Maldera, S.; Manfreda, A.; Mazziotta, M.N.; Michelson, P.F.; Mizuno, T.; Moiseev, A.A.; Monzani, M.E.; Moretti, E.; Morselli, A.; Moskalenko, I.V.; Negro, M.; Nuss, E.; Ojha, R.; Omodei, N.; Orlando, E.; Ormes, J.F.; Palatiello, M.; Paliya, V.S.; Paneque, D.; Persic, M.; Pesce-Rollins, M.; Petrosian, V.; Piron, F.; Porter, T.A.; Principe, G.; Racusin, J.L.; Rainò, S.; Rando, R.; Razzano, M.; Razzaque, S.; Reimer, A.; Reimer, O.; Ritz, S.; Rochester, L.S.; Ryde, F.; Parkinson, P.M. Saz; Sgrò, C.; Siskind, E.J.; Spada, F.; Spandre, G.; Spinelli, P.; Suson, D.J.; Tajima, H.; Takahashi, M.; Tak, D.; Thayer, J.G.; Thayer, J.B.; Torres, D.F.; Torresi, E.; Tosti, G.; Troja, E.; Valverde, J.; Venters, T.M.; Vianello, G.; Wood, K.; Yang, C.; Zaharijas, G.
    We present the Fermi Large Area Telescope (LAT) observations of the binary neutron star merger event GW170817 and the associated short gamma-ray burst (SGRB) GRB 170817A detected by the Fermi Gamma-ray Burst Monitor. The LAT was entering the South Atlantic Anomaly at the time of the LIGO/Virgo trigger (t GW) and therefore cannot place constraints on the existence of high-energy (E > 100 MeV) emission associated with the moment of binary coalescence. We focus instead on constraining high-energy emission on longer timescales. No candidate electromagnetic counterpart was detected by the LAT on timescales of minutes, hours, or days after the LIGO/Virgo detection. The resulting flux upper bound (at 95% C.L.) from the LAT is 4.5 × 10−10 erg cm−2 s−1 in the 0.1–1 GeV range covering a period from t GW + 1153 s to t GW + 2027 s. At the distance of GRB 170817A, this flux upper bound corresponds to a luminosity upper bound of 9.7 × 1043 erg s−1, which is five orders of magnitude less luminous than the only other LAT SGRB with known redshift, GRB 090510. We also discuss the prospects for LAT detection of electromagnetic counterparts to future gravitational-wave events from Advanced LIGO/Virgo in the context of GW170817/GRB 170817A.
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    The First Pulse of the Extremely Bright GRB 130427A: A Test Lab for Synchrotron Shocks
    (American Association for the Advancement of Science, 2014) Preece, R.; Burgess, J. Michael; von Kienlin, A.; Bhat, P.N.; Briggs, M.S.; Byrne, D.; Chaplin, V.; Cleveland, W.; Collazzi, A.C.; Connaughton, V.; Diekmann, A.; Fitzpatrick, G.; Foley, S.; Gibby, M.; Giles, M.; Goldstein, A.; Greiner, J.; Gruber, D.; Jenke, P.; Kippen, R.M.; Kouveliotou, C.; McBreen, S.; Meegan, C.; Paciesas, W.S.; Pelassa, V.; Tierney, D.; van der Horst, A.J.; Wilson-Hodge, C.; Xiong, S.; Younes, G.; Yu, H.-F.; Ackermann, M.; Ajello, M.; Axelsson, M.; Baldini, L.; Barbiellini, G.; Baring, M.G.; Bastieri, D.; Bellazzini, R.; Bissaldi, E.; Bonamente, E.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G.A.; Cameron, R.A.; Caraveo, P.A.; Cecchi, C.; Charles, E.; Chekhtman, A.; Chiang, J.; Chiaro, G.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Cominsky, L.R.; Conrad, J.; D'Ammando, F.; de Angelis, A.; de Palma, F.; Dermer, C.D.; Desiante, R.; Digel, S.W.; Di Venere, L.; Drell, P.S.; Drlica-Wagner, A.; Favuzzi, C.; Franckowiak, A.; Fukazawa, Y.; Fusco, P.; Gargano, F.; Gehrels, N.; Germani, S.; Giglietto, N.; Giordano, F.; Giroletti, M.; Godfrey, G.; Granot, J.; Grenier, I.A.; Guiriec, S.; Hadasch, D.; Hanabata, Y.; Harding, A.K.; Hayashida, M.; Iyyani, S.; Jogler, T.; Jóhannesson, G.; Kawano, T.; Knödlseder, J.; Kocevski, D.; Kuss, M.; Lande, J.; Larsson, J.; Larsson, S.; Latronico, L.; Longo, F.; Loparco, F.; Lovellette, M.N.; Lubrano, P.; Mayer, M.; Mazziotta, M.N.; Michelson, P.F.; Mizuno, T.; Monzani, M.E.; Moretti, E.; Morselli, A.; Murgia, S.; Nemmen, R.; Nuss, E.; Nymark, T.; Ohno, M.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orienti, M.; Paneque, D.; Perkins, J.S.; Pesce-Rollins, M.; Piron, F.; Pivato, G.; Porter, T.A.; Racusin, J.L.; Rainò, S.; Rando, R.; Razzano, M.; Razzaque, S.; Reimer, A.; Reimer, O.; Ritz, S.; Roth, M.; Ryde, F.; Sartori, A.; Scargle, J.D.; Schulz, A.; Sgrò, C.; Siskind, E.J.; Spandre, G.; Spinelli, P.; Suson, D.J.; Tajima, H.; Takahashi, H.; Thayer, J.G.; Thayer, J.B.; Tibaldo, L.; Tinivella, M.; Torres, D.F.; Tosti, G.; Troja, E.; Usher, T.L.; Vandenbroucke, J.; Vasileiou, V.; Vianello, G.; Vitale, V.; Werner, M.; Winer, B.L.; Wood, K.S.; Zhu, S.
    Gamma-ray burst (GRB) 130427A is one of the most energetic GRBs ever observed. The initial pulse up to 2.5 seconds is possibly the brightest well-isolated pulse observed to date. A fine time resolution spectral analysis shows power-law decays of the peak energy from the onset of the pulse, consistent with models of internal synchrotron shock pulses. However, a strongly correlated power-law behavior is observed between the luminosity and the spectral peak energy that is inconsistent with curvature effects arising in the relativistic outflow. It is difficult for any of the existing models to account for all of the observed spectral and temporal behaviors simultaneously.
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    GRB110721A: An Extreme Peak Energy and Signatures of the Photosphere
    (The American Astronomical Society, 2012) Baring, M.G.; Axelsson, M.; Baldini, L.; Barbiellini, G.; Bellazzini, R.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Caliandro, G.A.; Cameron, R.A.; Caraveo, P.A.; Cecchi, C.; Chaves, R.C.G.; Chekhtman, A.; Chiang, J.; Claus, R.; Conrad, J.; Cutini, S.; D'Ammando, F.; de Palma, F.; Dermer, C.D.; do Couto e Silva, E.; Drell, P.S.; Favuzzi, C.; Fegan, S.J.; Ferrara, E.C.; Focke, W.B.; Fukazawa, Y.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Giglietto, N.; Giroletti, M.; Godfrey, G.; Guiriec, S.; Hadasch, D.; Hanabata, Y.; Hayashida, M.; Hou, X.; Iyyani, S.; Jackson, M.S.; Kocevski, D.; Kuss, M.; Larsson, J.; Longo, F.; Loparco, F.; Lundman, C.; Mazziotta, M.N.; McEnery, J.E.; Mizuno, T.; Monzani, M.E.; Moretti, E.; Morselli, A.; Murgia, S.; Nuss, E.; Nymark, T.; Ohno, M.; Omodei, N.; Pesce-Rollins, M.; Piron, F.; Pivato, G.; Racusin, J.L.; Rainò, S.; Razzano, M.; Razzaque, S.; Reimer, A.; Roth, M.; Ryde, F.; Sanchez, D.A.; Sgrò, C.; Siskind, E.J.; Spandre, G.; Spinelli, P.; Stamatikos, M.; Tibaldo, L.; Tinivella, M.; Usher, T.L.; Vandenbroucke, J.; Vasileiou, V.; Vianello, G.; Vitale, V.; Waite, A.P.; Winer, B.L.; Wood, K.S.; Burgess, J.M.; Bhat, P.N.; Bissaldi, E.; Briggs, M.S.; Connaughton, V.; Fishman, G.; Fitzpatrick, G.; Foley, S.; Gruber, D.; Kippen, R.M.; Kouveliotou, C.; Jenke, P.; McBreen, S.; McGlynn, S.; Meegan, C.; Paciesas, W.S.; Pelassa, V.; Preece, R.; Tierney, D.; von Kienlin, A.; Wilson-Hodge, C.; Xiong, S.; Pe'er, A.; Pe'er, A.
    GRB110721A was observed by the Fermi Gamma-ray Space Telescope using its two instruments, the Large Area Telescope (LAT) and the Gamma-ray Burst Monitor (GBM). The burst consisted of one major emission episode which lasted for ~24.5 s (in the GBM) and had a peak flux of (5.7 ± 0.2) × 10–5 erg s–1 cm–2. The time-resolved emission spectrum is best modeled with a combination of a Band function and a blackbody spectrum. The peak energy of the Band component was initially 15 ± 2 MeV, which is the highest value ever detected in a GRB. This measurement was made possible by combining GBM/BGO data with LAT Low Energy events to achieve continuous 10-100 MeV coverage. The peak energy later decreased as a power law in time with an index of –1.89 ± 0.10. The temperature of the blackbody component also decreased, starting from ~80 keV, and the decay showed a significant break after ~2 s. The spectrum provides strong constraints on the standard synchrotron model, indicating that alternative mechanisms may give rise to the emission at these energies.
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    Hard X-ray quiescent emission in magnetars via resonant Compton upscattering
    (IOP Publishing, 2017) Baring, M.G.; Wadiasingh, Z.; Gonthier, P.L.; Harding, A.K.
    Non-thermal quiescent X-ray emission extending between 10 keV and around 150 keV has been seen in about 10 magnetars by RXTE, INTEGRAL, Suzaku, NuSTAR and Fermi-GBM. For inner magnetospheric models of such hard X-ray signals, inverse Compton scattering is anticipated to be the most efficient process for generating the continuum radiation, because the scattering cross section is resonant at the cyclotron frequency. We present hard X-ray upscattering spectra for uncooled monoenergetic relativistic electrons injected in inner regions of pulsar magnetospheres. These model spectra are integrated over bundles of closed field lines and obtained for different observing perspectives. The spectral turnover energies are critically dependent on the observer viewing angles and electron Lorentz factor. We find that electrons with energies less than around 15 MeV will emit most of their radiation below 250 keV, consistent with the turnovers inferred in magnetar hard X-ray tails. Electrons of higher energy still emit most of the radiation below around 1 MeV, except for quasi-equatorial emission locales for select pulse phases. Our spectral computations use a new state-of-the-art, spin-dependent formalism for the QED Compton scattering cross section in strong magnetic fields.
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    Identification of an X-Ray Pulsar in the BeXRB System IGR J18219-1347
    (IOP Publishing, 2022) O'Connor, B.; Göğüş, E.; Huppenkothen, D.; Kouveliotou, C.; Gorgone, N.; Townsend, L.J.; Calamida, A.; Fruchter, A.; Buckley, D.A.H.; Baring, M.G.; Kennea, J.A.; Younes, G.; Arzoumanian, Z.; Bellm, E.; Cenko, S.B.; Gendreau, K.; Granot, J.; Hailey, C.; Harrison, F.; Hartmann, D.; Kaper, L.; Kutyrev, A.; Slane, P.O.; Stern, D.; Troja, E.; Horst, A.J. van der; Wijers, R.A.M.J.; Woudt, P.
    We report on observations of the candidate Be/X-ray binary (BeXRB) IGR J18219−1347 with the Swift/X-ray Telescope, the Nuclear Spectroscopic Telescope ARray, and the Neutron Star Interior Composition Explorer during Type-I outbursts in 2020 March and June. Our timing analysis revealed the spin period of a neutron star with P spin = 52.46 s. This periodicity, combined with the known orbital period of 72.4 days, indicates that the system is a BeXRB. Furthermore, by comparing the spectral energy distribution of the infrared counterpart to that of known BeXRBs, we confirm this classification and set a distance of approximately 10–15 kpc for the source. The broadband X-ray spectrum (1.5–50 keV) of the source is described by an absorbed power law with a photon index Γ ∼ 0.5 and a cutoff energy at ∼13 keV.
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    PSR J1838−0537: DISCOVERY OF A YOUNG, ENERGETIC GAMMA-RAY PULSAR
    (The American Astronomical Society, 2012) Pletsch, H.J.; Guillemot, L.; Allen, B.; Kramer, M.; Aulbert, C.; Fehrmann, H.; Baring, M.G.; Camilo, F.; Caraveo, P.A.; Grove, J.E.; Kerr, M.; Marelli, M.; Ransom, S.M.; Ray, P.S.; Parkinson, P.M. Saz
    We report the discovery of PSR J1838−0537, a gamma-ray pulsar found through a blind search of data from the Fermi Large Area Telescope (LAT). The pulsar has a spin frequency of 6.9 Hz and a frequency derivative of −2.2 × 10−11 Hz s−1, implying a young characteristic age of 4970 yr and a large spin-down power of 5.9 × 1036 erg s−1. Follow-up observations with radio telescopes detected no pulsations; thus PSR J1838−0537 appears radio-quiet as viewed from Earth. In 2009 September the pulsar suffered the largest glitch so far seen in any gamma-ray-only pulsar, causing a relative increase in spin frequency of about 5.5 × 10−6. After the glitch, during a putative recovery period, the timing analysis is complicated by the sparsity of the LAT photon data, the weakness of the pulsations, and the reduction in average exposure from a coincidental, contemporaneous change in LAT’s sky-survey observing pattern. The pulsar’s sky position is coincident with the spatially extended TeV source HESS J1841−055 detected by the High Energy Stereoscopic System (H.E.S.S.). The inferred energetics suggest that HESS J1841−055 contains a pulsar wind nebula powered by the pulsar.
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    PSR J2021+4026 in the Gamma Cygni Region: The First Variable y-Ray Pulsar Seen by the Fermi Lat
    (The American Astronomical Society, 2013) Baring, M.G.; Allafort, A.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bellazzini, R.; Bonamente, E.; Bottacini, E.; Brandt, T.J.; Bregeon, J.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G.A.; Cameron, R.A.; Caraveo, P.A.; Cecchi, C.; Chaves, R.C.G.; Chekhtman, A.; Chiang, J.; Chiaro, G.; Ciprini, S.; Claus, R.; D'Ammando, F.; de Palma, F.; Digel, S.W.; Di Venere, L.; Drell, P.S.; Favuzzi, C.; Ferrara, E.C.; Franckowiak, A.; Fusco, P.; Gargano, F.; Gasparrini, D.; Giglietto, N.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Grenier, I.A.; Guiriec, S.; Hadasch, D.; Harding, A.K.; Hayashida, M.; Hayashi, K.; Hays, E.; Hewitt, J.; Hill, A.B.; Horan, D.; Hou, X.; Jogler, T.; Johnson, A.S.; Johnson, T.J.; Kerr, M.; Knödlseder, J.; Kuss, M.; Lande, J.; Larsson, S.; Latronico, L.; Lemoine-Goumard, M.; Lande, J.; Loparco, F.; Lubrano, P.; Malyshev, D.; Marelli, M.; Mayer, M.; Mazziotta, M.N.; Mehault, J.; Mizuno, T.; Monzani, M.E.; Morselli, A.; Murgia, S.; Nemmen, R.; Nuss, E.; Ohsugi, T.; Omodei, N.; Orienti, M.; Orlando, E.; Paneque, D.; Pesce-Rollins, M.; Pierbattista, M.; Piron, F.; Pivato, G.; Porter, T.A.; Rainò, S.; Rando, R.; Ray, P.S.; Razzano, M.; Reimer, O.; Reposeur, T.; Romani, R.W.; Sartori, A.; Saz Parkinson, P.M.; Sgrò, C.; Siskind, E.J.; Smith, D.A.; Spinelli, P.; Strong, A.W.; Takahashi, H.; Thayer, J.B.; Thompson, D.J.; Tibaldo, L.; Tinivella, M.; Torres, D.F.; Tosti, G.; Uchiyama, Y.; Usher, T.L.; Vandenbroucke, J.; Vasileiou, V.; Venter, C.; Vianello, G.; Vitale, V.; Winer, B.L.; Wood, K.S.
    Long-term monitoring of PSR J2021+4026 in the heart of the Cygnus region with the Fermi Large Area Telescope unveiled a sudden decrease in flux above 100 MeV over a timescale shorter than a week. The "jump" was near MJD 55850 (2011 October 16), with the flux decreasing from (8.33 ± 0.08) × 10–10 erg cm–2 s–1 to (6.86 ± 0.13) × 10–10 erg cm–2 s–1. Simultaneously, the frequency spindown rate increased from (7.8 ± 0.1) × 10–13 Hz s–1 to (8.1 ± 0.1) × 10–13 Hz s–1. Significant (>5σ) changes in the pulse profile and marginal (<3σ) changes in the emission spectrum occurred at the same time. There is also evidence for a small, steady flux increase over the 3 yr preceding MJD 55850. This is the first observation at γ-ray energies of mode changes and intermittent behavior, observed at radio wavelengths for other pulsars. We argue that the change in pulsed γ-ray emission is due to a change in emission beaming and we speculate that it is precipitated by a shift in the magnetic field structure, leading to a change of either effective magnetic inclination or effective current.
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    Searching the Gamma-Ray Sky for Counterparts to Gravitational Wave Sources: Fermi Gamma-Ray Burst Monitor and Large Area Telescope Observations of LVT151012 and GW151226
    (IOP, 2017) Racusin, J.L.; Burns, E.; Goldstein, A.; Connaughton, V.; Wilson-Hodge, C.A.; Jenke, P.; Blackburn, L.; Briggs, M.S.; Broida, J.; Camp, J.; Christensen, N.; Hui, C.M.; Littenberg, T.; Shawhan, P.; Singer, L.; Veitch, J.; Bhat, P.N.; Cleveland, W.; Fitzpatrick, G.; Gibby, M.H.; von Kienlin, A.; McBreen, S.; Mailyan, B.; Meegan, C.A.; Paciesas, W.S.; Preece, R.D.; Roberts, O.J.; Stanbro, M.; Veres, P.; Zhang, B.-B.; Fermi LAT Collaboration; Ackermann, M.; Albert, A.; Atwood, W.B.; Axelsson, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Baring, M.G.; Bastieri, D.; Bellazzini, R.; Bissaldi, E.; Blandford, R.D.; Bloom, E.D.; Bonino, R.; Bregeon, J.; Bruel, P.; Buson, S.; Caliandro, G.A.; Cameron, R.A.; Caputo, R.; Caragiulo, M.; Caraveo, P.A.; Cavazzuti, E.; Charles, E.; Chiang, J.; Ciprini, S.; Costanza, F.; Cuoco, A.; Cutini, S.; D'Ammando, F.; de Palma, F.; Desiante, R.; Digel, S.W.; Di Lalla, N.; Di Mauro, M.; Di Venere, L.; Drell, P.S.; Favuzzi, C.; Ferrara, E.C.; Focke, W.B.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Giglietto, N.; Gill, R.; Giroletti, M.; Glanzman, T.; Granot, J.; Green, D.; Grove, J.E.; Guillemot, L.; Guiriec, S.; Harding, A.K.; Jogler, T.; Jóhannesson, G.; Kamae, T.; Kensei, S.; Kocevski, D.; Kuss, M.; Larsson, S.; Latronico, L.; Li, J.; Longo, F.; Loparco, F.; Lubrano, P.; Magill, J.D.; Maldera, S.; Malyshev, D.; Mazziotta, M.N.; McEnery, J.E.; Michelson, P.F.; Mizuno, T.; Monzani, M.E.; Morselli, A.; Moskalenko, I.V.; Negro, M.; Nuss, E.; Omodei, N.; Orienti, M.; Orlando, E.; Ormes, J.F.; Paneque, D.; Perkins, J.S.; Pesce-Rollins, M.; Piron, F.; Pivato, G.; Porter, T.A.; Principe, G.; Rainò, S.; Rando, R.; Razzano, M.; Razzaque, S.; Reimer, A.; Reimer, O.; Saz Parkinson, P.M.; Scargle, J.D.; Sgrò, C.; Simone, D.; Siskind, E.J.; Smith, D.A.; Spada, F.; Spinelli, P.; Suson, D.J.; Tajima, H.; Thayer, J.B.; Torres, D.F.; Troja, E.; Uchiyama, Y.; Vianello, G.; Wood, K.S.; Wood, M.
    We present the Fermi Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT) observations of the LIGO binary black hole merger event GW151226 and candidate LVT151012. At the time of the LIGO triggers on LVT151012 and GW151226, GBM was observing 68% and 83% of the localization regions, and LAT was observing 47% and 32%, respectively. No candidate electromagnetic counterparts were detected by either the GBM or LAT. We present a detailed analysis of the GBM and LAT data over a range of timescales from seconds to years, using automated pipelines and new techniques for characterizing the flux upper bounds across large areas of the sky. Due to the partial GBM and LAT coverage of the large LIGO localization regions at the trigger times for both events, differences in source distances and masses, as well as the uncertain degree to which emission from these sources could be beamed, these non-detections cannot be used to constrain the variety of theoretical models recently applied to explain the candidate GBM counterpart to GW150914.
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    The Second Fermi Large Area Telescope Catalog of Gamma-Ray Pulsars
    (The American Astronomical Society, 2013-10) Baring, M.G.; Abdo, A.A.; Ajello, M.; Allafort, A.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Belfiore, A.; Bellazzini, R.; Bhattacharyya, B.; Bissaldi, E.; Bloom, E.D.; Bonamente, E.; Bottacini, E.; Brandt, T.J.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Burgay, M.; Burnett, T.H.; Busetto, G.; Buson, S.; Cameron, R.A.; Camilo, F.; Caraveo, P.A.; Casandjian, J.M.; Cecchi, C.; Çelik, Ö.; Charles, E.; Chaty, S.; Chaves, R.C.G.; Chekhtman, A.; Chen, A.W.; Chiang, J.; Chiaro, G.; Ciprini, S.; Claus, R.; Cognard, I.; Cohen-Tanugi, J.; Cominsky, L.R.; Conrad, J.; Cutini, S.; D'Ammando, F.; de Angelis, A.; DeCesar, M.E.; De Luca, A.; den Hartog, P.R.; de Palma, F.; Dermer, C.D.; Desvignes, G.; Digel, S.W.; Di Venere, L.; Drell, P.S.; Drlica-Wagner, A.; Dubois, R.; Dumora, D.; Espinoza, C.M.; Falletti, L.; Favuzzi, C.; Ferrara, E.C.; Focke, W.B.; Franckowiak, A.; Freire, P.C.C.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Germani, S.; Giglietto, N.; Giommi, P.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Gotthelf, E.V.; Grenier, I.A.; Grondin, M.-H.; Grove, J.E.; Guillemot, L.; Guiriec, S.; Hadasch, D.; Hanabata, Y.; Harding, A.K.; Hayashida, M.; Hays, E.; Hessels, J.; Hewitt, J.; Hill, A.B.; Horan, D.; Hou, X.; Hughes, R.E.; Jackson, M.S.; Janssen, G.H.; Jogler, T.; Jóhannesson, G.; Johnson, R.P.; Johnson, A.S.; Johnson, T.J.; Johnson, W.N.; Johnston, S.; Kamae, T.; Kataoka, J.; Keith, M.; Kerr, M.; Knӧdlseder, J.; Kramer, M.; Kuss, M.; Lande, J.; Larsson, S.; Latronico, L.; Lemoine-Goumard, M.; Longo, F.; Loparco, F.; Lovellette, M.N.; Lubrano, P.; Lyne, A.G.; Manchester, R.N.; Marelli, M.; Massaro, F.; Mayer, M.; Mazziotta, M.N.; McEnery, J.E.; McLaughlin, M.A.; Mehault, J.; Michelson, P.F.; Mignani, R.P.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A.A.; Monzani, M.E.; Morselli, A.; Moskalenko, I.V.; Murgia, S.; Nakamori, T.; Nemmen, R.; Nuss, E.; Ohno, M.; Ohsugi, T.; Orienti, M.; Orlando, E.; Ormes, J.F.; Paneque, D.; Panetta, J.H.; Parent, D.; Perkins, J.S.; Pesce-Rollins, M.; Pierbattista, M.; Piron, F.; Pivato, G.; Pletsch, H.J.; Porter, T.A.; Possenti, A.; Rainò, S.; Rando, R.; Ransom, S.M.; Ray, P.S.; Razzano, M.; Rea, N.; Reimer, A.; Reimer, O.; Renault, N.; Reposeur, T.; Ritz, S.; Romani, R.W.; Roth, M.; Rousseau, R.; Roy, J.; Ruan, J.; Sartori, A.; Saz Parkinson, P.M.; Scargle, J.D.; Schulz, A.; Sgrò, C.; Shannon, R.; Siskind, E.J.; Smith, D.A.; Spandre, G.; Spinelli, P.; Stappers, B.W.; Strong, A.W.; Suson, D.J.; Takahashi, H.; Thayer, J.G.; Thayer, J.B.; Theureau, G.; Thompson, D.J.; Thorsett, S.E.; Tibaldo, L.; Tibolla, O.; Tinivella, M.; Torres, D.F.; Tosti, G.; Troja, E.; Uchiyama, Y.; Usher, T.L.; Vandenbroucke, J.; Vasileiou, V.; Venter, C.; Vianello, G.; Vitale, V.; Wang, N.; Weltevrede, P.; Winer, B.L.; Wolff, M.T.; Wood, D.L.; Wood, K.S.; Wood, M.; Yang, Z.
    This catalog summarizes 117 high-confidence 0.1 GeV gamma-ray pulsar detections using three years of data acquired by the Large Area Telescope (LAT) on the Fermi satellite. Half are neutron stars discovered using LAT data through periodicity searches in gamma-ray and radio data around LAT unassociated source positions. The 117 pulsars are evenly divided into three groups: millisecond pulsars, young radio-loud pulsars, and young radio-quiet pulsars. We characterize the pulse profiles and energy spectra and derive luminosities when distance information exists. Spectral analysis of the off-peak phase intervals indicates probable pulsar wind nebula emission for four pulsars, and off-peak magnetospheric emission for several young and millisecond pulsars.We compare the gammaray properties with those in the radio, optical, and X-ray bands.We provide flux limits for pulsars with no observed gamma-ray emission, highlighting a small number of gamma-faint, radio-loud pulsars. The large, varied gamma-ray pulsar sample constrains emission models. Fermiﾒs selection biases complement those of radio surveys, enhancing comparisons with predicted population distributions.
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    SGR J1550–5418 BURSTS DETECTED WITH THE FERMI GAMMA-RAY BURST MONITOR DURING ITS MOST PROLIFIC ACTIVITY
    (The American Astronomical Society, 2012) Van Der Horst, A.J.; Kouveliotou, C.; Gorgone, N.M.; Kaneko, Y.; Baring, M.G.; Guiriec, S.; Gogus, E.; Granot, J.; Watts, A.L.; Lin, L.; Bhat, P.N.; Bissaldi, E.; Chaplin, V.L.; Finger, M.H.; Gehrels, N.; Gibby, M.H.; Giles, M.M.; Goldstein, A.; Gruber, D.; Harding, A.K.; Kaper, L.; Von Kienlin, A.; Van Der Klis, M.; McBreen, S.; Mcenery, J.; Meegan, C.A.; Paciesas, W.S.; Pe'er, A.; Preece, R.D.; Ramirez-Ruiz, E.; Rau, A.; Wachter, S.; Wilson-Hodge, C.; Woods, P.M.; Wijers, R.A.M.
    We have performed detailed temporal and time-integrated spectral analysis of 286 bursts from SGR J1550−5418 detected with the Fermi Gamma-ray Burst Monitor (GBM) in 2009 January, resulting in the largest uniform sample of temporal and spectral properties of SGR J1550−5418 bursts. We have used the combination of broadband and high time-resolution data provided with GBM to perform statistical studies for the source properties.We determine the durations, emission times, duty cycles, and rise times for all bursts, and find that they are typical of SGR bursts. We explore various models in our spectral analysis, and conclude that the spectra of SGR J1550−5418 bursts in the 8–200 keV band are equally well described by optically thin thermal bremsstrahlung (OTTB), a power law (PL) with an exponential cutoff (Comptonized model), and two blackbody (BB) functions (BB+BB). In the spectral fits with the Comptonized model, we find a mean PL index of −0.92, close to the OTTB index of −1. We show that there is an anti-correlation between the Comptonized Epeak and the burst fluence and average flux. For the BB+BB fits, we find that the fluences and emission areas of the two BB functions are correlated. The low-temperature BB has an emission area comparable to the neutron star surface area, independent of the temperature, while the hightemperature BB has a much smaller area and shows an anti-correlation between emission area and temperature.We compare the properties of these bursts with bursts observed from other SGR sources during extreme activations, and discuss the implications of our results in the context of magnetar burst models.
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    Time resolved spectroscopy of SGR J1550−5418 bursts detected with Fermi/gamma-ray burst monitor
    (The American Astronomical Society, 2014) Younes, G.; Kouveliotou, C.; van der Horst, A.J.; Baring, M.G.; Granot, J.; Watts, A.L.; Bhat, P.N.; Collazzi, A.; Gehrels, N.; Gorgone, N.; Gogus, E.; Gruber, D.; Grunblatt, S.; Huppenkothen, D.; Kaneko, Y.; von Kienlin, A.; van der Klis, M.; Lin, L.; Mcenery, J.; van Putten, T.; Wijers, R.A.M.J.
    We report on a time-resolved spectroscopy of the 63 brightest bursts of SGR J1550–5418, detected with the Fermi/Gamma-ray Burst Monitor during its 2008-2009 intense bursting episode. We performed spectral analysis down to 4 ms timescales to characterize the spectral evolution of the bursts. Using a Comptonized model, we find that the peak energy, E peak, anti-correlates with flux, while the low-energy photon index remains constant at ~ – 0.8 up to a flux limit F ≈ 10–5 erg s–1 cm–2. Above this flux value, the E peak–flux correlation changes sign, and the index positively correlates with the flux reaching ~1 at the highest fluxes. Using a two blackbody model, we find that the areas and fluxes of the two emitting regions correlate positively. Further, we study here for the first time the evolution of the temperatures and areas as a function of flux. We find that the area–kT relation follows the lines of constant luminosity at the lowest fluxes, R 2vpropkT –4, with a break at the higher fluxes (F > 10–5.5 erg s–1 cm–2). The area of the high-kT component increases with the flux while its temperature decreases, which we interpret as being due to an adiabatic cooling process. The area of the low-kT component, on the other hand, appears to saturate at the highest fluxes, toward R max ≈ 30 km. Assuming that crust quakes are responsible for soft gamma repeater (SGR) bursts and considering R max as the maximum radius of the emitting photon-pair plasma fireball, we relate this saturation radius to a minimum excitation radius of the magnetosphere, and we put a lower limit on the internal magnetic field of SGR J1550–5418, B int gsim 4.5 × 1015 G.
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    X-Ray through Very High Energy Intrabinary Shock Emission from Black Widows and Redbacks
    (IOP Publishing, 2020) van der Merwe, C.J.T.; Wadiasingh, Z.; Venter, C.; Harding, A.K.; Baring, M.G.
    Black widow and redback systems are compact binaries in which a millisecond pulsar heats and may even ablate its low-mass companion by its intense wind of relativistic particles and radiation. In such systems, an intrabinary shock can form as a site of particle acceleration and associated nonthermal emission. We model the X-ray and gamma-ray synchrotron and inverse Compton spectral components for select spider binaries, including diffusion, convection, and radiative energy losses in an axially symmetric, steady-state approach. Our new multizone code simultaneously yields energy-dependent light curves and orbital-phase-resolved spectra. Using parameter studies and matching the observed X-ray spectra and light curves, as well as Fermi Large Area Telescope spectra where available, with a synchrotron component, we can constrain certain model parameters. For PSR J1723–2837 these are notably the magnetic field and bulk flow speed of plasma moving along the shock tangent, the shock acceleration efficiency, and the multiplicity and spectrum of pairs accelerated by the pulsar. This affords a more robust prediction of the expected high-energy and very high energy gamma-ray flux. We find that nearby pulsars with hot or flaring companions may be promising targets for the future Cerenkov Telescope Array. Moreover, many spiders are likely to be of significant interest to future MeV-band missions such as AMEGO and e-ASTROGAM.