Browsing by Author "Venter, C."

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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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    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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    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.