Mostrando recursos 1 - 20 de 401

  1. Observation of the black widow B1957+20 millisecond pulsar binary system with the MAGIC telescopes

    Ahnen, M,; Ansoldi, S.; Antonelli, L.,; Arcaro, C.; Babić, A; Banerjee, B.; Bangale, P.; Barres De Almeida, U.; Barrio, J.; Becerra González, J; Bednarek, W.; Bernardini, E.; Berti, A.; Biasuzzi, B.; Biland, A.; Blanch, O.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Bretz, T.; Carosi, R.; Carosi, A.; CHATTERJEE, A.; Colin, P.; Colombo, E.; Contreras, J,; Cortina, J.; Covino, S.; Cumani, P.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Lotto, B.; De Oña Wilhelmi, E.; Pierro, F.,; Doert, M.; Domínguez, A.; Dominis, D; Dorner, D.; Doro, M.; Einecke, S.; Eisenacher Glawion, D; Elsaesser, D.; Engelkemeier, M.; Fallah Ramazani, V; Fernández-Barral, A.; Fidalgo, D.; Fonseca, M.,; Font, L.; Fruck, C.; Galindo, D.; García López, R,; Garczarczyk, M.; Gaug, M.; Giammaria, P.; Godinović, N; Gora, D.; Gozzini, S.,; Griffiths, S.; Guberman, D.; Hadasch, D.; Hahn, A.; Hassan, T.; Hayashida, M.; Herrera, J.; Hose, J.; Hrupec, D.; Hughes, G.; Ishio, K.; Konno, Y.; Kubo, H.; Kushida, J.; Kuveždić, D; Lelas, D.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; Majumdar, P.; Makariev, M.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martinez, M.; Mazin, D.; Menzel, U.; Mirzoyan, R.; Moralejo, A.; Moreno, V.; Moretti, E.; Neustroev, V.; Niedzwiecki, A.; Nievas Rosillo, M; Nilsson, K.; Nishijima, K.; Noda, K.; Nogués, L.; Paiano, S.; Palacio, J.; Paneque, D.; Paoletti, R.; Paredes, J.; Paredes-Fortuny, X.; Pedaletti, G.; Peresano, M.; Perri, L.; Persic, M.; Poutanen, J.; Prada Moroni, P,; Prandini, E.; Puljak, I.; Garcia, J.,; Reichardt, I.; Rhode, W.; Ribó, M.; Rico, J.; Saito, T.; Satalecka, K.; Schroeder, S.; Schweizer, T.; Sillanpää, A.; Sitarek, J.; Sobczynska, D.; Stamerra, A.; Strzys, M.; Surić, T; Takalo, L.; Tavecchio, F.; Temnikov, P.; Terzić, T; Tescaro, D.; Teshima, M.; Torres, D.; Torres-Albà, N.; Treves, A.; Vanzo, G.; Vazquez Acosta, M; Vovk, I.; Ward, J. E.; Will, M.; Wu, M. H.; Zarić, D; Cognard, Ismaël; Guillemot, Lucas
    International audience

  2. Scattering analysis of LOFAR pulsar observations

    Geyer, M.; Karastergiou, A.; Kondratiev, V. I.; Zagkouris, K.; Kramer, M.; Stappers, B. W.; Grießmeier, M.; Hessels, J. W. T.; Michilli, D.; Pilia, M.; Sobey, C.
    International audience

  3. First high-resolution radio study of the supernova remnant G338.3-0.0 associated with the gamma-ray source HESS J1640-465

    Castelletti, G.; Giacani, E.; Dubner, G.; Joshi, B. C.; Rao, A. P.; Terrier, R.
    Aims: We perform a multifrequency radio study of the supernova remnant (SNR) G338.3-0.0, in positional coincidence with the TeV source HESS J1640 - 465. We study the morphological and spectral properties of this remnant and its surroundings searching for plausible radio counterparts to the gamma-ray emission. Methods: We observed the SNR G338.3-0.0 using the Giant Metrewave Radio Telescope (GMRT) at 235, 610, and 1280 MHz. We also reprocessed archival data from the Australia Telescope Compact Array (ATCA) at 1290 and 2300 MHz. We conducted a search for radio pulsations towards a central point-like source, using the GMRT antennas at 610...

  4. Observation of the black widow B1957+20 millisecond pulsar binary system with the MAGIC telescopes

    Ahnen, L.; Ansoldi, S.; Antonelli, L.; Arcaro, C.; Babić, A.; Banerjee, B.; Bangale, P.; de Almeida, U.; Barrio, A.; González, J.; Bednarek, W.; Bernardini, E.; Berti, A.; Biasuzzi, B.; Biland, A.; Blanch, O.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Bretz, T.; Carosi, R.; Carosi, A.; CHATTERJEE, A.; Colin, P.; Colombo, E.; Contreras, L.; Cortina, J.; Covino, S.; Cumani, P.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Lotto, B.; Wilhelmi, E.; Pierro, F.; Doert, M.; Domínguez, A.; Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Glawion, D.; Elsaesser, D.; Engelkemeier, M.; Ramazani, V.; Fernández-Barral, A.; Fidalgo, D.; Fonseca, M.; Font, L.; Fruck, C.; Galindo, D.; Lopez, J.; Garczarczyk, M.; Gaug, M.; Giammaria, P.; Godinović, N.; Gora, D.; Gozzini, S.; Griffiths, S.; Guberman, D.; Hadasch, D.; Hahn, A.; Hassan, T.; Hayashida, M.; Herrera, J.; Hose, J.; Hrupec, D.; Hughes, G.; Ishio, K.; Konno, Y.; Kubo, H.; Kushida, J.; Kuveždić, D.; Lelas, D.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; Majumdar, P.; Makariev, M.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Mazin, D.; Menzel, U.; Mirzoyan, R.; Moralejo, A.; Moreno, V.; Moretti, E.; Neustroev, V.; Niedzwiecki, A.; Rosillo, M.; Nilsson, K.; Nishijima, K.; Noda, K.; Nogués, L.; Paiano, S.; Palacio, J.; Paneque, D.; Paoletti, R.; Paredes, M.; Paredes-Fortuny, X.; Pedaletti, G.; Peresano, M.; Perri, L.; Persic, M.; Poutanen, J.; Moroni, G.; Prandini, E.; Puljak, I.; Garcia, J.; Reichardt, I.; Rhode, W.; Ribó, M.; Rico, J.; Saito, T.; Satalecka, K.; Schroeder, S.; Schweizer, T.; Sillanpää, A.; Sitarek, J.; Šnidarić, I.; Sobczynska, D.; Stamerra, A.; Strzys, M.; Surić, T.; Takalo, L.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Torres, D.; Torres-Albà, N.; Treves, A.; Vanzo, G.; Acosta, M.; Vovk, I.; Ward, J. E.; Will, M.; Wu, M. H.; Zarić, D.; Collaboration), (MAGIC; Cognard, Ismaël; Guillemot, Lucas
    International audience

  5. Observation of the black widow B1957+20 millisecond pulsar binary system with the MAGIC telescopes

    Ahnen, L.; Ansoldi, S.; Antonelli, L.; Arcaro, C.; Babić, A.; Banerjee, B.; Bangale, P.; de Almeida, U.; Barrio, A.; González, J.; Bednarek, W.; Bernardini, E.; Berti, A.; Biasuzzi, B.; Biland, A.; Blanch, O.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Bretz, T.; Carosi, R.; Carosi, A.; CHATTERJEE, A.; Colin, P.; Colombo, E.; Contreras, L.; Cortina, J.; Covino, S.; Cumani, P.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Lotto, B.; Wilhelmi, E.; Pierro, F.; Doert, M.; Domínguez, A.; Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Glawion, D.; Elsaesser, D.; Engelkemeier, M.; Ramazani, V.; Fernández-Barral, A.; Fidalgo, D.; Fonseca, M.; Font, L.; Fruck, C.; Galindo, D.; Lopez, J.; Garczarczyk, M.; Gaug, M.; Giammaria, P.; Godinović, N.; Gora, D.; Gozzini, S.; Griffiths, S.; Guberman, D.; Hadasch, D.; Hahn, A.; Hassan, T.; Hayashida, M.; Herrera, J.; Hose, J.; Hrupec, D.; Hughes, G.; Ishio, K.; Konno, Y.; Kubo, H.; Kushida, J.; Kuveždić, D.; Lelas, D.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; Majumdar, P.; Makariev, M.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Mazin, D.; Menzel, U.; Mirzoyan, R.; Moralejo, A.; Moreno, V.; Moretti, E.; Neustroev, V.; Niedzwiecki, A.; Rosillo, M.; Nilsson, K.; Nishijima, K.; Noda, K.; Nogués, L.; Paiano, S.; Palacio, J.; Paneque, D.; Paoletti, R.; Paredes, M.; Paredes-Fortuny, X.; Pedaletti, G.; Peresano, M.; Perri, L.; Persic, M.; Poutanen, J.; Moroni, G.; Prandini, E.; Puljak, I.; Garcia, J.; Reichardt, I.; Rhode, W.; Ribó, M.; Rico, J.; Saito, T.; Satalecka, K.; Schroeder, S.; Schweizer, T.; Sillanpää, A.; Sitarek, J.; Šnidarić, I.; Sobczynska, D.; Stamerra, A.; Strzys, M.; Surić, T.; Takalo, L.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Torres, D.; Torres-Albà, N.; Treves, A.; Vanzo, G.; Acosta, M.; Vovk, I.; Ward, J. E.; Will, M.; Wu, M. H.; Zarić, D.; Collaboration), (MAGIC; Cognard, Ismaël; Guillemot, Lucas
    International audience

  6. Observation of the black widow B1957+20 millisecond pulsar binary system with the MAGIC telescopes

    Ahnen, L.; Ansoldi, S.; Antonelli, L.; Arcaro, C.; Babić, A.; Banerjee, B.; Bangale, P.; de Almeida, U.; Barrio, A.; González, J.; Bednarek, W.; Bernardini, E.; Berti, A.; Biasuzzi, B.; Biland, A.; Blanch, O.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Bretz, T.; Carosi, R.; Carosi, A.; CHATTERJEE, A.; Colin, P.; Colombo, E.; Contreras, L.; Cortina, J.; Covino, S.; Cumani, P.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Lotto, B.; Wilhelmi, E.; Pierro, F.; Doert, M.; Domínguez, A.; Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Glawion, D.; Elsaesser, D.; Engelkemeier, M.; Ramazani, V.; Fernández-Barral, A.; Fidalgo, D.; Fonseca, M.; Font, L.; Fruck, C.; Galindo, D.; Lopez, J.; Garczarczyk, M.; Gaug, M.; Giammaria, P.; Godinović, N.; Gora, D.; Gozzini, S.; Griffiths, S.; Guberman, D.; Hadasch, D.; Hahn, A.; Hassan, T.; Hayashida, M.; Herrera, J.; Hose, J.; Hrupec, D.; Hughes, G.; Ishio, K.; Konno, Y.; Kubo, H.; Kushida, J.; Kuveždić, D.; Lelas, D.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; Majumdar, P.; Makariev, M.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Mazin, D.; Menzel, U.; Mirzoyan, R.; Moralejo, A.; Moreno, V.; Moretti, E.; Neustroev, V.; Niedzwiecki, A.; Rosillo, M.; Nilsson, K.; Nishijima, K.; Noda, K.; Nogués, L.; Paiano, S.; Palacio, J.; Paneque, D.; Paoletti, R.; Paredes, M.; Paredes-Fortuny, X.; Pedaletti, G.; Peresano, M.; Perri, L.; Persic, M.; Poutanen, J.; Moroni, G.; Prandini, E.; Puljak, I.; Garcia, J.; Reichardt, I.; Rhode, W.; Ribó, M.; Rico, J.; Saito, T.; Satalecka, K.; Schroeder, S.; Schweizer, T.; Sillanpää, A.; Sitarek, J.; Šnidarić, I.; Sobczynska, D.; Stamerra, A.; Strzys, M.; Surić, T.; Takalo, L.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Torres, D.; Torres-Albà, N.; Treves, A.; Vanzo, G.; Acosta, M.; Vovk, I.; Ward, J. E.; Will, M.; Wu, M. H.; Zarić, D.; Collaboration), (MAGIC; Cognard, Ismaël; Guillemot, Lucas
    International audience

  7. Study of measured pulsar masses and their possible conclusions

    Zhang, C. M.; Wang, J.; Zhao, Y. H.; Yin, H. X.; Song, L. M.; Menezes, D. P.; Wickramasinghe, D. T.; Ferrario, L.; Chardonnet, P.
    6 pages, 5 figures, in press, Astronomy and Astrophysics 2011, 527, 83

  8. A Possible Evolutionary Channel for the Recently Discovered Class of Millisecond Pulsars in Long, Eccentric Orbits

    Taylor, Andrew
    We consider an evolutionary channel for the recently discovered class of millisecond pulsars (MSPs) on relatively long, eccentric binary orbits. If the standard model for formation of MSPs involving a low-mass X-ray binary (LMXB) mass transfer stage is the origin of these systems, the observed companion cannot have been the star involved in the binary interaction with the pulsar. Instead, we consider a tight triple system, where the nearby binary companion is ablated away, as in observed black widow and redback systems. The tertiary induces Kozai-Lidov eccentricity oscillations, enhancing mass loss. We solve the secular equations for triple dynamics including...

  9. The UTMOST: A Hybrid Digital Signal Processor Transforms the Molonglo Observatory Synthesis Telescope

    Bailes, M.; Jameson, A.; Flynn, C.; Bateman, T.; Barr, E. D.; Bhandari, S.; Bunton, J. D.; Caleb, M.; Campbell-Wilson, D.; Farah, W.; Gaensler, B.; Green, A. J.; Hunstead, R. W.; Jankowski, F.; Keane, E. F.; Krishnan, V. Venkatraman; Murphy, Tara; O’Neill, M.; Osłowski, S.; Parthasarathy, A.; Ravi, V.; Rosado, P.; Temby, D.
    The Molonglo Observatory Synthesis Telescope (MOST) is an 18000 m^2 radio telescope located 40 km from Canberra, Australia. Its operating band (820–851 MHz) is partly allocated to telecommunications, making radio astronomy challenging. We describe how the deployment of new digital receivers, Field Programmable Gate Array-based filterbanks, and server-class computers equipped with 43 Graphics Processing Units, has transformed the telescope into a versatile new instrument (UTMOST) for studying the radio sky on millisecond timescales. UTMOST has 10 times the bandwidth and double the field of view compared to the MOST, and voltage record and playback capability has facilitated rapid implementaton of...

  10. NuSTAR Hard X-ray Observation of the Gamma-ray Binary Candidate HESS J1832-093

    Mori, Kaya; Gotthelf, E. V.; Hailey, Charles J.; Hord, Ben J.; de Ona Wilhelmi, Emma; Rahoui, Farid; Tomsick, John A.; Zhang, Shuo; Hong, Jaesub; Garvin, Amani M.; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; Harrison, Fiona A.; Stern, Daniel; Zhang, William W.
    We present a hard X-ray observation of the TeV gamma-ray binary candidate HESS J1832-093 coincident with supernova remnant (SNR) G22.7-0.2 using the Nuclear Spectroscopic Telescope Array (NuSTAR). Non-thermal X-ray emission from XMMU J183245-0921539, the X-ray source associated with HESS J1832-093, is detected up to ~30 keV and is well-described by an absorbed power-law model with the best-fit photon index $\Gamma = 1.5\pm0.1$. A re-analysis of archival Chandra and XMM-Newton data finds that the long-term X-ray flux increase of XMMU J183245-0921539 is $50^{+40}_{-20}$% (90% C.L.), much less than previously reported. A search for a pulsar spin period or binary orbit modulation yields no significant signal to a pulse fraction limit...

  11. NuSTAR Hard X-ray Observation of the Gamma-ray Binary Candidate HESS J1832-093

    Mori, Kaya; Gotthelf, E. V.; Hailey, Charles J.; Hord, Ben J.; de Oña Wilhelmi, Emma; Rahoui, Farid; Tomsick, John A.; Zhang, Shuo; Hong, Jaesub; Garvin, Amani M.; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; Harrison, Fiona A.; Stern, Daniel; Zhang, William W.
    We present a hard X-ray observation of the TeV gamma-ray binary candidate HESS J1832−093, which is coincident with the supernova remnant G22.7−0.2, using the Nuclear Spectroscopic Telescope Array. Non-thermal X-ray emission from XMMU J183245−0921539, the X-ray source associated with HESS J1832−093, is detected up to ~30 keV and is well-described by an absorbed power-law model with a best-fit photon index Γ = 1.5 ± 0.1. A re-analysis of archival Chandra and XMM-Newtondata finds that the long-term X-ray flux increase of XMMU J183245−0921539 is 50^(+40)_(-20)% (90% C.L.), much less than previously reported. A search for a pulsar spin period or binary...

  12. HD 49798: Its History of Binary Interaction and Future Evolution

    Brooks, Jared; Kupfer, Thomas; Bildsten, Lars
    The bright subdwarf-O star (sdO) HD 49798 is in a 1.55 day orbit with a compact companion that is spinning at 13.2 s. Using the measurements of the effective temperature (T_(eff)), surface gravity (log g), and surface abundances of the sdO, we construct models to study the evolution of this binary system using Modules for Experiments in Stellar Astrophysics (MESA). Previous studies of the compact companion have disagreed on whether it is a white dwarf (WD) or a neutron star (NS). From the published measurements of the companion's spin and spin-up rate, we agree with Mereghetti and collaborators that an...

  13. Neutron Stars Observations as Astrophysical Probes

    Romani, Roger William

    Several aspects of observations of neutron stars and compact extragalactic radio sources are considered, with particular regard to their use in constraining certain astrophysical phenomena.

    A theoretical treatment of the pulse arrival time analysis of millisecond pulsars is made; we consider how a detailed timing analysis can be used to quantitatively probe noise processes affecting the pulsar period and the propagation of the radiation. The intrinsic noise may be used to study the neutron star interior, while propagation effects due to gravitational perturbations of the neutron star and interstellar refraction of the emitted radio waves provide probes of the pulsar environment and...

  14. The first direct detection of gravitational waves opens a vast new frontier in astronomy

    Raab, F. J.; Reitze, D. H.
    The first direct detection of gravitational waves (GWs), announced on 11 February 2016, has opened a vast new frontier in astronomy. Albert Einstein predicted the existence of these waves about a century ago as a consequence of his general theory of relativity. Radio astronomy observations of the binary pulsar system PSR 1913 + 16 over a 20 year period beginning in 1975 provided strong observational evidence that gravitational waves carried energy away from the orbits of neutron stars at precisely the level predicted by general relativity (GR). This relentless conversion of orbital energy into gravitational wave energy causes binary orbits to decay until the objects eventually collide and...

  15. Detailed VHE Studies of the Pulsar Wind Nebula HESS J1825-137

    Mitchell, Alison; Mariaud, C.; Eger, P.; Funk, S.; Hahn, J.; Hinton, J.; Parsons, R.D.; Marandon, V.
    International audience

  16. Spectral Changes in the Hyperluminous Pulsar in NGC 5907 as a Function of Super-Orbital Phase

    Fürst, F.; Walton, D.J.; Stern, D.; Bachetti, M.; Barret, D.; Brightman, M.; HARRISON, F.A.; Rana, V.
    International audience

  17. A recent change in the optical and $\gamma$-ray polarization of the Crab nebula and pulsar

    Moran, P.; Kyne, G.; Gouiffès, C.; Laurent, P.; Hallinan, G.; Redfern, R.M.; Shearer, A.
    International audience

  18. Electrodynamics of pulsar magnetospheres

    Cerutti, Benoît; Beloborodov, Andrei
    International audience

  19. Electrodynamics of pulsar magnetospheres

    Cerutti, Benoît; Beloborodov, Andrei
    International audience

  20. Black-Hole Electrodynamics

    Macdonald, Douglas Alan
    This dissertation considers several aspects of the structure and dynamics of electromagnetic fields around black holes. The four-dimensional, covariant laws of electrodynamics are reformulated in a 3 + 1 (space+time) language in which the key quantities are three-dimensional vectors lying in hypersurfaces of a constant global time t. This formulation is applied to the Blandford-Znajek model of power generation in quasars, which consists of a supermassive black hole surrounded by an accretion disk that holds a magnetic field on the hole, with the rotational energy and angular momentum of the hole and disk being extracted by electromagnetic torques. The 3...

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