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36 results on '"PESCE-ROLLINS, M."'

1. X-ray polarization evidence for a 200-year-old flare of Sgr A .

Author: Marin F, Churazov E, Khabibullin I, Ferrazzoli R, Di Gesu L, Barnouin T, Di Marco A, Middei R, Vikhlinin A, Costa E, Soffitta P, Muleri F, Sunyaev R, Forman W, Kraft R, Bianchi S, Donnarumma I, Petrucci PO, Enoto T, Agudo I, Antonelli LA, Bachetti M, Baldini L, Baumgartner WH, Bellazzini R, Bongiorno SD, Bonino R, Brez A, Bucciantini N, Capitanio F, Castellano S, Cavazzuti E, Chen CT, Ciprini S, De Rosa A, Del Monte E, Di Lalla N, Doroshenko V, Dovčiak M, Ehlert SR, Evangelista Y, Fabiani S, Garcia JA, Gunji S, Hayashida K, Heyl J, Ingram A, Iwakiri W, Jorstad SG, Kaaret P, Karas V, Kitaguchi T, Kolodziejczak JJ, Krawczynski H, La Monaca F, Latronico L, Liodakis I, Maldera S, Manfreda A, Marinucci A, Marscher AP, Marshall HL, Massaro F, Matt G, Mitsuishi I, Mizuno T, Negro M, Ng CY, O'Dell SL, Omodei N, Oppedisano C, Papitto A, Pavlov GG, Peirson AL, Perri M, Pesce-Rollins M, Pilia M, Possenti A, Poutanen J, Puccetti S, Ramsey BD, Rankin J, Ratheesh A, Roberts OJ, Romani RW, Sgrò C, Slane P, Spandre G, Swartz D, Tamagawa T, Tavecchio F, Taverna R, Tawara Y, Tennant AF, Thomas NE, Tombesi F, Trois A, Tsygankov SS, Turolla R, Vink J, Weisskopf MC, Wu K, Xie F, and Zane S
Abstract: The centre of the Milky Way Galaxy hosts a black hole with a solar mass of about 4 million (Sagittarius A * (Sgr A)) that is very quiescent at present with a luminosity many orders of magnitude below those of active galactic nuclei 1 . Reflection of X-rays from Sgr A * by dense gas in the Galactic Centre region offers a means to study its past flaring activity on timescales of hundreds and thousands of years 2 . The shape of the X-ray continuum and the strong fluorescent iron line observed from giant molecular clouds in the vicinity of Sgr A * are consistent with the reflection scenario 3-5 . If this interpretation is correct, the reflected continuum emission should be polarized 6 . Here we report observations of polarized X-ray emission in the direction of the molecular clouds in the Galactic Centre using the Imaging X-ray Polarimetry Explorer. We measure a polarization degree of 31% ± 11%, and a polarization angle of -48° ± 11°. The polarization angle is consistent with Sgr A * being the primary source of the emission, and the polarization degree implies that some 200 years ago, the X-ray luminosity of Sgr A * was briefly comparable to that of a Seyfert galaxy., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)
Published: 2023
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2. Vela pulsar wind nebula X-rays are polarized to near the synchrotron limit.

Author: Xie F, Di Marco A, La Monaca F, Liu K, Muleri F, Bucciantini N, Romani RW, Costa E, Rankin J, Soffitta P, Bachetti M, Di Lalla N, Fabiani S, Ferrazzoli R, Gunji S, Latronico L, Negro M, Omodei N, Pilia M, Trois A, Watanabe E, Agudo I, Antonelli LA, Baldini L, Baumgartner WH, Bellazzini R, Bianchi S, Bongiorno SD, Bonino R, Brez A, Capitanio F, Castellano S, Cavazzuti E, Ciprini S, De Rosa A, Del Monte E, Di Gesu L, Donnarumma I, Doroshenko V, Dovčiak M, Ehlert SR, Enoto T, Evangelista Y, Garcia JA, Hayashida K, Heyl J, Iwakiri W, Jorstad SG, Karas V, Kitaguchi T, Kolodziejczak JJ, Krawczynski H, Liodakis I, Maldera S, Manfreda A, Marin F, Marinucci A, Marscher AP, Marshall HL, Massaro F, Matt G, Mitsuishi I, Mizuno T, Ng CY, O'Dell SL, Oppedisano C, Papitto A, Pavlov GG, Peirson AL, Perri M, Pesce-Rollins M, Petrucci PO, Possenti A, Poutanen J, Puccetti S, Ramsey BD, Ratheesh A, Sgró C, Slane P, Spandre G, Tamagawa T, Tavecchio F, Taverna R, Tawara Y, Tennant AF, Thomas NE, Tombesi F, Tsygankov SS, Turolla R, Vink J, Weisskopf MC, Wu K, and Zane S
Abstract: Pulsar wind nebulae are formed when outflows of relativistic electrons and positrons hit the surrounding supernova remnant or interstellar medium at a shock front. The Vela pulsar wind nebula is powered by a young pulsar (B0833-45, aged 11,000 years) 1 and located inside an extended structure called Vela X, which is itself inside the supernova remnant 2 . Previous X-ray observations revealed two prominent arcs that are bisected by a jet and counter jet 3,4 . Radio maps have shown high linear polarization of 60% in the outer regions of the nebula 5 . Here we report an X-ray observation of the inner part of the nebula, where polarization can exceed 60% at the leading edge-approaching the theoretical limit of what can be produced by synchrotron emission. We infer that, in contrast with the case of the supernova remnant, the electrons in the pulsar wind nebula are accelerated with little or no turbulence in a highly uniform magnetic field., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)
Published: 2022
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3. Polarized x-rays from a magnetar.

Author: Taverna R, Turolla R, Muleri F, Heyl J, Zane S, Baldini L, González-Caniulef D, Bachetti M, Rankin J, Caiazzo I, Di Lalla N, Doroshenko V, Errando M, Gau E, Kırmızıbayrak D, Krawczynski H, Negro M, Ng M, Omodei N, Possenti A, Tamagawa T, Uchiyama K, Weisskopf MC, Agudo I, Antonelli LA, Baumgartner WH, Bellazzini R, Bianchi S, Bongiorno SD, Bonino R, Brez A, Bucciantini N, Capitanio F, Castellano S, Cavazzuti E, Ciprini S, Costa E, De Rosa A, Del Monte E, Di Gesu L, Di Marco A, Donnarumma I, Dovčiak M, Ehlert SR, Enoto T, Evangelista Y, Fabiani S, Ferrazzoli R, Garcia JA, Gunji S, Hayashida K, Iwakiri W, Jorstad SG, Karas V, Kitaguchi T, Kolodziejczak JJ, La Monaca F, Latronico L, Liodakis I, Maldera S, Manfreda A, Marin F, Marinucci A, Marscher AP, Marshall HL, Matt G, Mitsuishi I, Mizuno T, Ng SC, O'Dell SL, Oppedisano C, Papitto A, Pavlov GG, Peirson AL, Perri M, Pesce-Rollins M, Pilia M, Poutanen J, Puccetti S, Ramsey BD, Ratheesh A, Romani RW, Sgrò C, Slane P, Soffitta P, Spandre G, Tavecchio F, Tawara Y, Tennant AF, Thomas NE, Tombesi F, Trois A, Tsygankov SS, Vink J, Wu K, and Xie F
Abstract: Magnetars are neutron stars with ultrastrong magnetic fields, which can be observed in x-rays. Polarization measurements could provide information on their magnetic fields and surface properties. We observed polarized x-rays from the magnetar 4U 0142+61 using the Imaging X-ray Polarimetry Explorer and found a linear polarization degree of 13.5 ± 0.8% averaged over the 2- to 8-kilo-electron volt band. The polarization changes with energy: The degree is 15.0 ± 1.0% at 2 to 4 kilo-electron volts, drops below the instrumental sensitivity ~4 to 5 kilo-electron volts, and rises to 35.2 ± 7.1% at 5.5 to 8 kilo-electron volts. The polarization angle also changes by 90° at ~4 to 5 kilo-electron volts. These results are consistent with a model in which thermal radiation from the magnetar surface is reprocessed by scattering off charged particles in the magnetosphere.
Published: 2022
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4. Polarized x-rays constrain the disk-jet geometry in the black hole x-ray binary Cygnus X-1.

Author: Krawczynski H, Muleri F, Dovčiak M, Veledina A, Rodriguez Cavero N, Svoboda J, Ingram A, Matt G, Garcia JA, Loktev V, Negro M, Poutanen J, Kitaguchi T, Podgorný J, Rankin J, Zhang W, Berdyugin A, Berdyugina SV, Bianchi S, Blinov D, Capitanio F, Di Lalla N, Draghis P, Fabiani S, Kagitani M, Kravtsov V, Kiehlmann S, Latronico L, Lutovinov AA, Mandarakas N, Marin F, Marinucci A, Miller JM, Mizuno T, Molkov SV, Omodei N, Petrucci PO, Ratheesh A, Sakanoi T, Semena AN, Skalidis R, Soffitta P, Tennant AF, Thalhammer P, Tombesi F, Weisskopf MC, Wilms J, Zhang S, Agudo I, Antonelli LA, Bachetti M, Baldini L, Baumgartner WH, Bellazzini R, Bongiorno SD, Bonino R, Brez A, Bucciantini N, Castellano S, Cavazzuti E, Ciprini S, Costa E, De Rosa A, Del Monte E, Di Gesu L, Di Marco A, Donnarumma I, Doroshenko V, Ehlert SR, Enoto T, Evangelista Y, Ferrazzoli R, Gunji S, Hayashida K, Heyl J, Iwakiri W, Jorstad SG, Karas V, Kolodziejczak JJ, La Monaca F, Liodakis I, Maldera S, Manfreda A, Marscher AP, Marshall HL, Mitsuishi I, Ng CY, O'Dell SL, Oppedisano C, Papitto A, Pavlov GG, Peirson AL, Perri M, Pesce-Rollins M, Pilia M, Possenti A, Puccetti S, Ramsey BD, Romani RW, Sgrò C, Slane P, Spandre G, Tamagawa T, Tavecchio F, Taverna R, Tawara Y, Thomas NE, Trois A, Tsygankov S, Turolla R, Vink J, Wu K, Xie F, and Zane S
Abstract: A black hole x-ray binary (XRB) system forms when gas is stripped from a normal star and accretes onto a black hole, which heats the gas sufficiently to emit x-rays. We report a polarimetric observation of the XRB Cygnus X-1 using the Imaging X-ray Polarimetry Explorer. The electric field position angle aligns with the outflowing jet, indicating that the jet is launched from the inner x-ray-emitting region. The polarization degree is 4.01 ± 0.20% at 2 to 8 kiloelectronvolts, implying that the accretion disk is viewed closer to edge-on than the binary orbit. These observations reveal that hot x-ray-emitting plasma is spatially extended in a plane perpendicular to, not parallel to, the jet axis.
Published: 2022
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5. Polarized blazar X-rays imply particle acceleration in shocks.

Author: Liodakis I, Marscher AP, Agudo I, Berdyugin AV, Bernardos MI, Bonnoli G, Borman GA, Casadio C, Casanova VC, Cavazzuti E, Rodriguez Cavero N, Di Gesu L, Di Lalla N, Donnarumma I, Ehlert SR, Errando M, Escudero J, Garcı A-Comas M, Agı S-González B, Husillos C, Jormanainen J, Jorstad SG, Kagitani M, Kopatskaya EN, Kravtsov V, Krawczynski H, Lindfors E, Larionova EG, Madejski GM, Marin F, Marchini A, Marshall HL, Morozova DA, Massaro F, Masiero JR, Mawet D, Middei R, Millar-Blanchaer MA, Myserlis I, Negro M, Nilsson K, O'Dell SL, Omodei N, Pacciani L, Paggi A, Panopoulou GV, Peirson AL, Perri M, Petrucci PO, Poutanen J, Puccetti S, Romani RW, Sakanoi T, Savchenko SS, Sota A, Tavecchio F, Tinyanont S, Vasilyev AA, Weaver ZR, Zhovtan AV, Antonelli LA, Bachetti M, Baldini L, Baumgartner WH, Bellazzini R, Bianchi S, Bongiorno SD, Bonino R, Brez A, Bucciantini N, Capitanio F, Castellano S, Ciprini S, Costa E, De Rosa A, Del Monte E, Di Marco A, Doroshenko V, Dovčiak M, Enoto T, Evangelista Y, Fabiani S, Ferrazzoli R, Garcia JA, Gunji S, Hayashida K, Heyl J, Iwakiri W, Karas V, Kitaguchi T, Kolodziejczak JJ, La Monaca F, Latronico L, Maldera S, Manfreda A, Marinucci A, Matt G, Mitsuishi I, Mizuno T, Muleri F, Ng SC, Oppedisano C, Papitto A, Pavlov GG, Pesce-Rollins M, Pilia M, Possenti A, Ramsey BD, Rankin J, Ratheesh A, Sgró C, Slane P, Soffitta P, Spandre G, Tamagawa T, Taverna R, Tawara Y, Tennant AF, Thomas NE, Tombesi F, Trois A, Tsygankov S, Turolla R, Vink J, Weisskopf MC, Wu K, Xie F, and Zane S
Abstract: Most of the light from blazars, active galactic nuclei with jets of magnetized plasma that point nearly along the line of sight, is produced by high-energy particles, up to around 1 TeV. Although the jets are known to be ultimately powered by a supermassive black hole, how the particles are accelerated to such high energies has been an unanswered question. The process must be related to the magnetic field, which can be probed by observations of the polarization of light from the jets. Measurements of the radio to optical polarization-the only range available until now-probe extended regions of the jet containing particles that left the acceleration site days to years earlier 1-3 , and hence do not directly explore the acceleration mechanism, as could X-ray measurements. Here we report the detection of X-ray polarization from the blazar Markarian 501 (Mrk 501). We measure an X-ray linear polarization degree Π X of around 10%, which is a factor of around 2 higher than the value at optical wavelengths, with a polarization angle parallel to the radio jet. This points to a shock front as the source of particle acceleration and also implies that the plasma becomes increasingly turbulent with distance from the shock., (© 2022. The Author(s).)
Published: 2022
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6. Unresolved Gamma-Ray Sky through its Angular Power Spectrum.

Author: Ackermann M, Ajello M, Baldini L, Ballet J, Barbiellini G, Bastieri D, Bellazzini R, Bissaldi E, Blandford RD, Bonino R, Bottacini E, Bregeon J, Bruel P, Buehler R, Burns E, Buson S, Cameron RA, Caputo R, Caraveo PA, Cavazzuti E, Chen S, Chiaro G, Ciprini S, Costantin D, Cuoco A, Cutini S, D'Ammando F, de la Torre Luque P, de Palma F, Desai A, Digel SW, Di Lalla N, Di Mauro M, Di Venere L, Fana Dirirsa F, Favuzzi C, Franckowiak A, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Giglietto N, Giordano F, Giroletti M, Green D, Grenier IA, Guillemot L, Guiriec S, Horan D, Jóhannesson G, Kuss M, Larsson S, Latronico L, Li J, Liodakis I, Longo F, Loparco F, Lubrano P, Magill JD, Maldera S, Malyshev D, Manfreda A, Mazziotta MN, Mereu I, Michelson PF, Mitthumsiri W, Mizuno T, Monzani ME, Morselli A, Moskalenko IV, Negro M, Nuss E, Orienti M, Orlando E, Palatiello M, Paliya VS, Paneque D, Persic M, Pesce-Rollins M, Petrosian V, Piron F, Porter TA, Principe G, Rainò S, Rando R, Razzano M, Razzaque S, Reimer A, Reimer O, Serini D, Sgrò C, Siskind EJ, Spandre G, Spinelli P, Suson DJ, Tajima H, Takahashi M, Thayer JB, Tibaldo L, Torres DF, Troja E, Venters TM, Vianello G, Wood K, Yassine M, Zaharijas G, Ammazzalorso S, Fornengo N, and Regis M
Abstract: The gamma-ray sky has been observed with unprecedented accuracy in the last decade by the Fermi -large area telescope (LAT), allowing us to resolve and understand the high-energy Universe. The nature of the remaining unresolved emission [unresolved gamma-ray background (UGRB)] below the LAT source detection threshold can be uncovered by characterizing the amplitude and angular scale of the UGRB fluctuation field. This Letter presents a measurement of the UGRB autocorrelation angular power spectrum based on eight years of Fermi-LAT Pass 8 data products. The analysis is designed to be robust against contamination from resolved sources and noise systematics. The sensitivity to subthreshold sources is greatly enhanced with respect to previous measurements. We find evidence (with ∼3.7σ significance) that the scenario in which two classes of sources contribute to the UGRB signal is favored over a single class. A double power law with exponential cutoff can explain the anisotropy energy spectrum well, with photon indices of the two populations being 2.55±0.23 and 1.86±0.15.
Published: 2018
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7. Investigating the Nature of Late-Time High-Energy GRB Emission Through Joint Fermi /Swift Observations.

Author: Ajello M, Baldini L, Barbiellini G, Bastieri D, Bellazzini R, Bissaldi E, Blandford RD, Bonino R, Bottacini E, Bregeon J, Bruel P, Buehler R, Cameron RA, Caputo R, Caraveo PA, Chiaro G, Ciprini S, Cohen-Tanugi J, Costantin D, D'Ammando F, DE Palma F, DI Lalla N, DI Mauro M, DI Venere L, Domínguez A, Favuzzi C, Franckowiak A, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Giglietto N, Giordano F, Giroletti M, Green D, Grenier IA, Guiriec S, Holt C, Horan D, Jóhannesson G, Kocevski D, Kuss M, LA Mura G, Larsson S, Li J, Longo F, Loparco F, Lubrano P, Magill JD, Maldera S, Manfreda A, Mazziotta MN, Michelson PF, Mizuno T, Monzani ME, Morselli A, Negro M, Nuss E, Omodei N, Orienti M, Orlando E, Paliya VS, Perkins JS, Persic M, Pesce-Rollins M, Piron F, Principe G, Racusin JL, Rainò S, Rando R, Razzano M, Razzaque S, Reimer A, Reimer O, Sgrò C, Siskind EJ, Spandre G, Spinelli P, Tak D, Thayer JB, Torres DF, Tosti G, Valverde J, Vogel M, and Wood K
Abstract: We use joint observations by the Neil Gehrels Swift X-ray Telescope (XRT) and the Fermi Large Area Telescope (LAT) of gamma-ray burst (GRB) afterglows to investigate the nature of the long-lived high-energy emission observed by Fermi LAT. Joint broadband spectral modeling of XRT and LAT data reveal that LAT non-detections of bright X-ray afterglows are consistent with a cooling break in the inferred electron synchrotron spectrum below the LAT and/or XRT energy ranges. Such a break is sufficient to suppress the high-energy emission so as to be below the LAT detection threshold. By contrast, LAT-detected bursts are best fit by a synchrotron spectrum with a cooling break that lies either between or above the XRT and LAT energy ranges. We speculate that the primary difference between GRBs with LAT afterglow detections and the non-detected population may be in the type of circumstellar environment in which these bursts occur, with late-time LAT detections preferentially selecting GRBs that occur in low wind-like circumburst density profiles. Furthermore, we find no evidence of high-energy emission in the LAT-detected population significantly in excess of the flux expected from the electron synchrotron spectrum fit to the observed X-ray emission. The lack of excess emission at high energies could be due to a shocked external medium in which the energy density in the magnetic field is stronger than or comparable to that of the relativistic electrons behind the shock, precluding the production of a dominant synchrotron self-Compton (SSC) component in the LAT energy range. Alternatively, the peak of the SSC emission could be beyond the 0.1-100 GeV energy range considered for this analysis.
Published: 2018
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8. Einstein@Home discovers a radio-quiet gamma-ray millisecond pulsar.

Author: Clark CJ, Pletsch HJ, Wu J, Guillemot L, Kerr M, Johnson TJ, Camilo F, Salvetti D, Allen B, Anderson D, Aulbert C, Beer C, Bock O, Cuéllar A, Eggenstein HB, Fehrmann H, Kramer M, Kwang SA, Machenschalk B, Nieder L, Ackermann M, Ajello M, Baldini L, Ballet J, Barbiellini G, Bastieri D, Bellazzini R, Bissaldi E, Blandford RD, Bloom ED, Bonino R, Bottacini E, Brandt TJ, Bregeon J, Bruel P, Buehler R, Burnett TH, Buson S, Cameron RA, Caputo R, Caraveo PA, Cavazzuti E, Cecchi C, Charles E, Chekhtman A, Ciprini S, Cominsky LR, Costantin D, Cutini S, D'Ammando F, De Luca A, Desiante R, Di Venere L, Di Mauro M, Di Lalla N, Digel SW, Favuzzi C, Ferrara EC, Franckowiak A, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Giglietto N, Giordano F, Giroletti M, Gomez-Vargas GA, Green D, Grenier IA, Guiriec S, Harding AK, Hewitt JW, Horan D, Jóhannesson G, Kensei S, Kuss M, La Mura G, Larsson S, Latronico L, Li J, Longo F, Loparco F, Lovellette MN, Lubrano P, Magill JD, Maldera S, Manfreda A, Mazziotta MN, McEnery JE, Michelson PF, Mirabal N, Mitthumsiri W, Mizuno T, Monzani ME, Morselli A, Moskalenko IV, Nuss E, Ohsugi T, Omodei N, Orienti M, Orlando E, Palatiello M, Paliya VS, de Palma F, Paneque D, Perkins JS, Persic M, Pesce-Rollins M, Porter TA, Principe G, Rainò S, Rando R, Ray PS, Razzano M, Reimer A, Reimer O, Romani RW, Saz Parkinson PM, Sgrò C, Siskind EJ, Smith DA, Spada F, Spandre G, Spinelli P, Thayer JB, Thompson DJ, Torres DF, Troja E, Vianello G, Wood K, and Wood M
Abstract: Millisecond pulsars (MSPs) are old neutron stars that spin hundreds of times per second and appear to pulsate as their emission beams cross our line of sight. To date, radio pulsations have been detected from all rotation-powered MSPs. In an attempt to discover radio-quiet gamma-ray MSPs, we used the aggregated power from the computers of tens of thousands of volunteers participating in the Einstein@Home distributed computing project to search for pulsations from unidentified gamma-ray sources in Fermi Large Area Telescope data. This survey discovered two isolated MSPs, one of which is the only known rotation-powered MSP to remain undetected in radio observations. These gamma-ray MSPs were discovered in completely blind searches without prior constraints from other observations, raising hopes for detecting MSPs from a predicted Galactic bulge population.
Published: 2018
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9. Search for Cosmic-Ray Electron and Positron Anisotropies with Seven Years of Fermi Large Area Telescope Data.

Author: Abdollahi S, Ackermann M, Ajello M, Albert A, Atwood WB, Baldini L, Barbiellini G, Bellazzini R, Bissaldi E, Bloom ED, Bonino R, Bottacini E, Brandt TJ, Bruel P, Buson S, Caragiulo M, Cavazzuti E, Chekhtman A, Ciprini S, Costanza F, Cuoco A, Cutini S, D'Ammando F, de Palma F, Desiante R, Digel SW, Di Lalla N, Di Mauro M, Di Venere L, Donaggio B, Drell PS, Favuzzi C, Focke WB, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Giglietto N, Giordano F, Giroletti M, Green D, Guiriec S, Harding AK, Jogler T, Jóhannesson G, Kamae T, Kuss M, Larsson S, Latronico L, Li J, Longo F, Loparco F, Lubrano P, Magill JD, Malyshev D, Manfreda A, Mazziotta MN, Meehan M, Michelson PF, Mitthumsiri W, Mizuno T, Moiseev AA, Monzani ME, Morselli A, Negro M, Nuss E, Ohsugi T, Omodei N, Paneque D, Perkins JS, Pesce-Rollins M, Piron F, Pivato G, Principe G, Rainò S, Rando R, Razzano M, Reimer A, Reimer O, Sgrò C, Simone D, Siskind EJ, Spada F, Spandre G, Spinelli P, Strong AW, Tajima H, Thayer JB, Torres DF, Troja E, Vandenbroucke J, Zaharijas G, and Zimmer S
Abstract: The Large Area Telescope on board the Fermi Gamma-ray Space Telescope has collected the largest ever sample of high-energy cosmic-ray electron and positron events since the beginning of its operation. Potential anisotropies in the arrival directions of cosmic-ray electrons or positrons could be a signature of the presence of nearby sources. We use almost seven years of data with energies above 42 GeV processed with the Pass 8 reconstruction. The present data sample can probe dipole anisotropies down to a level of 10^{-3}. We take into account systematic effects that could mimic true anisotropies at this level. We present a detailed study of the event selection optimization of the cosmic-ray electrons and positrons to be used for anisotropy searches. Since no significant anisotropies have been detected on any angular scale, we present upper limits on the dipole anisotropy. The present constraints are among the strongest to date probing the presence of nearby young and middle-aged sources.
Published: 2017
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10. Search for Spectral Irregularities due to Photon-Axionlike-Particle Oscillations with the Fermi Large Area Telescope.

Author: Ajello M, Albert A, Anderson B, Baldini L, Barbiellini G, Bastieri D, Bellazzini R, Bissaldi E, Blandford RD, Bloom ED, Bonino R, Bottacini E, Bregeon J, Bruel P, Buehler R, Caliandro GA, Cameron RA, Caragiulo M, Caraveo PA, Cecchi C, Chekhtman A, Ciprini S, Cohen-Tanugi J, Conrad J, Costanza F, D'Ammando F, de Angelis A, de Palma F, Desiante R, Di Mauro M, Di Venere L, Domínguez A, Drell PS, Favuzzi C, Focke WB, Franckowiak A, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Giglietto N, Glanzman T, Godfrey G, Guiriec S, Horan D, Jóhannesson G, Katsuragawa M, Kensei S, Kuss M, Larsson S, Latronico L, Li J, Li L, Longo F, Loparco F, Lubrano P, Madejski GM, Maldera S, Manfreda A, Mayer M, Mazziotta MN, Meyer M, Michelson PF, Mirabal N, Mizuno T, Monzani ME, Morselli A, Moskalenko IV, Murgia S, Negro M, Nuss E, Okada C, Orlando E, Ormes JF, Paneque D, Perkins JS, Pesce-Rollins M, Piron F, Pivato G, Porter TA, Rainò S, Rando R, Razzano M, Reimer A, Sánchez-Conde M, Sgrò C, Simone D, Siskind EJ, Spada F, Spandre G, Spinelli P, Takahashi H, Thayer JB, Torres DF, Tosti G, Troja E, Uchiyama Y, Wood KS, Wood M, Zaharijas G, and Zimmer S
Abstract: We report on the search for spectral irregularities induced by oscillations between photons and axionlike-particles (ALPs) in the γ-ray spectrum of NGC 1275, the central galaxy of the Perseus cluster. Using 6 years of Fermi Large Area Telescope data, we find no evidence for ALPs and exclude couplings above 5×10^{-12} GeV^{-1} for ALP masses 0.5≲m_{a}≲5 neV at 95% confidence. The limits are competitive with the sensitivity of planned laboratory experiments, and, together with other bounds, strongly constrain the possibility that ALPs can reduce the γ-ray opacity of the Universe.
Published: 2016
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11. Measurement of the high-energy gamma-ray emission from the Moon with the Fermi Large Area Telescope.

Author: Ackermann M, Ajello M, Albert A, Atwood WB, Baldini L, Barbiellini G, Bastieri D, Bellazzini R, Bissaldi E, Blandford RD, Bonino R, Bottacini E, Bregeon J, Bruel P, Buehler R, Caliandro GA, Cameron RA, Caragiulo M, Caraveo PA, Cavazzuti E, Cecchi C, Chekhtman A, Chiang J, Chiaro G, Ciprini S, Claus R, Cohen-Tanugi J, Costanza F, Cuoco A, Cutini S, D'Ammando F, de Angelis A, de Palma F, Desiante R, Digel SW, Di Venere L, Drell PS, Favuzzi C, Fegan SJ, Focke WB, Franckowiak A, Funk S, Fusco P, Gargano F, Gasparrini D, Giglietto N, Giordano F, Giroletti M, Glanzman T, Godfrey G, Grenier IA, Grove JE, Guiriec S, Harding AK, Hewitt JW, Horan D, Hou X, Iafrate G, Jóhannesson G, Kamae T, Kuss M, Larsson S, Latronico L, Li J, Li L, Longo F, Loparco F, Lovellette MN, Lubrano P, Magill J, Maldera S, Manfreda A, Mayer M, Mazziotta MN, Michelson PF, Mitthumsiri W, Mizuno T, Monzani ME, Morselli A, Murgia S, Nuss E, Omodei N, Orlando E, Ormes JF, Paneque D, Perkins JS, Pesce-Rollins M, Petrosian V, Piron F, Pivato G, Rainò S, Rando R, Razzano M, Reimer A, Reimer O, Reposeur T, Sgrò C, Siskind EJ, Spada F, Spandre G, Spinelli P, Takahashi H, Thayer JB, Thompson DJ, Tibaldo L, Torres DF, Tosti G, Troja E, Vianello G, Winer BL, Wood KS, Yassine M, Cerutti F, Ferrari A, and Sala PR
Abstract: We have measured the gamma-ray emission spectrum of the Moon using the data collected by the Large Area Telescope onboard the Fermi satellite during its first seven years of operation, in the energy range from 30 MeV up to a few GeV. We have also studied the time evolution of the flux, finding a correlation with the solar activity. We have developed a full Monte Carlo simulation describing the interactions of cosmic rays with the lunar surface. The results of the present analysis can be explained in the framework of this model, where the production of gamma rays is due to the interactions of cosmic-ray proton and helium nuclei with the surface of the Moon. Finally, we have used our simulation to derive the cosmic-ray proton and helium spectra near Earth from the Moon gamma-ray data.
Published: 2016
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12. Resolving the Extragalactic γ-Ray Background above 50 GeV with the Fermi Large Area Telescope.

Author: Ackermann M, Ajello M, Albert A, Atwood WB, Baldini L, Ballet J, Barbiellini G, Bastieri D, Bechtol K, Bellazzini R, Bissaldi E, Blandford RD, Bloom ED, Bonino R, Bregeon J, Britto RJ, Bruel P, Buehler R, Caliandro GA, Cameron RA, Caragiulo M, Caraveo PA, Cavazzuti E, Cecchi C, Charles E, Chekhtman A, Chiang J, Chiaro G, Ciprini S, Cohen-Tanugi J, Cominsky LR, Costanza F, Cutini S, D'Ammando F, de Angelis A, de Palma F, Desiante R, Digel SW, Di Mauro M, Di Venere L, Domínguez A, Drell PS, Favuzzi C, Fegan SJ, Ferrara EC, Franckowiak A, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Giglietto N, Giommi P, Giordano F, Giroletti M, Godfrey G, Green D, Grenier IA, Guiriec S, Hays E, Horan D, Iafrate G, Jogler T, Jóhannesson G, Kuss M, La Mura G, Larsson S, Latronico L, Li J, Li L, Longo F, Loparco F, Lott B, Lovellette MN, Lubrano P, Madejski GM, Magill J, Maldera S, Manfreda A, Mayer M, Mazziotta MN, Michelson PF, Mitthumsiri W, Mizuno T, Moiseev AA, Monzani ME, Morselli A, Moskalenko IV, Murgia S, Negro M, Nuss E, Ohsugi T, Okada C, Omodei N, Orlando E, Ormes JF, Paneque D, Perkins JS, Pesce-Rollins M, Petrosian V, Piron F, Pivato G, Porter TA, Rainò S, Rando R, Razzano M, Razzaque S, Reimer A, Reimer O, Reposeur T, Romani RW, Sánchez-Conde M, Schmid J, Schulz A, Sgrò C, Simone D, Siskind EJ, Spada F, Spandre G, Spinelli P, Suson DJ, Takahashi H, Thayer JB, Tibaldo L, Torres DF, Troja E, Vianello G, Yassine M, and Zimmer S
Abstract: The Fermi Large Area Telescope (LAT) Collaboration has recently released a catalog of 360 sources detected above 50 GeV (2FHL). This catalog was obtained using 80 months of data re-processed with Pass 8, the newest event-level analysis, which significantly improves the acceptance and angular resolution of the instrument. Most of the 2FHL sources at high Galactic latitude are blazars. Using detailed Monte Carlo simulations, we measure, for the first time, the source count distribution, dN/dS, of extragalactic γ-ray sources at E>50 GeV and find that it is compatible with a Euclidean distribution down to the lowest measured source flux in the 2FHL (∼8×10^{-12} ph cm^{-2} s^{-1}). We employ a one-point photon fluctuation analysis to constrain the behavior of dN/dS below the source detection threshold. Overall, the source count distribution is constrained over three decades in flux and found compatible with a broken power law with a break flux, S_{b}, in the range [8×10^{-12},1.5×10^{-11}] ph cm^{-2} s^{-1} and power-law indices below and above the break of α_{2}∈[1.60,1.75] and α_{1}=2.49±0.12, respectively. Integration of dN/dS shows that point sources account for at least 86_{-14}^{+16}% of the total extragalactic γ-ray background. The simple form of the derived source count distribution is consistent with a single population (i.e., blazars) dominating the source counts to the minimum flux explored by this analysis. We estimate the density of sources detectable in blind surveys that will be performed in the coming years by the Cherenkov Telescope Array.
Published: 2016
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13. Searching for Dark Matter Annihilation from Milky Way Dwarf Spheroidal Galaxies with Six Years of Fermi Large Area Telescope Data.

Author: Ackermann M, Albert A, Anderson B, Atwood WB, Baldini L, Barbiellini G, Bastieri D, Bechtol K, Bellazzini R, Bissaldi E, Blandford RD, Bloom ED, Bonino R, Bottacini E, Brandt TJ, Bregeon J, Bruel P, Buehler R, Caliandro GA, Cameron RA, Caputo R, Caragiulo M, Caraveo PA, Cecchi C, Charles E, Chekhtman A, Chiang J, Chiaro G, Ciprini S, Claus R, Cohen-Tanugi J, Conrad J, Cuoco A, Cutini S, D'Ammando F, de Angelis A, de Palma F, Desiante R, Digel SW, Di Venere L, Drell PS, Drlica-Wagner A, Essig R, Favuzzi C, Fegan SJ, Ferrara EC, Focke WB, Franckowiak A, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Giglietto N, Giordano F, Giroletti M, Glanzman T, Godfrey G, Gomez-Vargas GA, Grenier IA, Guiriec S, Gustafsson M, Hays E, Hewitt JW, Horan D, Jogler T, Jóhannesson G, Kuss M, Larsson S, Latronico L, Li J, Li L, Llena Garde M, Longo F, Loparco F, Lubrano P, Malyshev D, Mayer M, Mazziotta MN, McEnery JE, Meyer M, Michelson PF, Mizuno T, Moiseev AA, Monzani ME, Morselli A, Murgia S, Nuss E, Ohsugi T, Orienti M, Orlando E, Ormes JF, Paneque D, Perkins JS, Pesce-Rollins M, Piron F, Pivato G, Porter TA, Rainò S, Rando R, Razzano M, Reimer A, Reimer O, Ritz S, Sánchez-Conde M, Schulz A, Sehgal N, Sgrò C, Siskind EJ, Spada F, Spandre G, Spinelli P, Strigari L, Tajima H, Takahashi H, Thayer JB, Tibaldo L, Torres DF, Troja E, Vianello G, Werner M, Winer BL, Wood KS, Wood M, Zaharijas G, and Zimmer S
Abstract: The dwarf spheroidal satellite galaxies (dSphs) of the Milky Way are some of the most dark matter (DM) dominated objects known. We report on γ-ray observations of Milky Way dSphs based on six years of Fermi Large Area Telescope data processed with the new Pass8 event-level analysis. None of the dSphs are significantly detected in γ rays, and we present upper limits on the DM annihilation cross section from a combined analysis of 15 dSphs. These constraints are among the strongest and most robust to date and lie below the canonical thermal relic cross section for DM of mass ≲100 GeV annihilating via quark and τ-lepton channels.
Published: 2015
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14. Inferred cosmic-ray spectrum from Fermi large area telescope γ-ray observations of Earth's limb.

Author: Ackermann M, Ajello M, Albert A, Allafort A, Baldini L, Barbiellini G, Bastieri D, Bechtol K, Bellazzini R, Blandford RD, Bloom ED, Bonamente E, Bottacini E, Bouvier A, Brandt TJ, Brigida M, Bruel P, Buehler R, Buson S, Caliandro GA, Cameron RA, Caraveo PA, Cecchi C, Charles E, Chaves RC, Chekhtman A, Chiang J, Chiaro G, Ciprini S, Claus R, Cohen-Tanugi J, Conrad J, Cutini S, Dalton M, D'Ammando F, de Angelis A, de Palma F, Dermer CD, Digel SW, Di Venere L, do Couto e Silva E, Drell PS, Drlica-Wagner A, Favuzzi C, Fegan SJ, Ferrara EC, Focke WB, Franckowiak A, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Germani S, Giglietto N, Giordano F, Giroletti M, Glanzman T, Godfrey G, Gomez-Vargas GA, Grenier IA, Grove JE, Guiriec S, Gustafsson M, Hadasch D, Hanabata Y, Harding AK, Hayashida M, Hayashi K, Hewitt JW, Horan D, Hou X, Hughes RE, Inoue Y, Jackson MS, Jogler T, Jóhannesson G, Johnson AS, Kamae T, Kawano T, Knödlseder J, Kuss M, Lande J, Larsson S, Latronico L, Longo F, Loparco F, Lovellette MN, Lubrano P, Mayer M, Mazziotta MN, McEnery JE, Mehault J, Michelson PF, Mitthumsiri W, Mizuno T, Moiseev AA, Monte C, Monzani ME, Morselli A, Moskalenko IV, Murgia S, Nemmen R, Nuss E, Ohsugi T, Okumura A, Orienti M, Orlando E, Ormes JF, Paneque D, Panetta JH, Perkins JS, Pesce-Rollins M, Piron F, Pivato G, Porter TA, Rainò S, Rando R, Razzano M, Razzaque S, Reimer A, Reimer O, Ritz S, Roth M, Schaal M, Schulz A, Sgrò C, Siskind EJ, Spandre G, Spinelli P, Strong AW, Takahashi H, Takeuchi Y, Thayer JG, Thayer JB, Thompson DJ, Tibaldo L, Tinivella M, Torres DF, Tosti G, Troja E, Tronconi V, Usher TL, Vandenbroucke J, Vasileiou V, Vianello G, Vitale V, Werner M, Winer BL, Wood KS, Wood M, and Yang Z
Abstract: Recent accurate measurements of cosmic-ray (CR) species by ATIC-2, CREAM, and PAMELA reveal an unexpected hardening in the proton and He spectra above a few hundred GeV, a gradual softening of the spectra just below a few hundred GeV, and a harder spectrum of He compared to that of protons. These newly discovered features may offer a clue to the origin of high-energy CRs. We use the Fermi Large Area Telescope observations of the γ-ray emission from Earth's limb for an indirect measurement of the local spectrum of CR protons in the energy range ∼90 GeV-6 TeV (derived from a photon energy range 15 GeV-1 TeV). Our analysis shows that single power law and broken power law spectra fit the data equally well and yield a proton spectrum with index 2.68±0.04 and 2.61±0.08 above ∼200 GeV, respectively.
Published: 2014
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15. Fermi-LAT observations of the gamma-ray burst GRB 130427A.

Author: Ackermann M, Ajello M, Asano K, Atwood WB, Axelsson M, Baldini L, Ballet J, Barbiellini G, Baring MG, Bastieri D, Bechtol K, Bellazzini R, Bissaldi E, Bonamente E, Bregeon J, Brigida M, Bruel P, Buehler R, Burgess JM, Buson S, Caliandro GA, Cameron RA, Caraveo PA, Cecchi C, Chaplin V, Charles E, Chekhtman A, Cheung CC, Chiang J, Chiaro G, Ciprini S, Claus R, Cleveland W, Cohen-Tanugi J, Collazzi A, Cominsky LR, Connaughton V, Conrad J, Cutini S, D'Ammando F, de Angelis A, DeKlotz M, de Palma F, Dermer CD, Desiante R, Diekmann A, Di Venere L, Drell PS, Drlica-Wagner A, Favuzzi C, Fegan SJ, Ferrara EC, Finke J, Fitzpatrick G, Focke WB, Franckowiak A, Fukazawa Y, Funk S, Fusco P, Gargano F, Gehrels N, Germani S, Gibby M, Giglietto N, Giles M, Giordano F, Giroletti M, Godfrey G, Granot J, Grenier IA, Grove JE, Gruber D, Guiriec S, Hadasch D, Hanabata Y, Harding AK, Hayashida M, Hays E, Horan D, Hughes RE, Inoue Y, Jogler T, Jóhannesson G, Johnson WN, Kawano T, Knödlseder J, Kocevski D, Kuss M, Lande J, Larsson S, Latronico L, Longo F, Loparco F, Lovellette MN, Lubrano P, Mayer M, Mazziotta MN, McEnery JE, Michelson PF, Mizuno T, Moiseev AA, Monzani ME, Moretti E, Morselli A, Moskalenko IV, Murgia S, Nemmen R, Nuss E, Ohno M, Ohsugi T, Okumura A, Omodei N, Orienti M, Paneque D, Pelassa V, Perkins JS, Pesce-Rollins M, Petrosian V, Piron F, Pivato G, Porter TA, Racusin JL, Rainò S, Rando R, Razzano M, Razzaque S, Reimer A, Reimer O, Ritz S, Roth M, Ryde F, Sartori A, Parkinson PM, Scargle JD, Schulz A, Sgrò C, Siskind EJ, Sonbas E, Spandre G, Spinelli P, Tajima H, Takahashi H, Thayer JG, Thayer JB, Thompson DJ, Tibaldo L, Tinivella M, Torres DF, Tosti G, Troja E, Usher TL, Vandenbroucke J, Vasileiou V, Vianello G, Vitale V, Winer BL, Wood KS, Yamazaki R, Younes G, Yu HF, Zhu SJ, Bhat PN, Briggs MS, Byrne D, Foley S, Goldstein A, Jenke P, Kippen RM, Kouveliotou C, McBreen S, Meegan C, Paciesas WS, Preece R, Rau A, Tierney D, van der Horst AJ, von Kienlin A, Wilson-Hodge C, Xiong S, Cusumano G, La Parola V, and Cummings JR
Abstract: The observations of the exceptionally bright gamma-ray burst (GRB) 130427A by the Large Area Telescope aboard the Fermi Gamma-ray Space Telescope provide constraints on the nature of these unique astrophysical sources. GRB 130427A had the largest fluence, highest-energy photon (95 GeV), longest γ-ray duration (20 hours), and one of the largest isotropic energy releases ever observed from a GRB. Temporal and spectral analyses of GRB 130427A challenge the widely accepted model that the nonthermal high-energy emission in the afterglow phase of GRBs is synchrotron emission radiated by electrons accelerated at an external shock.
Published: 2014
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16. The first pulse of the extremely bright GRB 130427A: a test lab for synchrotron shocks.

Author: Preece R, Burgess JM, von Kienlin A, Bhat PN, Briggs MS, Byrne D, Chaplin V, Cleveland W, Collazzi AC, Connaughton V, Diekmann A, Fitzpatrick G, Foley S, Gibby M, Giles M, Goldstein A, Greiner J, Gruber D, Jenke P, Kippen RM, Kouveliotou C, McBreen S, Meegan C, Paciesas WS, Pelassa V, Tierney D, van der Horst AJ, Wilson-Hodge C, Xiong S, Younes G, Yu HF, Ackermann M, Ajello M, Axelsson M, Baldini L, Barbiellini G, Baring MG, Bastieri D, Bellazzini R, Bissaldi E, Bonamente E, Bregeon J, Brigida M, Bruel P, Buehler R, Buson S, Caliandro GA, Cameron RA, Caraveo PA, Cecchi C, Charles E, Chekhtman A, Chiang J, Chiaro G, Ciprini S, Claus R, Cohen-Tanugi J, Cominsky LR, Conrad J, D'Ammando F, de Angelis A, de Palma F, Dermer CD, Desiante R, Digel SW, Di Venere L, Drell PS, 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 IA, Guiriec S, Hadasch D, Hanabata Y, Harding AK, 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 MN, Lubrano P, Mayer M, Mazziotta MN, Michelson PF, Mizuno T, Monzani ME, 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 JS, Pesce-Rollins M, Piron F, Pivato G, Porter TA, Racusin JL, Rainò S, Rando R, Razzano M, Razzaque S, Reimer A, Reimer O, Ritz S, Roth M, Ryde F, Sartori A, Scargle JD, Schulz A, Sgrò C, Siskind EJ, Spandre G, Spinelli P, Suson DJ, Tajima H, Takahashi H, Thayer JG, Thayer JB, Tibaldo L, Tinivella M, Torres DF, Tosti G, Troja E, Usher TL, Vandenbroucke J, Vasileiou V, Vianello G, Vitale V, Werner M, Winer BL, Wood KS, and Zhu S
Abstract: 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.
Published: 2014
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17. Detection of the characteristic pion-decay signature in supernova remnants.

Author: Ackermann M, Ajello M, Allafort A, Baldini L, Ballet J, Barbiellini G, Baring MG, Bastieri D, Bechtol K, Bellazzini R, Blandford RD, Bloom ED, Bonamente E, Borgland AW, Bottacini E, Brandt TJ, Bregeon J, Brigida M, Bruel P, Buehler R, Busetto G, Buson S, Caliandro GA, Cameron RA, Caraveo PA, Casandjian JM, Cecchi C, Celik O, Charles E, Chaty S, Chaves RC, Chekhtman A, Cheung CC, Chiang J, Chiaro G, Cillis AN, Ciprini S, Claus R, Cohen-Tanugi J, Cominsky LR, Conrad J, Corbel S, Cutini S, D'Ammando F, de Angelis A, de Palma F, Dermer CD, do Couto e Silva E, Drell PS, Drlica-Wagner A, Falletti L, Favuzzi C, Ferrara EC, Franckowiak A, Fukazawa Y, Funk S, Fusco P, Gargano F, Germani S, Giglietto N, Giommi P, Giordano F, Giroletti M, Glanzman T, Godfrey G, Grenier IA, Grondin MH, Grove JE, Guiriec S, Hadasch D, Hanabata Y, Harding AK, Hayashida M, Hayashi K, Hays E, Hewitt JW, Hill AB, Hughes RE, Jackson MS, Jogler T, Jóhannesson G, Johnson AS, Kamae T, Kataoka J, Katsuta J, Knödlseder J, Kuss M, Lande J, Larsson S, Latronico L, Lemoine-Goumard M, Longo F, Loparco F, Lovellette MN, Lubrano P, Madejski GM, Massaro F, Mayer M, Mazziotta MN, McEnery JE, Mehault J, Michelson PF, Mignani RP, Mitthumsiri W, Mizuno T, Moiseev AA, Monzani ME, Morselli A, Moskalenko IV, Murgia S, Nakamori T, Nemmen R, Nuss E, Ohno M, Ohsugi T, Omodei N, Orienti M, Orlando E, Ormes JF, Paneque D, Perkins JS, Pesce-Rollins M, Piron F, Pivato G, Rainò S, Rando R, Razzano M, Razzaque S, Reimer A, Reimer O, Ritz S, Romoli C, Sánchez-Conde M, Schulz A, Sgrò C, Simeon PE, Siskind EJ, Smith DA, Spandre G, Spinelli P, Stecker FW, Strong AW, Suson DJ, Tajima H, Takahashi H, Takahashi T, Tanaka T, Thayer JG, Thayer JB, Thompson DJ, Thorsett SE, Tibaldo L, Tibolla O, Tinivella M, Troja E, Uchiyama Y, Usher TL, Vandenbroucke J, Vasileiou V, Vianello G, Vitale V, Waite AP, Werner M, Winer BL, Wood KS, Wood M, Yamazaki R, Yang Z, and Zimmer S
Abstract: Cosmic rays are particles (mostly protons) accelerated to relativistic speeds. Despite wide agreement that supernova remnants (SNRs) are the sources of galactic cosmic rays, unequivocal evidence for the acceleration of protons in these objects is still lacking. When accelerated protons encounter interstellar material, they produce neutral pions, which in turn decay into gamma rays. This offers a compelling way to detect the acceleration sites of protons. The identification of pion-decay gamma rays has been difficult because high-energy electrons also produce gamma rays via bremsstrahlung and inverse Compton scattering. We detected the characteristic pion-decay feature in the gamma-ray spectra of two SNRs, IC 443 and W44, with the Fermi Large Area Telescope. This detection provides direct evidence that cosmic-ray protons are accelerated in SNRs.
Published: 2013
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18. The imprint of the extragalactic background light in the gamma-ray spectra of blazars.

Author: Ackermann M, Ajello M, Allafort A, Schady P, Baldini L, Ballet J, Barbiellini G, Bastieri D, Bellazzini R, Blandford RD, Bloom ED, Borgland AW, Bottacini E, Bouvier A, Bregeon J, Brigida M, Bruel P, Buehler R, Buson S, Caliandro GA, Cameron RA, Caraveo PA, Cavazzuti E, Cecchi C, Charles E, Chaves RC, Chekhtman A, Cheung CC, Chiang J, Chiaro G, Ciprini S, Claus R, Cohen-Tanugi J, Conrad J, Cutini S, D'Ammando F, de Palma F, Dermer CD, Digel SW, do Couto e Silva E, Domínguez A, Drell PS, Drlica-Wagner A, Favuzzi C, Fegan SJ, Focke WB, Franckowiak A, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Gehrels N, Germani S, Giglietto N, Giordano F, Giroletti M, Glanzman T, Godfrey G, Grenier IA, Grove JE, Guiriec S, Gustafsson M, Hadasch D, Hayashida M, Hays E, Jackson MS, Jogler T, Kataoka J, Knödlseder J, Kuss M, Lande J, Larsson S, Latronico L, Longo F, Loparco F, Lovellette MN, Lubrano P, Mazziotta MN, McEnery JE, Mehault J, Michelson PF, Mizuno T, Monte C, Monzani ME, Morselli A, Moskalenko IV, Murgia S, Tramacere A, Nuss E, Greiner J, Ohno M, Ohsugi T, Omodei N, Orienti M, Orlando E, Ormes JF, Paneque D, Perkins JS, Pesce-Rollins M, Piron F, Pivato G, Porter TA, Rainò S, Rando R, Razzano M, Razzaque S, Reimer A, Reimer O, Reyes LC, Ritz S, Rau A, Romoli C, Roth M, Sánchez-Conde M, Sanchez DA, Scargle JD, Sgrò C, Siskind EJ, Spandre G, Spinelli P, Stawarz Ł, Suson DJ, Takahashi H, Tanaka T, Thayer JG, Thompson DJ, Tibaldo L, Tinivella M, Torres DF, Tosti G, Troja E, Usher TL, Vandenbroucke J, Vasileiou V, Vianello G, Vitale V, Waite AP, Winer BL, Wood KS, and Wood M
Abstract: The light emitted by stars and accreting compact objects through the history of the universe is encoded in the intensity of the extragalactic background light (EBL). Knowledge of the EBL is important to understand the nature of star formation and galaxy evolution, but direct measurements of the EBL are limited by galactic and other foreground emissions. Here, we report an absorption feature seen in the combined spectra of a sample of gamma-ray blazars out to a redshift of z ∼ 1.6. This feature is caused by attenuation of gamma rays by the EBL at optical to ultraviolet frequencies and allowed us to measure the EBL flux density in this frequency band.
Published: 2012
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19. Periodic emission from the gamma-ray binary 1FGL J1018.6-5856.

Author: Fermi LAT Collaboration, Ackermann M, Ajello M, Ballet J, Barbiellini G, Bastieri D, Belfiore A, Bellazzini R, Berenji B, Blandford RD, Bloom ED, Bonamente E, Borgland AW, Bregeon J, Brigida M, Bruel P, Buehler R, Buson S, Caliandro GA, Cameron RA, Caraveo PA, Cavazzuti E, Cecchi C, Çelik Ö, Charles E, Chaty S, Chekhtman A, Cheung CC, Chiang J, Ciprini S, Claus R, Cohen-Tanugi J, Corbel S, Corbet RH, Cutini S, de Luca A, den Hartog PR, de Palma F, Dermer CD, Digel SW, do Couto e Silva E, Donato D, Drell PS, Drlica-Wagner A, Dubois R, Dubus G, Favuzzi C, Fegan SJ, Ferrara EC, Focke WB, Fortin P, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Gehrels N, Germani S, Giglietto N, Giordano F, Giroletti M, Glanzman T, Godfrey G, Grenier IA, Grove JE, Guiriec S, Hadasch D, Hanabata Y, Harding AK, Hayashida M, Hays E, Hill AB, Hughes RE, Jóhannesson G, Johnson AS, Johnson TJ, Kamae T, Katagiri H, Kataoka J, Kerr M, Knödlseder J, Kuss M, Lande J, Longo F, Loparco F, Lovellette MN, Lubrano P, Mazziotta MN, McEnery JE, Michelson PF, Mitthumsiri W, Mizuno T, Monte C, Monzani ME, Morselli A, Moskalenko IV, Murgia S, Nakamori T, Naumann-Godo M, Norris JP, Nuss E, Ohno M, Ohsugi T, Okumura A, Omodei N, Orlando E, Ozaki M, Paneque D, Parent D, Pesce-Rollins M, Pierbattista M, Piron F, Pivato G, Porter TA, Rainò S, Rando R, Razzano M, Reimer A, Reimer O, Ritz S, Romani RW, Roth M, Saz Parkinson PM, Sgrò C, Siskind EJ, Spandre G, Spinelli P, Suson DJ, Takahashi H, Tanaka T, Thayer JG, Thayer JB, Thompson DJ, Tibaldo L, Tinivella M, Torres DF, Tosti G, Troja E, Uchiyama Y, Usher TL, Vandenbroucke J, Vianello G, Vitale V, Waite AP, Winer BL, Wood KS, Wood M, Yang Z, Zimmer S, Coe MJ, Di Mille F, Edwards PG, Filipović MD, Payne JL, Stevens J, and Torres MA
Abstract: Gamma-ray binaries are stellar systems containing a neutron star or black hole, with gamma-ray emission produced by an interaction between the components. These systems are rare, even though binary evolution models predict dozens in our Galaxy. A search for gamma-ray binaries with the Fermi Large Area Telescope (LAT) shows that 1FGL J1018.6-5856 exhibits intensity and spectral modulation with a 16.6-day period. We identified a variable x-ray counterpart, which shows a sharp maximum coinciding with maximum gamma-ray emission, as well as an O6V((f)) star optical counterpart and a radio counterpart that is also apparently modulated on the orbital period. 1FGL J1018.6-5856 is thus a gamma-ray binary, and its detection suggests the presence of other fainter binaries in the Galaxy.
Published: 2012
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20. Measurement of separate cosmic-ray electron and positron spectra with the fermi large area telescope.

Author: Ackermann M, Ajello M, Allafort A, Atwood WB, Baldini L, Barbiellini G, Bastieri D, Bechtol K, Bellazzini R, Berenji B, Blandford RD, Bloom ED, Bonamente E, Borgland AW, Bouvier A, Bregeon J, Brigida M, Bruel P, Buehler R, Buson S, Caliandro GA, Cameron RA, Caraveo PA, Casandjian JM, Cecchi C, Charles E, Chekhtman A, Cheung CC, Chiang J, Ciprini S, Claus R, Cohen-Tanugi J, Conrad J, Cutini S, de Angelis A, de Palma F, Dermer CD, Digel SW, do Couto E Silva E, Drell PS, Drlica-Wagner A, Favuzzi C, Fegan SJ, Ferrara EC, Focke WB, Fortin P, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Germani S, Giglietto N, Giommi P, Giordano F, Giroletti M, Glanzman T, Godfrey G, Grenier IA, Grove JE, Guiriec S, Gustafsson M, Hadasch D, Harding AK, Hayashida M, Hughes RE, Jóhannesson G, Johnson AS, Kamae T, Katagiri H, Kataoka J, Knödlseder J, Kuss M, Lande J, Latronico L, Lemoine-Goumard M, Llena Garde M, Longo F, Loparco F, Lovellette MN, Lubrano P, Madejski GM, Mazziotta MN, McEnery JE, Michelson PF, Mitthumsiri W, Mizuno T, Moiseev AA, Monte C, Monzani ME, Morselli A, Moskalenko IV, Murgia S, Nakamori T, Nolan PL, Norris JP, Nuss E, Ohno M, Ohsugi T, Okumura A, Omodei N, Orlando E, Ormes JF, Ozaki M, Paneque D, Parent D, Pesce-Rollins M, Pierbattista M, Piron F, Pivato G, Porter TA, Rainò S, Rando R, Razzano M, Razzaque S, Reimer A, Reimer O, Reposeur T, Ritz S, Romani RW, Roth M, Sadrozinski HF, Sbarra C, Schalk TL, Sgrò C, Siskind EJ, Spandre G, Spinelli P, Strong AW, Takahashi H, Takahashi T, Tanaka T, Thayer JG, Thayer JB, Tibaldo L, Tinivella M, Torres DF, Tosti G, Troja E, Uchiyama Y, Usher TL, Vandenbroucke J, Vasileiou V, Vianello G, Vitale V, Waite AP, Winer BL, Wood KS, Wood M, Yang Z, and Zimmer S
Abstract: We measured separate cosmic-ray electron and positron spectra with the Fermi Large Area Telescope. Because the instrument does not have an onboard magnet, we distinguish the two species by exploiting Earth's shadow, which is offset in opposite directions for opposite charges due to Earth's magnetic field. We estimate and subtract the cosmic-ray proton background using two different methods that produce consistent results. We report the electron-only spectrum, the positron-only spectrum, and the positron fraction between 20 and 200 GeV. We confirm that the fraction rises with energy in the 20-100 GeV range. The three new spectral points between 100 and 200 GeV are consistent with a fraction that is continuing to rise with energy.
Published: 2012
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21. Constraining dark matter models from a combined analysis of Milky Way satellites with the Fermi Large Area Telescope.

Author: Ackermann M, Ajello M, Albert A, Atwood WB, Baldini L, Ballet J, Barbiellini G, Bastieri D, Bechtol K, Bellazzini R, Berenji B, Blandford RD, Bloom ED, Bonamente E, Borgland AW, Bregeon J, Brigida M, Bruel P, Buehler R, Burnett TH, Buson S, Caliandro GA, Cameron RA, Cañadas B, Caraveo PA, Casandjian JM, Cecchi C, Charles E, Chekhtman A, Chiang J, Ciprini S, Claus R, Cohen-Tanugi J, Conrad J, Cutini S, de Angelis A, de Palma F, Dermer CD, Digel SW, do Couto e Silva E, Drell PS, Drlica-Wagner A, Falletti L, Favuzzi C, Fegan SJ, Ferrara EC, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Gehrels N, Germani S, Giglietto N, Giordano F, Giroletti M, Glanzman T, Godfrey G, Grenier IA, Guiriec S, Gustafsson M, Hadasch D, Hayashida M, Hays E, Hughes RE, Jeltema TE, Jóhannesson G, Johnson RP, Johnson AS, Kamae T, Katagiri H, Kataoka J, Knödlseder J, Kuss M, Lande J, Latronico L, Lionetto AM, Llena Garde M, Longo F, Loparco F, Lott B, Lovellette MN, Lubrano P, Madejski GM, Mazziotta MN, McEnery JE, Mehault J, Michelson PF, Mitthumsiri W, Mizuno T, Monte C, Monzani ME, Morselli A, Moskalenko IV, Murgia S, Naumann-Godo M, Norris JP, Nuss E, Ohsugi T, Okumura A, Omodei N, Orlando E, Ormes JF, Ozaki M, Paneque D, Parent D, Pesce-Rollins M, Pierbattista M, Piron F, Pivato G, Porter TA, Profumo S, Rainò S, Razzano M, Reimer A, Reimer O, Ritz S, Roth M, Sadrozinski HF, Sbarra C, Scargle JD, Schalk TL, Sgrò C, Siskind EJ, Spandre G, Spinelli P, Strigari L, Suson DJ, Tajima H, Takahashi H, Tanaka T, Thayer JG, Thayer JB, Thompson DJ, Tibaldo L, Tinivella M, Torres DF, Troja E, Uchiyama Y, Vandenbroucke J, Vasileiou V, Vianello G, Vitale V, Waite AP, Wang P, Winer BL, Wood KS, Wood M, Yang Z, Zimmer S, Kaplinghat M, and Martinez GD
Abstract: Satellite galaxies of the Milky Way are among the most promising targets for dark matter searches in gamma rays. We present a search for dark matter consisting of weakly interacting massive particles, applying a joint likelihood analysis to 10 satellite galaxies with 24 months of data of the Fermi Large Area Telescope. No dark matter signal is detected. Including the uncertainty in the dark matter distribution, robust upper limits are placed on dark matter annihilation cross sections. The 95% confidence level upper limits range from about 10(-26) cm3 s(-1) at 5 GeV to about 5×10(-23) cm3 s(-1) at 1 TeV, depending on the dark matter annihilation final state. For the first time, using gamma rays, we are able to rule out models with the most generic cross section (∼3×10(-26) cm3 s(-1) for a purely s-wave cross section), without assuming additional boost factors.
Published: 2011
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22. A cocoon of freshly accelerated cosmic rays detected by Fermi in the Cygnus superbubble.

Author: Ackermann M, Ajello M, Allafort A, Baldini L, Ballet J, Barbiellini G, Bastieri D, Belfiore A, Bellazzini R, Berenji B, Blandford RD, Bloom ED, Bonamente E, Borgland AW, Bottacini E, Brigida M, Bruel P, Buehler R, Buson S, Caliandro GA, Cameron RA, Caraveo PA, Casandjian JM, Cecchi C, Chekhtman A, Cheung CC, Chiang J, Ciprini S, Claus R, Cohen-Tanugi J, de Angelis A, de Palma F, Dermer CD, do Couto E Silva E, Drell PS, Dumora D, Favuzzi C, Fegan SJ, Focke WB, Fortin P, Fukazawa Y, Fusco P, Gargano F, Germani S, Giglietto N, Giordano F, Giroletti M, Glanzman T, Godfrey G, Grenier IA, Guillemot L, Guiriec S, Hadasch D, Hanabata Y, Harding AK, Hayashida M, Hayashi K, Hays E, Jóhannesson G, Johnson AS, Kamae T, Katagiri H, Kataoka J, Kerr M, Knödlseder J, Kuss M, Lande J, Latronico L, Lee SH, Longo F, Loparco F, Lott B, Lovellette MN, Lubrano P, Martin P, Mazziotta MN, McEnery JE, Mehault J, Michelson PF, Mitthumsiri W, Mizuno T, Monte C, Monzani ME, Morselli A, Moskalenko IV, Murgia S, Naumann-Godo M, Nolan PL, Norris JP, Nuss E, Ohsugi T, Okumura A, Orlando E, Ormes JF, Ozaki M, Paneque D, Parent D, Pesce-Rollins M, Pierbattista M, Piron F, Pohl M, Prokhorov D, Rainò S, Rando R, Razzano M, Reposeur T, Ritz S, Parkinson PM, Sgrò C, Siskind EJ, Smith PD, Spinelli P, Strong AW, Takahashi H, Tanaka T, Thayer JG, Thayer JB, Thompson DJ, Tibaldo L, Torres DF, Tosti G, Tramacere A, Troja E, Uchiyama Y, Vandenbroucke J, Vasileiou V, Vianello G, Vitale V, Waite AP, Wang P, Winer BL, Wood KS, Yang Z, Zimmer S, and Bontemps S
Abstract: The origin of Galactic cosmic rays is a century-long puzzle. Indirect evidence points to their acceleration by supernova shockwaves, but we know little of their escape from the shock and their evolution through the turbulent medium surrounding massive stars. Gamma rays can probe their spreading through the ambient gas and radiation fields. The Fermi Large Area Telescope (LAT) has observed the star-forming region of Cygnus X. The 1- to 100-gigaelectronvolt images reveal a 50-parsec-wide cocoon of freshly accelerated cosmic rays that flood the cavities carved by the stellar winds and ionization fronts from young stellar clusters. It provides an example to study the youth of cosmic rays in a superbubble environment before they merge into the older Galactic population.
Published: 2011
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23. Gamma-ray flares from the Crab Nebula.

Author: Abdo AA, Ackermann M, Ajello M, Allafort A, Baldini L, Ballet J, Barbiellini G, Bastieri D, Bechtol K, Bellazzini R, Berenji B, Blandford RD, Bloom ED, Bonamente E, Borgland AW, Bouvier A, Brandt TJ, Bregeon J, Brez A, Brigida M, Bruel P, Buehler R, Buson S, Caliandro GA, Cameron RA, Cannon A, Caraveo PA, Casandjian JM, Çelik Ö, Charles E, Chekhtman A, Cheung CC, Chiang J, Ciprini S, Claus R, Cohen-Tanugi J, Costamante L, Cutini S, D'Ammando F, Dermer CD, de Angelis A, de Luca A, de Palma F, Digel SW, do Couto e Silva E, Drell PS, Drlica-Wagner A, Dubois R, Dumora D, Favuzzi C, Fegan SJ, Ferrara EC, Focke WB, Fortin P, Frailis M, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Gehrels N, Germani S, Giglietto N, Giordano F, Giroletti M, Glanzman T, Godfrey G, Grenier IA, Grondin MH, Grove JE, Guiriec S, Hadasch D, Hanabata Y, Harding AK, Hayashi K, Hayashida M, Hays E, Horan D, Itoh R, Jóhannesson G, Johnson AS, Johnson TJ, Khangulyan D, Kamae T, Katagiri H, Kataoka J, Kerr M, Knödlseder J, Kuss M, Lande J, Latronico L, Lee SH, Lemoine-Goumard M, Longo F, Loparco F, Lubrano P, Madejski GM, Makeev A, Marelli M, Mazziotta MN, McEnery JE, Michelson PF, Mitthumsiri W, Mizuno T, Moiseev AA, Monte C, Monzani ME, Morselli A, Moskalenko IV, Murgia S, Nakamori T, Naumann-Godo M, Nolan PL, Norris JP, Nuss E, Ohsugi T, Okumura A, Omodei N, Ormes JF, Ozaki M, Paneque D, Parent D, Pelassa V, Pepe M, Pesce-Rollins M, Pierbattista M, Piron F, Porter TA, Rainò S, Rando R, Ray PS, Razzano M, Reimer A, Reimer O, Reposeur T, Ritz S, Romani RW, Sadrozinski HF, Sanchez D, Saz Parkinson PM, Scargle JD, Schalk TL, Sgrò C, Siskind EJ, Smith PD, Spandre G, Spinelli P, Strickman MS, Suson DJ, Takahashi H, Takahashi T, Tanaka T, Thayer JB, Thompson DJ, Tibaldo L, Torres DF, Tosti G, Tramacere A, Troja E, Uchiyama Y, Vandenbroucke J, Vasileiou V, Vianello G, Vitale V, Wang P, Wood KS, Yang Z, and Ziegler M
Abstract: A young and energetic pulsar powers the well-known Crab Nebula. Here, we describe two separate gamma-ray (photon energy greater than 100 mega-electron volts) flares from this source detected by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. The first flare occurred in February 2009 and lasted approximately 16 days. The second flare was detected in September 2010 and lasted approximately 4 days. During these outbursts, the gamma-ray flux from the nebula increased by factors of four and six, respectively. The brevity of the flares implies that the gamma rays were emitted via synchrotron radiation from peta-electron-volt (10(15) electron volts) electrons in a region smaller than 1.4 × 10(-2) parsecs. These are the highest-energy particles that can be associated with a discrete astronomical source, and they pose challenges to particle acceleration theory.
Published: 2011
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24. Gamma-ray emission concurrent with the nova in the symbiotic binary V407 Cygni.

Author: Abdo AA, Ackermann M, Ajello M, Atwood WB, Baldini L, Ballet J, Barbiellini G, Bastieri D, Bechtol K, Bellazzini R, Berenji B, Blandford RD, Bloom ED, Bonamente E, Borgland AW, Bouvier A, Brandt TJ, Bregeon J, Brez A, Brigida M, Bruel P, Buehler R, Burnett TH, Buson S, Caliandro GA, Cameron RA, Caraveo PA, Carrigan S, Casandjian JM, Cecchi C, Celik O, Charles E, Chaty S, Chekhtman A, Cheung CC, Chiang J, Ciprini S, Claus R, Cohen-Tanugi J, Conrad J, Corbel S, Corbet R, DeCesar ME, den Hartog PR, Dermer CD, de Palma F, Digel SW, Donato D, do Couto e Silva E, Drell PS, Dubois R, Dubus G, Dumora D, Favuzzi C, Fegan SJ, Ferrara EC, Fortin P, Frailis M, Fuhrmann L, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Gehrels N, Germani S, Giglietto N, Giordano F, Giroletti M, Glanzman T, Godfrey G, Grenier IA, Grondin MH, Grove JE, Guiriec S, Hadasch D, Harding AK, Hayashida M, Hays E, Healey SE, Hill AB, Horan D, Hughes RE, Itoh R, Jean P, Jóhannesson G, Johnson AS, Johnson RP, Johnson TJ, Johnson WN, Kamae T, Katagiri H, Kataoka J, Kerr M, Knödlseder J, Koerding E, Kuss M, Lande J, Latronico L, Lee SH, Lemoine-Goumard M, Garde ML, Longo F, Loparco F, Lott B, Lovellette MN, Lubrano P, Makeev A, Mazziotta MN, McConville W, McEnery JE, Mehault J, Michelson PF, Mizuno T, Moiseev AA, Monte C, Monzani ME, Morselli A, Moskalenko IV, Murgia S, Nakamori T, Naumann-Godo M, Nestoras I, Nolan PL, Norris JP, Nuss E, Ohno M, Ohsugi T, Okumura A, Omodei N, Orlando E, Ormes JF, Ozaki M, Paneque D, Panetta JH, Parent D, Pelassa V, Pepe M, Pesce-Rollins M, Piron F, Porter TA, Rainò S, Rando R, Ray PS, Razzano M, Razzaque S, Rea N, Reimer A, Reimer O, Reposeur T, Ripken J, Ritz S, Romani RW, Roth M, Sadrozinski HF, Sander A, Parkinson PM, Scargle JD, Schinzel FK, Sgrò C, Shaw MS, Siskind EJ, Smith DA, Smith PD, Sokolovsky KV, Spandre G, Spinelli P, Stawarz Ł, Strickman MS, Suson DJ, Takahashi H, Takahashi T, Tanaka T, Tanaka Y, Thayer JB, Thayer JG, Thompson DJ, Tibaldo L, Torres DF, Tosti G, Tramacere A, Uchiyama Y, Usher TL, Vandenbroucke J, Vasileiou V, Vilchez N, Vitale V, Waite AP, Wallace E, Wang P, Winer BL, Wolff MT, Wood KS, Yang Z, Ylinen T, Ziegler M, Maehara H, Nishiyama K, Kabashima F, Bach U, Bower GC, Falcone A, Forster JR, Henden A, Kawabata KS, Koubsky P, Mukai K, Nelson T, Oates SR, Sakimoto K, Sasada M, Shenavrin VI, Shore SN, Skinner GK, Sokoloski J, Stroh M, Tatarnikov AM, Uemura M, Wahlgren GM, and Yamanaka M
Abstract: Novae are thermonuclear explosions on a white dwarf surface fueled by mass accreted from a companion star. Current physical models posit that shocked expanding gas from the nova shell can produce x-ray emission, but emission at higher energies has not been widely expected. Here, we report the Fermi Large Area Telescope detection of variable gamma-ray emission (0.1 to 10 billion electron volts) from the recently detected optical nova of the symbiotic star V407 Cygni. We propose that the material of the nova shell interacts with the dense ambient medium of the red giant primary and that particles can be accelerated effectively to produce pi(0) decay gamma-rays from proton-proton interactions. Emission involving inverse Compton scattering of the red giant radiation is also considered and is not ruled out.
Published: 2010
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25. Fermi gamma-ray imaging of a radio galaxy.

Author: Abdo AA, Ackermann M, Ajello M, Atwood WB, Baldini L, Ballet J, Barbiellini G, Bastieri D, Baughman BM, Bechtol K, Bellazzini R, Berenji B, Blandford RD, Bloom ED, Bonamente E, Borgland AW, Bregeon J, Brez A, Brigida M, Bruel P, Burnett TH, Buson S, Caliandro GA, Cameron RA, Caraveo PA, Casandjian JM, Cavazzuti E, Cecchi C, Celik O, Chekhtman A, Cheung CC, Chiang J, Ciprini S, Claus R, Cohen-Tanugi J, Colafrancesco S, Cominsky LR, Conrad J, Costamante L, Cutini S, Davis DS, Dermer CD, de Angelis A, de Palma F, Digel SW, do Couto e Silva E, Drell PS, Dubois R, Dumora D, Farnier C, Favuzzi C, Fegan SJ, Finke J, Focke WB, Fortin P, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Gehrels N, Georganopoulos M, Germani S, Giebels B, Giglietto N, Giordano F, Giroletti M, Glanzman T, Godfrey G, Grenier IA, Grove JE, Guillemot L, Guiriec S, Hanabata Y, Harding AK, Hayashida M, Hays E, Hughes RE, Jackson MS, Jóhannesson G, Johnson AS, Johnson TJ, Johnson WN, Kamae T, Katagiri H, Kataoka J, Kawai N, Kerr M, Knödlseder J, Kocian ML, Kuss M, Lande J, Latronico L, Lemoine-Goumard M, Longo F, Loparco F, Lott B, Lovellette MN, Lubrano P, Madejski GM, Makeev A, Mazziotta MN, McConville W, McEnery JE, Meurer C, Michelson PF, Mitthumsiri W, Mizuno T, Moiseev AA, Monte C, Monzani ME, Morselli A, Moskalenko IV, Murgia S, Nolan PL, Norris JP, Nuss E, Ohsugi T, Omodei N, Orlando E, Ormes JF, Paneque D, Parent D, Pelassa V, Pepe M, Pesce-Rollins M, Piron F, Porter TA, Rainò S, Rando R, Razzano M, Razzaque S, Reimer A, Reimer O, Reposeur T, Ritz S, Rochester LS, Rodriguez AY, Romani RW, Roth M, Ryde F, Sadrozinski HF, Sambruna R, Sanchez D, Sander A, Saz Parkinson PM, Scargle JD, Sgrò C, Siskind EJ, Smith DA, Smith PD, Spandre G, Spinelli P, Starck JL, Stawarz Ł, Strickman MS, Suson DJ, Tajima H, Takahashi H, Takahashi T, Tanaka T, Thayer JB, Thayer JG, Thompson DJ, Tibaldo L, Torres DF, Tosti G, Tramacere A, Uchiyama Y, Usher TL, Vasileiou V, Vilchez N, Vitale V, Waite AP, Wallace E, Wang P, Winer BL, Wood KS, Ylinen T, Ziegler M, Hardcastle MJ, and Kazanas D
Abstract: The Fermi Gamma-ray Space Telescope has detected the gamma-ray glow emanating from the giant radio lobes of the radio galaxy Centaurus A. The resolved gamma-ray image shows the lobes clearly separated from the central active source. In contrast to all other active galaxies detected so far in high-energy gamma-rays, the lobe flux constitutes a considerable portion (greater than one-half) of the total source emission. The gamma-ray emission from the lobes is interpreted as inverse Compton-scattered relic radiation from the cosmic microwave background, with additional contribution at higher energies from the infrared-to-optical extragalactic background light. These measurements provide gamma-ray constraints on the magnetic field and particle energy content in radio galaxy lobes, as well as a promising method to probe the cosmic relic photon fields.
Published: 2010
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26. Spectrum of the isotropic diffuse gamma-ray emission derived from first-year Fermi Large Area Telescope data.

Author: Abdo AA, Ackermann M, Ajello M, Atwood WB, Baldini L, Ballet J, Barbiellini G, Bastieri D, Baughman BM, Bechtol K, Bellazzini R, Berenji B, Blandford RD, Bloom ED, Bonamente E, Borgland AW, Bregeon J, Brez A, Brigida M, Bruel P, Burnett TH, Buson S, Caliandro GA, Cameron RA, Caraveo PA, Casandjian JM, Cavazzuti E, Cecchi C, Celik O, Charles E, Chekhtman A, Cheung CC, Chiang J, Ciprini S, Claus R, Cohen-Tanugi J, Cominsky LR, Conrad J, Cutini S, Dermer CD, de Angelis A, de Palma F, Digel SW, Di Bernardo G, do Couto e Silva E, Drell PS, Drlica-Wagner A, Dubois R, Dumora D, Farnier C, Favuzzi C, Fegan SJ, Focke WB, Fortin P, Frailis M, Fukazawa Y, Funk S, Fusco P, Gaggero D, Gargano F, Gasparrini D, Gehrels N, Germani S, Giebels B, Giglietto N, Giommi P, Giordano F, Glanzman T, Godfrey G, Grenier IA, Grondin MH, Grove JE, Guillemot L, Guiriec S, Gustafsson M, Hanabata Y, Harding AK, Hayashida M, Hughes RE, Itoh R, Jackson MS, Jóhannesson G, Johnson AS, Johnson RP, Johnson TJ, Johnson WN, Kamae T, Katagiri H, Kataoka J, Kawai N, Kerr M, Knödlseder J, Kocian ML, Kuehn F, Kuss M, Lande J, Latronico L, Lemoine-Goumard M, Longo F, Loparco F, Lott B, Lovellette MN, Lubrano P, Madejski GM, Makeev A, Mazziotta MN, McConville W, McEnery JE, Meurer C, Michelson PF, Mitthumsiri W, Mizuno T, Moiseev AA, Monte C, Monzani ME, Morselli A, Moskalenko IV, Murgia S, Nolan PL, Norris JP, Nuss E, Ohsugi T, Omodei N, Orlando E, Ormes JF, Paneque D, Panetta JH, Parent D, Pelassa V, Pepe M, Pesce-Rollins M, Piron F, Porter TA, Rainò S, Rando R, Razzano M, Reimer A, Reimer O, Reposeur T, Ritz S, Rochester LS, Rodriguez AY, Roth M, Ryde F, Sadrozinski HF, Sanchez D, Sander A, Saz Parkinson PM, Scargle JD, Sellerholm A, Sgrò C, Shaw MS, Siskind EJ, Smith DA, Smith PD, Spandre G, Spinelli P, Starck JL, Strickman MS, Strong AW, Suson DJ, Tajima H, Takahashi H, Takahashi T, Tanaka T, Thayer JB, Thayer JG, Thompson DJ, Tibaldo L, Torres DF, Tosti G, Tramacere A, Uchiyama Y, Usher TL, Vasileiou V, Vilchez N, Vitale V, Waite AP, Wang P, Winer BL, Wood KS, Ylinen T, and Ziegler M
Abstract: We report on the first Fermi Large Area Telescope (LAT) measurements of the so-called "extragalactic" diffuse gamma-ray emission (EGB). This component of the diffuse gamma-ray emission is generally considered to have an isotropic or nearly isotropic distribution on the sky with diverse contributions discussed in the literature. The derivation of the EGB is based on detailed modeling of the bright foreground diffuse Galactic gamma-ray emission, the detected LAT sources, and the solar gamma-ray emission. We find the spectrum of the EGB is consistent with a power law with a differential spectral index gamma = 2.41 +/- 0.05 and intensity I(>100 MeV) = (1.03 +/- 0.17) x 10(-5) cm(-2) s(-1) sr(-1), where the error is systematics dominated. Our EGB spectrum is featureless, less intense, and softer than that derived from EGRET data.
Published: 2010
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27. Fermi large area telescope search for photon lines from 30 to 200 GeV and dark matter implications.

Author: Abdo AA, Ackermann M, Ajello M, Atwood WB, Baldini L, Ballet J, Barbiellini G, Bastieri D, Bechtol K, Bellazzini R, Berenji B, Bloom ED, Bonamente E, Borgland AW, Bouvier A, Bregeon J, Brez A, Brigida M, Bruel P, Burnett TH, Buson S, Caliandro GA, Cameron RA, Caraveo PA, Carrigan S, Casandjian JM, Cecchi C, Celik O, Chekhtman A, Chiang J, Ciprini S, Claus R, Cohen-Tanugi J, Conrad J, Dermer CD, de Angelis A, de Palma F, Digel SW, do Couto E Silva E, Drell PS, Drlica-Wagner A, Dubois R, Dumora D, Edmonds Y, Essig R, Farnier C, Favuzzi C, Fegan SJ, Focke WB, Fortin P, Frailis M, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Gehrels N, Germani S, Giglietto N, Giordano F, Glanzman T, Godfrey G, Grenier IA, Grove JE, Guillemot L, Guiriec S, Gustafsson M, Hadasch D, Harding AK, Horan D, Hughes RE, Jackson MS, Jóhannesson G, Johnson AS, Johnson RP, Johnson WN, Kamae T, Katagiri H, Kataoka J, Kawai N, Kerr M, Knödlseder J, Kuss M, Lande J, Latronico L, Llena Garde M, Longo F, Loparco F, Lott B, Lovellette MN, Lubrano P, Makeev A, Mazziotta MN, McEnery JE, Meurer C, Michelson PF, Mitthumsiri W, Mizuno T, Moiseev AA, Monte C, Monzani ME, Morselli A, Moskalenko IV, Murgia S, Nolan PL, Norris JP, Nuss E, Ohsugi T, Omodei N, Orlando E, Ormes JF, Ozaki M, Paneque D, Panetta JH, Parent D, Pelassa V, Pepe M, Pesce-Rollins M, Piron F, Rainò S, Rando R, Razzano M, Reimer A, Reimer O, Reposeur T, Ripken J, Ritz S, Rodriguez AY, Roth M, Sadrozinski HF, Sander A, Parkinson PM, Scargle JD, Schalk TL, Sellerholm A, Sgrò C, Siskind EJ, Smith DA, Smith PD, Spandre G, Spinelli P, Starck JL, Strickman MS, Suson DJ, Tajima H, Takahashi H, Tanaka T, Thayer JB, Thayer JG, Tibaldo L, Torres DF, Uchiyama Y, Usher TL, Vasileiou V, Vilchez N, Vitale V, Waite AP, Wang P, Winer BL, Wood KS, Ylinen T, and Ziegler M
Abstract: Dark matter (DM) particle annihilation or decay can produce monochromatic gamma rays readily distinguishable from astrophysical sources. gamma-ray line limits from 30 to 200 GeV obtained from 11 months of Fermi Large Area Space Telescope data from 20-300 GeV are presented using a selection based on requirements for a gamma-ray line analysis, and integrated over most of the sky. We obtain gamma-ray line flux upper limits in the range 0.6-4.5x10{-9} cm{-2} s{-1}, and give corresponding DM annihilation cross-section and decay lifetime limits. Theoretical implications are briefly discussed.
Published: 2010
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28. Gamma-ray emission from the shell of supernova remnant W44 revealed by the Fermi LAT.

Author: Abdo AA, Ackermann M, Ajello M, Baldini L, Ballet J, Barbiellini G, Baring MG, Bastieri D, Baughman BM, Bechtol K, Bellazzini R, Berenji B, Blandford RD, Bloom ED, Bonamente E, Borgland AW, Bregeon J, Brez A, Brigida M, Bruel P, Burnett TH, Buson S, Caliandro GA, Cameron RA, Caraveo PA, Casandjian JM, Cecchi C, Celik O, Chekhtman A, Cheung CC, Chiang J, Ciprini S, Claus R, Cognard I, Cohen-Tanugi J, Cominsky LR, Conrad J, Cutini S, Dermer CD, de Angelis A, de Palma F, Digel SW, do Couto e Silva E, Drell PS, Dubois R, Dumora D, Espinoza C, Farnier C, Favuzzi C, Fegan SJ, Focke WB, Fortin P, Frailis M, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Gehrels N, Germani S, Giavitto G, Giebels B, Giglietto N, Giordano F, Glanzman T, Godfrey G, Grenier IA, Grondin MH, Grove JE, Guillemot L, Guiriec S, Hanabata Y, Harding AK, Hayashida M, Hays E, Hughes RE, Jackson MS, Jóhannesson G, Johnson AS, Johnson TJ, Johnson WN, Kamae T, Katagiri H, Kataoka J, Katsuta J, Kawai N, Kerr M, Knödlseder J, Kocian ML, Kramer M, Kuss M, Lande J, Latronico L, Lemoine-Goumard M, Longo F, Loparco F, Lott B, Lovellette MN, Lubrano P, Lyne AG, Madejski GM, Makeev A, Mazziotta MN, McEnery JE, Meurer C, Michelson PF, Mitthumsiri W, Mizuno T, Monte C, Monzani ME, Morselli A, Moskalenko IV, Murgia S, Nakamori T, Nolan PL, Norris JP, Noutsos A, Nuss E, Ohsugi T, Omodei N, Orlando E, Ormes JF, Paneque D, Parent D, Pelassa V, Pepe M, Pesce-Rollins M, Piron F, Porter TA, Rainò S, Rando R, Razzano M, Reimer A, Reimer O, Reposeur T, Rochester LS, Rodriguez AY, Romani RW, Roth M, Ryde F, Sadrozinski HF, Sanchez D, Sander A, Saz Parkinson PM, Scargle JD, Sgrò C, Siskind EJ, Smith DA, Smith PD, Spandre G, Spinelli P, Stappers BW, Stecker FW, Strickman MS, Suson DJ, Tajima H, Takahashi H, Takahashi T, Tanaka T, Thayer JB, Thayer JG, Theureau G, Thompson DJ, Tibaldo L, Tibolla O, Torres DF, Tosti G, Tramacere A, Uchiyama Y, Usher TL, Vasileiou V, Venter C, Vilchez N, Vitale V, Waite AP, Wang P, Winer BL, Wood KS, Yamazaki R, Ylinen T, and Ziegler M
Abstract: Recent observations of supernova remnants (SNRs) hint that they accelerate cosmic rays to energies close to ~10(15) electron volts. However, the nature of the particles that produce the emission remains ambiguous. We report observations of SNR W44 with the Fermi Large Area Telescope at energies between 2 x 10(8) electron volts and 3 x10(11) electron volts. The detection of a source with a morphology corresponding to the SNR shell implies that the emission is produced by particles accelerated there. The gamma-ray spectrum is well modeled with emission from protons and nuclei. Its steepening above approximately 10(9) electron volts provides a probe with which to study how particle acceleration responds to environmental effects such as shock propagation in dense clouds and how accelerated particles are released into interstellar space.
Published: 2010
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29. Fermi large area telescope measurements of the diffuse gamma-ray emission at intermediate galactic latitudes.

Author: Abdo AA, Ackermann M, Ajello M, Anderson B, Atwood WB, Axelsson M, Baldini L, Ballet J, Barbiellini G, Bastieri D, Baughman BM, Bechtol K, Bellazzini R, Berenji B, Blandford RD, Bloom ED, Bonamente E, Borgland AW, Bregeon J, Brez A, Brigida M, Bruel P, Burnett TH, Caliandro GA, Cameron RA, Caraveo PA, Casandjian JM, Cecchi C, Charles E, Chekhtman A, Cheung CC, Chiang J, Ciprini S, Claus R, Cohen-Tanugi J, Conrad J, Dereli H, Dermer CD, de Angelis A, de Palma F, Digel SW, Di Bernardo G, Dormody M, do Couto e Silva E, Drell PS, Dubois R, Dumora D, Edmonds Y, Farnier C, Favuzzi C, Fegan SJ, Focke WB, Frailis M, Fukazawa Y, Funk S, Fusco P, Gaggero D, Gargano F, Gehrels N, Germani S, Giebels B, Giglietto N, Giordano F, Glanzman T, Godfrey G, Grenier IA, Grondin MH, Grove JE, Guillemot L, Guiriec S, Hanabata Y, Harding AK, Hayashida M, Hays E, Hughes RE, Jóhannesson G, Johnson AS, Johnson RP, Johnson TJ, Johnson WN, Kamae T, Katagiri H, Kataoka J, Kawai N, Kerr M, Knödlseder J, Kocian ML, Kuehn F, Kuss M, Lande J, Latronico L, Longo F, Loparco F, Lott B, Lovellette MN, Lubrano P, Madejski GM, Makeev A, Mazziotta MN, McConville W, McEnery JE, Meurer C, Michelson PF, Mitthumsiri W, Mizuno T, Moiseev AA, Monte C, Monzani ME, Morselli A, Moskalenko IV, Murgia S, Nolan PL, Nuss E, Ohsugi T, Okumura A, Omodei N, Orlando E, Ormes JF, Paneque D, Panetta JH, Parent D, Pelassa V, Pepe M, Pesce-Rollins M, Piron F, Porter TA, Rainò S, Rando R, Razzano M, Reimer A, Reimer O, Reposeur T, Ritz S, Rodriguez AY, Roth M, Ryde F, Sadrozinski HF, Sanchez D, Sander A, Saz Parkinson PM, Scargle JD, Sellerholm A, Sgrò C, Smith DA, Smith PD, Spandre G, Spinelli P, Starck JL, Stecker FW, Striani E, Strickman MS, Strong AW, Suson DJ, Tajima H, Takahashi H, Tanaka T, Thayer JB, Thayer JG, Thompson DJ, Tibaldo L, Torres DF, Tosti G, Tramacere A, Uchiyama Y, Usher TL, Vasileiou V, Vilchez N, Vitale V, Waite AP, Wang P, Winer BL, Wood KS, Ylinen T, and Ziegler M
Abstract: The diffuse galactic gamma-ray emission is produced by cosmic rays (CRs) interacting with the interstellar gas and radiation field. Measurements by the Energetic Gamma-Ray Experiment Telescope (EGRET) instrument on the Compton Gamma-Ray Observatory indicated excess gamma-ray emission greater, > or approximately equal to 1 GeV relative to diffuse galactic gamma-ray emission models consistent with directly measured CR spectra (the so-called "EGRET GeV excess"). The Large Area Telescope (LAT) instrument on the Fermi Gamma-Ray Space Telescope has measured the diffuse gamma-ray emission with improved sensitivity and resolution compared to EGRET. We report on LAT measurements for energies 100 MeV to 10 GeV and galactic latitudes 10 degrees < or = |b| < or = 20 degrees. The LAT spectrum for this region of the sky is well reproduced by a diffuse galactic gamma-ray emission model that is consistent with local CR spectra and inconsistent with the EGRET GeV excess.
Published: 2009
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30. Modulated high-energy gamma-ray emission from the microquasar Cygnus X-3.

Author: Abdo AA, Ackermann M, Ajello M, Axelsson M, Baldini L, Ballet J, Barbiellini G, Bastieri D, Baughman BM, Bechtol K, Bellazzini R, Berenji B, Blandford RD, Bloom ED, Bonamente E, Borgland AW, Brez A, Brigida M, Bruel P, Burnett TH, Buson S, Caliandro GA, Cameron RA, Caraveo PA, Casandjian JM, Cecchi C, Celik O, Chaty S, Cheung CC, Chiang J, Ciprini S, Claus R, Cohen-Tanugi J, Cominsky LR, Conrad J, Corbel S, Corbet R, Dermer CD, de Palma F, Digel SW, do Couto e Silva E, Drell PS, Dubois R, Dubus G, Dumora D, Farnier C, Favuzzi C, Fegan SJ, Focke WB, Fortin P, Frailis M, Fusco P, Gargano F, Gehrels N, Germani S, Giavitto G, Giebels B, Giglietto N, Giordano F, Glanzman T, Godfrey G, Grenier IA, Grondin MH, Grove JE, Guillemot L, Guiriec S, Hanabata Y, Harding AK, Hayashida M, Hays E, Hill AB, Hjalmarsdotter L, Horan D, Hughes RE, Jackson MS, Jóhannesson G, Johnson AS, Johnson TJ, Johnson WN, Kamae T, Katagiri H, Kawai N, Kerr M, Knödlseder J, Kocian ML, Koerding E, Kuss M, Lande J, Latronico L, Lemoine-Goumard M, Longo F, Loparco F, Lott B, Lovellette MN, Lubrano P, Madejski GM, Makeev A, Marchand L, Marelli M, Max-Moerbeck W, Mazziotta MN, McColl N, McEnery JE, Meurer C, Michelson PF, Migliari S, Mitthumsiri W, Mizuno T, Monte C, Monzani ME, Morselli A, Moskalenko IV, Murgia S, Nolan PL, Norris JP, Nuss E, Ohsugi T, Omodei N, Ong RA, Ormes JF, Paneque D, Parent D, Pelassa V, Pepe M, Pesce-Rollins M, Piron F, Pooley G, Porter TA, Pottschmidt K, Rainò S, Rando R, Ray PS, Razzano M, Rea N, Readhead A, Reimer A, Reimer O, Richards JL, Rochester LS, Rodriguez J, Rodriguez AY, Romani RW, Ryde F, Sadrozinski HF, Sander A, Saz Parkinson PM, Sgrò C, Siskind EJ, Smith DA, Smith PD, Spinelli P, Starck JL, Stevenson M, Strickman MS, Suson DJ, Takahashi H, Tanaka T, Thayer JB, Thompson DJ, Tibaldo L, Tomsick JA, Torres DF, Tosti G, Tramacere A, Uchiyama Y, Usher TL, Vasileiou V, Vilchez N, Vitale V, Waite AP, Wang P, Wilms J, Winer BL, Wood KS, Ylinen T, and Ziegler M
Abstract: Microquasars are accreting black holes or neutron stars in binary systems with associated relativistic jets. Despite their frequent outburst activity, they have never been unambiguously detected emitting high-energy gamma rays. The Fermi Large Area Telescope (LAT) has detected a variable high-energy source coinciding with the position of the x-ray binary and microquasar Cygnus X-3. Its identification with Cygnus X-3 is secured by the detection of its orbital period in gamma rays, as well as the correlation of the LAT flux with radio emission from the relativistic jets of Cygnus X-3. The gamma-ray emission probably originates from within the binary system, opening new areas in which to study the formation of relativistic jets.
Published: 2009
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31. A limit on the variation of the speed of light arising from quantum gravity effects.

Author: Abdo AA, Ackermann M, Ajello M, Asano K, Atwood WB, Axelsson M, Baldini L, Ballet J, Barbiellini G, Baring MG, Bastieri D, Bechtol K, Bellazzini R, Berenji B, Bhat PN, Bissaldi E, Bloom ED, Bonamente E, Bonnell J, Borgland AW, Bouvier A, Bregeon J, Brez A, Briggs MS, Brigida M, Bruel P, Burgess JM, Burnett TH, Caliandro GA, Cameron RA, Caraveo PA, Casandjian JM, Cecchi C, Celik O, Chaplin V, Charles E, Cheung CC, Chiang J, Ciprini S, Claus R, Cohen-Tanugi J, Cominsky LR, Connaughton V, Conrad J, Cutini S, Dermer CD, de Angelis A, de Palma F, Digel SW, Dingus BL, do Couto E Silva E, Drell PS, Dubois R, Dumora D, Farnier C, Favuzzi C, Fegan SJ, Finke J, Fishman G, Focke WB, Foschini L, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Gehrels N, Germani S, Gibby L, Giebels B, Giglietto N, Giordano F, Glanzman T, Godfrey G, Granot J, Greiner J, Grenier IA, Grondin MH, Grove JE, Grupe D, Guillemot L, Guiriec S, Hanabata Y, Harding AK, Hayashida M, Hays E, Hoversten EA, Hughes RE, Jóhannesson G, Johnson AS, Johnson RP, Johnson WN, Kamae T, Katagiri H, Kataoka J, Kawai N, Kerr M, Kippen RM, Knödlseder J, Kocevski D, Kouveliotou C, Kuehn F, Kuss M, Lande J, Latronico L, Lemoine-Goumard M, Longo F, Loparco F, Lott B, Lovellette MN, Lubrano P, Madejski GM, Makeev A, Mazziotta MN, McBreen S, McEnery JE, McGlynn S, Mészáros P, Meurer C, Michelson PF, Mitthumsiri W, Mizuno T, Moiseev AA, Monte C, Monzani ME, Moretti E, Morselli A, Moskalenko IV, Murgia S, Nakamori T, Nolan PL, Norris JP, Nuss E, Ohno M, Ohsugi T, Omodei N, Orlando E, Ormes JF, Ozaki M, Paciesas WS, Paneque D, Panetta JH, Parent D, Pelassa V, Pepe M, Pesce-Rollins M, Petrosian V, Piron F, Porter TA, Preece R, Rainò S, Ramirez-Ruiz E, Rando R, Razzano M, Razzaque S, Reimer A, Reimer O, Reposeur T, Ritz S, Rochester LS, Rodriguez AY, Roth M, Ryde F, Sadrozinski HF, Sanchez D, Sander A, Saz Parkinson PM, Scargle JD, Schalk TL, Sgrò C, Siskind EJ, Smith DA, Smith PD, Spandre G, Spinelli P, Stamatikos M, Stecker FW, Strickman MS, Suson DJ, Tajima H, Takahashi H, Takahashi T, Tanaka T, Thayer JB, Thayer JG, Thompson DJ, Tibaldo L, Toma K, Torres DF, Tosti G, Troja E, Uchiyama Y, Uehara T, Usher TL, van der Horst AJ, Vasileiou V, Vilchez N, Vitale V, von Kienlin A, Waite AP, Wang P, Wilson-Hodge C, Winer BL, Wood KS, Wu XF, Yamazaki R, Ylinen T, and Ziegler M
Abstract: A cornerstone of Einstein's special relativity is Lorentz invariance-the postulate that all observers measure exactly the same speed of light in vacuum, independent of photon-energy. While special relativity assumes that there is no fundamental length-scale associated with such invariance, there is a fundamental scale (the Planck scale, l(Planck) approximately 1.62 x 10(-33) cm or E(Planck) = M(Planck)c(2) approximately 1.22 x 10(19) GeV), at which quantum effects are expected to strongly affect the nature of space-time. There is great interest in the (not yet validated) idea that Lorentz invariance might break near the Planck scale. A key test of such violation of Lorentz invariance is a possible variation of photon speed with energy. Even a tiny variation in photon speed, when accumulated over cosmological light-travel times, may be revealed by observing sharp features in gamma-ray burst (GRB) light-curves. Here we report the detection of emission up to approximately 31 GeV from the distant and short GRB 090510. We find no evidence for the violation of Lorentz invariance, and place a lower limit of 1.2E(Planck) on the scale of a linear energy dependence (or an inverse wavelength dependence), subject to reasonable assumptions about the emission (equivalently we have an upper limit of l(Planck)/1.2 on the length scale of the effect). Our results disfavour quantum-gravity theories in which the quantum nature of space-time on a very small scale linearly alters the speed of light.
Published: 2009
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32. Detection of 16 gamma-ray pulsars through blind frequency searches using the Fermi LAT.

Author: Abdo AA, Ackermann M, Ajello M, Anderson B, Atwood WB, Axelsson M, Baldini L, Ballet J, Barbiellini G, Baring MG, Bastieri D, Baughman BM, Bechtol K, Bellazzini R, Berenji B, Bignami GF, Blandford RD, Bloom ED, Bonamente E, Borgland AW, Bregeon J, Brez A, Brigida M, Bruel P, Burnett TH, Caliandro GA, Cameron RA, Caraveo PA, Casandjian JM, Cecchi C, Celik O, Chekhtman A, Cheung CC, Chiang J, Ciprini S, Claus R, Cohen-Tanugi J, Conrad J, Cutini S, Dermer CD, de Angelis A, de Luca A, de Palma F, Digel SW, Dormody M, do Couto e Silva E, Drell PS, Dubois R, Dumora D, Farnier C, Favuzzi C, Fegan SJ, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Gehrels N, Germani S, Giebels B, Giglietto N, Giommi P, Giordano F, Glanzman T, Godfrey G, Grenier IA, Grondin MH, Grove JE, Guillemot L, Guiriec S, Gwon C, Hanabata Y, Harding AK, Hayashida M, Hays E, Hughes RE, Jóhannesson G, Johnson RP, Johnson TJ, Johnson WN, Kamae T, Katagiri H, Kataoka J, Kawai N, Kerr M, Knödlseder J, Kocian ML, Kuss M, Lande J, Latronico L, Lemoine-Goumard M, Longo F, Loparco F, Lott B, Lovellette MN, Lubrano P, Madejski GM, Makeev A, Marelli M, Mazziotta MN, McConville W, McEnery JE, Meurer C, Michelson PF, Mitthumsiri W, Mizuno T, Monte C, Monzani ME, Morselli A, Moskalenko IV, Murgia S, Nolan PL, Norris JP, Nuss E, Ohsugi T, Omodei N, Orlando E, Ormes JF, Paneque D, Parent D, Pelassa V, Pepe M, Pesce-Rollins M, Pierbattista M, Piron F, Porter TA, Primack JR, Rainò S, Rando R, Ray PS, Razzano M, Rea N, Reimer A, Reimer O, Reposeur T, Ritz S, Rochester LS, Rodriguez AY, Romani RW, Ryde F, Sadrozinski HF, Sanchez D, Sander A, Saz Parkinson PM, Scargle JD, Sgrò C, Siskind EJ, Smith DA, Smith PD, Spandre G, Spinelli P, Starck JL, Strickman MS, Suson DJ, Tajima H, Takahashi H, Takahashi T, Tanaka T, Thayer JG, Thompson DJ, Tibaldo L, Tibolla O, Torres DF, Tosti G, Tramacere A, Uchiyama Y, Usher TL, Van Etten A, Vasileiou V, Vilchez N, Vitale V, Waite AP, Wang P, Watters K, Winer BL, Wolff MT, Wood KS, Ylinen T, and Ziegler M
Abstract: Pulsars are rapidly rotating, highly magnetized neutron stars emitting radiation across the electromagnetic spectrum. Although there are more than 1800 known radio pulsars, until recently only seven were observed to pulse in gamma rays, and these were all discovered at other wavelengths. The Fermi Large Area Telescope (LAT) makes it possible to pinpoint neutron stars through their gamma-ray pulsations. We report the detection of 16 gamma-ray pulsars in blind frequency searches using the LAT. Most of these pulsars are coincident with previously unidentified gamma-ray sources, and many are associated with supernova remnants. Direct detection of gamma-ray pulsars enables studies of emission mechanisms, population statistics, and the energetics of pulsar wind nebulae and supernova remnants.
Published: 2009
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33. A population of gamma-ray millisecond pulsars seen with the Fermi Large Area Telescope.

Author: Abdo AA, Ackermann M, Ajello M, Atwood WB, Axelsson M, Baldini L, Ballet J, Barbiellini G, Baring MG, Bastieri D, Baughman BM, Bechtol K, Bellazzini R, Berenji B, Bignami GF, Blandford RD, Bloom ED, Bonamente E, Borgland AW, Bregeon J, Brez A, Brigida M, Bruel P, Burnett TH, Caliandro GA, Cameron RA, Camilo F, Caraveo PA, Carlson P, Casandjian J, Cecchi C, Celik O, Charles E, Chekhtman A, Cheung CC, Chiang J, Ciprini S, Claus R, Cognard I, Cohen-Tanugi J, Cominsky LR, Conrad J, Corbet R, Cutini S, Dermer CD, Desvignes G, de Angelis A, de Luca A, de Palma F, Digel SW, Dormody M, do Couto e Silva E, Drell PS, Dubois R, Dumora D, Edmonds Y, Farnier C, Favuzzi C, Fegan SJ, Focke WB, Frailis M, Freire PC, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Gehrels N, Germani S, Giebels B, Giglietto N, Giordano F, Glanzman T, Godfrey G, Grenier IA, Grondin MH, Grove JE, Guillemot L, Guiriec S, Hanabata Y, Harding AK, Hayashida M, Hays E, Hobbs G, Hughes RE, Jóhannesson G, Johnson AS, Johnson RP, Johnson TJ, Johnson WN, Johnston S, Kamae T, Katagiri H, Kataoka J, Kawai N, Kerr M, Knödlseder J, Kocian ML, Kramer M, Kuss M, Lande J, Latronico L, Lemoine-Goumard M, Longo F, Loparco F, Lott B, Lovellette MN, Lubrano P, Madejski GM, Makeev A, Manchester RN, Marelli M, Mazziotta MN, McConville W, McEnery JE, McLaughlin MA, Meurer C, Michelson PF, Mitthumsiri W, Mizuno T, Moiseev AA, Monte C, Monzani ME, Morselli A, Moskalenko IV, Murgia S, Nolan PL, Norris JP, Nuss E, Ohsugi T, Omodei N, Orlando E, Ormes JF, Paneque D, Panetta JH, Parent D, Pelassa V, Pepe M, Pesce-Rollins M, Piron F, Porter TA, Rainò S, Rando R, Ransom SM, Ray PS, Razzano M, Rea N, Reimer A, Reimer O, Reposeur T, Ritz S, Rochester LS, Rodriguez AY, Romani RW, Roth M, Ryde F, Sadrozinski HF, Sanchez D, Sander A, Saz Parkinson PM, Scargle JD, Schalk TL, Sgrò C, Siskind EJ, Smith DA, Smith PD, Spandre G, Spinelli P, Stappers BW, Starck JL, Striani E, Strickman MS, Suson DJ, Tajima H, Takahashi H, Tanaka T, Thayer JB, Thayer JG, Theureau G, Thompson DJ, Thorsett SE, Tibaldo L, Torres DF, Tosti G, Tramacere A, Uchiyama Y, Usher TL, Van Etten A, Vasileiou V, Venter C, Vilchez N, Vitale V, Waite AP, Wallace E, Wang P, Watters K, Webb N, Weltevrede P, Winer BL, Wood KS, Ylinen T, and Ziegler M
Abstract: Pulsars are born with subsecond spin periods and slow by electromagnetic braking for several tens of millions of years, when detectable radiation ceases. A second life can occur for neutron stars in binary systems. They can acquire mass and angular momentum from their companions, to be spun up to millisecond periods and begin radiating again. We searched Fermi Large Area Telescope data for pulsations from all known millisecond pulsars (MSPs) outside of globular clusters, using rotation parameters from radio telescopes. Strong gamma-ray pulsations were detected for eight MSPs. The gamma-ray pulse profiles and spectral properties resemble those of young gamma-ray pulsars. The basic emission mechanism seems to be the same for MSPs and young pulsars, with the emission originating in regions far from the neutron star surface.
Published: 2009
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34. Measurement of the cosmic ray e+ +e- spectrum from 20 GeV to 1 TeV with the Fermi Large Area Telescope.

Author: Abdo AA, Ackermann M, Ajello M, Atwood WB, Axelsson M, Baldini L, Ballet J, Barbiellini G, Bastieri D, Battelino M, Baughman BM, Bechtol K, Bellazzini R, Berenji B, Blandford RD, Bloom ED, Bogaert G, Bonamente E, Borgland AW, Bregeon J, Brez A, Brigida M, Bruel P, Burnett TH, Caliandro GA, Cameron RA, Caraveo PA, Carlson P, Casandjian JM, Cecchi C, Charles E, Chekhtman A, Cheung CC, Chiang J, Ciprini S, Claus R, Cohen-Tanugi J, Cominsky LR, Conrad J, Cutini S, Dermer CD, de Angelis A, de Palma F, Digel SW, Di Bernardo G, do Couto E Silva E, Drell PS, Dubois R, Dumora D, Edmonds Y, Farnier C, Favuzzi C, Focke WB, Frailis M, Fukazawa Y, Funk S, Fusco P, Gaggero D, Gargano F, Gasparrini D, Gehrels N, Germani S, Giebels B, Giglietto N, Giordano F, Glanzman T, Godfrey G, Grasso D, Grenier IA, Grondin MH, Grove JE, Guillemot L, Guiriec S, Hanabata Y, Harding AK, Hartman RC, Hayashida M, Hays E, Hughes RE, Jóhannesson G, Johnson AS, Johnson RP, Johnson WN, Kamae T, Katagiri H, Kataoka J, Kawai N, Kerr M, Knödlseder J, Kocevski D, Kuehn F, Kuss M, Lande J, Latronico L, Lemoine-Goumard M, Longo F, Loparco F, Lott B, Lovellette MN, Lubrano P, Madejski GM, Makeev A, Massai MM, Mazziotta MN, McConville W, McEnery JE, Meurer C, Michelson PF, Mitthumsiri W, Mizuno T, Moiseev AA, Monte C, Monzani ME, Moretti E, Morselli A, Moskalenko IV, Murgia S, Nolan PL, Norris JP, Nuss E, Ohsugi T, Omodei N, Orlando E, Ormes JF, Ozaki M, Paneque D, Panetta JH, Parent D, Pelassa V, Pepe M, Pesce-Rollins M, Piron F, Pohl M, Porter TA, Profumo S, Rainò S, Rando R, Razzano M, Reimer A, Reimer O, Reposeur T, Ritz S, Rochester LS, Rodriguez AY, Romani RW, Roth M, Ryde F, Sadrozinski HF, Sanchez D, Sander A, Saz Parkinson PM, Scargle JD, Schalk TL, Sellerholm A, Sgrò C, Smith DA, Smith PD, Spandre G, Spinelli P, Starck JL, Stephens TE, Strickman MS, Strong AW, Suson DJ, Tajima H, Takahashi H, Takahashi T, Tanaka T, Thayer JB, Thayer JG, Thompson DJ, Tibaldo L, Tibolla O, Torres DF, Tosti G, Tramacere A, Uchiyama Y, Usher TL, Van Etten A, Vasileiou V, Vilchez N, Vitale V, Waite AP, Wallace E, Wang P, Winer BL, Wood KS, Ylinen T, and Ziegler M
Abstract: Designed as a high-sensitivity gamma-ray observatory, the Fermi Large Area Telescope is also an electron detector with a large acceptance exceeding 2 m;{2} sr at 300 GeV. Building on the gamma-ray analysis, we have developed an efficient electron detection strategy which provides sufficient background rejection for measurement of the steeply falling electron spectrum up to 1 TeV. Our high precision data show that the electron spectrum falls with energy as E-3.0 and does not exhibit prominent spectral features. Interpretations in terms of a conventional diffusive model as well as a potential local extra component are briefly discussed.
Published: 2009
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35. Fermi observations of high-energy gamma-ray emission from GRB 080916C.

Author: Abdo AA, Ackermann M, Arimoto M, Asano K, Atwood WB, Axelsson M, Baldini L, Ballet J, Band DL, Barbiellini G, Baring MG, Bastieri D, Battelino M, Baughman BM, Bechtol K, Bellardi F, Bellazzini R, Berenji B, Bhat PN, Bissaldi E, Blandford RD, Bloom ED, Bogaert G, Bogart JR, Bonamente E, Bonnell J, Borgland AW, Bouvier A, Bregeon J, Brez A, Briggs MS, Brigida M, Bruel P, Burnett TH, Burrows D, Busetto G, Caliandro GA, Cameron RA, Caraveo PA, Casandjian JM, Ceccanti M, Cecchi C, Celotti A, Charles E, Chekhtman A, Cheung CC, Chiang J, Ciprini S, Claus R, Cohen-Tanugi J, Cominsky LR, Connaughton V, Conrad J, Costamante L, Cutini S, Deklotz M, Dermer CD, de Angelis A, de Palma F, Digel SW, Dingus BL, do Couto E Silva E, Drell PS, Dubois R, Dumora D, Edmonds Y, Evans PA, Fabiani D, Farnier C, Favuzzi C, Finke J, Fishman G, Focke WB, Frailis M, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Gehrels N, Germani S, Giebels B, Giglietto N, Giommi P, Giordano F, Glanzman T, Godfrey G, Goldstein A, Granot J, Greiner J, Grenier IA, Grondin MH, Grove JE, Guillemot L, Guiriec S, Haller G, Hanabata Y, Harding AK, Hayashida M, Hays E, Hernando Morat JA, Hoover A, Hughes RE, Jóhannesson G, Johnson AS, Johnson RP, Johnson TJ, Johnson WN, Kamae T, Katagiri H, Kataoka J, Kavelaars A, Kawai N, Kelly H, Kennea J, Kerr M, Kippen RM, Knödlseder J, Kocevski D, Kocian ML, Komin N, Kouveliotou C, Kuehn F, Kuss M, Lande J, Landriu D, Larsson S, Latronico L, Lavalley C, Lee B, Lee SH, Lemoine-Goumard M, Lichti GG, Longo F, Loparco F, Lott B, Lovellette MN, Lubrano P, Madejski GM, Makeev A, Marangelli B, Mazziotta MN, McBreen S, McEnery JE, McGlynn S, Meegan C, Mészáros P, Meurer C, Michelson PF, Minuti M, Mirizzi N, Mitthumsiri W, Mizuno T, Moiseev AA, Monte C, Monzani ME, Moretti E, Morselli A, Moskalenko IV, Murgia S, Nakamori T, Nelson D, Nolan PL, Norris JP, Nuss E, Ohno M, Ohsugi T, Okumura A, Omodei N, Orlando E, Ormes JF, Ozaki M, Paciesas WS, Paneque D, Panetta JH, Parent D, Pelassa V, Pepe M, Perri M, Pesce-Rollins M, Petrosian V, Pinchera M, Piron F, Porter TA, Preece R, Rainò S, Ramirez-Ruiz E, Rando R, Rapposelli E, Razzano M, Razzaque S, Rea N, Reimer A, Reimer O, Reposeur T, Reyes LC, Ritz S, Rochester LS, Rodriguez AY, Roth M, Ryde F, Sadrozinski HF, Sanchez D, Sander A, Saz Parkinson PM, Scargle JD, Schalk TL, Segal KN, Sgrò C, Shimokawabe T, Siskind EJ, Smith DA, Smith PD, Spandre G, Spinelli P, Stamatikos M, Starck JL, Stecker FW, Steinle H, Stephens TE, Strickman MS, Suson DJ, Tagliaferri G, Tajima H, Takahashi H, Takahashi T, Tanaka T, Tenze A, Thayer JB, Thayer JG, Thompson DJ, Tibaldo L, Torres DF, Tosti G, Tramacere A, Turri M, Tuvi S, Usher TL, van der Horst AJ, Vigiani L, Vilchez N, Vitale V, von Kienlin A, Waite AP, Williams DA, Wilson-Hodge C, Winer BL, Wood KS, Wu XF, Yamazaki R, Ylinen T, and Ziegler M
Abstract: Gamma-ray bursts (GRBs) are highly energetic explosions signaling the death of massive stars in distant galaxies. The Gamma-ray Burst Monitor and Large Area Telescope onboard the Fermi Observatory together record GRBs over a broad energy range spanning about 7 decades of gammaray energy. In September 2008, Fermi observed the exceptionally luminous GRB 080916C, with the largest apparent energy release yet measured. The high-energy gamma rays are observed to start later and persist longer than the lower energy photons. A simple spectral form fits the entire GRB spectrum, providing strong constraints on emission models. The known distance of the burst enables placing lower limits on the bulk Lorentz factor of the outflow and on the quantum gravity mass.
Published: 2009
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36. The Fermi Gamma-Ray Space Telescope discovers the pulsar in the young galactic supernova remnant CTA 1.

Author: Abdo AA, Ackermann M, Atwood WB, Baldini L, Ballet J, Barbiellini G, Baring MG, Bastieri D, Baughman BM, Bechtol K, Bellazzini R, Berenji B, Blandford RD, Bloom ED, Bogaert G, Bonamente E, Borgland AW, Bregeon J, Brez A, Brigida M, Bruel P, Burnett TH, Caliandro GA, Cameron RA, Caraveo PA, Carlson P, Casandjian JM, Cecchi C, Charles E, Chekhtman A, Cheung CC, Chiang J, Ciprini S, Claus R, Cohen-Tanugi J, Cominsky LR, Conrad J, Cutini S, Davis DS, Dermer CD, de Angelis A, de Palma F, Digel SW, Dormody M, do Couto E Silva E, Drell PS, Dubois R, Dumora D, Edmonds Y, Farnier C, Focke WB, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Gehrels N, Germani S, Giebels B, Giglietto N, Giordano F, Glanzman T, Godfrey G, Grenier IA, Grondin MH, Grove JE, Guillemot L, Guiriec S, Harding AK, Hartman RC, Hays E, Hughes RE, Jóhannesson G, Johnson AS, Johnson RP, Johnson TJ, Johnson WN, Kamae T, Kanai Y, Kanbach G, Katagiri H, Kawai N, Kerr M, Kishishita T, Kiziltan B, Knödlseder J, Kocian ML, Komin N, Kuehn F, Kuss M, Latronico L, Lemoine-Goumard M, Longo F, Lonjou V, Loparco F, Lott B, Lovellette MN, Lubrano P, Makeev A, Marelli M, Mazziotta MN, McEnery JE, McGlynn S, Meurer C, Michelson PF, Mineo T, Mitthumsiri W, Mizuno T, Moiseev AA, Monte C, Monzani ME, Morselli A, Moskalenko IV, Murgia S, Nakamori T, Nolan PL, Nuss E, Ohno M, Ohsugi T, Okumura A, Omodei N, Orlando E, Ormes JF, Ozaki M, Paneque D, Panetta JH, Parent D, Pelassa V, Pepe M, Pesce-Rollins M, Piano G, Pieri L, Piron F, Porter TA, Rainò S, Rando R, Ray PS, Razzano M, Reimer A, Reimer O, Reposeur T, Ritz S, Rochester LS, Rodriguez AY, Romani RW, Roth M, Ryde F, Sadrozinski HF, Sanchez D, Sander A, Parkinson PM, Schalk TL, Sellerholm A, Sgrò C, Siskind EJ, Smith DA, Smith PD, Spandre G, Spinelli P, Starck JL, Strickman MS, Suson DJ, Tajima H, Takahashi H, Takahashi T, Tanaka T, Thayer JB, Thayer JG, Thompson DJ, Thorsett SE, Tibaldo L, Torres DF, Tosti G, Tramacere A, Usher TL, Van Etten A, Vilchez N, Vitale V, Wang P, Watters K, Winer BL, Wood KS, Yasuda H, Ylinen T, and Ziegler M
Abstract: Energetic young pulsars and expanding blast waves [supernova remnants (SNRs)] are the most visible remains after massive stars, ending their lives, explode in core-collapse supernovae. The Fermi Gamma-Ray Space Telescope has unveiled a radio quiet pulsar located near the center of the compact synchrotron nebula inside the supernova remnant CTA 1. The pulsar, discovered through its gamma-ray pulsations, has a period of 316.86 milliseconds and a period derivative of 3.614 x 10(-13) seconds per second. Its characteristic age of 10(4) years is comparable to that estimated for the SNR. We speculate that most unidentified Galactic gamma-ray sources associated with star-forming regions and SNRs are such young pulsars.
Published: 2008
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