Fermi large area telescope observations of the supernova remnant W28 (G6.4-0.1)

A. A. Abdo, M. Ackermann, M. Ajello, A. Allafort, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, K. Bechtol, R. Bellazzini, B. Berenji, R. D. Blandford, E. D. Bloom, E. Bonamente, A. W. Borgland, A. Bouvier, T. J. Brandt, J. Bregeon, M. Brigida, P. BruelR. Buehler, S. Buson, G. A. Caliandro, R. A. Cameron, P. A. Caraveo, S. Carrigan, J. M. Casandjian, C. Cecchi, Çelik, A. Chekhtman, J. Chiang, S. Ciprini, R. Claus, J. Cohen-Tanugi, J. Conrad, C. D. Dermer, F. De Palma, E. Do Couto E Silva, P. S. Drell, R. Dubois, D. Dumora, C. Farnier, C. Favuzzi, S. J. Fegan, Y. Fukazawa, Y. Fukui, S. Funk, P. Fusco, F. Gargano, N. Gehrels, S. Germani, N. Giglietto, F. Giordano, T. Glanzman, G. Godfrey, I. A. Grenier, J. E. Grove, S. Guiriec, D. Hadasch, Y. Hanabata, A. K. Harding, E. Hays, D. Horan, R. E. Hughes, G. Jóhannesson, A. S. Johnson, W. N. Johnson, T. Kamae, H. Katagiri, Jun Kataoka, J. Knöodlseder, M. Kuss, J. Lande, L. Latronico, S. H. Lee, M. Lemoine-Goumard, M. Llena Garde, F. Longo, F. Loparco, M. N. Lovellette, P. Lubrano, A. Makeev, M. N. Mazziotta, P. F. Michelson, W. Mitthumsiri, T. Mizuno, A. A. Moiseev, C. Monte, M. E. Monzani, A. Morselli, I. V. Moskalenko, S. Murgia, T. Nakamori, P. L. Nolan, J. P. Norris, E. Nuss, M. Ohno, T. Ohsugi, N. Omodei, E. Orlando, J. F. Ormes, M. Ozaki, J. H. Panetta, D. Parent, V. Pelassa, M. Pepe, M. Pesce-Rollins, F. Piron, T. A. Porter, S. Rainò, R. Rando, M. Razzano, A. Reimer, O. Reimer, T. Reposeur, A. Y. Rodriguez, M. Roth, H. F W Sadrozinski, A. Sander, P. M. Saz Parkinson, C. Sgrò, E. J. Siskind, D. A. Smith, P. D. Smith, G. Spandre, P. Spinelli, M. S. Strickman, D. J. Suson, H. Tajima, H. Takahashi, T. Takahashi, T. Tanaka, J. B. Thayer, J. G. Thayer, D. J. Thompson, L. Tibaldo, O. Tibolla, D. F. Torres, G. Tosti, Y. Uchiyama, T. Uehara, T. L. Usher, V. Vasileiou, N. Vilchez, V. Vitale, A. P. Waite, P. Wang, B. L. Winer, K. S. Wood, H. Yamamoto, R. Yamazaki, Z. Yang, T. Ylinen, M. Ziegler

    Research output: Contribution to journalArticle

    176 Citations (Scopus)

    Abstract

    We present detailed analysis of two gamma-ray sources, 1FGL J1801.3-2322c and 1FGL J1800.5-2359c, that have been found toward the supernova remnant (SNR) W28 with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. 1FGL J1801.3-2322c is found to be an extended source within the boundary of SNR W28, and to extensively overlap with the TeV gamma-ray source HESS J1801-233, which is associated with a dense molecular cloud interacting with the SNR. The gamma-ray spectrum measured with the LAT from 0.2 to 100 GeV can be described by a broken power-law function with a break at ∼1 GeV and photon indices of 2.09 ± 0.08 (stat) ± 0.28 (sys) below the break and 2.74 ± 0.06 (stat) ± 0.09 (sys) above the break. Given the clear association between HESS J1801-233 and the shocked molecular cloud and a smoothly connected spectrum in the GeV-TeV band, we consider the origin of the gamma-ray emission in both GeV and TeV ranges to be the interaction between particles accelerated in the SNR and the molecular cloud. The decay of neutral pions produced in interactions between accelerated hadrons and dense molecular gas provides a reasonable explanation for the broadband gamma-ray spectrum. 1FGL J1800.5-2359c, located outside the southern boundary of SNR W28, cannot be resolved. An upper limit on the size of the gamma-ray emission was estimated to be ∼16′ using events above ∼2 GeV under the assumption of a circular shape with uniform surface brightness. It appears to coincide with the TeV source HESS J1800-240B, which is considered to be associated with a dense molecular cloud that contains the ultra compact H II region W28A2 (G5.89-0.39). We found no significant gamma-ray emission in the LAT energy band at the positions of TeV sources HESS J1800-230A and HESS J1800-230C. The LAT data for HESS J1800-230A combined with the TeV data points indicate a spectral break between 10 GeV and 100 GeV.

    Original languageEnglish
    Pages (from-to)348-356
    Number of pages9
    JournalAstrophysical Journal
    Volume718
    Issue number1
    DOIs
    Publication statusPublished - 2010 Jul 20

    Fingerprint

    supernova remnants
    molecular clouds
    telescopes
    gamma ray spectra
    gamma rays
    power law
    Fermi Gamma-ray Space Telescope
    H II regions
    molecular gases
    hadrons
    energy bands
    brightness
    gas
    pions
    energy
    interactions
    broadband
    photons
    decay

    Keywords

    • Acceleration of particles
    • Cosmic rays
    • Gamma rays: ISM
    • ISM: individual objects (W28, G6.4-0.1)
    • ISM: supernova remnants

    ASJC Scopus subject areas

    • Space and Planetary Science
    • Astronomy and Astrophysics

    Cite this

    Abdo, A. A., Ackermann, M., Ajello, M., Allafort, A., Baldini, L., Ballet, J., ... Ziegler, M. (2010). Fermi large area telescope observations of the supernova remnant W28 (G6.4-0.1). Astrophysical Journal, 718(1), 348-356. https://doi.org/10.1088/0004-637X/718/1/348

    Fermi large area telescope observations of the supernova remnant W28 (G6.4-0.1). / Abdo, A. A.; Ackermann, M.; Ajello, M.; Allafort, A.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bouvier, A.; Brandt, T. J.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Carrigan, S.; Casandjian, J. M.; Cecchi, C.; Çelik; Chekhtman, A.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; Dermer, C. D.; De Palma, F.; Do Couto E Silva, E.; Drell, P. S.; Dubois, R.; Dumora, D.; Farnier, C.; Favuzzi, C.; Fegan, S. J.; Fukazawa, Y.; Fukui, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gehrels, N.; Germani, S.; Giglietto, N.; Giordano, F.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Grove, J. E.; Guiriec, S.; Hadasch, D.; Hanabata, Y.; Harding, A. K.; Hays, E.; Horan, D.; Hughes, R. E.; Jóhannesson, G.; Johnson, A. S.; Johnson, W. N.; Kamae, T.; Katagiri, H.; Kataoka, Jun; Knöodlseder, J.; Kuss, M.; Lande, J.; Latronico, L.; Lee, S. H.; Lemoine-Goumard, M.; Llena Garde, M.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Makeev, A.; Mazziotta, M. N.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nakamori, T.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohno, M.; Ohsugi, T.; Omodei, N.; Orlando, E.; Ormes, J. F.; Ozaki, M.; Panetta, J. H.; Parent, D.; Pelassa, V.; Pepe, M.; Pesce-Rollins, M.; Piron, F.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Reimer, A.; Reimer, O.; Reposeur, T.; Rodriguez, A. Y.; Roth, M.; Sadrozinski, H. F W; Sander, A.; Saz Parkinson, P. M.; Sgrò, C.; Siskind, E. J.; Smith, D. A.; Smith, P. D.; Spandre, G.; Spinelli, P.; Strickman, M. S.; Suson, D. J.; Tajima, H.; Takahashi, H.; Takahashi, T.; Tanaka, T.; Thayer, J. B.; Thayer, J. G.; Thompson, D. J.; Tibaldo, L.; Tibolla, O.; Torres, D. F.; Tosti, G.; Uchiyama, Y.; Uehara, T.; Usher, T. L.; Vasileiou, V.; Vilchez, N.; Vitale, V.; Waite, A. P.; Wang, P.; Winer, B. L.; Wood, K. S.; Yamamoto, H.; Yamazaki, R.; Yang, Z.; Ylinen, T.; Ziegler, M.

    In: Astrophysical Journal, Vol. 718, No. 1, 20.07.2010, p. 348-356.

    Research output: Contribution to journalArticle

    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, Brigida, M, Bruel, P, Buehler, R, Buson, S, Caliandro, GA, Cameron, RA, Caraveo, PA, Carrigan, S, Casandjian, JM, Cecchi, C, Çelik, Chekhtman, A, Chiang, J, Ciprini, S, Claus, R, Cohen-Tanugi, J, Conrad, J, Dermer, CD, De Palma, F, Do Couto E Silva, E, Drell, PS, Dubois, R, Dumora, D, Farnier, C, Favuzzi, C, Fegan, SJ, Fukazawa, Y, Fukui, Y, Funk, S, Fusco, P, Gargano, F, Gehrels, N, Germani, S, Giglietto, N, Giordano, F, Glanzman, T, Godfrey, G, Grenier, IA, Grove, JE, Guiriec, S, Hadasch, D, Hanabata, Y, Harding, AK, Hays, E, Horan, D, Hughes, RE, Jóhannesson, G, Johnson, AS, Johnson, WN, Kamae, T, Katagiri, H, Kataoka, J, Knöodlseder, J, Kuss, M, Lande, J, Latronico, L, Lee, SH, Lemoine-Goumard, M, Llena Garde, M, Longo, F, Loparco, F, Lovellette, MN, Lubrano, P, Makeev, A, Mazziotta, MN, 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, Omodei, N, Orlando, E, Ormes, JF, Ozaki, M, 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, Rodriguez, AY, Roth, M, Sadrozinski, HFW, Sander, A, Saz Parkinson, PM, Sgrò, C, Siskind, EJ, Smith, DA, Smith, PD, Spandre, G, Spinelli, P, Strickman, MS, Suson, DJ, Tajima, H, Takahashi, H, Takahashi, T, Tanaka, T, Thayer, JB, Thayer, JG, Thompson, DJ, Tibaldo, L, Tibolla, O, Torres, DF, Tosti, G, Uchiyama, Y, Uehara, T, Usher, TL, Vasileiou, V, Vilchez, N, Vitale, V, Waite, AP, Wang, P, Winer, BL, Wood, KS, Yamamoto, H, Yamazaki, R, Yang, Z, Ylinen, T & Ziegler, M 2010, 'Fermi large area telescope observations of the supernova remnant W28 (G6.4-0.1)', Astrophysical Journal, vol. 718, no. 1, pp. 348-356. https://doi.org/10.1088/0004-637X/718/1/348
    Abdo AA, Ackermann M, Ajello M, Allafort A, Baldini L, Ballet J et al. Fermi large area telescope observations of the supernova remnant W28 (G6.4-0.1). Astrophysical Journal. 2010 Jul 20;718(1):348-356. https://doi.org/10.1088/0004-637X/718/1/348
    Abdo, A. A. ; Ackermann, M. ; Ajello, M. ; Allafort, A. ; Baldini, L. ; Ballet, J. ; Barbiellini, G. ; Bastieri, D. ; Bechtol, K. ; Bellazzini, R. ; Berenji, B. ; Blandford, R. D. ; Bloom, E. D. ; Bonamente, E. ; Borgland, A. W. ; Bouvier, A. ; Brandt, T. J. ; Bregeon, J. ; Brigida, M. ; Bruel, P. ; Buehler, R. ; Buson, S. ; Caliandro, G. A. ; Cameron, R. A. ; Caraveo, P. A. ; Carrigan, S. ; Casandjian, J. M. ; Cecchi, C. ; Çelik ; Chekhtman, A. ; Chiang, J. ; Ciprini, S. ; Claus, R. ; Cohen-Tanugi, J. ; Conrad, J. ; Dermer, C. D. ; De Palma, F. ; Do Couto E Silva, E. ; Drell, P. S. ; Dubois, R. ; Dumora, D. ; Farnier, C. ; Favuzzi, C. ; Fegan, S. J. ; Fukazawa, Y. ; Fukui, Y. ; Funk, S. ; Fusco, P. ; Gargano, F. ; Gehrels, N. ; Germani, S. ; Giglietto, N. ; Giordano, F. ; Glanzman, T. ; Godfrey, G. ; Grenier, I. A. ; Grove, J. E. ; Guiriec, S. ; Hadasch, D. ; Hanabata, Y. ; Harding, A. K. ; Hays, E. ; Horan, D. ; Hughes, R. E. ; Jóhannesson, G. ; Johnson, A. S. ; Johnson, W. N. ; Kamae, T. ; Katagiri, H. ; Kataoka, Jun ; Knöodlseder, J. ; Kuss, M. ; Lande, J. ; Latronico, L. ; Lee, S. H. ; Lemoine-Goumard, M. ; Llena Garde, M. ; Longo, F. ; Loparco, F. ; Lovellette, M. N. ; Lubrano, P. ; Makeev, A. ; Mazziotta, M. N. ; Michelson, P. F. ; Mitthumsiri, W. ; Mizuno, T. ; Moiseev, A. A. ; Monte, C. ; Monzani, M. E. ; Morselli, A. ; Moskalenko, I. V. ; Murgia, S. ; Nakamori, T. ; Nolan, P. L. ; Norris, J. P. ; Nuss, E. ; Ohno, M. ; Ohsugi, T. ; Omodei, N. ; Orlando, E. ; Ormes, J. F. ; Ozaki, M. ; Panetta, J. H. ; Parent, D. ; Pelassa, V. ; Pepe, M. ; Pesce-Rollins, M. ; Piron, F. ; Porter, T. A. ; Rainò, S. ; Rando, R. ; Razzano, M. ; Reimer, A. ; Reimer, O. ; Reposeur, T. ; Rodriguez, A. Y. ; Roth, M. ; Sadrozinski, H. F W ; Sander, A. ; Saz Parkinson, P. M. ; Sgrò, C. ; Siskind, E. J. ; Smith, D. A. ; Smith, P. D. ; Spandre, G. ; Spinelli, P. ; Strickman, M. S. ; Suson, D. J. ; Tajima, H. ; Takahashi, H. ; Takahashi, T. ; Tanaka, T. ; Thayer, J. B. ; Thayer, J. G. ; Thompson, D. J. ; Tibaldo, L. ; Tibolla, O. ; Torres, D. F. ; Tosti, G. ; Uchiyama, Y. ; Uehara, T. ; Usher, T. L. ; Vasileiou, V. ; Vilchez, N. ; Vitale, V. ; Waite, A. P. ; Wang, P. ; Winer, B. L. ; Wood, K. S. ; Yamamoto, H. ; Yamazaki, R. ; Yang, Z. ; Ylinen, T. ; Ziegler, M. / Fermi large area telescope observations of the supernova remnant W28 (G6.4-0.1). In: Astrophysical Journal. 2010 ; Vol. 718, No. 1. pp. 348-356.
    @article{68b21360d36b44fbbef312efc37b27e8,
    title = "Fermi large area telescope observations of the supernova remnant W28 (G6.4-0.1)",
    abstract = "We present detailed analysis of two gamma-ray sources, 1FGL J1801.3-2322c and 1FGL J1800.5-2359c, that have been found toward the supernova remnant (SNR) W28 with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. 1FGL J1801.3-2322c is found to be an extended source within the boundary of SNR W28, and to extensively overlap with the TeV gamma-ray source HESS J1801-233, which is associated with a dense molecular cloud interacting with the SNR. The gamma-ray spectrum measured with the LAT from 0.2 to 100 GeV can be described by a broken power-law function with a break at ∼1 GeV and photon indices of 2.09 ± 0.08 (stat) ± 0.28 (sys) below the break and 2.74 ± 0.06 (stat) ± 0.09 (sys) above the break. Given the clear association between HESS J1801-233 and the shocked molecular cloud and a smoothly connected spectrum in the GeV-TeV band, we consider the origin of the gamma-ray emission in both GeV and TeV ranges to be the interaction between particles accelerated in the SNR and the molecular cloud. The decay of neutral pions produced in interactions between accelerated hadrons and dense molecular gas provides a reasonable explanation for the broadband gamma-ray spectrum. 1FGL J1800.5-2359c, located outside the southern boundary of SNR W28, cannot be resolved. An upper limit on the size of the gamma-ray emission was estimated to be ∼16′ using events above ∼2 GeV under the assumption of a circular shape with uniform surface brightness. It appears to coincide with the TeV source HESS J1800-240B, which is considered to be associated with a dense molecular cloud that contains the ultra compact H II region W28A2 (G5.89-0.39). We found no significant gamma-ray emission in the LAT energy band at the positions of TeV sources HESS J1800-230A and HESS J1800-230C. The LAT data for HESS J1800-230A combined with the TeV data points indicate a spectral break between 10 GeV and 100 GeV.",
    keywords = "Acceleration of particles, Cosmic rays, Gamma rays: ISM, ISM: individual objects (W28, G6.4-0.1), ISM: supernova remnants",
    author = "Abdo, {A. A.} and M. Ackermann and M. Ajello and A. Allafort and L. Baldini and J. Ballet and G. Barbiellini and D. Bastieri and K. Bechtol and R. Bellazzini and B. Berenji and Blandford, {R. D.} and Bloom, {E. D.} and E. Bonamente and Borgland, {A. W.} and A. Bouvier and Brandt, {T. J.} and J. Bregeon and M. Brigida and P. Bruel and R. Buehler and S. Buson and Caliandro, {G. A.} and Cameron, {R. A.} and Caraveo, {P. A.} and S. Carrigan and Casandjian, {J. M.} and C. Cecchi and {\cC}elik and A. Chekhtman and J. Chiang and S. Ciprini and R. Claus and J. Cohen-Tanugi and J. Conrad and Dermer, {C. D.} and {De Palma}, F. and {Do Couto E Silva}, E. and Drell, {P. S.} and R. Dubois and D. Dumora and C. Farnier and C. Favuzzi and Fegan, {S. J.} and Y. Fukazawa and Y. Fukui and S. Funk and P. Fusco and F. Gargano and N. Gehrels and S. Germani and N. Giglietto and F. Giordano and T. Glanzman and G. Godfrey and Grenier, {I. A.} and Grove, {J. E.} and S. Guiriec and D. Hadasch and Y. Hanabata and Harding, {A. K.} and E. Hays and D. Horan and Hughes, {R. E.} and G. J{\'o}hannesson and Johnson, {A. S.} and Johnson, {W. N.} and T. Kamae and H. Katagiri and Jun Kataoka and J. Kn{\"o}odlseder and M. Kuss and J. Lande and L. Latronico and Lee, {S. H.} and M. Lemoine-Goumard and {Llena Garde}, M. and F. Longo and F. Loparco and Lovellette, {M. N.} and P. Lubrano and A. Makeev and Mazziotta, {M. N.} and Michelson, {P. F.} and W. Mitthumsiri and T. Mizuno and Moiseev, {A. A.} and C. Monte and Monzani, {M. E.} and A. Morselli and Moskalenko, {I. V.} and S. Murgia and T. Nakamori and Nolan, {P. L.} and Norris, {J. P.} and E. Nuss and M. Ohno and T. Ohsugi and N. Omodei and E. Orlando and Ormes, {J. F.} and M. Ozaki and Panetta, {J. H.} and D. Parent and V. Pelassa and M. Pepe and M. Pesce-Rollins and F. Piron and Porter, {T. A.} and S. Rain{\`o} and R. Rando and M. Razzano and A. Reimer and O. Reimer and T. Reposeur and Rodriguez, {A. Y.} and M. Roth and Sadrozinski, {H. F W} and A. Sander and {Saz Parkinson}, {P. M.} and C. Sgr{\`o} and Siskind, {E. J.} and Smith, {D. A.} and Smith, {P. D.} and G. Spandre and P. Spinelli and Strickman, {M. S.} and Suson, {D. J.} and H. Tajima and H. Takahashi and T. Takahashi and T. Tanaka and Thayer, {J. B.} and Thayer, {J. G.} and Thompson, {D. J.} and L. Tibaldo and O. Tibolla and Torres, {D. F.} and G. Tosti and Y. Uchiyama and T. Uehara and Usher, {T. L.} and V. Vasileiou and N. Vilchez and V. Vitale and Waite, {A. P.} and P. Wang and Winer, {B. L.} and Wood, {K. S.} and H. Yamamoto and R. Yamazaki and Z. Yang and T. Ylinen and M. Ziegler",
    year = "2010",
    month = "7",
    day = "20",
    doi = "10.1088/0004-637X/718/1/348",
    language = "English",
    volume = "718",
    pages = "348--356",
    journal = "Astrophysical Journal",
    issn = "0004-637X",
    publisher = "IOP Publishing Ltd.",
    number = "1",

    }

    TY - JOUR

    T1 - Fermi large area telescope observations of the supernova remnant W28 (G6.4-0.1)

    AU - Abdo, A. A.

    AU - Ackermann, M.

    AU - Ajello, M.

    AU - Allafort, A.

    AU - Baldini, L.

    AU - Ballet, J.

    AU - Barbiellini, G.

    AU - Bastieri, D.

    AU - Bechtol, K.

    AU - Bellazzini, R.

    AU - Berenji, B.

    AU - Blandford, R. D.

    AU - Bloom, E. D.

    AU - Bonamente, E.

    AU - Borgland, A. W.

    AU - Bouvier, A.

    AU - Brandt, T. J.

    AU - Bregeon, J.

    AU - Brigida, M.

    AU - Bruel, P.

    AU - Buehler, R.

    AU - Buson, S.

    AU - Caliandro, G. A.

    AU - Cameron, R. A.

    AU - Caraveo, P. A.

    AU - Carrigan, S.

    AU - Casandjian, J. M.

    AU - Cecchi, C.

    AU - Çelik,

    AU - Chekhtman, A.

    AU - Chiang, J.

    AU - Ciprini, S.

    AU - Claus, R.

    AU - Cohen-Tanugi, J.

    AU - Conrad, J.

    AU - Dermer, C. D.

    AU - De Palma, F.

    AU - Do Couto E Silva, E.

    AU - Drell, P. S.

    AU - Dubois, R.

    AU - Dumora, D.

    AU - Farnier, C.

    AU - Favuzzi, C.

    AU - Fegan, S. J.

    AU - Fukazawa, Y.

    AU - Fukui, Y.

    AU - Funk, S.

    AU - Fusco, P.

    AU - Gargano, F.

    AU - Gehrels, N.

    AU - Germani, S.

    AU - Giglietto, N.

    AU - Giordano, F.

    AU - Glanzman, T.

    AU - Godfrey, G.

    AU - Grenier, I. A.

    AU - Grove, J. E.

    AU - Guiriec, S.

    AU - Hadasch, D.

    AU - Hanabata, Y.

    AU - Harding, A. K.

    AU - Hays, E.

    AU - Horan, D.

    AU - Hughes, R. E.

    AU - Jóhannesson, G.

    AU - Johnson, A. S.

    AU - Johnson, W. N.

    AU - Kamae, T.

    AU - Katagiri, H.

    AU - Kataoka, Jun

    AU - Knöodlseder, J.

    AU - Kuss, M.

    AU - Lande, J.

    AU - Latronico, L.

    AU - Lee, S. H.

    AU - Lemoine-Goumard, M.

    AU - Llena Garde, M.

    AU - Longo, F.

    AU - Loparco, F.

    AU - Lovellette, M. N.

    AU - Lubrano, P.

    AU - Makeev, A.

    AU - Mazziotta, M. N.

    AU - Michelson, P. F.

    AU - Mitthumsiri, W.

    AU - Mizuno, T.

    AU - Moiseev, A. A.

    AU - Monte, C.

    AU - Monzani, M. E.

    AU - Morselli, A.

    AU - Moskalenko, I. V.

    AU - Murgia, S.

    AU - Nakamori, T.

    AU - Nolan, P. L.

    AU - Norris, J. P.

    AU - Nuss, E.

    AU - Ohno, M.

    AU - Ohsugi, T.

    AU - Omodei, N.

    AU - Orlando, E.

    AU - Ormes, J. F.

    AU - Ozaki, M.

    AU - Panetta, J. H.

    AU - Parent, D.

    AU - Pelassa, V.

    AU - Pepe, M.

    AU - Pesce-Rollins, M.

    AU - Piron, F.

    AU - Porter, T. A.

    AU - Rainò, S.

    AU - Rando, R.

    AU - Razzano, M.

    AU - Reimer, A.

    AU - Reimer, O.

    AU - Reposeur, T.

    AU - Rodriguez, A. Y.

    AU - Roth, M.

    AU - Sadrozinski, H. F W

    AU - Sander, A.

    AU - Saz Parkinson, P. M.

    AU - Sgrò, C.

    AU - Siskind, E. J.

    AU - Smith, D. A.

    AU - Smith, P. D.

    AU - Spandre, G.

    AU - Spinelli, P.

    AU - Strickman, M. S.

    AU - Suson, D. J.

    AU - Tajima, H.

    AU - Takahashi, H.

    AU - Takahashi, T.

    AU - Tanaka, T.

    AU - Thayer, J. B.

    AU - Thayer, J. G.

    AU - Thompson, D. J.

    AU - Tibaldo, L.

    AU - Tibolla, O.

    AU - Torres, D. F.

    AU - Tosti, G.

    AU - Uchiyama, Y.

    AU - Uehara, T.

    AU - Usher, T. L.

    AU - Vasileiou, V.

    AU - Vilchez, N.

    AU - Vitale, V.

    AU - Waite, A. P.

    AU - Wang, P.

    AU - Winer, B. L.

    AU - Wood, K. S.

    AU - Yamamoto, H.

    AU - Yamazaki, R.

    AU - Yang, Z.

    AU - Ylinen, T.

    AU - Ziegler, M.

    PY - 2010/7/20

    Y1 - 2010/7/20

    N2 - We present detailed analysis of two gamma-ray sources, 1FGL J1801.3-2322c and 1FGL J1800.5-2359c, that have been found toward the supernova remnant (SNR) W28 with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. 1FGL J1801.3-2322c is found to be an extended source within the boundary of SNR W28, and to extensively overlap with the TeV gamma-ray source HESS J1801-233, which is associated with a dense molecular cloud interacting with the SNR. The gamma-ray spectrum measured with the LAT from 0.2 to 100 GeV can be described by a broken power-law function with a break at ∼1 GeV and photon indices of 2.09 ± 0.08 (stat) ± 0.28 (sys) below the break and 2.74 ± 0.06 (stat) ± 0.09 (sys) above the break. Given the clear association between HESS J1801-233 and the shocked molecular cloud and a smoothly connected spectrum in the GeV-TeV band, we consider the origin of the gamma-ray emission in both GeV and TeV ranges to be the interaction between particles accelerated in the SNR and the molecular cloud. The decay of neutral pions produced in interactions between accelerated hadrons and dense molecular gas provides a reasonable explanation for the broadband gamma-ray spectrum. 1FGL J1800.5-2359c, located outside the southern boundary of SNR W28, cannot be resolved. An upper limit on the size of the gamma-ray emission was estimated to be ∼16′ using events above ∼2 GeV under the assumption of a circular shape with uniform surface brightness. It appears to coincide with the TeV source HESS J1800-240B, which is considered to be associated with a dense molecular cloud that contains the ultra compact H II region W28A2 (G5.89-0.39). We found no significant gamma-ray emission in the LAT energy band at the positions of TeV sources HESS J1800-230A and HESS J1800-230C. The LAT data for HESS J1800-230A combined with the TeV data points indicate a spectral break between 10 GeV and 100 GeV.

    AB - We present detailed analysis of two gamma-ray sources, 1FGL J1801.3-2322c and 1FGL J1800.5-2359c, that have been found toward the supernova remnant (SNR) W28 with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. 1FGL J1801.3-2322c is found to be an extended source within the boundary of SNR W28, and to extensively overlap with the TeV gamma-ray source HESS J1801-233, which is associated with a dense molecular cloud interacting with the SNR. The gamma-ray spectrum measured with the LAT from 0.2 to 100 GeV can be described by a broken power-law function with a break at ∼1 GeV and photon indices of 2.09 ± 0.08 (stat) ± 0.28 (sys) below the break and 2.74 ± 0.06 (stat) ± 0.09 (sys) above the break. Given the clear association between HESS J1801-233 and the shocked molecular cloud and a smoothly connected spectrum in the GeV-TeV band, we consider the origin of the gamma-ray emission in both GeV and TeV ranges to be the interaction between particles accelerated in the SNR and the molecular cloud. The decay of neutral pions produced in interactions between accelerated hadrons and dense molecular gas provides a reasonable explanation for the broadband gamma-ray spectrum. 1FGL J1800.5-2359c, located outside the southern boundary of SNR W28, cannot be resolved. An upper limit on the size of the gamma-ray emission was estimated to be ∼16′ using events above ∼2 GeV under the assumption of a circular shape with uniform surface brightness. It appears to coincide with the TeV source HESS J1800-240B, which is considered to be associated with a dense molecular cloud that contains the ultra compact H II region W28A2 (G5.89-0.39). We found no significant gamma-ray emission in the LAT energy band at the positions of TeV sources HESS J1800-230A and HESS J1800-230C. The LAT data for HESS J1800-230A combined with the TeV data points indicate a spectral break between 10 GeV and 100 GeV.

    KW - Acceleration of particles

    KW - Cosmic rays

    KW - Gamma rays: ISM

    KW - ISM: individual objects (W28, G6.4-0.1)

    KW - ISM: supernova remnants

    UR - http://www.scopus.com/inward/record.url?scp=84885598152&partnerID=8YFLogxK

    UR - http://www.scopus.com/inward/citedby.url?scp=84885598152&partnerID=8YFLogxK

    U2 - 10.1088/0004-637X/718/1/348

    DO - 10.1088/0004-637X/718/1/348

    M3 - Article

    AN - SCOPUS:84885598152

    VL - 718

    SP - 348

    EP - 356

    JO - Astrophysical Journal

    JF - Astrophysical Journal

    SN - 0004-637X

    IS - 1

    ER -