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Title: Fermi LAT Observations of the Supernova Remnant W28 (G6.4-0.1)

Abstract

Here, 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. 1FGLmore » 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). In conclusion, 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.« less

Authors:
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Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE; National Aeronautics and Space Administration (NASA)
Contributing Org.:
The Fermi LAT Collaboration
OSTI Identifier:
1357544
Grant/Contract Number:  
AC02-76SF00515
Resource Type:
Accepted Manuscript
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 718; Journal Issue: 1; Journal ID: ISSN 0004-637X
Publisher:
Institute of Physics (IOP)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; acceleration of particles; cosmic rays; gamma rays ISM; ISM individual objects (W28, G6.4−0.1); ISM: supernova remnants

Citation Formats

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, Ö., 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, J., Knödlseder, J., Kuss, M., Lande, J., Latronico, L., Lee, S. -H., Lemoine-Goumard, M., Garde, M. Llena, 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., Parkinson, P. M. Saz, 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., and Ziegler, M. Fermi LAT Observations of the Supernova Remnant W28 (G6.4-0.1). United States: N. p., 2010. Web. doi: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, Ö., 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, J., Knödlseder, J., Kuss, M., Lande, J., Latronico, L., Lee, S. -H., Lemoine-Goumard, M., Garde, M. Llena, 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., Parkinson, P. M. Saz, 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 LAT Observations of the Supernova Remnant W28 (G6.4-0.1). United States. doi: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, Ö., 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, J., Knödlseder, J., Kuss, M., Lande, J., Latronico, L., Lee, S. -H., Lemoine-Goumard, M., Garde, M. Llena, 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., Parkinson, P. M. Saz, 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., and Ziegler, M. Wed . "Fermi LAT Observations of the Supernova Remnant W28 (G6.4-0.1)". United States. doi:10.1088/0004-637X/718/1/348. https://www.osti.gov/servlets/purl/1357544.
@article{osti_1357544,
title = {Fermi LAT Observations of the Supernova Remnant W28 (G6.4-0.1)},
author = {Abdo, A. A. and Ackermann, M. and Ajello, M. and Allafort, A. and Baldini, L. and Ballet, J. and Barbiellini, G. and Bastieri, D. and Bechtol, K. and Bellazzini, R. and Berenji, B. and Blandford, R. D. and Bloom, E. D. and Bonamente, E. and Borgland, A. W. and Bouvier, A. and Brandt, T. J. and Bregeon, J. and Brigida, M. and Bruel, P. and Buehler, R. and Buson, S. and Caliandro, G. A. and Cameron, R. A. and Caraveo, P. A. and Carrigan, S. and Casandjian, J. M. and Cecchi, C. and Çelik, Ö. and Chekhtman, A. and Chiang, J. and Ciprini, S. and Claus, R. and Cohen-Tanugi, J. and Conrad, J. and Dermer, C. D. and de Palma, F. and do Couto e Silva, E. and Drell, P. S. and Dubois, R. and Dumora, D. and Farnier, C. and Favuzzi, C. and Fegan, S. J. and Fukazawa, Y. and Fukui, Y. and Funk, S. and Fusco, P. and Gargano, F. and Gehrels, N. and Germani, S. and Giglietto, N. and Giordano, F. and Glanzman, T. and Godfrey, G. and Grenier, I. A. and Grove, J. E. and Guiriec, S. and Hadasch, D. and Hanabata, Y. and Harding, A. K. and Hays, E. and Horan, D. and Hughes, R. E. and Jóhannesson, G. and Johnson, A. S. and Johnson, W. N. and Kamae, T. and Katagiri, H. and Kataoka, J. and Knödlseder, J. and Kuss, M. and Lande, J. and Latronico, L. and Lee, S. -H. and Lemoine-Goumard, M. and Garde, M. Llena and Longo, F. and Loparco, F. and Lovellette, M. N. and Lubrano, P. and Makeev, A. and Mazziotta, M. N. and Michelson, P. F. and Mitthumsiri, W. and Mizuno, T. and Moiseev, A. A. and Monte, C. and Monzani, M. E. and Morselli, A. and Moskalenko, I. V. and Murgia, S. and Nakamori, T. and Nolan, P. L. and Norris, J. P. and Nuss, E. and Ohno, M. and Ohsugi, T. and Omodei, N. and Orlando, E. and Ormes, J. F. and Ozaki, M. and Panetta, J. H. and Parent, D. and Pelassa, V. and Pepe, M. and Pesce-Rollins, M. and Piron, F. and Porter, T. A. and Rainò, S. and Rando, R. and Razzano, M. and Reimer, A. and Reimer, O. and Reposeur, T. and Rodriguez, A. Y. and Roth, M. and Sadrozinski, H. F. -W. and Sander, A. and Parkinson, P. M. Saz and Sgrò, C. and Siskind, E. J. and Smith, D. A. and Smith, P. D. and Spandre, G. and Spinelli, P. and Strickman, M. S. and Suson, D. J. and Tajima, H. and Takahashi, H. and Takahashi, T. and Tanaka, T. and Thayer, J. B. and Thayer, J. G. and Thompson, D. J. and Tibaldo, L. and Tibolla, O. and Torres, D. F. and Tosti, G. and Uchiyama, Y. and Uehara, T. and Usher, T. L. and Vasileiou, V. and Vilchez, N. and Vitale, V. and Waite, A. P. and Wang, P. and Winer, B. L. and Wood, K. S. and Yamamoto, H. and Yamazaki, R. and Yang, Z. and Ylinen, T. and Ziegler, M.},
abstractNote = {Here, 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). In conclusion, 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.},
doi = {10.1088/0004-637X/718/1/348},
journal = {Astrophysical Journal},
number = 1,
volume = 718,
place = {United States},
year = {2010},
month = {6}
}

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