Simultaneous observations of pks 2155-304 with hess, fermi, rxte, and atom: Spectral energy distributions and variability in a low state

F. Aharonian, A. G. Akhperjanian, G. Anton, U. Barres De Almeida, A. R. Bazer-Bachi, Y. Becherini, B. Behera, K. Bernlöhr, C. Boisson, A. Bochow, V. Borrel, E. Brion, J. Brucker, P. Brun, R. Bühler, T. Bulik, I. Büsching, T. Boutelier, P. M. Chadwick, A. CharbonnierR. C G Chaves, A. Cheesebrough, L. M. Chounet, A. C. Clapson, G. Coignet, M. Dalton, M. K. Daniel, I. D. Davids, B. Degrange, C. Deil, H. J. Dickinson, A. Djannati-Ata, W. Domainko, L. O'C. Drury, F. Dubois, G. Dubus, J. Dyks, M. Dyrda, K. Egberts, D. Emmanoulopoulos, P. Espigat, C. Farnier, F. Feinstein, A. Fiasson, A. Förster, G. Fontaine, M. Füling, S. Gabici, Y. A. Gallant, L. Gérard, B. Giebels, J. F. Glicenstein, B. Glück, P. Goret, D. Göhring, D. Hauser, M. Hauser, S. Heinz, G. Heinzelmann, G. Henri, G. Hermann, J. A. Hinton, A. Hoffmann, W. Hofmann, M. Holleran, S. Hoppe, D. Horns, A. Jacholkowska, O. C. De Jager, C. Jahn, I. Jung, K. Katarzyński, U. Katz, S. Kaufmann, E. Kendziorra, M. Kerschhaggl, D. Khangulyan, B. Khélifi, D. Keogh, W. Kluźniak, Nu Komin, K. Kosack, G. Lamanna, J. P. Lenain, T. Lohse, V. Marandon, J. M. Martin, O. Martineau-Huynh, A. Marcowith, D. Maurin, T. J L McComb, M. C. Medina, R. Moderski, E. Moulin, M. Naumann-Godo, M. De Naurois, D. Nedbal, D. Nekrassov, J. Niemiec, S. J. Nolan, S. Ohm, J. F. Olive, E. De Õa Wilhelmi, K. J. Orford, M. Ostrowski, M. Panter, M. Paz Arribas, G. Pedaletti, G. Pelletier, P. O. Petrucci, S. Pita, G. Pühlhofer, M. Punch, A. Quirrenbach, B. C. Raubenheimer, M. Raue, S. M. Rayner, M. Renaud, F. Rieger, J. Ripken, L. Rob, S. Rosier-Lees, G. Rowell, B. Rudak, C. B. Rulten, J. Ruppel, V. Sahakian, A. Santangelo, R. Schlickeiser, F. M. Schöck, R. Schröder, U. Schwanke, S. Schwarzburg, S. Schwemmer, A. Shalchi, M. Sikora, J. L. Skilton, H. Sol, D. Spangler, Stawarz, R. Steenkamp, C. Stegmann, G. Superina, A. Szostek, P. H. Tam, J. P. Tavernet, R. Terrier, O. Tibolla, C. Van Eldik, G. Vasileiadis, C. Venter, L. Venter, J. P. Vialle, P. Vincent, M. Vivier, H. J. Völk, F. Volpe, S. J. Wagner, M. Ward, A. A. Zdziarski, A. Zech, A. A. Abdo, M. Ackermann, M. Ajello, W. B. Atwood, M. Axelsson, L. Baldini, J. Ballet, G. Barbiellini, M. G. Baring, D. Bastieri, M. Battelino, B. M. Baughman, K. Bechtol, R. Bellazzini, B. Berenji, E. D. Bloom, E. Bonamente, A. W. Borgland, J. Bregeon, A. Brez, M. Brigida, P. Bruel, G. A. Caliandro, R. A. Cameron, P. A. Caraveo, J. M. Casandjian, E. Cavazzuti, C. Cecchi, E. Charles, A. Chekhtman, A. W. Chen, C. C. Cheung, J. Chiang, S. Ciprini, R. Claus, J. Cohen-Tanugi, S. Colafrancesco, J. Conrad, L. Costamante, S. Cutini, C. D. Dermer, A. De Angelis, F. De Palma, S. W. Digel, E. Do Couto E Silva, P. S. Drell, R. Dubois, G. Dubus, D. Dumora, C. Farnier, C. Favuzzi, S. J. Fegan, E. C. Ferrara, P. Fleury, W. B. Focke, M. Frailis, Y. Fukazawa, S. Funk, P. Fusco, F. Gargano, D. Gasparrini, N. Gehrels, S. Germani, B. Giebels, N. Giglietto, F. Giordano, M. H. Grondin, J. E. Grove, L. Guillemot, S. Guiriec, Y. Hanabata, A. K. Harding, M. Hayashida, E. Hays, D. Horan, G. Jóhannesson, A. S. Johnson, R. P. Johnson, W. N. Johnson, M. Kadler, T. Kamae, H. Katagiri, Jun Kataoka, M. Kerr, J. Knödlseder, F. Kuehn, M. Kuss, J. Lande, L. Latronico, S. H. Lee, M. Lemoine-Goumard, F. Longo, F. Loparco, B. Lott, M. N. Lovellette, G. M. Madejski, A. Makeev, M. N. Mazziotta, J. E. McEnery, C. Meurer, P. F. Michelson, W. Mitthumsiri, T. Mizuno, A. A. Moiseev, C. Monte, M. E. Monzani, A. Morselli, I. V. Moskalenko, S. Murgia, P. L. Nolan, E. Nuss, T. Ohsugi, N. Omodei, E. Orlando, J. F. Ormes, D. Paneque, J. H. Panetta, D. Parent, V. Pelassa, M. Pepe, M. Pesce-Rollins, F. Piron, T. A. Porter, S. Rainò, M. Razzano, A. Reimer, O. Reimer, T. Reposeur, S. Ritz, A. Y. Rodriguez, F. Ryde, H. F W Sadrozinski, D. Sanchez, A. Sander, J. D. Scargle, T. L. Schalk, A. Sellerholm, C. Sgrò, M. Shaw, D. A. Smith, G. Spandre, P. Spinelli, J. L. Starck, M. S. Strickman, H. Tajima, H. Takahashi, T. Takahashi, T. Tanaka, J. G. Thayer, D. J. Thompson, L. Tibaldo, D. F. Torres, G. Tosti, A. Tramacere, Y. Uchiyama, T. L. Usher, N. Vilchez, M. Villata, V. Vitale, A. P. Waite, K. S. Wood, T. Ylinen, M. Ziegler

Research output: Contribution to journalArticle

118 Citations (Scopus)

Abstract

We report on the first simultaneous observations that cover the optical, X-ray, and high-energy gamma-ray bands of the BL Lac object PKS2155-304. The gamma-ray bands were observed for 11 days, between 2008 August 25 and 2008 September 6 (MJD 54704-54715), jointly with the Fermi Gamma-ray Space Telescope and the HESS atmospheric Cherenkov array, providing the first simultaneous MeV-TeV spectral energy distribution (SED) with the new generation of γ-ray telescopes. The ATOM telescope and the RXTE and Swift observatories provided optical and X-ray coverage of the low-energy component over the same time period. The object was close to the lowest archival X-ray and very high energy (VHE; >100 GeV) state, whereas the optical flux was much higher. The light curves show relatively little (30%) variability overall when compared to past flaring episodes, but we find a clear optical/VHE correlation and evidence for a correlation of the X-rays with the high-energy spectral index. Contrary to previous observations in the flaring state, we do not find any correlation between the X-ray and VHE components. Although synchrotron self-Compton models are often invoked to explain the SEDs of BL Lac objects, the most common versions of these models are at odds with the correlated variability we find in the various bands for PKS2155-304.

Original languageEnglish
JournalAstrophysical Journal
Volume696
Issue number2 PART 2
DOIs
Publication statusPublished - 2009
Externally publishedYes

Fingerprint

spectral energy distribution
atoms
energy
x rays
Swift observatory
gamma rays
telescopes
Fermi Gamma-ray Space Telescope
X Ray Timing Explorer
light curve
rays
observatories
synchrotrons
observatory
distribution
flaring

Keywords

  • BL Lacertae objects: individual (PKS 2155-304)
  • Galaxies: active
  • Gamma rays: observations

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Aharonian, F., Akhperjanian, A. G., Anton, G., Barres De Almeida, U., Bazer-Bachi, A. R., Becherini, Y., ... Ziegler, M. (2009). Simultaneous observations of pks 2155-304 with hess, fermi, rxte, and atom: Spectral energy distributions and variability in a low state. Astrophysical Journal, 696(2 PART 2). https://doi.org/10.1088/0004-637X/696/2/L150

Simultaneous observations of pks 2155-304 with hess, fermi, rxte, and atom : Spectral energy distributions and variability in a low state. / Aharonian, F.; Akhperjanian, A. G.; Anton, G.; Barres De Almeida, U.; Bazer-Bachi, A. R.; Becherini, Y.; Behera, B.; Bernlöhr, K.; Boisson, C.; Bochow, A.; Borrel, V.; Brion, E.; Brucker, J.; Brun, P.; Bühler, R.; Bulik, T.; Büsching, I.; Boutelier, T.; Chadwick, P. M.; Charbonnier, A.; Chaves, R. C G; Cheesebrough, A.; Chounet, L. M.; Clapson, A. C.; Coignet, G.; Dalton, M.; Daniel, M. K.; Davids, I. D.; Degrange, B.; Deil, C.; Dickinson, H. J.; Djannati-Ata, A.; Domainko, W.; O'C. Drury, L.; Dubois, F.; Dubus, G.; Dyks, J.; Dyrda, M.; Egberts, K.; Emmanoulopoulos, D.; Espigat, P.; Farnier, C.; Feinstein, F.; Fiasson, A.; Förster, A.; Fontaine, G.; Füling, M.; Gabici, S.; Gallant, Y. A.; Gérard, L.; Giebels, B.; Glicenstein, J. F.; Glück, B.; Goret, P.; Göhring, D.; Hauser, D.; Hauser, M.; Heinz, S.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hinton, J. A.; Hoffmann, A.; Hofmann, W.; Holleran, M.; Hoppe, S.; Horns, D.; Jacholkowska, A.; De Jager, O. C.; Jahn, C.; Jung, I.; Katarzyński, K.; Katz, U.; Kaufmann, S.; Kendziorra, E.; Kerschhaggl, M.; Khangulyan, D.; Khélifi, B.; Keogh, D.; Kluźniak, W.; Komin, Nu; Kosack, K.; Lamanna, G.; Lenain, J. P.; Lohse, T.; Marandon, V.; Martin, J. M.; Martineau-Huynh, O.; Marcowith, A.; Maurin, D.; McComb, T. J L; Medina, M. C.; Moderski, R.; Moulin, E.; Naumann-Godo, M.; De Naurois, M.; Nedbal, D.; Nekrassov, D.; Niemiec, J.; Nolan, S. J.; Ohm, S.; Olive, J. F.; De Õa Wilhelmi, E.; Orford, K. J.; Ostrowski, M.; Panter, M.; Arribas, M. Paz; Pedaletti, G.; Pelletier, G.; Petrucci, P. O.; Pita, S.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raubenheimer, B. C.; Raue, M.; Rayner, S. M.; Renaud, M.; Rieger, F.; Ripken, J.; Rob, L.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Ruppel, J.; Sahakian, V.; Santangelo, A.; Schlickeiser, R.; Schöck, F. M.; Schröder, R.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Shalchi, A.; Sikora, M.; Skilton, J. L.; Sol, H.; Spangler, D.; Stawarz; Steenkamp, R.; Stegmann, C.; Superina, G.; Szostek, A.; Tam, P. H.; Tavernet, J. P.; Terrier, R.; Tibolla, O.; Van Eldik, C.; Vasileiadis, G.; Venter, C.; Venter, L.; Vialle, J. P.; Vincent, P.; Vivier, M.; Völk, H. J.; Volpe, F.; Wagner, S. J.; Ward, M.; Zdziarski, A. A.; Zech, A.; Abdo, A. A.; Ackermann, M.; Ajello, M.; Atwood, W. B.; Axelsson, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Baring, M. G.; Bastieri, D.; Battelino, M.; Baughman, B. M.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bregeon, J.; Brez, A.; Brigida, M.; Bruel, P.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Casandjian, J. M.; Cavazzuti, E.; Cecchi, C.; Charles, E.; Chekhtman, A.; Chen, A. W.; Cheung, C. C.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Colafrancesco, S.; Conrad, J.; Costamante, L.; Cutini, S.; Dermer, C. D.; De Angelis, A.; De Palma, F.; Digel, S. W.; Do Couto E Silva, E.; Drell, P. S.; Dubois, R.; Dubus, G.; Dumora, D.; Farnier, C.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Fleury, P.; Focke, W. B.; Frailis, M.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Giebels, B.; Giglietto, N.; Giordano, F.; Grondin, M. H.; Grove, J. E.; Guillemot, L.; Guiriec, S.; Hanabata, Y.; Harding, A. K.; Hayashida, M.; Hays, E.; Horan, D.; Jóhannesson, G.; Johnson, A. S.; Johnson, R. P.; Johnson, W. N.; Kadler, M.; Kamae, T.; Katagiri, H.; Kataoka, Jun; Kerr, M.; Knödlseder, J.; Kuehn, F.; Kuss, M.; Lande, J.; Latronico, L.; Lee, S. H.; Lemoine-Goumard, M.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Madejski, G. M.; Makeev, A.; Mazziotta, M. N.; McEnery, J. E.; Meurer, C.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nolan, P. L.; Nuss, E.; Ohsugi, T.; Omodei, N.; Orlando, E.; Ormes, J. F.; Paneque, D.; Panetta, J. H.; Parent, D.; Pelassa, V.; Pepe, M.; Pesce-Rollins, M.; Piron, F.; Porter, T. A.; Rainò, S.; Razzano, M.; Reimer, A.; Reimer, O.; Reposeur, T.; Ritz, S.; Rodriguez, A. Y.; Ryde, F.; Sadrozinski, H. F W; Sanchez, D.; Sander, A.; Scargle, J. D.; Schalk, T. L.; Sellerholm, A.; Sgrò, C.; Shaw, M.; Smith, D. A.; Spandre, G.; Spinelli, P.; Starck, J. L.; Strickman, M. S.; Tajima, H.; Takahashi, H.; Takahashi, T.; Tanaka, T.; Thayer, J. G.; Thompson, D. J.; Tibaldo, L.; Torres, D. F.; Tosti, G.; Tramacere, A.; Uchiyama, Y.; Usher, T. L.; Vilchez, N.; Villata, M.; Vitale, V.; Waite, A. P.; Wood, K. S.; Ylinen, T.; Ziegler, M.

In: Astrophysical Journal, Vol. 696, No. 2 PART 2, 2009.

Research output: Contribution to journalArticle

Aharonian, F, Akhperjanian, AG, Anton, G, Barres De Almeida, U, Bazer-Bachi, AR, Becherini, Y, Behera, B, Bernlöhr, K, Boisson, C, Bochow, A, Borrel, V, Brion, E, Brucker, J, Brun, P, Bühler, R, Bulik, T, Büsching, I, Boutelier, T, Chadwick, PM, Charbonnier, A, Chaves, RCG, Cheesebrough, A, Chounet, LM, Clapson, AC, Coignet, G, Dalton, M, Daniel, MK, Davids, ID, Degrange, B, Deil, C, Dickinson, HJ, Djannati-Ata, A, Domainko, W, O'C. Drury, L, Dubois, F, Dubus, G, Dyks, J, Dyrda, M, Egberts, K, Emmanoulopoulos, D, Espigat, P, Farnier, C, Feinstein, F, Fiasson, A, Förster, A, Fontaine, G, Füling, M, Gabici, S, Gallant, YA, Gérard, L, Giebels, B, Glicenstein, JF, Glück, B, Goret, P, Göhring, D, Hauser, D, Hauser, M, Heinz, S, Heinzelmann, G, Henri, G, Hermann, G, Hinton, JA, Hoffmann, A, Hofmann, W, Holleran, M, Hoppe, S, Horns, D, Jacholkowska, A, De Jager, OC, Jahn, C, Jung, I, Katarzyński, K, Katz, U, Kaufmann, S, Kendziorra, E, Kerschhaggl, M, Khangulyan, D, Khélifi, B, Keogh, D, Kluźniak, W, Komin, N, Kosack, K, Lamanna, G, Lenain, JP, Lohse, T, Marandon, V, Martin, JM, Martineau-Huynh, O, Marcowith, A, Maurin, D, McComb, TJL, Medina, MC, Moderski, R, Moulin, E, Naumann-Godo, M, De Naurois, M, Nedbal, D, Nekrassov, D, Niemiec, J, Nolan, SJ, Ohm, S, Olive, JF, De Õa Wilhelmi, E, Orford, KJ, Ostrowski, M, Panter, M, Arribas, MP, Pedaletti, G, Pelletier, G, Petrucci, PO, Pita, S, Pühlhofer, G, Punch, M, Quirrenbach, A, Raubenheimer, BC, Raue, M, Rayner, SM, Renaud, M, Rieger, F, Ripken, J, Rob, L, Rosier-Lees, S, Rowell, G, Rudak, B, Rulten, CB, Ruppel, J, Sahakian, V, Santangelo, A, Schlickeiser, R, Schöck, FM, Schröder, R, Schwanke, U, Schwarzburg, S, Schwemmer, S, Shalchi, A, Sikora, M, Skilton, JL, Sol, H, Spangler, D, Stawarz, Steenkamp, R, Stegmann, C, Superina, G, Szostek, A, Tam, PH, Tavernet, JP, Terrier, R, Tibolla, O, Van Eldik, C, Vasileiadis, G, Venter, C, Venter, L, Vialle, JP, Vincent, P, Vivier, M, Völk, HJ, Volpe, F, Wagner, SJ, Ward, M, Zdziarski, AA, Zech, A, Abdo, AA, Ackermann, M, Ajello, M, Atwood, WB, Axelsson, M, Baldini, L, Ballet, J, Barbiellini, G, Baring, MG, Bastieri, D, Battelino, M, Baughman, BM, Bechtol, K, Bellazzini, R, Berenji, B, Bloom, ED, Bonamente, E, Borgland, AW, Bregeon, J, Brez, A, Brigida, M, Bruel, P, Caliandro, GA, Cameron, RA, Caraveo, PA, Casandjian, JM, Cavazzuti, E, Cecchi, C, Charles, E, Chekhtman, A, Chen, AW, Cheung, CC, Chiang, J, Ciprini, S, Claus, R, Cohen-Tanugi, J, Colafrancesco, S, Conrad, J, Costamante, L, Cutini, S, Dermer, CD, De Angelis, A, De Palma, F, Digel, SW, Do Couto E Silva, E, Drell, PS, Dubois, R, Dubus, G, Dumora, D, Farnier, C, Favuzzi, C, Fegan, SJ, Ferrara, EC, Fleury, P, Focke, WB, Frailis, M, Fukazawa, Y, Funk, S, Fusco, P, Gargano, F, Gasparrini, D, Gehrels, N, Germani, S, Giebels, B, Giglietto, N, Giordano, F, Grondin, MH, Grove, JE, Guillemot, L, Guiriec, S, Hanabata, Y, Harding, AK, Hayashida, M, Hays, E, Horan, D, Jóhannesson, G, Johnson, AS, Johnson, RP, Johnson, WN, Kadler, M, Kamae, T, Katagiri, H, Kataoka, J, Kerr, M, Knödlseder, J, Kuehn, F, Kuss, M, Lande, J, Latronico, L, Lee, SH, Lemoine-Goumard, M, Longo, F, Loparco, F, Lott, B, Lovellette, MN, Madejski, GM, 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, 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, Razzano, M, Reimer, A, Reimer, O, Reposeur, T, Ritz, S, Rodriguez, AY, Ryde, F, Sadrozinski, HFW, Sanchez, D, Sander, A, Scargle, JD, Schalk, TL, Sellerholm, A, Sgrò, C, Shaw, M, Smith, DA, Spandre, G, Spinelli, P, Starck, JL, Strickman, MS, Tajima, H, Takahashi, H, Takahashi, T, Tanaka, T, Thayer, JG, Thompson, DJ, Tibaldo, L, Torres, DF, Tosti, G, Tramacere, A, Uchiyama, Y, Usher, TL, Vilchez, N, Villata, M, Vitale, V, Waite, AP, Wood, KS, Ylinen, T & Ziegler, M 2009, 'Simultaneous observations of pks 2155-304 with hess, fermi, rxte, and atom: Spectral energy distributions and variability in a low state', Astrophysical Journal, vol. 696, no. 2 PART 2. https://doi.org/10.1088/0004-637X/696/2/L150
Aharonian, F. ; Akhperjanian, A. G. ; Anton, G. ; Barres De Almeida, U. ; Bazer-Bachi, A. R. ; Becherini, Y. ; Behera, B. ; Bernlöhr, K. ; Boisson, C. ; Bochow, A. ; Borrel, V. ; Brion, E. ; Brucker, J. ; Brun, P. ; Bühler, R. ; Bulik, T. ; Büsching, I. ; Boutelier, T. ; Chadwick, P. M. ; Charbonnier, A. ; Chaves, R. C G ; Cheesebrough, A. ; Chounet, L. M. ; Clapson, A. C. ; Coignet, G. ; Dalton, M. ; Daniel, M. K. ; Davids, I. D. ; Degrange, B. ; Deil, C. ; Dickinson, H. J. ; Djannati-Ata, A. ; Domainko, W. ; O'C. Drury, L. ; Dubois, F. ; Dubus, G. ; Dyks, J. ; Dyrda, M. ; Egberts, K. ; Emmanoulopoulos, D. ; Espigat, P. ; Farnier, C. ; Feinstein, F. ; Fiasson, A. ; Förster, A. ; Fontaine, G. ; Füling, M. ; Gabici, S. ; Gallant, Y. A. ; Gérard, L. ; Giebels, B. ; Glicenstein, J. F. ; Glück, B. ; Goret, P. ; Göhring, D. ; Hauser, D. ; Hauser, M. ; Heinz, S. ; Heinzelmann, G. ; Henri, G. ; Hermann, G. ; Hinton, J. A. ; Hoffmann, A. ; Hofmann, W. ; Holleran, M. ; Hoppe, S. ; Horns, D. ; Jacholkowska, A. ; De Jager, O. C. ; Jahn, C. ; Jung, I. ; Katarzyński, K. ; Katz, U. ; Kaufmann, S. ; Kendziorra, E. ; Kerschhaggl, M. ; Khangulyan, D. ; Khélifi, B. ; Keogh, D. ; Kluźniak, W. ; Komin, Nu ; Kosack, K. ; Lamanna, G. ; Lenain, J. P. ; Lohse, T. ; Marandon, V. ; Martin, J. M. ; Martineau-Huynh, O. ; Marcowith, A. ; Maurin, D. ; McComb, T. J L ; Medina, M. C. ; Moderski, R. ; Moulin, E. ; Naumann-Godo, M. ; De Naurois, M. ; Nedbal, D. ; Nekrassov, D. ; Niemiec, J. ; Nolan, S. J. ; Ohm, S. ; Olive, J. F. ; De Õa Wilhelmi, E. ; Orford, K. J. ; Ostrowski, M. ; Panter, M. ; Arribas, M. Paz ; Pedaletti, G. ; Pelletier, G. ; Petrucci, P. O. ; Pita, S. ; Pühlhofer, G. ; Punch, M. ; Quirrenbach, A. ; Raubenheimer, B. C. ; Raue, M. ; Rayner, S. M. ; Renaud, M. ; Rieger, F. ; Ripken, J. ; Rob, L. ; Rosier-Lees, S. ; Rowell, G. ; Rudak, B. ; Rulten, C. B. ; Ruppel, J. ; Sahakian, V. ; Santangelo, A. ; Schlickeiser, R. ; Schöck, F. M. ; Schröder, R. ; Schwanke, U. ; Schwarzburg, S. ; Schwemmer, S. ; Shalchi, A. ; Sikora, M. ; Skilton, J. L. ; Sol, H. ; Spangler, D. ; Stawarz ; Steenkamp, R. ; Stegmann, C. ; Superina, G. ; Szostek, A. ; Tam, P. H. ; Tavernet, J. P. ; Terrier, R. ; Tibolla, O. ; Van Eldik, C. ; Vasileiadis, G. ; Venter, C. ; Venter, L. ; Vialle, J. P. ; Vincent, P. ; Vivier, M. ; Völk, H. J. ; Volpe, F. ; Wagner, S. J. ; Ward, M. ; Zdziarski, A. A. ; Zech, A. ; Abdo, A. A. ; Ackermann, M. ; Ajello, M. ; Atwood, W. B. ; Axelsson, M. ; Baldini, L. ; Ballet, J. ; Barbiellini, G. ; Baring, M. G. ; Bastieri, D. ; Battelino, M. ; Baughman, B. M. ; Bechtol, K. ; Bellazzini, R. ; Berenji, B. ; Bloom, E. D. ; Bonamente, E. ; Borgland, A. W. ; Bregeon, J. ; Brez, A. ; Brigida, M. ; Bruel, P. ; Caliandro, G. A. ; Cameron, R. A. ; Caraveo, P. A. ; Casandjian, J. M. ; Cavazzuti, E. ; Cecchi, C. ; Charles, E. ; Chekhtman, A. ; Chen, A. W. ; Cheung, C. C. ; Chiang, J. ; Ciprini, S. ; Claus, R. ; Cohen-Tanugi, J. ; Colafrancesco, S. ; Conrad, J. ; Costamante, L. ; Cutini, S. ; Dermer, C. D. ; De Angelis, A. ; De Palma, F. ; Digel, S. W. ; Do Couto E Silva, E. ; Drell, P. S. ; Dubois, R. ; Dubus, G. ; Dumora, D. ; Farnier, C. ; Favuzzi, C. ; Fegan, S. J. ; Ferrara, E. C. ; Fleury, P. ; Focke, W. B. ; Frailis, M. ; Fukazawa, Y. ; Funk, S. ; Fusco, P. ; Gargano, F. ; Gasparrini, D. ; Gehrels, N. ; Germani, S. ; Giebels, B. ; Giglietto, N. ; Giordano, F. ; Grondin, M. H. ; Grove, J. E. ; Guillemot, L. ; Guiriec, S. ; Hanabata, Y. ; Harding, A. K. ; Hayashida, M. ; Hays, E. ; Horan, D. ; Jóhannesson, G. ; Johnson, A. S. ; Johnson, R. P. ; Johnson, W. N. ; Kadler, M. ; Kamae, T. ; Katagiri, H. ; Kataoka, Jun ; Kerr, M. ; Knödlseder, J. ; Kuehn, F. ; Kuss, M. ; Lande, J. ; Latronico, L. ; Lee, S. H. ; Lemoine-Goumard, M. ; Longo, F. ; Loparco, F. ; Lott, B. ; Lovellette, M. N. ; Madejski, G. M. ; Makeev, A. ; Mazziotta, M. N. ; McEnery, J. E. ; Meurer, C. ; Michelson, P. F. ; Mitthumsiri, W. ; Mizuno, T. ; Moiseev, A. A. ; Monte, C. ; Monzani, M. E. ; Morselli, A. ; Moskalenko, I. V. ; Murgia, S. ; Nolan, P. L. ; Nuss, E. ; Ohsugi, T. ; Omodei, N. ; Orlando, E. ; Ormes, J. F. ; Paneque, D. ; Panetta, J. H. ; Parent, D. ; Pelassa, V. ; Pepe, M. ; Pesce-Rollins, M. ; Piron, F. ; Porter, T. A. ; Rainò, S. ; Razzano, M. ; Reimer, A. ; Reimer, O. ; Reposeur, T. ; Ritz, S. ; Rodriguez, A. Y. ; Ryde, F. ; Sadrozinski, H. F W ; Sanchez, D. ; Sander, A. ; Scargle, J. D. ; Schalk, T. L. ; Sellerholm, A. ; Sgrò, C. ; Shaw, M. ; Smith, D. A. ; Spandre, G. ; Spinelli, P. ; Starck, J. L. ; Strickman, M. S. ; Tajima, H. ; Takahashi, H. ; Takahashi, T. ; Tanaka, T. ; Thayer, J. G. ; Thompson, D. J. ; Tibaldo, L. ; Torres, D. F. ; Tosti, G. ; Tramacere, A. ; Uchiyama, Y. ; Usher, T. L. ; Vilchez, N. ; Villata, M. ; Vitale, V. ; Waite, A. P. ; Wood, K. S. ; Ylinen, T. ; Ziegler, M. / Simultaneous observations of pks 2155-304 with hess, fermi, rxte, and atom : Spectral energy distributions and variability in a low state. In: Astrophysical Journal. 2009 ; Vol. 696, No. 2 PART 2.
@article{acd92a003f1f4f2498aa34e2a29965e3,
title = "Simultaneous observations of pks 2155-304 with hess, fermi, rxte, and atom: Spectral energy distributions and variability in a low state",
abstract = "We report on the first simultaneous observations that cover the optical, X-ray, and high-energy gamma-ray bands of the BL Lac object PKS2155-304. The gamma-ray bands were observed for 11 days, between 2008 August 25 and 2008 September 6 (MJD 54704-54715), jointly with the Fermi Gamma-ray Space Telescope and the HESS atmospheric Cherenkov array, providing the first simultaneous MeV-TeV spectral energy distribution (SED) with the new generation of γ-ray telescopes. The ATOM telescope and the RXTE and Swift observatories provided optical and X-ray coverage of the low-energy component over the same time period. The object was close to the lowest archival X-ray and very high energy (VHE; >100 GeV) state, whereas the optical flux was much higher. The light curves show relatively little (30{\%}) variability overall when compared to past flaring episodes, but we find a clear optical/VHE correlation and evidence for a correlation of the X-rays with the high-energy spectral index. Contrary to previous observations in the flaring state, we do not find any correlation between the X-ray and VHE components. Although synchrotron self-Compton models are often invoked to explain the SEDs of BL Lac objects, the most common versions of these models are at odds with the correlated variability we find in the various bands for PKS2155-304.",
keywords = "BL Lacertae objects: individual (PKS 2155-304), Galaxies: active, Gamma rays: observations",
author = "F. Aharonian and Akhperjanian, {A. G.} and G. Anton and {Barres De Almeida}, U. and Bazer-Bachi, {A. R.} and Y. Becherini and B. Behera and K. Bernl{\"o}hr and C. Boisson and A. Bochow and V. Borrel and E. Brion and J. Brucker and P. Brun and R. B{\"u}hler and T. Bulik and I. B{\"u}sching and T. Boutelier and Chadwick, {P. M.} and A. Charbonnier and Chaves, {R. C G} and A. Cheesebrough and Chounet, {L. M.} and Clapson, {A. C.} and G. Coignet and M. Dalton and Daniel, {M. K.} and Davids, {I. D.} and B. Degrange and C. Deil and Dickinson, {H. J.} and A. Djannati-Ata and W. Domainko and {O'C. Drury}, L. and F. Dubois and G. Dubus and J. Dyks and M. Dyrda and K. Egberts and D. Emmanoulopoulos and P. Espigat and C. Farnier and F. Feinstein and A. Fiasson and A. F{\"o}rster and G. Fontaine and M. F{\"u}ling and S. Gabici and Gallant, {Y. A.} and L. G{\'e}rard and B. Giebels and Glicenstein, {J. F.} and B. Gl{\"u}ck and P. Goret and D. G{\"o}hring and D. Hauser and M. Hauser and S. Heinz and G. Heinzelmann and G. Henri and G. Hermann and Hinton, {J. A.} and A. Hoffmann and W. Hofmann and M. Holleran and S. Hoppe and D. Horns and A. Jacholkowska and {De Jager}, {O. C.} and C. Jahn and I. Jung and K. Katarzyński and U. Katz and S. Kaufmann and E. Kendziorra and M. Kerschhaggl and D. Khangulyan and B. Kh{\'e}lifi and D. Keogh and W. Kluźniak and Nu Komin and K. Kosack and G. Lamanna and Lenain, {J. P.} and T. Lohse and V. Marandon and Martin, {J. M.} and O. Martineau-Huynh and A. Marcowith and D. Maurin and McComb, {T. J L} and Medina, {M. C.} and R. Moderski and E. Moulin and M. Naumann-Godo and {De Naurois}, M. and D. Nedbal and D. Nekrassov and J. Niemiec and Nolan, {S. J.} and S. Ohm and Olive, {J. F.} and {De {\~O}a Wilhelmi}, E. and Orford, {K. J.} and M. Ostrowski and M. Panter and Arribas, {M. Paz} and G. Pedaletti and G. Pelletier and Petrucci, {P. O.} and S. Pita and G. P{\"u}hlhofer and M. Punch and A. Quirrenbach and Raubenheimer, {B. C.} and M. Raue and Rayner, {S. M.} and M. Renaud and F. Rieger and J. Ripken and L. Rob and S. Rosier-Lees and G. Rowell and B. Rudak and Rulten, {C. B.} and J. Ruppel and V. Sahakian and A. Santangelo and R. Schlickeiser and Sch{\"o}ck, {F. M.} and R. Schr{\"o}der and U. Schwanke and S. Schwarzburg and S. Schwemmer and A. Shalchi and M. Sikora and Skilton, {J. L.} and H. Sol and D. Spangler and Stawarz and R. Steenkamp and C. Stegmann and G. Superina and A. Szostek and Tam, {P. H.} and Tavernet, {J. P.} and R. Terrier and O. Tibolla and {Van Eldik}, C. and G. Vasileiadis and C. Venter and L. Venter and Vialle, {J. P.} and P. Vincent and M. Vivier and V{\"o}lk, {H. J.} and F. Volpe and Wagner, {S. J.} and M. Ward and Zdziarski, {A. A.} and A. Zech and Abdo, {A. A.} and M. Ackermann and M. Ajello and Atwood, {W. B.} and M. Axelsson and L. Baldini and J. Ballet and G. Barbiellini and Baring, {M. G.} and D. Bastieri and M. Battelino and Baughman, {B. M.} and K. Bechtol and R. Bellazzini and B. Berenji and Bloom, {E. D.} and E. Bonamente and Borgland, {A. W.} and J. Bregeon and A. Brez and M. Brigida and P. Bruel and Caliandro, {G. A.} and Cameron, {R. A.} and Caraveo, {P. A.} and Casandjian, {J. M.} and E. Cavazzuti and C. Cecchi and E. Charles and A. Chekhtman and Chen, {A. W.} and Cheung, {C. C.} and J. Chiang and S. Ciprini and R. Claus and J. Cohen-Tanugi and S. Colafrancesco and J. Conrad and L. Costamante and S. Cutini and Dermer, {C. D.} and {De Angelis}, A. and {De Palma}, F. and Digel, {S. W.} and {Do Couto E Silva}, E. and Drell, {P. S.} and R. Dubois and G. Dubus and D. Dumora and C. Farnier and C. Favuzzi and Fegan, {S. J.} and Ferrara, {E. C.} and P. Fleury and Focke, {W. B.} and M. Frailis and Y. Fukazawa and S. Funk and P. Fusco and F. Gargano and D. Gasparrini and N. Gehrels and S. Germani and B. Giebels and N. Giglietto and F. Giordano and Grondin, {M. H.} and Grove, {J. E.} and L. Guillemot and S. Guiriec and Y. Hanabata and Harding, {A. K.} and M. Hayashida and E. Hays and D. Horan and G. J{\'o}hannesson and Johnson, {A. S.} and Johnson, {R. P.} and Johnson, {W. N.} and M. Kadler and T. Kamae and H. Katagiri and Jun Kataoka and M. Kerr and J. Kn{\"o}dlseder and F. Kuehn and M. Kuss and J. Lande and L. Latronico and Lee, {S. H.} and M. Lemoine-Goumard and F. Longo and F. Loparco and B. Lott and Lovellette, {M. N.} and Madejski, {G. M.} and A. Makeev and Mazziotta, {M. N.} and McEnery, {J. E.} and C. Meurer 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 Nolan, {P. L.} and E. Nuss and T. Ohsugi and N. Omodei and E. Orlando and Ormes, {J. F.} and D. Paneque 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 M. Razzano and A. Reimer and O. Reimer and T. Reposeur and S. Ritz and Rodriguez, {A. Y.} and F. Ryde and Sadrozinski, {H. F W} and D. Sanchez and A. Sander and Scargle, {J. D.} and Schalk, {T. L.} and A. Sellerholm and C. Sgr{\`o} and M. Shaw and Smith, {D. A.} and G. Spandre and P. Spinelli and Starck, {J. L.} and Strickman, {M. S.} and H. Tajima and H. Takahashi and T. Takahashi and T. Tanaka and Thayer, {J. G.} and Thompson, {D. J.} and L. Tibaldo and Torres, {D. F.} and G. Tosti and A. Tramacere and Y. Uchiyama and Usher, {T. L.} and N. Vilchez and M. Villata and V. Vitale and Waite, {A. P.} and Wood, {K. S.} and T. Ylinen and M. Ziegler",
year = "2009",
doi = "10.1088/0004-637X/696/2/L150",
language = "English",
volume = "696",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing Ltd.",
number = "2 PART 2",

}

TY - JOUR

T1 - Simultaneous observations of pks 2155-304 with hess, fermi, rxte, and atom

T2 - Spectral energy distributions and variability in a low state

AU - Aharonian, F.

AU - Akhperjanian, A. G.

AU - Anton, G.

AU - Barres De Almeida, U.

AU - Bazer-Bachi, A. R.

AU - Becherini, Y.

AU - Behera, B.

AU - Bernlöhr, K.

AU - Boisson, C.

AU - Bochow, A.

AU - Borrel, V.

AU - Brion, E.

AU - Brucker, J.

AU - Brun, P.

AU - Bühler, R.

AU - Bulik, T.

AU - Büsching, I.

AU - Boutelier, T.

AU - Chadwick, P. M.

AU - Charbonnier, A.

AU - Chaves, R. C G

AU - Cheesebrough, A.

AU - Chounet, L. M.

AU - Clapson, A. C.

AU - Coignet, G.

AU - Dalton, M.

AU - Daniel, M. K.

AU - Davids, I. D.

AU - Degrange, B.

AU - Deil, C.

AU - Dickinson, H. J.

AU - Djannati-Ata, A.

AU - Domainko, W.

AU - O'C. Drury, L.

AU - Dubois, F.

AU - Dubus, G.

AU - Dyks, J.

AU - Dyrda, M.

AU - Egberts, K.

AU - Emmanoulopoulos, D.

AU - Espigat, P.

AU - Farnier, C.

AU - Feinstein, F.

AU - Fiasson, A.

AU - Förster, A.

AU - Fontaine, G.

AU - Füling, M.

AU - Gabici, S.

AU - Gallant, Y. A.

AU - Gérard, L.

AU - Giebels, B.

AU - Glicenstein, J. F.

AU - Glück, B.

AU - Goret, P.

AU - Göhring, D.

AU - Hauser, D.

AU - Hauser, M.

AU - Heinz, S.

AU - Heinzelmann, G.

AU - Henri, G.

AU - Hermann, G.

AU - Hinton, J. A.

AU - Hoffmann, A.

AU - Hofmann, W.

AU - Holleran, M.

AU - Hoppe, S.

AU - Horns, D.

AU - Jacholkowska, A.

AU - De Jager, O. C.

AU - Jahn, C.

AU - Jung, I.

AU - Katarzyński, K.

AU - Katz, U.

AU - Kaufmann, S.

AU - Kendziorra, E.

AU - Kerschhaggl, M.

AU - Khangulyan, D.

AU - Khélifi, B.

AU - Keogh, D.

AU - Kluźniak, W.

AU - Komin, Nu

AU - Kosack, K.

AU - Lamanna, G.

AU - Lenain, J. P.

AU - Lohse, T.

AU - Marandon, V.

AU - Martin, J. M.

AU - Martineau-Huynh, O.

AU - Marcowith, A.

AU - Maurin, D.

AU - McComb, T. J L

AU - Medina, M. C.

AU - Moderski, R.

AU - Moulin, E.

AU - Naumann-Godo, M.

AU - De Naurois, M.

AU - Nedbal, D.

AU - Nekrassov, D.

AU - Niemiec, J.

AU - Nolan, S. J.

AU - Ohm, S.

AU - Olive, J. F.

AU - De Õa Wilhelmi, E.

AU - Orford, K. J.

AU - Ostrowski, M.

AU - Panter, M.

AU - Arribas, M. Paz

AU - Pedaletti, G.

AU - Pelletier, G.

AU - Petrucci, P. O.

AU - Pita, S.

AU - Pühlhofer, G.

AU - Punch, M.

AU - Quirrenbach, A.

AU - Raubenheimer, B. C.

AU - Raue, M.

AU - Rayner, S. M.

AU - Renaud, M.

AU - Rieger, F.

AU - Ripken, J.

AU - Rob, L.

AU - Rosier-Lees, S.

AU - Rowell, G.

AU - Rudak, B.

AU - Rulten, C. B.

AU - Ruppel, J.

AU - Sahakian, V.

AU - Santangelo, A.

AU - Schlickeiser, R.

AU - Schöck, F. M.

AU - Schröder, R.

AU - Schwanke, U.

AU - Schwarzburg, S.

AU - Schwemmer, S.

AU - Shalchi, A.

AU - Sikora, M.

AU - Skilton, J. L.

AU - Sol, H.

AU - Spangler, D.

AU - Stawarz,

AU - Steenkamp, R.

AU - Stegmann, C.

AU - Superina, G.

AU - Szostek, A.

AU - Tam, P. H.

AU - Tavernet, J. P.

AU - Terrier, R.

AU - Tibolla, O.

AU - Van Eldik, C.

AU - Vasileiadis, G.

AU - Venter, C.

AU - Venter, L.

AU - Vialle, J. P.

AU - Vincent, P.

AU - Vivier, M.

AU - Völk, H. J.

AU - Volpe, F.

AU - Wagner, S. J.

AU - Ward, M.

AU - Zdziarski, A. A.

AU - Zech, A.

AU - Abdo, A. A.

AU - Ackermann, M.

AU - Ajello, M.

AU - Atwood, W. B.

AU - Axelsson, M.

AU - Baldini, L.

AU - Ballet, J.

AU - Barbiellini, G.

AU - Baring, M. G.

AU - Bastieri, D.

AU - Battelino, M.

AU - Baughman, B. M.

AU - Bechtol, K.

AU - Bellazzini, R.

AU - Berenji, B.

AU - Bloom, E. D.

AU - Bonamente, E.

AU - Borgland, A. W.

AU - Bregeon, J.

AU - Brez, A.

AU - Brigida, M.

AU - Bruel, P.

AU - Caliandro, G. A.

AU - Cameron, R. A.

AU - Caraveo, P. A.

AU - Casandjian, J. M.

AU - Cavazzuti, E.

AU - Cecchi, C.

AU - Charles, E.

AU - Chekhtman, A.

AU - Chen, A. W.

AU - Cheung, C. C.

AU - Chiang, J.

AU - Ciprini, S.

AU - Claus, R.

AU - Cohen-Tanugi, J.

AU - Colafrancesco, S.

AU - Conrad, J.

AU - Costamante, L.

AU - Cutini, S.

AU - Dermer, C. D.

AU - De Angelis, A.

AU - De Palma, F.

AU - Digel, S. W.

AU - Do Couto E Silva, E.

AU - Drell, P. S.

AU - Dubois, R.

AU - Dubus, G.

AU - Dumora, D.

AU - Farnier, C.

AU - Favuzzi, C.

AU - Fegan, S. J.

AU - Ferrara, E. C.

AU - Fleury, P.

AU - Focke, W. B.

AU - Frailis, M.

AU - Fukazawa, Y.

AU - Funk, S.

AU - Fusco, P.

AU - Gargano, F.

AU - Gasparrini, D.

AU - Gehrels, N.

AU - Germani, S.

AU - Giebels, B.

AU - Giglietto, N.

AU - Giordano, F.

AU - Grondin, M. H.

AU - Grove, J. E.

AU - Guillemot, L.

AU - Guiriec, S.

AU - Hanabata, Y.

AU - Harding, A. K.

AU - Hayashida, M.

AU - Hays, E.

AU - Horan, D.

AU - Jóhannesson, G.

AU - Johnson, A. S.

AU - Johnson, R. P.

AU - Johnson, W. N.

AU - Kadler, M.

AU - Kamae, T.

AU - Katagiri, H.

AU - Kataoka, Jun

AU - Kerr, M.

AU - Knödlseder, J.

AU - Kuehn, F.

AU - Kuss, M.

AU - Lande, J.

AU - Latronico, L.

AU - Lee, S. H.

AU - Lemoine-Goumard, M.

AU - Longo, F.

AU - Loparco, F.

AU - Lott, B.

AU - Lovellette, M. N.

AU - Madejski, G. M.

AU - Makeev, A.

AU - Mazziotta, M. N.

AU - McEnery, J. E.

AU - Meurer, C.

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 - Nolan, P. L.

AU - Nuss, E.

AU - Ohsugi, T.

AU - Omodei, N.

AU - Orlando, E.

AU - Ormes, J. F.

AU - Paneque, D.

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 - Razzano, M.

AU - Reimer, A.

AU - Reimer, O.

AU - Reposeur, T.

AU - Ritz, S.

AU - Rodriguez, A. Y.

AU - Ryde, F.

AU - Sadrozinski, H. F W

AU - Sanchez, D.

AU - Sander, A.

AU - Scargle, J. D.

AU - Schalk, T. L.

AU - Sellerholm, A.

AU - Sgrò, C.

AU - Shaw, M.

AU - Smith, D. A.

AU - Spandre, G.

AU - Spinelli, P.

AU - Starck, J. L.

AU - Strickman, M. S.

AU - Tajima, H.

AU - Takahashi, H.

AU - Takahashi, T.

AU - Tanaka, T.

AU - Thayer, J. G.

AU - Thompson, D. J.

AU - Tibaldo, L.

AU - Torres, D. F.

AU - Tosti, G.

AU - Tramacere, A.

AU - Uchiyama, Y.

AU - Usher, T. L.

AU - Vilchez, N.

AU - Villata, M.

AU - Vitale, V.

AU - Waite, A. P.

AU - Wood, K. S.

AU - Ylinen, T.

AU - Ziegler, M.

PY - 2009

Y1 - 2009

N2 - We report on the first simultaneous observations that cover the optical, X-ray, and high-energy gamma-ray bands of the BL Lac object PKS2155-304. The gamma-ray bands were observed for 11 days, between 2008 August 25 and 2008 September 6 (MJD 54704-54715), jointly with the Fermi Gamma-ray Space Telescope and the HESS atmospheric Cherenkov array, providing the first simultaneous MeV-TeV spectral energy distribution (SED) with the new generation of γ-ray telescopes. The ATOM telescope and the RXTE and Swift observatories provided optical and X-ray coverage of the low-energy component over the same time period. The object was close to the lowest archival X-ray and very high energy (VHE; >100 GeV) state, whereas the optical flux was much higher. The light curves show relatively little (30%) variability overall when compared to past flaring episodes, but we find a clear optical/VHE correlation and evidence for a correlation of the X-rays with the high-energy spectral index. Contrary to previous observations in the flaring state, we do not find any correlation between the X-ray and VHE components. Although synchrotron self-Compton models are often invoked to explain the SEDs of BL Lac objects, the most common versions of these models are at odds with the correlated variability we find in the various bands for PKS2155-304.

AB - We report on the first simultaneous observations that cover the optical, X-ray, and high-energy gamma-ray bands of the BL Lac object PKS2155-304. The gamma-ray bands were observed for 11 days, between 2008 August 25 and 2008 September 6 (MJD 54704-54715), jointly with the Fermi Gamma-ray Space Telescope and the HESS atmospheric Cherenkov array, providing the first simultaneous MeV-TeV spectral energy distribution (SED) with the new generation of γ-ray telescopes. The ATOM telescope and the RXTE and Swift observatories provided optical and X-ray coverage of the low-energy component over the same time period. The object was close to the lowest archival X-ray and very high energy (VHE; >100 GeV) state, whereas the optical flux was much higher. The light curves show relatively little (30%) variability overall when compared to past flaring episodes, but we find a clear optical/VHE correlation and evidence for a correlation of the X-rays with the high-energy spectral index. Contrary to previous observations in the flaring state, we do not find any correlation between the X-ray and VHE components. Although synchrotron self-Compton models are often invoked to explain the SEDs of BL Lac objects, the most common versions of these models are at odds with the correlated variability we find in the various bands for PKS2155-304.

KW - BL Lacertae objects: individual (PKS 2155-304)

KW - Galaxies: active

KW - Gamma rays: observations

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U2 - 10.1088/0004-637X/696/2/L150

DO - 10.1088/0004-637X/696/2/L150

M3 - Article

AN - SCOPUS:67649695521

VL - 696

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 2 PART 2

ER -