The first fermi multifrequency campaign on BL Lacertae: Characterizing the low-activity state of the eponymous blazar

A. A. Abdo, M. Ackermann, M. Ajello, E. Antolini, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, K. Bechtol, R. Bellazzini, B. Berenji, R. D. Blandford, E. Bonamente, A. W. Borgland, J. Bregeon, A. Brez, M. Brigida, P. Bruel, R. Buehler, S. BusonG. A. Caliandro, R. A. Cameron, A. Cannon, P. A. Caraveo, S. Carrigan, J. M. Casandjian, C. Cecchi, Ö Çlik, E. Charles, A. Chekhtman, C. C. Cheung, J. Chiang, S. Ciprini, R. Claus, J. Cohen-Tanugi, J. Conrad, L. Costamante, S. Cutini, C. D. Dermer, F. De Palma, D. Donato, E. Do Couto E Silva, P. S. Drell, R. Dubois, L. Escande, C. Favuzzi, S. J. Fegan, J. Finke, W. B. Focke, P. Fortin, M. Frailis, Y. Fukazawa, S. Funk, P. Fusco, F. Gargano, D. Gasparrini, N. Gehrels, S. Germani, N. Giglietto, F. Giordano, M. Giroletti, T. Glanzman, G. Godfrey, I. A. Grenier, S. Guiriec, D. Hadasch, M. Hayashida, E. Hays, R. E. Hughes, R. Itoh, G. Jóhannesson, A. S. Johnson, W. N. Johnson, T. Kamae, H. Katagiri, Jun Kataoka, J. Knödlseder, M. Kuss, J. Lande, S. Larsson, L. Latronico, S. H. Lee, M. Llena Garde, F. Longo, F. Loparco, B. Lott, M. N. Lovellette, P. Lubrano, A. Makeev, M. N. Mazziotta, J. E. McEnery, J. Mehault, P. F. Michelson, T. Mizuno, C. Monte, M. E. Monzani, A. Morselli, I. V. Moskalenko, S. Murgia, T. Nakamori, M. Naumann-Godo, S. Nishino, P. L. Nolan, J. P. Norris, E. Nuss, T. Ohsugi, A. Okumura, N. Omodei, E. Orlando, J. F. Ormes, M. Ozaki, D. Paneque, 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, S. Ritz, M. Roth, H. F W Sadrozinski, D. Sanchez, A. Sander, F. K. Schinzel, C. Sgrò, E. J. Siskind, P. D. Smith, K. V. Sokolovsky, G. Spandre, P. Spinelli, M. S. Strickman, D. J. Suson, H. Takahashi, T. Tanaka, J. B. Thayer, J. G. Thayer, D. J. Thompson, L. Tibaldo, D. F. Torres, G. Tosti, A. Tramacere, T. Uehara, T. L. Usher, J. Vandenbroucke, V. Vasileiou, N. Vilchez, V. Vitale, A. P. Waite, E. Wallace, P. Wang, B. L. Winer, K. S. Wood, Z. Yang, T. Ylinen, M. Ziegler, A. Berdyugin, M. Boettcher, A. Carramĩana, L. Carrasco, E. De La Fuente, C. Diltz, T. Hovatta, V. Kadenius, Y. Y. Kovalev, A. Lähteenmäki, E. Lindfors, A. P. Marscher, K. Nilsson, D. Pereira, R. Reinthal, P. Roustazadeh, T. Savolainen, A. Sillanpää, L. O. Takalo, M. Tornikoski

Research output: Contribution to journalArticle

39 Citations (Scopus)

Abstract

We report on observations of BLLacertae during the first 18 months of Fermi LAT science operations and present results from a 48 day multifrequency coordinated campaign from 2008 August 19 to 2008 October 7. The radio to gamma-ray behavior of BLLac is unveiled during a low-activity state thanks to the coordinated observations of radio-band (Metsähovi and VLBA), near-IR/optical (Tuorla, Steward, OAGH, and MDM), and X-ray (RXTE and Swift) observatories. No variability was resolved in gamma rays during the campaign, and the brightness level was 15 times lower than the level of the 1997 EGRET outburst. Moderate and uncorrelated variability has been detected in UV and X-rays. The X-ray spectrum is found to be concave, indicating the transition region between the low- and high-energy components of the spectral energy distribution (SED). VLBA observation detected a synchrotron spectrum self-absorption turnover in the innermost part of the radio jet appearing to be elongated and inhomogeneous, and constrained the average magnetic field there to be less than 3 G. Over the following months, BLLac appeared variable in gamma rays, showing flares (in 2009 April and 2010 January). There is no evidence for the correlation of gamma rays with the optical flux monitored from the ground in 18 months. The SED may be described by a single-zone or a two-zone synchrotron self-Compton (SSC) model, but a hybrid SSC plus external radiation Compton model seems to be preferred based on the observed variability and the fact that it provides a fit closest to equipartition.

Original languageEnglish
Article number101
JournalAstrophysical Journal
Volume730
Issue number2
DOIs
Publication statusPublished - 2011 Apr 1
Externally publishedYes

Fingerprint

gamma rays
synchrotrons
radio
spectral energy distribution
energy
Swift observatory
x rays
self absorption
X Ray Timing Explorer
outburst
flares
turnover
brightness
observatory
magnetic field
radiation
magnetic fields
distribution
science

Keywords

  • BL Lacertae objects: general
  • BL Lacertae objects: individual (BL Lacertae)
  • galaxies: jets
  • gamma rays: galaxies
  • radiation mechanisms: non-thermal
  • X-rays: galaxies

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Abdo, A. A., Ackermann, M., Ajello, M., Antolini, E., Baldini, L., Ballet, J., ... Tornikoski, M. (2011). The first fermi multifrequency campaign on BL Lacertae: Characterizing the low-activity state of the eponymous blazar. Astrophysical Journal, 730(2), [101]. https://doi.org/10.1088/0004-637X/730/2/101

The first fermi multifrequency campaign on BL Lacertae : Characterizing the low-activity state of the eponymous blazar. / Abdo, A. A.; Ackermann, M.; Ajello, M.; Antolini, E.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bonamente, E.; Borgland, A. W.; Bregeon, J.; Brez, A.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Cannon, A.; Caraveo, P. A.; Carrigan, S.; Casandjian, J. M.; Cecchi, C.; Çlik, Ö; Charles, E.; Chekhtman, A.; Cheung, C. C.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; Costamante, L.; Cutini, S.; Dermer, C. D.; De Palma, F.; Donato, D.; Do Couto E Silva, E.; Drell, P. S.; Dubois, R.; Escande, L.; Favuzzi, C.; Fegan, S. J.; Finke, J.; Focke, W. B.; 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, I. A.; Guiriec, S.; Hadasch, D.; Hayashida, M.; Hays, E.; Hughes, R. E.; Itoh, R.; Jóhannesson, G.; Johnson, A. S.; Johnson, W. N.; Kamae, T.; Katagiri, H.; Kataoka, Jun; Knödlseder, J.; Kuss, M.; Lande, J.; Larsson, S.; Latronico, L.; Lee, S. H.; Garde, M. Llena; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Makeev, A.; Mazziotta, M. N.; McEnery, J. E.; Mehault, J.; Michelson, P. F.; Mizuno, T.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nakamori, T.; Naumann-Godo, M.; Nishino, S.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orlando, E.; Ormes, J. F.; Ozaki, M.; Paneque, D.; 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.; Ritz, S.; Roth, M.; Sadrozinski, H. F W; Sanchez, D.; Sander, A.; Schinzel, F. K.; Sgrò, C.; Siskind, E. J.; Smith, P. D.; Sokolovsky, K. V.; Spandre, G.; Spinelli, P.; Strickman, M. S.; Suson, D. J.; Takahashi, H.; Tanaka, T.; Thayer, J. B.; Thayer, J. G.; Thompson, D. J.; Tibaldo, L.; Torres, D. F.; Tosti, G.; Tramacere, A.; Uehara, T.; Usher, T. L.; Vandenbroucke, J.; Vasileiou, V.; Vilchez, N.; Vitale, V.; Waite, A. P.; Wallace, E.; Wang, P.; Winer, B. L.; Wood, K. S.; Yang, Z.; Ylinen, T.; Ziegler, M.; Berdyugin, A.; Boettcher, M.; Carramĩana, A.; Carrasco, L.; De La Fuente, E.; Diltz, C.; Hovatta, T.; Kadenius, V.; Kovalev, Y. Y.; Lähteenmäki, A.; Lindfors, E.; Marscher, A. P.; Nilsson, K.; Pereira, D.; Reinthal, R.; Roustazadeh, P.; Savolainen, T.; Sillanpää, A.; Takalo, L. O.; Tornikoski, M.

In: Astrophysical Journal, Vol. 730, No. 2, 101, 01.04.2011.

Research output: Contribution to journalArticle

Abdo, AA, Ackermann, M, Ajello, M, Antolini, E, Baldini, L, Ballet, J, Barbiellini, G, Bastieri, D, Bechtol, K, Bellazzini, R, Berenji, B, Blandford, RD, Bonamente, E, Borgland, AW, Bregeon, J, Brez, A, Brigida, M, Bruel, P, Buehler, R, Buson, S, Caliandro, GA, Cameron, RA, Cannon, A, Caraveo, PA, Carrigan, S, Casandjian, JM, Cecchi, C, Çlik, Ö, Charles, E, Chekhtman, A, Cheung, CC, Chiang, J, Ciprini, S, Claus, R, Cohen-Tanugi, J, Conrad, J, Costamante, L, Cutini, S, Dermer, CD, De Palma, F, Donato, D, Do Couto E Silva, E, Drell, PS, Dubois, R, Escande, L, Favuzzi, C, Fegan, SJ, Finke, J, 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, Guiriec, S, Hadasch, D, Hayashida, M, Hays, E, Hughes, RE, Itoh, R, Jóhannesson, G, Johnson, AS, Johnson, WN, Kamae, T, Katagiri, H, Kataoka, J, Knödlseder, J, Kuss, M, Lande, J, Larsson, S, Latronico, L, Lee, SH, Garde, ML, Longo, F, Loparco, F, Lott, B, Lovellette, MN, Lubrano, P, Makeev, A, Mazziotta, MN, McEnery, JE, Mehault, J, Michelson, PF, Mizuno, T, Monte, C, Monzani, ME, Morselli, A, Moskalenko, IV, Murgia, S, Nakamori, T, Naumann-Godo, M, Nishino, S, Nolan, PL, Norris, JP, Nuss, E, 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, Razzano, M, Reimer, A, Reimer, O, Ritz, S, Roth, M, Sadrozinski, HFW, Sanchez, D, Sander, A, Schinzel, FK, Sgrò, C, Siskind, EJ, Smith, PD, Sokolovsky, KV, Spandre, G, Spinelli, P, Strickman, MS, Suson, DJ, Takahashi, H, Tanaka, T, Thayer, JB, Thayer, JG, Thompson, DJ, Tibaldo, L, Torres, DF, Tosti, G, Tramacere, A, Uehara, T, Usher, TL, Vandenbroucke, J, Vasileiou, V, Vilchez, N, Vitale, V, Waite, AP, Wallace, E, Wang, P, Winer, BL, Wood, KS, Yang, Z, Ylinen, T, Ziegler, M, Berdyugin, A, Boettcher, M, Carramĩana, A, Carrasco, L, De La Fuente, E, Diltz, C, Hovatta, T, Kadenius, V, Kovalev, YY, Lähteenmäki, A, Lindfors, E, Marscher, AP, Nilsson, K, Pereira, D, Reinthal, R, Roustazadeh, P, Savolainen, T, Sillanpää, A, Takalo, LO & Tornikoski, M 2011, 'The first fermi multifrequency campaign on BL Lacertae: Characterizing the low-activity state of the eponymous blazar', Astrophysical Journal, vol. 730, no. 2, 101. https://doi.org/10.1088/0004-637X/730/2/101
Abdo, A. A. ; Ackermann, M. ; Ajello, M. ; Antolini, E. ; Baldini, L. ; Ballet, J. ; Barbiellini, G. ; Bastieri, D. ; Bechtol, K. ; Bellazzini, R. ; Berenji, B. ; Blandford, R. D. ; Bonamente, E. ; Borgland, A. W. ; Bregeon, J. ; Brez, A. ; Brigida, M. ; Bruel, P. ; Buehler, R. ; Buson, S. ; Caliandro, G. A. ; Cameron, R. A. ; Cannon, A. ; Caraveo, P. A. ; Carrigan, S. ; Casandjian, J. M. ; Cecchi, C. ; Çlik, Ö ; Charles, E. ; Chekhtman, A. ; Cheung, C. C. ; Chiang, J. ; Ciprini, S. ; Claus, R. ; Cohen-Tanugi, J. ; Conrad, J. ; Costamante, L. ; Cutini, S. ; Dermer, C. D. ; De Palma, F. ; Donato, D. ; Do Couto E Silva, E. ; Drell, P. S. ; Dubois, R. ; Escande, L. ; Favuzzi, C. ; Fegan, S. J. ; Finke, J. ; Focke, W. B. ; 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, I. A. ; Guiriec, S. ; Hadasch, D. ; Hayashida, M. ; Hays, E. ; Hughes, R. E. ; Itoh, R. ; Jóhannesson, G. ; Johnson, A. S. ; Johnson, W. N. ; Kamae, T. ; Katagiri, H. ; Kataoka, Jun ; Knödlseder, J. ; Kuss, M. ; Lande, J. ; Larsson, S. ; Latronico, L. ; Lee, S. H. ; Garde, M. Llena ; Longo, F. ; Loparco, F. ; Lott, B. ; Lovellette, M. N. ; Lubrano, P. ; Makeev, A. ; Mazziotta, M. N. ; McEnery, J. E. ; Mehault, J. ; Michelson, P. F. ; Mizuno, T. ; Monte, C. ; Monzani, M. E. ; Morselli, A. ; Moskalenko, I. V. ; Murgia, S. ; Nakamori, T. ; Naumann-Godo, M. ; Nishino, S. ; Nolan, P. L. ; Norris, J. P. ; Nuss, E. ; Ohsugi, T. ; Okumura, A. ; Omodei, N. ; Orlando, E. ; Ormes, J. F. ; Ozaki, M. ; Paneque, D. ; 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. ; Ritz, S. ; Roth, M. ; Sadrozinski, H. F W ; Sanchez, D. ; Sander, A. ; Schinzel, F. K. ; Sgrò, C. ; Siskind, E. J. ; Smith, P. D. ; Sokolovsky, K. V. ; Spandre, G. ; Spinelli, P. ; Strickman, M. S. ; Suson, D. J. ; Takahashi, H. ; Tanaka, T. ; Thayer, J. B. ; Thayer, J. G. ; Thompson, D. J. ; Tibaldo, L. ; Torres, D. F. ; Tosti, G. ; Tramacere, A. ; Uehara, T. ; Usher, T. L. ; Vandenbroucke, J. ; Vasileiou, V. ; Vilchez, N. ; Vitale, V. ; Waite, A. P. ; Wallace, E. ; Wang, P. ; Winer, B. L. ; Wood, K. S. ; Yang, Z. ; Ylinen, T. ; Ziegler, M. ; Berdyugin, A. ; Boettcher, M. ; Carramĩana, A. ; Carrasco, L. ; De La Fuente, E. ; Diltz, C. ; Hovatta, T. ; Kadenius, V. ; Kovalev, Y. Y. ; Lähteenmäki, A. ; Lindfors, E. ; Marscher, A. P. ; Nilsson, K. ; Pereira, D. ; Reinthal, R. ; Roustazadeh, P. ; Savolainen, T. ; Sillanpää, A. ; Takalo, L. O. ; Tornikoski, M. / The first fermi multifrequency campaign on BL Lacertae : Characterizing the low-activity state of the eponymous blazar. In: Astrophysical Journal. 2011 ; Vol. 730, No. 2.
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title = "The first fermi multifrequency campaign on BL Lacertae: Characterizing the low-activity state of the eponymous blazar",
abstract = "We report on observations of BLLacertae during the first 18 months of Fermi LAT science operations and present results from a 48 day multifrequency coordinated campaign from 2008 August 19 to 2008 October 7. The radio to gamma-ray behavior of BLLac is unveiled during a low-activity state thanks to the coordinated observations of radio-band (Mets{\"a}hovi and VLBA), near-IR/optical (Tuorla, Steward, OAGH, and MDM), and X-ray (RXTE and Swift) observatories. No variability was resolved in gamma rays during the campaign, and the brightness level was 15 times lower than the level of the 1997 EGRET outburst. Moderate and uncorrelated variability has been detected in UV and X-rays. The X-ray spectrum is found to be concave, indicating the transition region between the low- and high-energy components of the spectral energy distribution (SED). VLBA observation detected a synchrotron spectrum self-absorption turnover in the innermost part of the radio jet appearing to be elongated and inhomogeneous, and constrained the average magnetic field there to be less than 3 G. Over the following months, BLLac appeared variable in gamma rays, showing flares (in 2009 April and 2010 January). There is no evidence for the correlation of gamma rays with the optical flux monitored from the ground in 18 months. The SED may be described by a single-zone or a two-zone synchrotron self-Compton (SSC) model, but a hybrid SSC plus external radiation Compton model seems to be preferred based on the observed variability and the fact that it provides a fit closest to equipartition.",
keywords = "BL Lacertae objects: general, BL Lacertae objects: individual (BL Lacertae), galaxies: jets, gamma rays: galaxies, radiation mechanisms: non-thermal, X-rays: galaxies",
author = "Abdo, {A. A.} and M. Ackermann and M. Ajello and E. Antolini 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 E. Bonamente and Borgland, {A. W.} and J. Bregeon and A. Brez and M. Brigida and P. Bruel and R. Buehler and S. Buson and Caliandro, {G. A.} and Cameron, {R. A.} and A. Cannon and Caraveo, {P. A.} and S. Carrigan and Casandjian, {J. M.} and C. Cecchi and {\"O} {\cC}lik and E. Charles and A. Chekhtman and Cheung, {C. C.} and J. Chiang and S. Ciprini and R. Claus and J. Cohen-Tanugi and J. Conrad and L. Costamante and S. Cutini and Dermer, {C. D.} and {De Palma}, F. and D. Donato and {Do Couto E Silva}, E. and Drell, {P. S.} and R. Dubois and L. Escande and C. Favuzzi and Fegan, {S. J.} and J. Finke and Focke, {W. B.} and P. Fortin 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 N. Giglietto and F. Giordano and M. Giroletti and T. Glanzman and G. Godfrey and Grenier, {I. A.} and S. Guiriec and D. Hadasch and M. Hayashida and E. Hays and Hughes, {R. E.} and R. Itoh 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}dlseder and M. Kuss and J. Lande and S. Larsson and L. Latronico and Lee, {S. H.} and Garde, {M. Llena} and F. Longo and F. Loparco and B. Lott and Lovellette, {M. N.} and P. Lubrano and A. Makeev and Mazziotta, {M. N.} and McEnery, {J. E.} and J. Mehault and Michelson, {P. F.} and T. Mizuno and C. Monte and Monzani, {M. E.} and A. Morselli and Moskalenko, {I. V.} and S. Murgia and T. Nakamori and M. Naumann-Godo and S. Nishino and Nolan, {P. L.} and Norris, {J. P.} and E. Nuss and T. Ohsugi and A. Okumura and N. Omodei and E. Orlando and Ormes, {J. F.} and M. Ozaki 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 R. Rando and M. Razzano and A. Reimer and O. Reimer and S. Ritz and M. Roth and Sadrozinski, {H. F W} and D. Sanchez and A. Sander and Schinzel, {F. K.} and C. Sgr{\`o} and Siskind, {E. J.} and Smith, {P. D.} and Sokolovsky, {K. V.} and G. Spandre and P. Spinelli and Strickman, {M. S.} and Suson, {D. J.} and H. Takahashi and T. Tanaka and Thayer, {J. B.} and Thayer, {J. G.} and Thompson, {D. J.} and L. Tibaldo and Torres, {D. F.} and G. Tosti and A. Tramacere and T. Uehara and Usher, {T. L.} and J. Vandenbroucke and V. Vasileiou and N. Vilchez and V. Vitale and Waite, {A. P.} and E. Wallace and P. Wang and Winer, {B. L.} and Wood, {K. S.} and Z. Yang and T. Ylinen and M. Ziegler and A. Berdyugin and M. Boettcher and A. Carramĩana and L. Carrasco and {De La Fuente}, E. and C. Diltz and T. Hovatta and V. Kadenius and Kovalev, {Y. Y.} and A. L{\"a}hteenm{\"a}ki and E. Lindfors and Marscher, {A. P.} and K. Nilsson and D. Pereira and R. Reinthal and P. Roustazadeh and T. Savolainen and A. Sillanp{\"a}{\"a} and Takalo, {L. O.} and M. Tornikoski",
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TY - JOUR

T1 - The first fermi multifrequency campaign on BL Lacertae

T2 - Characterizing the low-activity state of the eponymous blazar

AU - Abdo, A. A.

AU - Ackermann, M.

AU - Ajello, M.

AU - Antolini, E.

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 - Bonamente, E.

AU - Borgland, A. W.

AU - Bregeon, J.

AU - Brez, A.

AU - Brigida, M.

AU - Bruel, P.

AU - Buehler, R.

AU - Buson, S.

AU - Caliandro, G. A.

AU - Cameron, R. A.

AU - Cannon, A.

AU - Caraveo, P. A.

AU - Carrigan, S.

AU - Casandjian, J. M.

AU - Cecchi, C.

AU - Çlik, Ö

AU - Charles, E.

AU - Chekhtman, A.

AU - Cheung, C. C.

AU - Chiang, J.

AU - Ciprini, S.

AU - Claus, R.

AU - Cohen-Tanugi, J.

AU - Conrad, J.

AU - Costamante, L.

AU - Cutini, S.

AU - Dermer, C. D.

AU - De Palma, F.

AU - Donato, D.

AU - Do Couto E Silva, E.

AU - Drell, P. S.

AU - Dubois, R.

AU - Escande, L.

AU - Favuzzi, C.

AU - Fegan, S. J.

AU - Finke, J.

AU - Focke, W. B.

AU - Fortin, P.

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 - Giglietto, N.

AU - Giordano, F.

AU - Giroletti, M.

AU - Glanzman, T.

AU - Godfrey, G.

AU - Grenier, I. A.

AU - Guiriec, S.

AU - Hadasch, D.

AU - Hayashida, M.

AU - Hays, E.

AU - Hughes, R. E.

AU - Itoh, R.

AU - Jóhannesson, G.

AU - Johnson, A. S.

AU - Johnson, W. N.

AU - Kamae, T.

AU - Katagiri, H.

AU - Kataoka, Jun

AU - Knödlseder, J.

AU - Kuss, M.

AU - Lande, J.

AU - Larsson, S.

AU - Latronico, L.

AU - Lee, S. H.

AU - Garde, M. Llena

AU - Longo, F.

AU - Loparco, F.

AU - Lott, B.

AU - Lovellette, M. N.

AU - Lubrano, P.

AU - Makeev, A.

AU - Mazziotta, M. N.

AU - McEnery, J. E.

AU - Mehault, J.

AU - Michelson, P. F.

AU - Mizuno, T.

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PY - 2011/4/1

Y1 - 2011/4/1

N2 - We report on observations of BLLacertae during the first 18 months of Fermi LAT science operations and present results from a 48 day multifrequency coordinated campaign from 2008 August 19 to 2008 October 7. The radio to gamma-ray behavior of BLLac is unveiled during a low-activity state thanks to the coordinated observations of radio-band (Metsähovi and VLBA), near-IR/optical (Tuorla, Steward, OAGH, and MDM), and X-ray (RXTE and Swift) observatories. No variability was resolved in gamma rays during the campaign, and the brightness level was 15 times lower than the level of the 1997 EGRET outburst. Moderate and uncorrelated variability has been detected in UV and X-rays. The X-ray spectrum is found to be concave, indicating the transition region between the low- and high-energy components of the spectral energy distribution (SED). VLBA observation detected a synchrotron spectrum self-absorption turnover in the innermost part of the radio jet appearing to be elongated and inhomogeneous, and constrained the average magnetic field there to be less than 3 G. Over the following months, BLLac appeared variable in gamma rays, showing flares (in 2009 April and 2010 January). There is no evidence for the correlation of gamma rays with the optical flux monitored from the ground in 18 months. The SED may be described by a single-zone or a two-zone synchrotron self-Compton (SSC) model, but a hybrid SSC plus external radiation Compton model seems to be preferred based on the observed variability and the fact that it provides a fit closest to equipartition.

AB - We report on observations of BLLacertae during the first 18 months of Fermi LAT science operations and present results from a 48 day multifrequency coordinated campaign from 2008 August 19 to 2008 October 7. The radio to gamma-ray behavior of BLLac is unveiled during a low-activity state thanks to the coordinated observations of radio-band (Metsähovi and VLBA), near-IR/optical (Tuorla, Steward, OAGH, and MDM), and X-ray (RXTE and Swift) observatories. No variability was resolved in gamma rays during the campaign, and the brightness level was 15 times lower than the level of the 1997 EGRET outburst. Moderate and uncorrelated variability has been detected in UV and X-rays. The X-ray spectrum is found to be concave, indicating the transition region between the low- and high-energy components of the spectral energy distribution (SED). VLBA observation detected a synchrotron spectrum self-absorption turnover in the innermost part of the radio jet appearing to be elongated and inhomogeneous, and constrained the average magnetic field there to be less than 3 G. Over the following months, BLLac appeared variable in gamma rays, showing flares (in 2009 April and 2010 January). There is no evidence for the correlation of gamma rays with the optical flux monitored from the ground in 18 months. The SED may be described by a single-zone or a two-zone synchrotron self-Compton (SSC) model, but a hybrid SSC plus external radiation Compton model seems to be preferred based on the observed variability and the fact that it provides a fit closest to equipartition.

KW - BL Lacertae objects: general

KW - BL Lacertae objects: individual (BL Lacertae)

KW - galaxies: jets

KW - gamma rays: galaxies

KW - radiation mechanisms: non-thermal

KW - X-rays: galaxies

UR - http://www.scopus.com/inward/record.url?scp=79953701380&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=79953701380&partnerID=8YFLogxK

U2 - 10.1088/0004-637X/730/2/101

DO - 10.1088/0004-637X/730/2/101

M3 - Article

AN - SCOPUS:79953701380

VL - 730

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 2

M1 - 101

ER -