Coordinated Multiwavelength Observations of BL Lacertae in 2000
| Autor: | Böttcher, M., Marscher, A. P., Ravasio, M., Villata, M., Raiteri, C. M., Aller, H. D., Aller, M. F., Teräsranta, H., Mang, O., Tagliaferri, G., Aharonian, F., Krawczynski, H., Kurtanidze, O. M., Nikolashvili, M. G., Ibrahimov, M. A., Papadakis, I. E., Tsinganos, K., Sadakane, K., Okada, N., Takalo, L. O., Sillanpää, A., Tosti, Gino, Ciprini, S., Frasca, A., Marilli, E., Robb, R., Noble, J. C., Jorstad, S. G., Hagen Thorn, V. A., Larionov, V. M., Nesci, R., Maesano, M., Schwartz, R. D., Basler, J., Gorham, P. W., Iwamatsu, H., Kato, T., Pullen, C., Benítez, E., J. A., De, Moilanen, M., Oksanen, A., Rodriguez, D., Sadun, A. C., Kelly, M., Carini, M. T., Miller, H. R., Catalano, S., Dultzin Hacyan, D., Fan, J. H., Ghisellini, G., Ishioka, R., Karttunen, H., Keinänen, P., Kudryavtseva, N. A., Lainela, M., Lanteri, L., Larionova, E. G., Matsumoto, K., Mattox, J. R., Mchardy, I., Montagni, F., Nucciarelli, Giuliano, Ostorero, L., Papamastorakis, J., Pasanen, M., Sobrito, G., Uemura, M. |
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| Jazyk: | angličtina |
| Rok vydání: | 2003 |
| Předmět: |
Physics
Electron energy Astrophysics (astro-ph) Galaxies: BL Lacertae Objects: Individual: Name: BL Lacertae Galaxies: Active- Gamma Rays: Theory Radiation Mechanisms: Nonthermal FOS: Physical sciences Flux Quiescent state HEGRA Astronomy and Astrophysics Astrophysics Light curve Synchrotron law.invention Space and Planetary Science law |
| Popis: | BL Lacertae was the target of an extensive multiwavelength monitoring campaign in the second half of 2000. Simultaneous or quasi-simultaneous observations were taken at radio (UMRAO and Metsaehovi) and optical(WEBT collaboration) frequencies, in X-rays (BeppoSAX and RXTE), and at VHE gamma-rays (HEGRA). The WEBT optical campaign achieved an unprecedented time coverage, virtually continuous over several 10 - 20 hour segments. It revealed intraday variability on time scales of ~ 1.5 hours and evidence for spectral hardening associated with increasing optical flux. During the campaign, BL Lacertae underwent a major transition from a rather quiescent state prior to September 2000, to a flaring state for the rest of the year. This was also evident in the X-ray activity of the source. BeppoSAX observations on July 26/27 revealed a rather low X-ray flux and a hard spectrum, while a BeppoSAX pointing on Oct. 31 - Nov. 2, 2000, indicated significant variability on time scales of < a few hours, and provided evidence for the synchrotron spectrum extending out to ~ 10 keV during that time. During the July 26/27 observation, there is a tantalizing, though not statistically significant, indication of a time delay of ~ 4 - 5 hr between the BeppoSAX and the R-band light curve. Also, a low-significance detection of a time delay of 15 d between the 14.5 GHz and the 22 GHz radio light curves is reported. Several independent methods to estimate the co-moving magnetic field in the source are presented, suggesting a value of ~ 2 e_B^{2/7} G, where e_B is the magnetic-field equipartition factor w.r.t. the electron energy density in the jet. Accepted for publication in ApJ |
| Databáze: | OpenAIRE |
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