Gamma-ray variability of BL lacs at E>300 GeV

• Published in: Advances in space research Vol. 21; no. 1; pp. 101 - 107
• Main Authors: Buckley, J.H, Akerlof, C.W, Biller, S, Boyle, P.J, Breslin, A.C, Carter-Lewis, D.A, Cantanese, M, Cawley, M.F, Connaughton, V, Fegan, D.J, Finley, J.P, Gaidos, J, Bussons Gordo, J, Hillas, A.M, Krennrich, F, Lamb, R.C, Lessard, R, Masterson, C, McEnery, J.E, Mohanty, G, Moriarty, P, Quinn, J, Rodgers, A.J, Rose, H.J, Samuelson, F, Schubnell, M.S, Sembroski, G, Srinivasan, R, Weekes, T.C, Wilson, C, Zweerink, J
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 1998
• ISSN: 0273-1177; 1879-1948
• DOI: 10.1016/S0273-1177(97)00620-0

We report on observations of Mrk 421 and Mrk 501 at E γ >300 GeV during the 1995 and 1996 seasons. A multiwavelength observing campaign on Mrk 421 in the period 1995 April 20 to May 5 indicates correlations in the γ-ray, X-ray, extreme ultraviolet, and optical wavelengths. Dramatic outbursts of TeV γ-rays were detected on two occasions in May of 1996 where the γ-ray flux reached the highest levels ever recorded (a factor of ∼20 greater than typical levels) with variability timescales ≲1hr. Together with the multiwavelength correlations these provide serious constraints on the Doppler factor ( δ ≳ 9.9), the size and location of the emission region ( R ≲ 10 −4pc) and the mechanism responsible for the γ-ray emission.