Simultaneous X-Ray and TeV Observations of a Rapid Flare from Markarian 421.
Mrk 421 was observed for about 2 days with BeppoSAX in 1998 April as part of a worldwide multiwavelength campaign. A large, well-defined flare was observed in X-rays. The same flare was observed simultaneously at TeV energies by the Whipple Observatory gamma-ray telescope. These data provide (1) the first evidence that the X-ray and TeV intensities are well correlated on timescales of hours and (2) the first exactly simultaneous X-ray and TeV spectra. The results imply that the X-ray and TeV photons derive from the same region and from the same population of relativistic electrons. The physical parameters deduced from a homogeneous synchrotron self-Compton model for the spectral energy distribution yield electron cooling times close to the observed variability timescales.
Maraschi
L
Fossati
G
Tavecchio
F
Chiappetti
L
Celotti
A
Ghisellini
G
Grandi
P
Pian
E
Tagliaferri
G
Treves
A
Breslin
AC
Buckley
JH
Carter-Lewis
DA
Catanese
M
Cawley
MF
Fegan
DJ
Fegan
S
Finley
J
Gaidos
J
Hall
T
Hillas
AM
Krennrich
F
Lessard
RW
Masterson
C
Moriarty
P
Quinn
J
Rose
J
Samuelson
F
Weekes
TC
Urry
CM
Takahashi
T