F. Aharonian et al., Rejection of the hypothesis that Markarian 501 TeV photons are pure Bose-Einstein condensates, ASTROPHYS J, 543(1), 2000, pp. L39-L42
The energy spectrum of the blazar-type galaxy Markarian 501 (Mrk 501), as m
easured by the High-Energy Gamma-Ray Astronomy (HEGRA) air Cerenkov telesco
pes, extends beyond 16 TeV and constitutes the most energetic photons obser
ved from an extragalactic object. A fraction of the emitted spectrum is pos
sibly absorbed in interactions with low-energy photons of the diffuse extra
galactic infrared radiation, which in turn offers the unique possibility to
measure the diffuse infrared radiation density by exact TeV spectroscopy.
The upper limit on the density of the extragalactic infrared radiation deri
ved from the TeV observations imposes constraints on models of galaxy forma
tion and stellar evolution. One of the recently published ideas to overcome
severe absorption of TeV photons is based on the assumption that sources l
ike Mrk 501 could produce Bose-Einstein condensates of coherent photons. Th
e condensates would have a higher survival probability during the transport
in the diffuse radiation field and could mimic TeV air shower events. The
powerful stereoscopic technique of the HEGRA air Cerenkov telescopes allows
us to test this hypothesis by reconstructing the penetration depths of TeV
air shower events: air showers initiated by Bose-Einstein condensates are
expected to reach the maximum of shower development in the atmosphere earli
er than single photon events. By comparing the energy-dependent penetration
depths of TeV photons from Mrk 501 with those from the TeV standard-candle
Crab Nebula and simulated air shower events, we can reject the hypothesis
that TeV photons from Mrk 501 are pure Bose-Einstein condensates.