Steve Biller

Abstract:

The evidence for supersymmetric dark matter annihilations presented by Strausz is based on both an analysis of data from the JACEE balloon-borne emulsion experiment which ignores systematic uncertainties and on a flawed analysis of background data from the Whipple gamma-ray observatory. When the latter analysis is corrected, it is found that there is no evidence for a peak in the 3.5–4.0 TeV regime in the Whipple data. Furthermore, were any such excess seen in the Whipple data, it would indicate a flux in gross conflict with the JACEE upper limits. It is therefore concluded that no evidence exists for an annihilation line due to supersymmetric dark matter. © 1998 The American Physical Society.

Abstract:

From considering the effect of γ-γ interactions on recently observed TeV gamma-ray spectra, improved limits are set to the density of extragalactic infrared photons which are robust and essentially model independent. The resulting limits are more than an order of magnitude more restrictive than direct observations in the 0.025‒0.3 eV regime. These limits are used to improve constraints on radiative neutrino decay in the mass range above 0.05 eV and to rule out very massive objects as providing the dark matter needed to explain galaxy rotation curves. Lower bounds on the maximum distance which TeV gamma rays may probe are also derived. © 1998 The American Physical Society.

Abstract:

The spectrum of gamma rays from the Crab Nebula has been measured in the energy range 500 GeV-8 TeV at the Whipple Observatory by the atmospheric Cerenkov technique. Two methods of analysis that were used to derive spectra, in order to reduce the chance of calibration errors, gave good agreement, as did analysis of observations made with changed equipment several years apart. It is concluded that stable and reliable energy spectra can now be made in the TeV range. The spectrum can be represented in this energy range by the power-law fit, J = (3.20 ± 0.17 ± 0.6) × (E/1 TeV)^{-2.49±0-06±0-04} m^-2 s^-1 TeV^-1, or by the following form, which extends much better to the GeV domain: J = (3.25 ± 0.14 ± 0.6) × 10^-7 E^{-2.44±0-06±0.04-0.151 log10 E} m^-2 s^-1 TeV^-1 (E in TeV) The integral flux above 1 TeV is (2.1 ± 0.2 ± 0.3) × 10^-7 m^-2 s^-1. Using the complete spectrum of the Crab Nebula, the spectrum of relativistic electrons is deduced, and the spectrum of the inverse Compton emission that they would generate is in good agreement with the observed gamma-ray flux from 1 GeV to many TeV, if the magnetic field in the region where these scattered photons originate (essentially the X-ray-emitting region, around 0.4 pc from the pulsar) is ∼16 nT (160 μG), in reasonable agreement with the field deduced by Aharonian & Atoyan. If the same field strength were present throughout the nebula, there would be no clear need for an additional radiation source in the GeV domain such as has recently been suggested; the results give an indication that the magnetic field is well below the often-assumed equipartition strength (35-60 nT). Further accurate gamma-ray spectral measurements over the range from 1 GeV to tens of TeV have the potential to probe the growth in the magnetic field in the inner region of the nebula. © 1998. The American Astronomical Society. All rights reserved.