A Possible New Absorption Feature in the EUV Spectrum of PKS 2155-304

Session 31 - Radiogalaxies - High Energy.
Oral session, Monday, January 13
Pier 4,

[31.04] A Possible New Absorption Feature in the EUV Spectrum of PKS 2155-304

H. L. Marshall (Eureka Scientific, Inc.), C. M. Urry, J. Pesce (STScI), A. Konigl (U. Chicago), L. Maraschi (U. Milan), A. Wehrle (IPAC)

We have obtained an EUV spectrum of PKS 2155-304 as part of the May 1996 campaign which included observations with ISO, RXTE and ROSAT. Preliminary analysis indicates that the count rate in the EUVE Deep Survey imaging detector was relatively constant during this observation at 0.5 count/s, even as the X-ray flux varied by a factor of 2 on a time scale of hours (see Sambruna et al., this meeting).

The EUV spectrum, with a spectral resolution (E/dE) of order 200, is nearly featureless over the 70-110 Angstrom band. There are possible broad features, such as those first noted by Konigl et al. (1995, Ap.J., 446, 598), but there appears to be a sharp feature at about 74 Angstroms, which is also apparent in another observation in 1994. Although statistics are poor, the feature appears sharper than in spectrum published by Konigl et al. In the model of Konigl et al., this feature may be due to absorption in a relativistic jet.

Program listing for Monday