Title: Multiwavelength observations of blazars detected by OSSE
Proposal ID: 0120283
Subject category: Extragalactic Object
Principal investigator: Watson
Institute: Leicester University
Abstract
OSSE (onboard the CGRO satellite) was designed to detect gamma-rays in the 50keV to 10 MeV energy range,
covering a similar energy band to INTEGRAL's IBIS and SPI instruments. OSSE detected seven blazars (3C 273,
3C 279, PKS 0528+134, CTA 102, 3C 454.3, H1517+65.6 and PKS 2155-304, providing crude spectra for these
sources. OSSE-detected blazars therefore make excellent candidates for observation with INTEGRAL. They are
known to be bright and highly variable at these energies, however their spectra are not well constrained
especially with regard to observations performed contemporaneously at other wavelengths. It is proposed to
monitor the seven OSSE-detected blazars for four exposures each (a total of between 40 and 160 kiloseconds
per source). The exposures are divided into four parts in order to examine the time-related spectral
variability properties of these sources. Simultaneous with the INTEGRAL observations we plan radio and
optical-near infrared monitoring as well as optical spectroscopy in order to study the SEDs of these sources
with unprecendented broadband coverage over an extended period and to constrain any relation between their
line emission and continuum variability. The blazars to be observed with total exposure time per source are:
3C 273 (40ks); 3C 279 (80ks); PKS 0528+134 (160ks); CTA 102 (160ks); 3C 454.3 (100ks); H1517+65.6 (100ks)
and PKS 2155-304 (100ks).