300 research outputs found
The Spectral Energy Distribution of the High-Z Blazar Q0906+693
We describe further observations of QSO J0906+6930, a z=5.48 blazar likely to
be detected in gamma-rays. New radio and X-ray data place significant
constraints on any kpc-scale extension of the VLBA-detected jet. Improved
optical spectroscopy detects absorption from an intervening galaxy at z=1.849
and raise the possibility that this distant, bright source is lensed. We
combine the new data into an improved SED for the blazar core and comment on
the Compton keV-GeV flux component.Comment: 10pp, 3 figures, accpeted for publication in the Astronomical Journa
Echelle Spectroscopy of gamma-ray binary 1FGL J1018.6-5856
We observed the Fermi-discovered gamma-ray binary 1FGL J1018.6-5856 at 20
epochs over 50 days using the CHIRON spectrograph, obtaining spectra at
R~25,000 covering 4090-8908A. The average spectrum confirms an O6 V((f))
spectral type and extinction E(B-V) = 1.35+/-0.04. Variable absorption line
equivalent widths suggest substantial contamination by wind line features. The
limited S/N ratio hindered accurate continuum definition and prevented
measurement of a high quality radial velocity curve. Nevertheless, the best
data indicate a radial velocity amplitude <40 km/s for the He II lines and
substantially lower for H I. We argue that this indicates a most likely compact
object mass <2.2Msun. While black hole solutions are not excluded, a neutron
star source of the gamma-ray emission seems preferred.Comment: 5 figures. To appear in the Astrophysical Journa
- …