PG 1553+11 : a bright optically selected BL Lacertae object.
Abstract
A detailed study of the bright optically selected BL Lac object PG 1553 + 11 is presented. UV observations, obtained during a high state of the source, together with simultaneous optical spectrophotometry and near-IR photometry, allow the spectral flux distribution to be examined from 8 x 10 to the 13th to 2.5 x 10 to the 15th Hz. This distribution is compared with that derived from quasi-simultaneous observations obtained when the source was a factor of about 3 fainter. It is found that, in the higher state, the spectrum can be described by two power laws connected by a break at about 10 to the 15th Hz, while in the low state the shape is more complex. The overall spectrum of the object is compared with the average energy distribution of X-ray and radio-selected BL Lac objects, showing that it is closer to the former class.
- Publication:
-
Publications of the Astronomical Society of the Pacific
- Pub Date:
- October 1990
- DOI:
- Bibcode:
- 1990PASP..102.1120F
- Keywords:
-
- Bl Lacertae Objects;
- Galactic Structure;
- Ultraviolet Astronomy;
- Astronomical Spectroscopy;
- Infrared Photometry;
- Radio Sources (Astronomy);
- Red Shift;
- X Ray Astronomy;
- Astronomy