X-ray observations of BL Lacertae objects.
Abstract
Results are reported for OSO 8 and HEAO 1 X-ray observations of the BL Lac objects Mrk 421, Mrk 501, and PKS 0548-322 over the energy range from 2 to 60 keV. It is found that the X-ray spectra of Mrk 421 and 501 are similar, exhibit statistically significant soft X-ray excesses, lack low-energy absorption, and are best fitted by power laws over the 2-30-keV range with respective photon indices of approximately 0.91 and 1.2 and respective hydrogen column densities of less than 8 x 10 to the 21st per sq cm and no more than 1.8 x 10 to the 22nd per sq cm. It is noted that the spectral index for both sources is identical, within errors, to the HF radio spectral index and that Mrk 421 experienced a factor of 6 decrease in the 2-10-keV band over a six-month period. A tentative identification of PKS 0548-322 with the source H0548-32 is suggested.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 1978
- DOI:
- 10.1086/182832
- Bibcode:
- 1978ApJ...226L..65M
- Keywords:
-
- Bl Lacertae Objects;
- X Ray Sources;
- X Ray Spectra;
- Heao 1;
- Oso-8;
- Spaceborne Astronomy;
- Astronomy;
- BL Lacertae Objects:X-Ray Sources;
- BL Lacertae Objects:X-Ray Spectra;
- X-Ray Sources: Identifications