Swift XRT and UVOT deep observations of the high-energy peaked BL Lacertae object PKS 0548-322 close to its brightest state

M. Perri, A. Maselli, P. Giommi, E. Massaro, R. Nesci, A. Tramacere, M. Capalbi, G. Cusumano, G. Chincarini, G. Tagliaferri, D. N. Burrows, D. V. Berk, N. Gehrels, R. M. Sambruna

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


Aims. We observed the high-energy peaked BL Lac object PKS 0548-322 (BZB J0550-3216) with Swift to study the temporal and spectral properties of its synchrotron emission simultaneously in the optical, ultraviolet, and X-ray energy bands. Methods. We carried out a spectral analysis of 5 Swift XRT and UVOT observations of PKS 0548-322 taken over the period April-June 2005. Results. The X-ray flux of this BL Lac source was found to be approximately constant at a level of F(2-10 keV) ≃ 4 × 10-11 erg cm-2 s-1 which is a factor of 2 brighter than when observed by BeppoSAX in 1999 and close to the maximum intensity reported in the Einstein Slew Survey. The very good statistics obtained in the 0.3-10 keV Swift X-ray spectrum allowed us to detect highly significant deviations from a simple power-law spectral distribution. A log-parabolic model describes the X-ray data well and gives a best-fit curvature parameter of 0.18 and a peak energy in the spectral energy distribution of about 2 keV. The UV spectral data from Swift UVOT join closely with a power-law extrapolation of the soft X-ray data points, suggesting that the same component is responsible for the observed emission in the two bands. The combination of synchrotron peak in the X-ray band and the high-intensity state confirms PKS 0548-322 as a prime target for TeV observations. X-ray monitoring and coordinated TeV campaigns are highly advisable.

Original languageEnglish (US)
Pages (from-to)889-893
Number of pages5
JournalAstronomy and Astrophysics
Issue number3
StatePublished - Feb 2007

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


Dive into the research topics of 'Swift XRT and UVOT deep observations of the high-energy peaked BL Lacertae object PKS 0548-322 close to its brightest state'. Together they form a unique fingerprint.

Cite this