2000A&A...364...43W


C.D.S. - SIMBAD4 rel 1.7 - 2019.10.20CEST04:25:02

2000A&A...364...43W - Astronomy and Astrophysics, volume 364, 43-52 (2000/12-1)

ASCA and other contemporaneous observations of the blazar B2 1308+326.

WATSON D., SMITH N., HANLON L., McBREEN B., QUILLIGAN F., TASHIRO M., METCALFE L., DOYLE P., TERAESRANTA H., CARRAMINANA A. and GUICHARD J.

Abstract (from CDS):

The high redshift (z=0.997) blazar B2 1308+326 was observed contemporaneously at x-ray, optical and radio wavelengths in June 1996. The x-ray observations were performed with ASCA. The ASCA results were found to be consistent with reanalysed data from two earlier ROSAT observations. The combined ASCA and ROSAT data reveal an x-ray spectrum that is best fit by a broken power law with absorber model with photon spectral indices of Γsoft=3.4–1.1+5.1 and Γhard=1.63–0.09+0.10 and a break energy at 1.1–0.4+0.4keV in the rest-frame of the blazar. The break in the x-ray spectrum is interpreted, from the shape of the simultaneous broadband spectral energy distribution, to be the emerging importance of inverse Compton (IC) emission which dominates the ASCA spectrum. The faint optical state reported for these observations (mV=18.3±0.25) is incompatible with the high synchrotron flux previously detected by ROSAT. The IC emission detected by both ROSAT and ASCA was not significantly affected by the large change in the synchrotron component. MgII emission was detected with an equivalent width (Wλ) of ∼15Å, significantly different from previously reported values. The small and variable Wλ in B2 1308+326 may be due to the highly variable continuum and not intrinsically weak lines in the source. A lower limit on the Doppler boost factor calculated from the contemporaneous data is consistent with expectations for highly polarised quasars and higher than expected for BL Lacs. Absorption at a level of NH=3.0–0.6+2.3x1020cm–2 was detected which is in excess of the Galactic value of N_ H_=1.1x1020cm–2, indicating the possible presence of a foreground absorber. A gravitational microlensing scenario cannot therefore be ruled out for this blazar. No significant variability on timescales of hours was detected in the optical or x-ray data. B2 1308+326 could be a typical radio-selected BL Lac in terms of peak synchrotron frequency and optical and radio variability but its high bolometric luminosity, variable line emission and high Doppler boost factor make it appear more like a quasar than a BL Lac. It is suggested that B2 1308+326 be considered as the prototype of this class of composite source.

Abstract Copyright:

Journal keyword(s): galaxies: BL Lacertae objects: individual: B2 1308+326 - galaxies: quasars: individual: B2 1308+326 - X-rays: galaxies - radio continuum: galaxies - cosmology: gravitational lensing

Simbad objects: 6

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Number of rows : 6

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2019
#notes
1 QSO B0205+350 BLL 02 08 38.1632218391 +35 23 12.802507619     19.24 18.8   ~ 88 0
2 QSO B0235+1624 BLL 02 38 38.93010 +16 36 59.2746   16.46 15.50 15.92   ~ 1366 2
3 QSO B0537-441 BLL 05 38 50.36155219 -44 05 08.9389165   15.77 16.48 16   ~ 764 2
4 8C 0716+714 BLL 07 21 53.4484901266 +71 20 36.362058601   15.5 14.17 14.27   ~ 1100 1
5 Mrk 421 BLL 11 04 27.3139210166 +38 12 31.798324828   13.50 12.90 8.31   ~ 2330 1
6 7C 1308+3236 BLL 13 10 28.66387 +32 20 43.7831   15.61 15.24 17.91   ~ 736 1

    Equat.    Gal    SGal    Ecl

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2019.10.20-04:25:02

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