Query : 2006A&A...448..143X

2006A&A...448..143X - Astronomy and Astrophysics, volume 448, 143-153 (2006/3-2)

B and I-band optical micro-variability observations of the BL Lac objects S5 2007+777 and 3C 371.


Abstract (from CDS):

We have observed S5 2007+777 and c in the B and I bands for 13 and 8 nights, respectively, during various observing runs in 2001, 2002 and 2004. The observations resulted in almost evenly sampled light curves, 6-9 h long. We do not detect any flares within the observed light curves, but we do observe small amplitude, significant variations, in both bands, on time scales of hours and days. The average variability amplitude on time scales of minutes/hours is ∼2.5% and ∼1-1.5% in the case of S5 2007+777 and c, respectively. The average amplitudes increase to ∼5-12% and ∼ 4-6%, respectively, on time scales of days. We find that the B and I band variations are highly correlated, on both short and long time scales. During the 2004 observations, which resulted in the longest light curves, we observe two well defined flux-decay and rising trends in the light curves of both objects. When the flux decays, we observe significant delays, with the B band flux decaying faster than the flux in the I band. As a result, we also observe significant, flux related spectral variations as well. The flux-spectral relation is rather complicated, with loop-like structures forming during the flux evolution. The presence of spectral variations imply that the observed variability is not caused by geometric effects. On the other hand, our results are fully consistent with the hypothesis that the observed variations are caused by perturbations which affect different regions in the jet of the sources.

Abstract Copyright:

Journal keyword(s): galaxies: active - galaxies: BL Lacertae objects: general - galaxies: BL Lacertae objects: individual: S5 2007+777 - galaxies: BL Lacertae objects: individual: 3C 371 - galaxies: jets

CDS comments: T.2,3: reference stars not in Simbad.

Simbad objects: 3

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Number of rows : 3
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
1 6C 095456+654857 BLL 09 58 47.2451872176 +65 33 54.819354600     17.0 15.75   ~ 691 1
2 3C 371 BLL 18 06 50.6802916920 +69 49 28.109609256   14.77 14.22 11.39   ~ 841 2
3 8C 2007+777 BLL 20 05 30.9987913056 +77 52 43.248139536     16.5 17.36   ~ 439 1

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