Optical and radio behaviour of the BL Lacertae object 0716+714 ⋆

By C. Raiteri, M. Villata, G. Tosti, R. Nesci, Enrico Massaro, M. Aller, H. Aller, H. Teräsranta, O. Kurtanidze, M. Nikolashvili and 17 more. 2003

209 citations recorded by the source corpus.

Eight optical and four radio observatories have been intensively monitoring the BL Lac object 0716+714 in the last years: 4854 data points have been collected in the UBVRI bands since 1994, while radio light curves extend back to 1978. Many of these data, which all together constitute the widest optical and radio database available on this object, are presented here for the first time. Four major optical outbursts were observed at the beginning of 1995, in late 1997, at the end of 2000, and in fall 2001. In particular, an exceptional brightening of 2.3 mag in 9 days was detected in the R band just before the BeppoSAX pointing of October 30, 2000. A big radio outburst lasted from early 1998 to the end of 1999. The long-term trend shown by the optical light curves seems to vary with a characteristic time scale of about 3.3 years, while a longer period of 5.5–6 years seems to characterize the radio long-term variations. In general, optical colour indices are only weakly correlated with brightness; a clear spectral steepening trend was observed during at least one long-lasting dimming phase. Moreover, the optical spectrum became steeper after $\rm JD \sim 2\,451\,000$, the change occurring in the decaying phase of the late-1997 outburst. The radio flux behaviour at different frequencies is similar, but the flux variation amplitude decreases with increasing wavelength. The radio spectral index varies with brightness (harder when brighter), but the radio fluxes seem to be the sum of two different-spectrum contributions: a steady base level and a harder-spectrum variable component. Once the base level is removed, the radio variations appear as essentially achromatic, similarly to the optical behaviour. Flux variations at the higher radio frequencies lead the lower-frequency ones with week–month time scales. The behaviour of the optical and radio light curves is quite different, the broad radio outbursts not corresponding in time to the faster optical ones and the cross-correlation analysis indicating only weak correlation with long time lags. However, minor radio flux enhancements simultaneous with the major optical flares can be recognized, which may imply that the mechanism producing the strong flux increases in the optical band also marginally affects the radio one. On the contrary, the process responsible for the big radio outbursts does not seem to affect the optical emission.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/41e0856dc8e9335d8d0c91ff49b3b64b80c8ba1e

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Nuclear and High Energy Physics

Citations in the corpus

THE 2MASS REDSHIFT SURVEY—DESCRIPTION AND DATA RELEASE (2011, unknown): “…Bergvall et al. (2003) 2003A&A...405..951M Makarov et al. (2003) 2003A&A...407...31P Proust et al. (2003) 2003A&A...408...67M Monnier Ragaigne et al. (2003a) 2003A&A...408..287D Dutra et al. (2003) 2003A&A...408..465M Monnier Ragaigne et al. (2003b) 2003A&A...408..873C Corsini et…”
VLBA Determination of the Distance to Nearby Star-forming Regions. I. The Distance to T Tauri with 0.4% Accuracy (2007, background): “A detailed comparison with the results of Smith et al. (2003) and with the numerous VLA observations available from the literature, however, will be postponed to a forthcoming article.”
X-ray spectroscopy of stars (2009, background): “Non-thermal radio emission from Class I protostars suggests the presence not only of magnetic fields but also accelerated particles in a stellar corona (e.g., Smith et al 2003).”
The Sun in Time: Activity and Environment (2007, background): “However, the discovery of polarization in T Tau(S) (Phillips et al., 1993; Smith et al., 2003), in IRS 5 (Feigelson et al.”
The electron–cyclotron maser for astrophysical application (2006, background): “Recent VLBI observations of T Tauri South (T Tauri Sb) (Smith et al. 2003) also indicate very high brightness temperatures of ∼106 K during the burst phases of the emission, which comes from very compact sources, and exhibits 100% circular polarization.”