Stochastic model of optical variability of BL Lacertae

We use optical photometric and polarimetric data of BL Lacertae that cover a period of 22 years to study the variability of the source. The long-term observations are employed for establishing parameters of a stochastic model consisting of the radiation from a steady polarized source and a number of variable components with different polarization parameters, proposed by Hagen-Thorn et al. earlier. We infer parameters of the model from the observations using numerical simulations based on a Monte Carlo method, with values of each model parameter selected from a Gaussian distribution. We determine the best set of model parameters by comparing model distributions to the observational ones using the chi-square criterion. We show that the observed photometric and polarimetric variability can be explained within a model with a steady source of high polarization, ~40%, and with direction of polarization parallel to the parsec scale jet, along with 10+-5 sources of variable polarization.Comment: 4 pages, 10 figures, published by Astronomy and Astrophysics; v2: typos correcte

The Outburst of the Blazar AO 0235+164 in 2006 December: Shock-in-Jet Interpretation

We present the results of polarimetric ($R$ band) and multicolor photometric ($BVRIJHK$) observations of the blazar AO 0235+16 during an outburst in 2006 December. The data reveal a short timescale of variability (several hours), which increases from optical to near-IR wavelengths; even shorter variations are detected in polarization. The flux density correlates with the degree of polarization, and at maximum degree of polarization the electric vector tends to align with the parsec-scale jet direction. We find that a variable component with a steady power-law spectral energy distribution and very high optical polarization (30-50%) is responsible for the variability. We interpret these properties of the blazar withina model of a transverse shock propagating down the jet. In this case a small change in the viewing angle of the jet, by $\lesssim 1^o$, and a decrease in the shocked plasma compression by a factor of $\sim$1.5 are sufficient to account for the variability.Comment: 22 pages, 8 figures, accepted for Ap

Life in Extraterrestrial Environments Quarterly Status Report No. 4, 15 Nov. 1965 - 15 Feb. 1966

Bacillus spore germination in simulated Martian environmen

Life in extraterrestrial environments Quarterly status report, 1 Sep. - 30 Nov. 1967

Importance of Bacillus cereus and Staphylococcus aureus survival and growth to extraterrestrial planetary contaminatio

Life in extraterrestrial environments Final report, 16 Feb. 1968 - 14 Jul. 1969

Ultraviolet irradiation of microorganisms in simulated Martian environmen

Life in extraterrestrial environments Quarterly status report, Feb. 15 - May 15, 1966

Simulated Martian atmospheric and ecological effects on Bacillus cereus spore germinatio

Life in Extraterrestrial Environments Quarterly Status Report, 15 Feb. - 15 May 1965

Growth response of Bacillus cereus and subtilis cells subjected to modified Martian environment with freeze cycles of different duration

Life in extraterrestrial environments Quarterly status report, 15 Aug. - 15 Nov. 1965

Effect of extraterrestrial environment on bacteri

Life in extraterrestrial environments Quarterly status report, Nov. 15, 1966 - Feb. 15, 1967

Simulated Martian environment growth experiments conducted with Staphylococcus aureu

LIFE IN EXTRATERRESTRIAL ENVIRONMENTS

Life in extraterrestrial environments - simulation of martian environment and survival of microorganism