Photometric Observations of the Eta Carinae 2009.0 Spectroscopic Event

We have observed Eta Carinae over 34 nights between 4th January 2009 and 27th March 2009 covering the estimated timeframe for a predicted spectroscopic event related to a suspected binary system concealed within the homunculus nebula. A photometric minimum feature was confirmed to be periodic and comparison to a previous event indicated that the period to within our error at 2022.6 +/-1.0 d. Using the E-region standard star system, the apparent V magnitudes determined for the local comparison stars were HD303308 8.14+/-0.02, HD 93205 7.77 +/-0.03 and HD93162 8.22 +/-0.05. The latter star was found to be dimmer than previously reported.Comment: 5 pages,4 figures, 1 tabl

Stochastic Variability of Luminous Blue Variables

Using the archives of the American Association of Variable Stars Observers and our own data, we analyse the long-term variability of several well-studied Luminous Blue Variables (LBVs) aiming on a general picture of stochastic variability of these objects. The power density spectra of all the selected objects may be generally described by a single power law contaminated by observational noise at higher frequencies. The slopes of the power-law component are close to p=2 (where PDS ~ f^{-p}, and f is frequency) for strongly variable flaring objects like AG Car and significantly smaller (p~1.3) for P Cyg where brightness variation amplitude is <~ 1 mag and dominated by slow low-amplitude variability. The slope holds for about two orders of magnitude in the frequency domain, though peaks and curvatures are present at f ~ 10^{-2}.. 10^{-3} d^{-1}. We show that pseudo-photosphere approach to variability may explain the power-law shape of the variability spectrum at higher frequencies. However, the observed spectra are actually rather "red" than "brown": flux variations are correlated up to tens of years that is much longer than the characteristic refreshment time scales of the pseudo-photosphere. We propose that several stochastic noise components produce the power spectra of LBV stars.Comment: 21 pages, 4 figures, 4 tables; accepted by New Astronom

Accretion onto the Companion of Eta Carinae During the Spectroscopic Event: III. the He II 4686 Line

We continue to explore the accretion model of the massive binary system eta Carinae by studying the anomalously high He II 4686 line. The line appears just before periastron and disappears immediately thereafter. Based on the He II 4686 line emission from O-stars and their modeling in the literature, we postulate that the He II 4686 line comes from the acceleration zone of the secondary stellar wind. We attribute the large increase in the line intensity to a slight increase in the density of the secondary stellar wind in its acceleration zone. The increase in density could be due to the ionization and subsequent deceleration of the wind by the enhanced X-ray emission arising from the shocked secondary wind further downstream or to accretion of the primary stellar wind. Accretion around the secondary equatorial plane gives rise to collimation of the secondary wind, which increases its density, hence enhancing the He II 4686 emission line. In contrast with previous explanations, the presently proposed model does not require a prohibitively high X-ray flux to directly photoionize the He.Comment: ApJ, in pres

Database management and implementation for coal fire detection and monitoring in the Ruijgou Coalfield, Northwest China

Coal fire monitoring by aerospace remote sensing and GIS techniques is an advanced approach, which has been implemented in the Rujigou coalfield, northwest China. A database of several different types of data, including remote sensing images, results of geological surveys, etc., has been collected and assembled in a PC-based information system, which is being developed by the International Institute for Aerospace Survey and Earth Sciences (ITC). This coal fire monitoring and management information system (CoalMan) comprises of two main parts: one is the database with its management tools, and the tools for data processing and analysis form the other. This paper first introduces the structure of the CoalMan information system, presents the data types and contents of CoalMan database, then shows the data management methods. A complex data analysis package is outlined too, as the core of the information system

Remote sensing of environmental pollution on teesside

A preliminary reconnaissance is being carried out to study the methods and procedures most useful for the detection of vegetation stress resulting from the various forms of environmental pollution, in the industrial area of Teesside, NE England, by means of a multiband remote sensing programme. Present results indicate the need for a carefully integrated programme of image analysis, as well as for field and laboratory methods. Sequential aerial multiband photography is an extremely useful technique for plotting the spread of industries and pollution with time, as well as for examining the changes in vegetation and land-use. Colour-infrared film is considered to be the single most useful remote sensing device for vegetation stress determination, as plants under stress are usually accompanied by a loss of infrared reflectance from the affected verdure. Image enhancement techniques are considered to be useful tools in delimiting certain areas under stress. The use of multiband photography, together with other remote sensing techniques, can greatly assist in the determination of areas of vegetation stress