Nova-like Cataclysmic Variables in the Infrared

Novalike cataclysmic variables have persistently high mass transfer rates and prominent steady state accretion disks. We present an analysis of infrared observations of twelve novalikes obtained from the Two Micron All Sky Survey, the Spitzer Space Telescope, and the Wide-field Infrared Survey Explorer All Sky Survey. The presence of an infrared excess at >3-5 microns over the expectation of a theoretical steady state accretion disk is ubiquitous in our sample. The strength of the infrared excess is not correlated with orbital period, but shows a statistically significant correlation (but shallow trend) with system inclination that might be partially (but not completely) linked to the increasing view of the cooler outer accretion disk and disk rim at higher inclinations. We discuss the possible origin of the infrared excess in terms of emission from bremsstrahlung or circumbinary dust, with either mechanism facilitated by the mass outflows (e.g., disk wind/corona, accretion stream overflow, and so on) present in novalikes. Our comparison of the relative advantages and disadvantages of either mechanism for explaining the observations suggests that the situation is rather ambiguous, largely circumstantial, and in need of stricter observational constraints.Peer reviewe

Newcomb’s data on ancient eclipses revisited1

Relying on the Greek text related to Babylonian-Hellenic observations of lunar eclipses in Ptolemy’s 'Almagest' (Halma M., 1813) and by analysing some Arabian notes about solar and lunar eclipses - for which S. Newcomb found considerable deviations from the adopted theory - a re-analysis of his results and conclusions is herewith undertaken. The results of ancient data revision are based on Newcomb’s alternative presumption that these discrepancies are caused by one or more unknown long-term inequalities in the motion of the Moon. A quantitative analysis of ancient eclipse observations unambiguously indicates that they definitely are not to be rejected provided, of course, that they are interpreted in proper way

Étude minéralogique des phyllites de quelques minerais de fer de Serbie (Yougoslavie)

Les minerais de fer oolithiques de Serbie d'âge crétacé forment des couches et des lentilles dans des grès et des conglomérats. Tous ces minerais sont constitués par des oxydes et des hydroxydes de fer associés à des quantités notables de silicates. Ceux-ci appartiennent à deux groupes, soit des phyllites à 7 Å de type berthiérine, soit des phyllites à 14 Å qui sont des chlorites peu stables auxquelles on réserve le nom de pseudochlorites. La présente étude a permis de retrouver dans la formation ferrifère oolithique de Serbie des constituants silicatés analogues à ceux identifiés dans le bassin de Lorraine. Signalons cependant que nous avons trouvé dans le gisement de Gledić, associée à la berthiérine, une phyllite dont les caractères sont ceux d'une véritable chlorite.Protitch M. Étude minéralogique des phyllites de quelques minerais de fer de Serbie (Yougoslavie). In: Bulletin de la Société française de Minéralogie et de Cristallographie, volume 78, 10-12, 1955. pp. 528-534

CCD astrometric observations of comets at the Belgrade observatory during 1998 - 2000 (I)

143 precise astrometric positions of seven comets were obtained with the CCD equipped Askania astrograph (13.5/160) of Belgrade Astronomical Observatory. The SBIG ST-8(1530 ? 1020 pixel array) camera was used in the observations.</jats:p

On The lunar Secular Acceleration: A Possible Approach

The secular quadratic term in the expression of the Moon's longitude has been introduced empirically after the conclusion that its mean motion is not constant (Halley, 1695).But, the explanation of this term and also of its numerical evaluation presented and still presents in our time great difficulties. All efforts, namely, to obtain an exact agreement between observed and theoretical value of Moon's secular acceleration were unsuccessful: the first of these two values exceeds always the second one by a very large amount. This discordance and unexplained residuals (O – C) in the mean longitude of the Moon gave rise finally to the statement that these are due to a retardation and irregularity in the Earth's rotation. But, after hardly a fifty years, this hypothesis revealed even more new difficulties and questions concerning also the problem of stability of the Earth-Moon system. It seems that there is a true reason for which this problem occurs as one of the unsolved problems of Celestial Mechanics (Brumberg and Kovalevsky, 1986; Seidelmann, 1986).</jats:p