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A. L. Tadross

Publications and source records attributed to A. L. Tadross.

24 records · Page 2Linked to original sources
arXiv2010

Discontinuity in the Brightness of the Twilight Sky at Different Wavelengths

A search for discontinuity in the sky twilight brightness at different wavelengths and different solar depressions for altitudes 0, 5, 10, 30, 50 & 70 degrees is done. It is found that the logarithmic of difference in the brightness log (I1-I2) of two similar patches lying at solar and anti-solar verticals are not suffering of any discontinuity, when plotted versus sun's depression. Whatever, the ratio I1/I2 shows that there is discontinuity in the curves at altitudes less than or equal 30 degrees. While for altitudes 50 & 70 degrees slight patches of discontinuities have been detected. The phenomenon of discontinuities may be referred to the changes in the sky twilight brightness due to the effect of the Earth's shadow on diffusing and luminescent layers in the upper atmosphere.

astro-ph.GA↗
arXiv2008

An Investigation of 11 previously unstudied open star clusters

The main astrophysical properties of 11 previously unstudied open star clusters are probed with JHK Near-IR (2MASS) photometry of Cutri et al. [Cutri, R., et al., 2003. The IRSA 2MASS All-sky Point Source Catalog, NASA/IPAC Infrared Science Archive] and proper motions (NOMAD) astrometry of Zacharias et al. [Zacharias, N., Monet, D., Levine, S., Urban, S., Gaume, R., Wycoff, G., 2004. American Astro. Soc. Meeting 36, 1418]. The fundamental parameters have been derived for IC (1434, 2156); King (17, 18, 20, 23, 26)}; and Dias (2, 3, 4, 7, 8)}, for which no prior parameters are available in the literature. The clusters' centers coordinates and angular diameters are re-determined, while ages, distances, and color excesses for these clusters are estimated here for the first time.

astro-ph↗
arXiv2008

A Reinvestigation of the Physical Properties of Pismis 3 based on 2MASS Photometry

As a continuation of a series of work, we aim to refine and re-determine the physical parameters of previously rarely or un-studied open star clusters with good quality CMDs using Near-IR JHK photometry. Here we present a morphological analysis of the 2MASS database (the digital Two Micron All Sky Survey) for the open cluster Pismis 3. Some of the physical parameters are estimated for the first time, and some others, re-determined.

astro-ph↗
arXiv2003

New analysis in the field of open cluster Collinder 223

The present study of the open cluster Collinder 223 (Cr 223) has been mainly depended on the photoelectric data of Claria & Lapasset (1991; hereafter CL91). This data of CL91 has been used with the cluster's image of AAO-DSS in order to re-investigate and improve the main parameters of Cr 223. Stellar count has been achieved to determine the stellar density, the cluster's center and the cluster's diameter. In addition, the luminosity function, mass function, and the total mass of the cluster have been estimated.

astro-ph↗
arXiv2003

Photometrical Review of Open Cluster M25

The young open star cluster M25 (IC 4725) is located in the direction of the galactic center in a crowded region, near much irregular absorption features on Sagittarius arm. This cluster has some difficult observing problems due to its southern location. The mass data available in the literature have been gathered to reinvestigate this cluster using most photometric tools to determine its main photometric parameters. This system is found to be at a distance of 600 pc from the sun, of -52.82 pc from the galactic plane; and the median age is 9.45 x 10^(7) yr. More than 220 stars with mean reddening of 0.50 mag and absorption of 1.62 mag are found within the cluster.

astro-ph↗