SearcharxivSearch

arXiv subjects

I. Helmy

Publications and source records attributed to I. Helmy.

2 recordsLinked to original sources

Multi-parameter study for a new Ground-Based telescope in Egypt

A multi-parameter analysis was conducted to evaluate the impact of meteorological parameters, night sky brightness and seismic hazard on proposed sites for the new optical/infrared Egyptian astronomical telescope. The ERA5 reanalysis data set is used to get the following meteorological parameters: Total cloud coverage fraction, precipitable water vapor, relative humidity, wind speed & direction and Air temperature. To estimate the aerosol optical depth we used the Modern-Era Retrospective analysis for Research and Applications version 2 (MERRA-2). Light pollution over the candidate sites was measured from Visible Infrared Imaging Radiometer Suite (VIIRS) Day Night Band (DNB). The seismic input in terms of maximum acceleration and response spectra were computed using a physics-based ground motion approach to assess the seismic hazards and consequently the designation of seismic resistant structure for the proposed sites to be able to assess the seismic hazards for the candidate sites. Of the seven nominated sites, two sites are found to have the best measurements and might be considered future sites for the new Egyptian Astronomical telescope. The first site is located in the south of the Sinai peninsula, while the second one is located in the Red Sea mountains region.

astro-ph.IM

Fundamental parameters of some B-type stars using NOAO Indo-U.S. Library

In the present article, we present a spectroscopic analysis of 83 field B-type stars from NOAO Indo-U.S. Library. We calculated the fundamental parameters e.g effective temperatures, surface gravities, and rotational velocities using Barbier-Chalonge-Divan (BCD) method and line blanketed LTE/NLTE model atmospheres. The projected rotational velocity was estimated by fitting the Mg II4481 Å line profile with theoretical lines calculated from LTE/NLTE models. The evolutionary masses for the program stars are estimated using the evolutionary models. In most of the cases, the present study gives fair agreement with earlier investigations and is even more accurate in some cases.

astro-ph.SR