## RMxAA: Abstracts of Accepted Papers for Volume 54 Number 2

March 8, 2018

2018: March

### March 2018

ON THE IMPACT OF CENTRAL OBSCURATION ON THE EFFECTIVENESS OF GROUND-BASED O/IR TELESCOPES

A. V. Hakobyan1

1Byurakan Astrophysical Observatory, Armenia.

Accepted: March 8 2018

Abstract: Annular apertures are typical in modern reflective telescopes. They exhibit altered shapes of PSF and OTF if compared with perfect circular one. As a consequence the optical power of such a telescope is also changing. This can be calculated with the use of classical optics theory. But presence of atmospheric optical turbulence contributes its own effects. In this work trend of the main performance characteristics through broad spectral region (300 - 5000~nm) for different obscuration and atmospheric conditions is considered. It turned out that in certain conditions performance (angular resolution, integral contrast and signal-to-noise ratio) of an obstructed telescope relative to a circular aperture case can be even worst than in the absence of turbulence. In particular, relative imaging performance of an 8m telescope with high (ϵ = 0.6) central obscuration as a typical example of modern large size survey telescope is analyzed.

OPTICAL POLARIZATION STUDY ON THE REGION CENTAURUS: NGC 5662

M. M. Vergne1,2, Carlos Feinstein1,2, and Ruben E. Martínez2,†

1Facultad de Ciencias Astronómicas y Geofísicas, Observatorio Astronómico, La Plata, Argentina.
2Instituto de Astrofísica de La Plata (UNLP - CONICET), Facultad de Ciencias Astronómicas y Geofísicas, La Plata, Argentina.
In memoriam.

Accepted: March 13 2018

Abstract: We present (BVRI) multicolor linear polarimetric data of 73 of the brightest stars in the open cluster NGC~5662. Our objective is study the characteristics of the interstellar medium (ISM) towards and in the environment of it. NGC~5662 is polarimetrically characterized by $P_{V}$ = 2.27$\% \pm 0.13$ and $\theta_{V}$=89$^0$.6 $\pm$ 1.17. Its Polarization Efficiency is much higher than the normal efficiency of ISM. The observed visual polarization in NGC~5662 is caused at least by three components of dust at $\sim$ 200 pc, 500 pc and 900 pc from the Sun.These have different polarimetric characteristics and the layer located at 500 pc has variable density. The absorption presents a different behavior to the polarization as the distance increase. A few of the observed stars present evidences of intrinsic polarization.

ESTIMATION OF THE STAR FORMATION RATE USING LONG-GAMMA RAY BURST OBSERVED BY SWIFT

M. Elías1 and M. Martínez1

1Benemérita Universidad Autónoma de Puebla, Puebla, Puebla, México.

Abstract: In this work we estimate the Star Formation Rate (SFR) through 333 Long-GRBs detected by Swift. This investigation is based on the empirical model proposed by \citet{Yuksel2008}, basically, the SFR is estimated using long-GRBs considering that they have an stellar origin based on the Collapsar model or the collapse of massive stars (Hypernova) $M>20 M_{\bigodot}$. The analysis starts with the study of $\varepsilon (z)$ which accounts the long-GRBs production rate and it is parameterized by $\varepsilon(z)=\varepsilon_{0}(1+z)^{\delta}$ where $\varepsilon_{0}$ include the SFR absolute conversion to GRBs rate in a luminosity range already defined and $\delta$ is a dynamical parameter which changes at different regions of redshift it accounts the SFR slope which is obtained by an analysis of linear regression over our Long-GRBs sample, the results obtained provide evidence that support our proposal to use Long-GRBs as tracers of SFR.