A carbon atmosphere on a neutron star

“The compact star at the center of this famous supernova remnant has been an enigma since its discovery,” said Wynn Ho of the University of Southampton and lead author of a paper that appears in the November 5 issue of Nature. “Now we finally understand that it can be produced by a hot neutron star with a carbon atmosphere.”

By analyzing Chandra’s X-ray spectrum — akin to a fingerprint of energy — and applying it to theoretical models, Ho and his colleague Craig Heinke, from the University of Alberta, determined that the neutron star in Cassiopeia A, or Cas A for short, has an ultra-thin coating of carbon. This is the first time the composition of an atmosphere of an isolated neutron star has been confirmed.

Review of constraining cosmological parameters using 21-cm signal from the era of Reionization

Finally I have finished the final thesis report of mu undergraduate project. Honestly, I am not satisfied with it myself. Because I could not do any real research I mean something innovative. But now I am trying to do some simulation using Java. This report can be considered as a theoretical database of 21-cm cosmology and observation which will be helpful for me in the coming years, at least I think so. Here I am presenting the report. Link of the pdf file is attached. Abstract and content is mentioned separately.

A. R. Taylor papers related to 21cm line

A. Russell Taylor
Director, University of Calgary Centre for Radio Astronomy
Professor, Department of Physics and Astronomy

The Outer Disk of the Milky Way Seen in 21-cm Absorption
(download pdf)

Authors: John M. Dickey, Simon Strasser, B.M. Gaensler, Marijke Haverkorn, Dain Kavars, N. M. McClure-Griffiths, Jeroen Stil, A. R. Taylor

(Submitted on 8 Jan 2009) on arXiv

Abstract: Three recent surveys of 21-cm line emission in the Galactic plane, combining single dish and interferometer observations to achieve resolution of 1 arcmin to 2 arcmin, 1 km/s, and good brightness sensitivity, have provided some 650 absorption spectra with corresponding emission spectra for study of the distribution of warm and cool phase H I in the interstellar medium. These emission-absorption spectrum pairs are used to study the temperature of the interstellar neutral hydrogen in the outer disk of the Milky Way, outside the solar circle, to a radius of 25 kpc.

The cool neutral medium is distributed in radius and height above the plane with very similar parameters to the warm neutral medium. In particular, the ratio of the emission to the absorption, which gives the mean spin temperature of the gas, stays nearly constant with radius to 25 kpc radius. This suggests that the mixture of cool and warm phases is a robust quantity, and that the changes in the interstellar environment do not force the H I into a regime where there is only one temperature allowed. The mixture of atomic gas phases in the outer disk is roughly 15% to 20% cool (40 K to 60 K), the rest warm, corresponding to mean spin temperature 250 to 400 K.

Constraining cosmological parameters using 21cm map of the universe

Here is the draft of my paper with the initial names of the reference papers.

Cover page
Abstract
Acknowledgments
Contents

1. Introduction

2. 21cm Cosmology

- First light
- In the beginning
- Wouthuysen-Field effct
- Detecting the earliest galaxies
- HI 21cm probe
- Cosmology at low frequencies

BSc. (EEE) Thesis project – Reionization

Studying Cosmic Reionization era using 21cm HI signal

I have started a new project because the previous one was not feasible enough in the perspectives of Bangladesh. Previously I tried to build an ameteur radio telescope in order to capture radio signals coming from sun, moon and nearby stars. But I coudn’t find necessary filters, amplifiers and mixers. So, it became obvious that I move on and do something academic.

Now I am no longer an ameteur, in fact now I am determined to do my masters on Radio Astronomy. For undergraduate thesis I have picked on of the most promising subjects in the field of Radio Astronomy and Astrophysics. Yes, it is nothing but the Dark ages and the Epoch of Reionization. And for observation and data analysis I have chosen 21cm HI signal which is considered by many scientists as the Philosopher’s stone for unveiling the secrets of structure formation and non-linear evolution of the universe.

C-band radio telescope with cassegrian antenna

Cassegrain antenna on the rooftop of IUT (Bangladesh) academic building. It was brought for communicating with the satellites of SingTel. In fact it was used as a VSat. IUT has taken BTTB internet connection. So VSat is of no use now. We have taken this chance and implementing this dish antenna to build our Radio Telescope.

Radio telescope operating at Ku-band

There are two kinds of radio astronomy projects: Low-cost projects for high schools and semi-professional projects for universities. We have decided to perform something in between these two projects. So, we have planned of a radio telescope that will operate at Ku-band, have sufficient sensitivity and resolution to make observations of the moon and it’s cost will be within the reach of our University.

Solar Storm Radio Telescope

Solar Storm Radio Telescope (SSRT) monitors solar storms indirectly by using radio waves to sense “Sudden Ionospheric Disturbances” (SID). The ionosphere is an ionized layer in the atmosphere roughly 50-600 km above the Earth’s surface. It’s ionization is caused by incoming UV and X-ray radiation from the sun. The degree of ionization increases with the amount of solar radiation received, and therefore tends to depend on the latitude, the season and the time of the day. Ionization is also dramatically affected by exceptional events such as solar flares and coronal mass ejections.

Radio Telescope Projects online

5.2 Meter Radio Astronomy Project for 1420 MHz

Website: http://www.signalone.com/radioastronomy/telescope/
Project owner: Randy Stegemeyer
Objective: Observing the natural radio emissions of neutral hydrogen atoms found throughout space.
Significancce: The study of the radio spectra of these emissions is used to determine the distribution and dynamics of hydrogen throughout our galaxy.