Very High Energy Gamma-Rays emitting BL LAC's Population Study

In this post, you can find my MS thesis abstract following with the link to the complete version. In my thesis, lots of useful astronomical information are available. If you want to use the data please cite my thesis as reference in your publication.

Abstract

Context: BL Lacs are the most numerous extragalactic objects which are detected in Very High Energy (VHE) gamma-rays band. They are a subclass of blazars. Large flux variability amplitude, sometimes happens in very short time scale, is a common characteristic of them. Significant optical polarization is another main characteristics of BL Lacs. BL Lacs' spectra have a continuous and featureless Spectral Energy Distribution (SED) which have two peaks.

Among 1442 BL Lacs in the Roma-BZB catalogue, only 51 are detected in VHE gamma-rays band. BL Lacs are most numerous (more than 50% of 514 objects) objects among the sources that are detected above 10 GeV by FERMI-LAT. Therefore, many BL Lacs are expected to be discovered in VHE gamma-rays band. However, due to the limitation on current and near future technology of Imaging Air Cherenkov Telescope, astronomers are forced to predict whether an object emits VHE gamma-rays or not.

Some VHE gamma-ray prediction methods are already introduced but still are not confirmed. Cross band correlations are the building blocks of introducing VHE gamma-rays prediction method.

Aims: We will attempt to investigate cross band correlations between flux energy density, luminosity and spectral index of the sample. Also, we will check whether recently discovered MAGIC J2001+435 is a typical BL Lac.

Methods: We select a sample of 42 TeV BL Lacs and collect 20 of their properties within five energy bands from literature and Tuorla blazar monitoring program database. All of the data are synchronized to be comparable to each other. Finally, we choose 55 pair of datasets for cross band correlations finding and investigating whether there is any correlation between each pair. For MAGIC J2001+435 we analyze the publicly available SWIFT-XRT data, and use the still unpublished VHE gamma-rays data from MAGIC collaboration. The results are compared to the other sources of the sample.

Results: Low state luminosity of multiple detected VHE gamma-rays is strongly correlated luminosities in all other bands. However, the high state does not show such strong correlations. VHE gamma-rays single detected sources have similar behaviour to the low state of multiple detected ones. Finally, MAGIC J2001+435 is a typical TeV BL Lac. However, for some of the properties this source is located at the edge of the whole sample (e.g. in terms of X-rays flux).

keywords: BL Lac(s), Population study, Correlations finding, Multi wavelengths analysis, VHE gamma-rays, gamma-rays, X-rays, Optical, Radio

https://www.doria.fi/handle/10024/98928

VHE Gamma-Ray Emission from H1722+119

H1722+119 is a BL Lac object, that was listed as candidate TeV blazar in Costamante & Ghisellini (2002) based on its X-ray and radio properties. Its redshift is uncertain; Sbarufatti et al. 2006 give z>0.17. The source has been detected by Fermi-LAT, in the Second Fermi Catalogue with F(>1 GeV) (3.7+-0.3)e-09 cm^-2 s^-1 and with spectral index 1.92+-0.06.

H1722+119 was observed for five nights by the MAGIC telescopes starting May 17th 2013 and collecting 11 hours of good quality data. A preliminary analysis yields a detection of the source with a statistical significance of more than 5 standard deviations. The VHE flux of this detection is about 2% of the flux from the Crab nebula above 140 GeV. The previous VHE gamma-ray observations of the source produced an upper limit of 4.2% Crab nebula flux above 140 GeV (Aleksic et al. 2011).

The MAGIC observations were triggered by the extended optical high state of the source, reported by the Tuorla blazar monitoring program (http://users.utu.fi/kani/1m). At the beginning of May 2013 the source reached an R-band magnitude of 14.65, the brightest ever observed since 2005, when the monitoring started. We also analyzed the Fermi-LAT data, finding indication of a spectral index harder than reported in the Second Fermi Catalog. A Swift-XRT ToO observation was performed on 20th May.

MAGIC will continue the observations of the source as soon as the moon conditions allow it again and multiwavelength observations are encouraged.

The MAGIC contact persons for these observations are J. Cortina (cortina@ifae.es) and E. Lindfors (elilin@utu.fi).

MAGIC is a system of two 17m-diameter Imaging Atmospheric Cherenkov Telescopes located at the Canary island of La Palma, Spain, and designed to perform gamma-ray astronomy in the energy range from 50 GeV to greater than 20 TeV. 

http://www.astronomerstelegram.org/?read=5080

Shockingly bright burst

A record-setting blast of gamma rays from a dying star in a distant galaxy has wowed astronomers around the world. The eruption, which is classified as a gamma-ray burst, or GRB, and designated GRB 130427A, produced the highest-energy light ever detected from such an event.

"We have waited a long time for a gamma-ray burst this shockingly, eye-wateringly bright," said Julie McEnery, project scientist for the Fermi Gamma-ray Space Telescope at NASA's Goddard Space Flight Center in Greenbelt, Md. "The GRB lasted so long that a record number of telescopes on the ground were able to catch it while space-based observations were still ongoing."

Just after 3:47 a.m. EDT on Saturday, April 27, Fermi's Gamma-ray Burst Monitor (GBM) triggered on eruption of high-energy light in the constellation Leo. The burst occurred as NASA's Swift satellite was slewing between targets, which delayed its Burst Alert Telescope's detection by a few seconds.....

You can see more details in this link: 

NASA's Fermi, Swift see 'shockingly bright' burst