Discovery of VHE Gamma-Ray Emission from the BL Lac S2 0109+22

I am very happy to announce this discovery as the first discovery that i was involved in.

The MAGIC collaboration reports the discovery of very high energy (VHE; E>100 GeV) gamma-ray emission from the BL Lac S2 0109+22 (z=0.265 RA: 01h12m05.8s Dec:+22d44m39s, J2000). The object was observed with the MAGIC telescopes for 5.3 hours from 2015/07/22 to 2015/07/25. The preliminary analysis of the first three nights of MAGIC data showed an excess with a statistical significance of ~5 standard deviations. The VHE flux of this detection was estimated to be (1.6+/-0.7)e-11 ph/cm2/s above 100 GeV, about 3% of the flux from the Crab nebula. The daily flux shows a marked enhancement on the night of 25 July up to (9.7+/-1.5)e-11 ph/cm^2/s, ~15% of the Crab flux at E>100 GeV, corresponding to an excess with >7 sigma statistical significance. S2 0109+22 is classified as an intermediate-synchrotron peaked BL Lac object. The multi-year optical and radio historical coverage showed optical variations with typical timescales from weeks to months.

See more:
http://www.astronomerstelegram.org/?read=7844  

Newest blazar discoveries in VHE gamma-rays band

1. Discovery of Very High Energy Gamma-Ray Emission from the distant FSRQ PKS 1441+25 with the MAGIC telescopes: This source is the second distant VHE gamma-ray source with the redshift of 0.939 (Shaw et al. 2012, ApJ, 748, 49). It is discovered by MAGIC on April 20, 2015. MAGIC is a system of two 17m-diameter Imaging Atmospheric Cherenkov Telescopes designed to perform gamma-ray astronomy in the energy range from 50 GeV to greater than 50 TeV. The flux above 80 GeV is estimated to be about 8e-11 cm^-2 s^-1 (16% of Crab Nebula flux). Preliminary analysis show detection significant of 6 standard deviations during ~2 hours observation in the night between 17 and 18 of April; and 11 standard deviations during ~4 hours observations in the night between 18 and 19 of April (http://www.astronomerstelegram.org/?read=7416 ). The highest optical R-band magnitude is 15.6 and was measured in the night between 21 and 22 April using KVA telescope (http://users.utu.fi/kani/1m/PKS_1441+25.html ).
   
2. MAGIC detects an increased activity from FSRQ PKS 1510-089 at very high energy gamma-rays: The redshift of this source is 0.36. The preliminary analysis shows a highly significant signal and a flux of ~20% from that of the Crab nebula above 100 GeV for the data taken from 2015/05/18 to 2015/05/19. This implies an increase by a factor of ~5 with respect to the flux reported previously in 2012. The source is active now in Optical and IR-band as well (http://www.astronomerstelegram.org/?read=7542 ). We are performing optical monitoring in R-band using KVA telescope. The current flare in Optical is the second one after 6 years since the monitoring of this source started in the Tuorla blazar monitoring program (http://users.utu.fi/kani/1m/PKS_1510-089.html )

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

Farthest ever detected TeV source (blazar: S3 0218+357)

Gravitationally lensed blazar S3 0218+357 was discovered in TeV band by MAGIC telescope in July 2014. MAGIC observed the source for 3.5 hours during the period of July 23 and July 26, 2014. Preliminary analysis of data resulted in detection of the source with a statistical significant of more than 5 standard deviations. This source is located at the redshift of 0.944. The measured flux is about 15% of Crab flux in the range of 100-200 GeV.

More information in:
http://www.astronomerstelegram.org/?read=6349

VHE Gamma-Ray Emission from MS1221.8+2452

The MAGIC collaboration reports the discovery of very high energy (VHE; E>100 GeV) gamma-ray emission from MS1221.8+2452 (12h24m24.2s +24d36m24s, J2000.0). MS1221.8+2452 is a blazar located at a redshift of 0.218 (Sbarufatti et al., 2005, ApJ 635, 173) and classified as a high synchrotron peaked (HSP) BL Lac. It is one of the very few BL Lacs that has been imaged with the Hubble Space Telescope (Jannuzzi et al., 1997, ApJ 491, 146). It has been included in the ROSAT Bright Source Catalog (Voges et al., 1999, A&A 349, 389) and identified as XBL (X-Ray-Selected BL Lac) by the Einstein Extended Medium Sensitivity Survey (Rector et al. 2000, AJ 120, 1626). 

The object was observed with the MAGIC telescopes for 4 hours from 2013/04/30 to 2013/05/01. The preliminary analysis of these data resulted in the detection of MS1221.8+2452 with a statistical significance of more than 5 standard deviations. The VHE flux of this detection was estimated to be about 4% of the Crab nebula flux above 200 GeV.

MS1221.8+2452 was observed with Swift during March and April 2013, showing flux variability ranging from 3e-12 erg/cm2/s to 13e-12 erg/cm2/s in the 0.3-10 keV energy range. This source was flagged as a promising VHE source candidate by the Fermi-LAT collaboration, information that was shared with the MAGIC collaboration (as well as other ground-based gamma-ray instruments).

MAGIC observations on MS1221.8+2452 will continue during the next days until 2013/05/12 and multiwavelength observations are encouraged.

The MAGIC contact persons for these observations are J. Cortina (cortina@ifae.es) and F. Borracci (frabor@mpp.mpg.de).

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. 

Link: http://www.astronomerstelegram.org/?read=5038

What are Active Galactic Nuclei and Blazars?

Active Galactic Nuclei (AGNs)areexceptionally luminous compared with normal galaxies in all parts of the electromagnetic spectrum. The radiation from AGN is believed to be a result of accretionof matter by the super-massive black holeat the center of the host galaxy. They are the most luminous persistent sources of electromagnetic radiation in the universe. Being distant objects, AGNs can be used as means of studying distant the universe.
Blazars constitute a subclass of AGNs, with jet axes oriented close to the observer’s line of sight. Relativistic beaming gives rise to distinctive observational features in blazars, such as strongly anisotropic radiation, super-luminal motion, high polarization and rapid variability. Blazars are divided into two subclasses, flat spectrum radio quasars (FSRQs) and BL Lacertae objects (BL Lacs). FSRQs are observationally characterized by broad spectral lines in the optical band, while such lines are weak or not present in BL Lacs.

How is it started?

The problem raised when I asked one of my lecturers to introduce an astronomical problem for me. After some negotiation she gave me a topic to work on. Also she said that the topic could be potentially my master thesis.

The topic is to find out whether MAGIC J2001+435 is a typical Blazar or not?

After reading some literature, it is found that the source is most similar to be a BL Lac. The problem became more clear.

To find out the answer of the question, I should compare the source to other BL Lacs` characteristics. An approach to answer would be a multi-wavelenght comparison which will be done in very high energy gamma ray, gamma ray, X-ray and optical bands.