TeV Gamma-Ray Observations of Mrk421 and H1426+428 with TACTIC Imaging Telescope A Thesis submitted to the University of Mumbai for the Ph. D. (SCIENCE) Degree in PHYSICS Submitted By Kuldeep Kumar Yadav Under the Guidance of Dr. R. C. Rannot arXiv:1109.1967v1 [astro-ph.CO] 9 Sep 2011 Astrophysical Sciences Division Bhabha Atomic Research Centre Trombay, Mumbai 400 085 October 2010 Dedicated to My Parents ii iii STATEMENT BY THE CANDIDATE As required by the University Ordinance 770, I wish to state that the work embodied in this thesis titled “ TeV Gamma-Ray Observations of Mrk421 and H1426+428 with TACTIC Imaging Telescope” forms my own contri- bution to the research work carried out under the guidance of Dr. R.C. Ran- not at Astrophysical Sciences Division, Bhabha Atomic Research Centre, Trombay, Mumbai. This work has not been submitted for any other degree of this or any other University. Whenever reference have been made to previ- ous works of others, it has been clearly indicated as such and included in the Bibliography. ———————————– Signature of candidate Name : Kuldeep Kumar Yadav Certified by ———————————– Signature of Guide Name : Dr. R. C. Rannot Abstract We have observed extragalactic sources Mrk421 (z=0:30) and H1426+428 (z=0:129) in very high energy γ-ray region using TACTIC telescope at Mount Abu (24:6◦N, 72:7◦E, 1300 m asl), Rajasthan, India. Both of these sources belong to the blazar sub-class of active galactic nuclei whose jets are closely aligned to our line of sight. Blazars are most extreme and pow- erful variable sources of radiation of energies ranging from the radio to the γ-ray regimes. Mrk421 was observed during 07 December 2005 to 18 April 2007 for a total of ∼331 hours while H1426+428 was observed for ∼244 hours between 22 March 2004 and 11 June 2007. Detailed analysis of Mrk421 data revealed the presence of a γ-ray signal with the excess of ∼(951 ± 82) γ-ray like events corresponding to a statistical significance of ∼12:0σ in ∼97 hours during 27 December 2005 to 07 February 2006. The combined average flux was measured to be ∼(1:04 ± 0:14) Crab units. Obseved time averaged differential en- ergy spectrum was found to be consistent with both a pure power law dΦ=dE = (4:66 ± 0:46)×10−11 E(−3:11±0:11) cm−2 s−1 T eV −1 and power law with an exponential cutoff func- −Γ −11 −2 −1 −1 tions dΦ=dE = f0E exp(−E=E0) with f0 = (4:88 ± 0:38) × 10 cm s T eV , Γ = 2:51 ± 0:26 and E0 = (4:7 ± 2:1)T eV . The later function fits the observed spectrum well with lower value of reduced χ2. However, during the observation period from 18 De- cember 2006 to 18 April 2007, the source was found to be in a low emission state and we have placed an upper limit of 1:44 × 10−12 photons cm−2 s−1 at 3σ level on the integrated γ-ray flux above 1 T eV . In addition, the TACTIC light curves have also been compared with those obtained with the RXTE/ASM and Swift/BAT satellite-based experiments. Fur- ther, we have obtained the SED of Mrk421 in the VHE range using TACTIC telescope and compared it with those obtained by the HESS, MAGIC, VERITAS, Whipple, HEGRA and CAT telescopes. The detection of T eV photons from the distant object H1426+428 have important implications for estimating the EBL, in addition to the understanding of the par- ticle acceleration and γ-ray production mechanisms in the AGN jets. Detailed analysis of H1426+428 data does not indicate the presence of any statistically significant T eV γ-ray sig- nal. Accordingly we have placed an upper limit of ≤ 1:18 × 10−12 photons cm−2 s−1 on the integrated γ-ray flux above 1 T eV at 3σ significance level. iv List of Publication Publications in refereed journals 1. Search for TeV γ-rays from H1426+428 during 2004-07 with the TACTIC telescope; K.K. Yadav, R.C. Rannot, P. Chandra, A. K. Tickoo, K. Venugopal, N. Bhatt, S. Bhattacharyya, K. Chanchalani, V.K. Dhar, H.C. Goyal, R.K. Kaul, M. Kothari, S. Kotwal, M.K. Koul, R. Koul, B.S. Sahaynathan, M. Sharma, S. Thoudam; J. Phys. G: Nucl. Part. Phys., 36 (2009) 085201. 2. ANN-based energy reconstruction procedure for TACTIC gamma-ray telescope and its comparison with other conventional methods; V. K. Dhar, A.K. Tickoo, M.K. Koul, R.C. Rannot, K.K. Yadav, P. Chandra, B. P. Dubey, R. Koul; Nucl. Instrum. and meth. A., 606 (2009) 795. 3. Very High Energy γ-ray observations of Mrk 501 using TACTIC imaging γ-ray tele- scope during 2005-06; S. V. Godambe, R.C. Rannot, P. Chandra, K. K. Yadav, A. K. Tickoo, K. Venugopal, N. Bhatt, S. Bhattacharyya, K. Chanchalani, V. K. Dhar, H. C. Goyal, R. K. Kaul, M. Kothari, S. Kotwal, M.K. Koul, R. Koul, B. S. Sahaynathan, M. Sharma, S. Thoudam; J. Phys. G: Nucl. Part. Phys., 35 (2008) 065202. 4. Observations of TeV γ-rays from Mrk421 during Dec.2005 to May2006 with the TAC- TIC telescope; K.K. Yadav, P. Chandra, A.K. Tickoo, R.C. Rannot, S. Godambe, M.K. Koul, V.K. Dhar, S. Thoudam, N. Bhatt, S. Bhattacharyya, K. Chanchalani, H.C. Goyal, R.K. Kaul, M. Kothari, S. Kotwal, R. Koul, S. Sahayanathan, M. Sharma, K. Venugopal; Astroparticle Physics, 27 (2007) 447. 5. Very High Energy γ -ray and Near Infrared observations of 1ES2344+514 during 2004-05; v List of Publication vi S.V. Godambe, R.C. Rannot, K.S. Baliyan, A.K. Tickoo, S. Thoudam, V.K. Dhar, P. Chandra, K.K. Yadav, K. Venugopal, N. Bhatt, S. Bhattacharyya, K. Chanchalani, S. Ganesh, H.C. Goyal, U.C. Joshi, R.K. Kaul, M. Kothari, S. Kotwal, M.K. Koul, R. Koul, S. Sahaynathan, C. Shah, M. Sharma; J. Phys. G: Nucl. Part. Phys., 34 (2007) 1683. 6. The TACTIC atmospheric Cherenkov Imaging telescope; R. Koul, A.K. Tickoo, S.K. Kaul, S.R. Kaul, N. Kumar, K.K. Yadav, N. Bhatt, K. Venugopal, H.C. Goyal, M. Kothari, P. Chandra, R.C. Rannot, V.K. Dhar, M.K. Koul, R.K. Kaul, S. Kotwal, K. Chanchalani, S. Thoudam, N. Chouhan, M. Sharma, S. Bhat- tacharyya, S. Sahayanathan; Nucl. Instrum. and meth. A., 578 (2007) 548. 7. A generalized ray-tracing procedure for an atmospheric Cherenkov imaging telescope and optical characteristics of the TACTIC light collector; A.K. Tickoo, R.L. Suthar, R. Koul, M.L. Sapru, N. Kumar, C.L. Kaul, K.K. Yadav, S. Thoudam, S.K. Kaul, K. Venugopal, M. Kothari, H.C. Goyal, P. Chandra, V.K. Dhar, R.C. Rannot, M.K. Koul, S.R. Kaul; Nucl. Instrum. and meth. A., 539 (2005) 177. 8. Real time data acquisition and control system for the 349-pixel TACTIC atmospheric Cerenkov imaging telescope; K.K. Yadav, R. Koul, A. Kanda, S.R. Kaul, A.K. Tickoo, R.C. Rannot, P.Chandra, N. Bhatt, N. Chouhan, K. Venugopal, M. Kothari, H.C. Goyal, V.K. Dhar and S.K. Kaul; Nucl. Instrum. and Meth.A 527 (2004) 411. 9. Programmable Topological Trigger Generator for the 349-pixel Imaging Camera of the TACTIC telescope; S.R. Kaul, R. Koul, I.K. Kaul, A.K. Tickoo, K.K. Yadav, M.L. Sapru and C.L. Bhat; Nucl. Instrrum. and Meth.A, 496 (2003) 400. 10. On a single-count rate stabilization scheme employed in the imaging camera of the TACTIC gamma-ray telescope; N. Bhatt, K.K. Yadav, A. Kanda, R. Koul, S.R. Kaul, H.C. Goyal, V.K. Dhar, S.K. Kaul, K. Venugopal, A.K. Tickoo, I.K. Kaul, M. Kothari and C.L. Bhat; Meas.Sci & Tech, 12(2001) 167-171. List of Publication vii Publications in conferences 1. Feasibility of operating TACTIC telescope during partial moonlit conditions; K.K. Singh, A.K. Tickoo, K.K. Yadav, R.C. Rannot, V.K. Dhar, R. Koul; Presented at 16th National Space Science Symposium ( NSSS-2010)”, Rajkot, India, (2010). 2. Recent TeV observations of Mrk 421 with the TACTIC gamma-ray telescope; R.C. Rannot, P. Chandra, K.K. Yadav, A.K. Tickoo, K. Chanchalani, A. Goyal, H.C. Goyal, M. Kothari, S. Kotwal, N. Kumar, P. Marandi, K. Venugopal, C.K. Bhat, N. Bhatt, S. Bhattacharyya, V.K. Dhar, M.K. Koul, R. Koul, S.Sahayanathan, M.Sharma and K.K.Singh; Presented at 16th National Space Science Symposium ( NSSS-2010)”, Rajkot, India, (2010). 3. VHE gamma-ray observations of 3C279 during 2008-09 using TACTIC telescope; P. Chandra, R.C. Rannot, K.K. Yadav, A.K. Tickoo, K. Venugopal, K. Chanchalani, A. Goyal, H.C. Goyal, M. Kothari, S. Kotwal, N. Kumar, P. Marandi, K.K. Singh, C.K. Bhat, N. Bhatt, S. Bhattacharyya, V.K. Dhar, M.K. Koul, R. Koul, S. Sahayanathan and M. Sharma; Presented at 16th National Space Science Symposium ( NSSS-2010)”, Rajkot, India, (2010). 4. Fractal and Wavelet analysis approach for detectiong gamma-rays from Cerenkov im- ages using Imaging Cerenkov Telescope; C.K. Bhat, K.K. Yadav, R. Koul; Presented at 16th National Space Science Symposium ( NSSS-2010)”, Rajkot, India, (2010). 5. Pulse profile digitization system for TACTIC gamma-ray telescope; N. Chouhan, R.C. Rannot, S.R. Kaul, A.K. Tickoo, K.K. Yadav, P. Chandra, S. Kot- wal, K. Venugopal, K. Chanchalani, M. Kothari, H.C. Goyal, P.