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OBSERVATIONS OF AGNs USING PACT

OBSERVATIONS OF AGNs USING PACT. (Pachmarhi Array of Cherenkov Telescopes). Debanjan Bose. (On behalf of PACT collaboration). “The Multi-Messenger Approach To High Energy Gamma Ray Sources” July 4 -July 7, Barcelona, Spain. Active Galactic Nuclei.

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OBSERVATIONS OF AGNs USING PACT

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  1. OBSERVATIONS OF AGNs USING PACT (Pachmarhi Array of Cherenkov Telescopes) Debanjan Bose (On behalf of PACT collaboration) “The Multi-Messenger Approach To High Energy Gamma Ray Sources” July 4 -July 7, Barcelona, Spain

  2. Active Galactic Nuclei • AGNs dominate extra-galactic astronomy • by virtue of their great luminosities • A super massive black hole at the centre • surrounded by an accretion disk • A strong jet of relativistic particles • emanates perpendicular to the plane of • the accretion disk • Blazars are a class of AGN with jet along • the line of sight

  3. B L Lac objects or Blazars • Variable at all wavelengths • SEDs are characterised by two • humps • Divided into two sub-classes • HBL and LBL • VHE flares are generally well • correlated with X-ray flare

  4. Pachmarhi Array of Cherenkov Telescopes • Pachmarhi located in central India, 22º28' N 78º25' E • altitude ~ 1075m • 24 telescopes spread over an area of 80m  100m • Each telescope has 7 para-axially mounted parabolic mirrors • of diameter 0.9m, f/d ~ 1 • A fast photo-tube (EMI9807B) of 2" diameter at the focus of • every mirror • A coincidence of 4 out of 6 telescopes in a sector generates • trigger • For each trigger TDC (timing) and ADC (photon density) • informations are recorded • Energy threshold of PACT ~ 750 GeV

  5. Pachmarhi Array of Cherenkov Telescopes • Pachmarhi located in central India, 22º28' N 78º25' E • altitude ~ 1075m • 24 telescopes spread over an area of 80m  100m • Each telescope has 7 para-axially mounted parabolic mirrors • of diameter 0.9m, f/d ~ 1 • A fast photo-tube (EMI9807B) of 2" diameter at the focus of • every mirror • A coincidence of 4 out of 6 telescopes in a sector generates • trigger • For each trigger TDC (timing) and ADC (photon density) • informations are recorded • Energy threshold of PACT ~ 750 GeV

  6. Pachmarhi Array of Cherenkov Telescopes • Pachmarhi located in central India, 22º28' N 78º25' E • altitude ~ 1075m • 24 telescopes spread over an area of 80m  100m • Each telescope has 7 para-axially mounted parabolic mirrors • of diameter 0.9m, f/d ~ 1 • A fast photo-tube (EMI9807B) of 2" diameter at the focus of • every mirror • A coincidence of 4 out of 6 telescopes in a sector generates • trigger • For each trigger TDC (timing) and ADC (photon density) • informations are recorded • Energy threshold of PACT ~ 750 GeV

  7. OBSERVATION LOG year Observation duration (mins.)

  8. ANALYSIS OF PACT DATA • Arrival direction of a shower is determined by reconstructing • the shower front using the relative arrival time of cherenkov • shower at each telescope • The Cherenkov front is fitted with a plane, normal to this • plane gives the direction of shower axis • Space angle between the direction of shower axis and • direction of source is obtained for events with  8 • telescopes • Space angle distributions of source and background runs are • compared over same zenith angle range

  9. ANALYSIS OF PACT DATA • Background space angle distributions are normalized w.r.t • Source distribution by comparing shape in 2.5º to 6.5º • window, since no γ-rays are expected in that region • γ-ray signal is obtained as excess of source events over • background events in 0º to 2.5º region as No. of γ-rays Where c is a constant

  10. Mkn 421 • First blazar detected at TeV energies by • WHIPPLE in 1992 • This is also the closest (z=0.031) • Quite often it goes into flaring state • Flare in TeV energies mostly associated with flare • in X-ray energies

  11. PACT ASM on board RXTE Mkn 421 • First blazar detected at TeV energies by • WHIPPLE in 1992 • This is also the closest (z=0.031) • Quite often it goes into flaring state • Flare in TeV energies mostly associated with flare • in X-ray energies

  12. Mkn 421 2001 Time average flux combining all data obtained using PACT during 2000-2005 is 4.45(1.9)10-12 photons cm-2 s-1 above 1.2 TeV

  13. Multiwavelength Campaign 2003 for Mkn421 • 26th February to 5th March there was a multiwavelength • campaign between X-ray and γ-ray • Source was in quiet state • PACT data was not so useful • X-ray data taken by RXTE satellite has been analysed

  14. Analysis of PCA data For timing analysis FTOOLS and XRONOS has been used

  15. Analysis of PCA data • Spectral data analysed using XSPEC • Model used : power law with exponential • cutoff • Best fit parameters for combined spectra • NH ~ 1.381020 cm-2 •  ~ 2.39 (0.03) • Ecutoff ~ 23.9 (  2.4) keV • Systematic error assumed was 1%

  16. Multiwavelength Campaign 2003 for Mkn421 • 26th February to 5th March there was a multiwavelength • campaign between X-ray and γ-ray • Source was in quiet state • PACT data was not so useful • X-ray data taken by RXTE satellite has been analysed • NIR data - Gurushikhar Observatory, Mount Abu, India • Radio data at 22 and 37 Ghz – Metsähovi radio telescope

  17. Multiwavelength Campaign 2003 for Mkn421 NIR X-ray radio

  18. Multiwavelength Campaign 2003 for Mkn421 NIR X-ray radio One zone SSC model :  =14, B=0.4G, R=0.7  1016 cm, we =0.06 erg cm-3, Eb=10.34, Emin=6.5, Emax=11.22, p1=2.05, p2=3.6 (Krawczynski et al 2004)

  19. Multiwavelength Campaign 2003 for Mkn421 NIR X-ray PACT radio One zone SSC model :  =14, B=0.4G, R=0.7  1016 cm, we =0.06 erg cm-3, Eb=10.34, Emin=6.5, Emax=11.22, p1=2.05, p2=3.6 (Krawczynski et al 2004)

  20. Multiwavelength Campaign 2003 for Mkn421

  21. SED of Mkn421 during flare in 2001 • Mkn421 was in very active state in early months of 2001 • We have analysed the RXTE data taken in March - April • Optical data (V-band) was taken by WEBT collaboration, • using KVA-telescope on La Palma • Radio data was taken by Metsähovi radio telescope

  22. Solid - 2001 Dotted - 2003 SED of Mkn421 during flare in 2001 X-ray optical radio One zone SSC model :  =15.2, B=0.12G, R=15  1016 cm, we =0.023 erg cm-3, Eb=11.0, Emin=6.5, Emax=11.6, p1=2.0, p2=3.0

  23. Spectral Index vs Flux 2003 2001 Spectra hardens as flux increases

  24. Other Blazars • In 1997 huge flare was detected from Mkn501 • by other experiment • During PACT observations from 2000-2005 • Mkn501 was in low state • We have estimated 3 upperlimit 1997

  25. Other Blazars • In 1997 huge flare was detected from Mkn501 • by other experiment • During PACT observations from 2000-2005 • Mkn501was in low state • We have estimated 3 upperlimit • 1ES1426+428 is a distant blazar, needs very • long observation

  26. Other Blazars • In 1997 huge flare was detected from Mkn501 • by other experiment • During PACT observations from 2000-2005 • Mkn501was in low state • We have estimated 3 upperlimit • 1ES1426+428 is a distant blazar, needs very • long observation • ON231, LBL type, no experiment has detected • significant excess above 100 GeV

  27. Conclusions • Sensitivity of PACT is not good enough to detect blazars in • reasonable time when they are not in active state • Out of 4 blazars for Mkn421 we have estimated average integral • flux and for others we have given upperlimits • γ-ray and X-ray seems to be correlated, during flare energy • spectrum hardens as flux increases • One-zone SSC model can not fit the measured fluxes at • radio and optical wavelengths, introduction of additional • zone improves the fit significantly • More sensitive detectors are needed like HAGAR to detect faint • sources

  28. High Altitude GAmma Ray (HAGAR) Observatory • A 7 telescopes array is coming up at Hanle in Himalayas • altitude 4.3 km

  29. High Altitude GAmma Ray (HAGAR) Observatory • A 7 telescopes array is coming up at Hanle in Himalayas • altitude 4.3 km • Lateral spread is less, near shower core density is 4-5 • times higher compare to sea level HAGAR PACT

  30. 60 GeV High Altitude GAmma Ray (HAGAR) Observatory • A 7 telescopes array is coming up at Hanle in Himalayas • altitude 4.3 km • Lateral spread is less, near shower core density is 4-5 • times higher compare to sea level • Low atmospheric attenuation : • @ Hanle 14% @ sea level 50% • Energy Threshold : 60 GeV ; sensitivity better than PACT

  31. High Altitude GAmma Ray (HAGAR) Observatory • A 7 telescopes array is coming up at Hanle in Himalayas • altitude 4.3 km • Lateral spread is less, near shower core density is 4-5 • times higher compare to sea level • Low atmospheric attenuation : • @ Hanle 14% @ sea level 50% • Energy Threshold : 60 GeV ; sensitivity better than PACT

  32. High Altitude GAmma Ray (HAGAR) Observatory • A 7 telescopes array is coming up at Hanle in Himalayas • altitude 4.3 km • Lateral spread is less, near shower core density is 4-5 • times higher compare to sea level • Low atmospheric attenuation : • @ Hanle 14% @ sea level 50% • Energy Threshold : 60 GeV ; sensitivity better than PACT

  33. Thank you !!

  34. SSC parameters for optical 2001 :  =14, B=0.055G, R=1.6  10^17 cm, we =0.00019 erg cm^(-3), Eb=10., Emin=6.5, Emax=11., p1=2.05, p2=3.4 SSC parameters for radio 2001 :  =14, B=0.003G, R=8  10^17 cm, we =0.000020 erg cm^(-3), E(b)=11, Emin=6.5, Emax=11.5, p1=2.05, p2=3.4 SSC parameters for optical 2003 :  =14, B=0.055G, R=1.6  10^17 cm, we =0.00017 erg cm^(-3), Eb=10., Emin=6.5, Emax=11., p1=2.05, p2=3.4 SSC parameters for radio 2003 :  =14, B=0.003G, R=8  10^17 cm, we =0.000015 erg cm^(-3), E(b)=11, Emin=6.5, Emax=11.5, p1=2.05, p2=3.4

  35. SED of Mkn421 for 2001

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