H.E.S.S. DISCOVERY OF VHE EMISSION FROM PKS 0736+017: on the - - PowerPoint PPT Presentation

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Oct 12, 2023 115 likes •319 views

H.E.S.S. DISCOVERY OF VHE EMISSION FROM PKS 0736+017: on the location of the g -ray emitting region in FSRQs Matteo Cerruti, Jean-Philippe Lenain, Heike Prokoph, for the H.E.S.S. Collaboration ICRC 2017, Busan, South Korea 1 07/13/17 THE T

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H.E.S.S. DISCOVERY OF VHE EMISSION FROM PKS 0736+017:

  • n the location of the g-ray emitting region in FSRQs

Matteo Cerruti, Jean-Philippe Lenain, Heike Prokoph, for the H.E.S.S. Collaboration

ICRC 2017, Busan, South Korea 07/13/17

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THE T eV (EXTRAGALACTIC) SKY

67 known VHE (E > 100 GeV) blazars

  • nly 6 are FSRQs

due to: -lower peak frequency compared to HBLs

  • higher (average) redshift compared to HBLs

tevcat.uchicago.edu

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Well known radio quasar

  • z = 0.1894 (Ho & Kim 2009)
  • typical FSRQ optical spectrum
  • presence of big-blue bump
  • SMBH mass = 108.47 M☉ (McLure

& Dunlop 2001)

  • Host galaxy is a standard giant

elliptical (Wright 1998, Kotilainen 1998, ++)

Milkan & Moore, 1986

PKS 0736+017

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Lister & Homan, 2005

Well known radio quasar

  • Core-jet radio morphology

(from MOJAVE)

PKS 0736+017

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Clements et al., 2003

Well known radio quasar

  • Extreme optical fmare in 2002,

with 0.6 mag/hr (which classifjes the source as Optically Violently Variable)

PKS 0736+017

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The source is detected by Fermi, and known as 3FGLJ0739.4+0137

  • Active in November 2014 (AT

el 6731)

  • and again in February 2015

(AT el 6975 from ASAS-SN)

From automatic aperture photometry analysis of Fermi-LAT data

PKS 0736+017

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PKS 0736+017 : LAT results

LAT likelihood data analysis – PASS8 – 12h bin „Double“ fmare in g-rays H.E.S.S. observations on 2015, Feb 18, 19, 21

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H.E.S.S. II

Array of 4+1 Cherenkov telescopes located on Khomas Highland, Namibia (23°16‘ S, 16°30‘ E) T wo difgerent reconstructions: Monoscopic (CT5 only) Stereoscopic (any 2 out of 5 telescopes)

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H.E.S.S. II

Array of 4+1 Cherenkov telescopes located on Khomas Highland, Namibia (23°16‘ S, 16°30‘ E) T wo difgerent reconstructions: Monoscopic (CT5 only) Stereoscopic (any 2 out of 5 telescopes)

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H.E.S.S. II

Array of 4+1 Cherenkov telescopes located on Khomas Highland, Namibia (23°16‘ S, 16°30‘ E) T wo difgerent reconstructions: Monoscopic (CT5 only) Stereoscopic (any 2 out of 5 telescopes)

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PKS 0736+017 : H.E.S.S. results

Discovery of VHE emission on the night of 2015 Feb 19 (both in Mono & Stereo reconstruction) H.E.S.S. Mono 11s detection H.E.S.S. Stereo 5.5s detection

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PKS 0736+017 : H.E.S.S. results

No detections during the other nights Correlation with the second Fermi-LAT fmare

Time selection for contemporaneous LAT analysis

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PKS 0736+017 : g-ray SED

Fermi-LAT and H.E.S.S. spectra (mono & stereo) Fermi-LAT spectrum extrapolated towards higher energies, including EBL absorption → spectral break between LAT and H.E.S.S.

G = 2.15 ± 0.10 Gmono = 3.1 ± 0.3 Gstereo = 4.2 ± 0.8

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Swift T

  • O triggered by H.E.S.S., with three 4ks exposures on 2015, Feb 20, 22 and 23

→ No simultaneous observations during the H.E.S.S. detection (Feb 19) ATOM long-term lightcurve: Feb 20, 2015

PKS 0736+017 : X-ray and optical

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Day-by-day variability in H.E.S.S. data, but

  • nly Fermi-LAT simultaneous with H.E.S.S.

PKS 0736+017 : MWL picture

H.E.S.S. Fermi-LAT XRT UVOT/ATOM

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  • No simultaneous SED during the HESS detection & nigh-by-night

variability → No SED modelling / fjtting

  • On the location of the g-ray emitting region using only

g-ray information

PKS 0736+017 : modeling

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Hypotheses:

  • MeV to T

eV emission is produced in the same region

  • Dominant radiative process in g-rays is leptonic

(External-Inverse-Compton)

  • Variability time-scale ~12 hours (from Fermi-LAT)

Constraints:

  • Opacity to g-g pair production on BLR photons (Bottcher & Els, 2016)
  • Collimation of the jet
  • Cooling time-scale (by EIC) is smaller than variability time-scale

(Nalewajko++ 2014)

PKS 0736+017 : modeling

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PKS 0736+017 : modeling

RBLR

Cooling constraint Opacity constraint Collimation constraint Scattering

  • n BLR

photons, G~10 Scattering

  • n torus

photons, G~50 Not possible, due to opacity

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PKS 0736+017 : CONCLUSIONS

Discovery of VHE emission from PKS 0736+017

  • is the sixth VHE FSRQ
  • the second one discovered with H.E.S.S.

Gamma-ray observations only can put constraints in the G-r plane

PKS 0736+017 : conclusions

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PKS 0736+017 : CONCLUSIONS

Perspectives: At z=0.189 it is the nearest FSRQ The best one to study internal absorption At dec~0, easily visible by H.E.S.S. / MAGIC / VERITAS / FACT / HAWC → be ready for the next g-ray fmare

PKS 0736+017 : conclusions