HESS J1943+213: An Extreme Blazar Shining through the Galactic Plane

The Veritas Collaboration, A. Archer, W. Benbow, R. Bird, R. Brose, M. Buchovecky, V. Bugaev, W. Cui, M. K. Daniel, A. Falcone, Q. Feng, J. P. Finley, A. Flinders, Lucy F Fortson, A. Furniss, G. H. Gillanders, M. Hütten, D. Hanna, O. Hervet, J. HolderG. Hughes, T. B. Humensky, C. A. Johnson, P. Kaaret, P. Kar, N. Kelley-Hoskins, D. Kieda, M. Krause, F. Krennrich, S. Kumar, M. J. Lang, T. T.Y. Lin, S. McArthur, P. Moriarty, R. Mukherjee, D. Nieto, S. O'Brien, R. A. Ong, A. N. Otte, N. Park, A. Petrashyk, M. Pohl, A. Popkow, E. Pueschel, J. Quinn, K. Ragan, P. T. Reynolds, G. T. Richards, E. Roache, Cameron B Rulten, I. Sadeh, G. H. Sembroski, Karlen Shahinyan, J. Tyler, S. P. Wakely, O. M. Weiner, A. Weinstein, R. M. Wells, P. Wilcox, A. Wilhelm, D. A. Williams, W. F. Brisken, P. Pontrelli

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

HESS J1943+213 is a very high energy (VHE; >100 GeV) γ-ray source in the direction of the Galactic plane. Studies exploring the classification of the source are converging toward its identification as an extreme synchrotron BL Lac object. Here we present 38 hr of VERITAS observations of HESS J1943+213 taken over 2 yr. The source is detected with a significance of ∼20 standard deviations, showing a remarkably stable flux and spectrum in VHE γ-rays. Multifrequency Very Long Baseline Array (VLBA) observations of the source confirm the extended, jet-like structure previously found in the 1.6 GHz band with the European VLBI Network and detect this component in the 4.6 and 7.3 GHz bands. The radio spectral indices of the core and the jet and the level of polarization derived from the VLBA observations are in a range typical for blazars. Data from VERITAS, Fermi-LAT, Swift-XRT, the FLWO 48″ telescope, and archival infrared and hard X-ray observations are used to construct and model the spectral energy distribution (SED) of the source with a synchrotron self-Compton model. The well-measured γ-ray peak of the SED with VERITAS and Fermi-LAT provides constraining upper limits on the source redshift. Possible contribution of secondary γ-rays from ultra-high-energy cosmic-ray-initiated electromagnetic cascades to the γ-ray emission is explored, finding that only a segment of the VHE spectrum can be accommodated with this process. A variability search is performed across X-ray and γ-ray bands. No statistically significant flux or spectral variability is detected.

Original languageEnglish (US)
Article number41
JournalAstrophysical Journal
Volume862
Issue number1
DOIs
StatePublished - Jul 20 2018

Fingerprint

rays
Very Long Baseline Array (VLBA)
energy
spectral energy distribution
synchrotrons
very long baseline interferometry
cosmic ray
blazars
very long base interferometry
polarization
radio
cosmic rays
standard deviation
cascades
x rays
telescopes
electromagnetism
distribution

Keywords

  • BL Lacertae objects: individual (HESS J1943+213, VER J1943+213)
  • astroparticle physics
  • galaxies: active
  • galaxies: jets
  • galaxies: nuclei
  • gamma rays: galaxies

Cite this

Veritas Collaboration, T., Archer, A., Benbow, W., Bird, R., Brose, R., Buchovecky, M., ... Pontrelli, P. (2018). HESS J1943+213: An Extreme Blazar Shining through the Galactic Plane. Astrophysical Journal, 862(1), [41]. https://doi.org/10.3847/1538-4357/aacbd0

HESS J1943+213 : An Extreme Blazar Shining through the Galactic Plane. / Veritas Collaboration, The; Archer, A.; Benbow, W.; Bird, R.; Brose, R.; Buchovecky, M.; Bugaev, V.; Cui, W.; Daniel, M. K.; Falcone, A.; Feng, Q.; Finley, J. P.; Flinders, A.; Fortson, Lucy F; Furniss, A.; Gillanders, G. H.; Hütten, M.; Hanna, D.; Hervet, O.; Holder, J.; Hughes, G.; Humensky, T. B.; Johnson, C. A.; Kaaret, P.; Kar, P.; Kelley-Hoskins, N.; Kieda, D.; Krause, M.; Krennrich, F.; Kumar, S.; Lang, M. J.; Lin, T. T.Y.; McArthur, S.; Moriarty, P.; Mukherjee, R.; Nieto, D.; O'Brien, S.; Ong, R. A.; Otte, A. N.; Park, N.; Petrashyk, A.; Pohl, M.; Popkow, A.; Pueschel, E.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Rulten, Cameron B; Sadeh, I.; Sembroski, G. H.; Shahinyan, Karlen; Tyler, J.; Wakely, S. P.; Weiner, O. M.; Weinstein, A.; Wells, R. M.; Wilcox, P.; Wilhelm, A.; Williams, D. A.; Brisken, W. F.; Pontrelli, P.

In: Astrophysical Journal, Vol. 862, No. 1, 41, 20.07.2018.

Research output: Contribution to journalArticle

Veritas Collaboration, T, Archer, A, Benbow, W, Bird, R, Brose, R, Buchovecky, M, Bugaev, V, Cui, W, Daniel, MK, Falcone, A, Feng, Q, Finley, JP, Flinders, A, Fortson, LF, Furniss, A, Gillanders, GH, Hütten, M, Hanna, D, Hervet, O, Holder, J, Hughes, G, Humensky, TB, Johnson, CA, Kaaret, P, Kar, P, Kelley-Hoskins, N, Kieda, D, Krause, M, Krennrich, F, Kumar, S, Lang, MJ, Lin, TTY, McArthur, S, Moriarty, P, Mukherjee, R, Nieto, D, O'Brien, S, Ong, RA, Otte, AN, Park, N, Petrashyk, A, Pohl, M, Popkow, A, Pueschel, E, Quinn, J, Ragan, K, Reynolds, PT, Richards, GT, Roache, E, Rulten, CB, Sadeh, I, Sembroski, GH, Shahinyan, K, Tyler, J, Wakely, SP, Weiner, OM, Weinstein, A, Wells, RM, Wilcox, P, Wilhelm, A, Williams, DA, Brisken, WF & Pontrelli, P 2018, 'HESS J1943+213: An Extreme Blazar Shining through the Galactic Plane', Astrophysical Journal, vol. 862, no. 1, 41. https://doi.org/10.3847/1538-4357/aacbd0
Veritas Collaboration T, Archer A, Benbow W, Bird R, Brose R, Buchovecky M et al. HESS J1943+213: An Extreme Blazar Shining through the Galactic Plane. Astrophysical Journal. 2018 Jul 20;862(1). 41. https://doi.org/10.3847/1538-4357/aacbd0
Veritas Collaboration, The ; Archer, A. ; Benbow, W. ; Bird, R. ; Brose, R. ; Buchovecky, M. ; Bugaev, V. ; Cui, W. ; Daniel, M. K. ; Falcone, A. ; Feng, Q. ; Finley, J. P. ; Flinders, A. ; Fortson, Lucy F ; Furniss, A. ; Gillanders, G. H. ; Hütten, M. ; Hanna, D. ; Hervet, O. ; Holder, J. ; Hughes, G. ; Humensky, T. B. ; Johnson, C. A. ; Kaaret, P. ; Kar, P. ; Kelley-Hoskins, N. ; Kieda, D. ; Krause, M. ; Krennrich, F. ; Kumar, S. ; Lang, M. J. ; Lin, T. T.Y. ; McArthur, S. ; Moriarty, P. ; Mukherjee, R. ; Nieto, D. ; O'Brien, S. ; Ong, R. A. ; Otte, A. N. ; Park, N. ; Petrashyk, A. ; Pohl, M. ; Popkow, A. ; Pueschel, E. ; Quinn, J. ; Ragan, K. ; Reynolds, P. T. ; Richards, G. T. ; Roache, E. ; Rulten, Cameron B ; Sadeh, I. ; Sembroski, G. H. ; Shahinyan, Karlen ; Tyler, J. ; Wakely, S. P. ; Weiner, O. M. ; Weinstein, A. ; Wells, R. M. ; Wilcox, P. ; Wilhelm, A. ; Williams, D. A. ; Brisken, W. F. ; Pontrelli, P. / HESS J1943+213 : An Extreme Blazar Shining through the Galactic Plane. In: Astrophysical Journal. 2018 ; Vol. 862, No. 1.
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abstract = "HESS J1943+213 is a very high energy (VHE; >100 GeV) γ-ray source in the direction of the Galactic plane. Studies exploring the classification of the source are converging toward its identification as an extreme synchrotron BL Lac object. Here we present 38 hr of VERITAS observations of HESS J1943+213 taken over 2 yr. The source is detected with a significance of ∼20 standard deviations, showing a remarkably stable flux and spectrum in VHE γ-rays. Multifrequency Very Long Baseline Array (VLBA) observations of the source confirm the extended, jet-like structure previously found in the 1.6 GHz band with the European VLBI Network and detect this component in the 4.6 and 7.3 GHz bands. The radio spectral indices of the core and the jet and the level of polarization derived from the VLBA observations are in a range typical for blazars. Data from VERITAS, Fermi-LAT, Swift-XRT, the FLWO 48″ telescope, and archival infrared and hard X-ray observations are used to construct and model the spectral energy distribution (SED) of the source with a synchrotron self-Compton model. The well-measured γ-ray peak of the SED with VERITAS and Fermi-LAT provides constraining upper limits on the source redshift. Possible contribution of secondary γ-rays from ultra-high-energy cosmic-ray-initiated electromagnetic cascades to the γ-ray emission is explored, finding that only a segment of the VHE spectrum can be accommodated with this process. A variability search is performed across X-ray and γ-ray bands. No statistically significant flux or spectral variability is detected.",
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T2 - An Extreme Blazar Shining through the Galactic Plane

AU - Veritas Collaboration, The

AU - Archer, A.

AU - Benbow, W.

AU - Bird, R.

AU - Brose, R.

AU - Buchovecky, M.

AU - Bugaev, V.

AU - Cui, W.

AU - Daniel, M. K.

AU - Falcone, A.

AU - Feng, Q.

AU - Finley, J. P.

AU - Flinders, A.

AU - Fortson, Lucy F

AU - Furniss, A.

AU - Gillanders, G. H.

AU - Hütten, M.

AU - Hanna, D.

AU - Hervet, O.

AU - Holder, J.

AU - Hughes, G.

AU - Humensky, T. B.

AU - Johnson, C. A.

AU - Kaaret, P.

AU - Kar, P.

AU - Kelley-Hoskins, N.

AU - Kieda, D.

AU - Krause, M.

AU - Krennrich, F.

AU - Kumar, S.

AU - Lang, M. J.

AU - Lin, T. T.Y.

AU - McArthur, S.

AU - Moriarty, P.

AU - Mukherjee, R.

AU - Nieto, D.

AU - O'Brien, S.

AU - Ong, R. A.

AU - Otte, A. N.

AU - Park, N.

AU - Petrashyk, A.

AU - Pohl, M.

AU - Popkow, A.

AU - Pueschel, E.

AU - Quinn, J.

AU - Ragan, K.

AU - Reynolds, P. T.

AU - Richards, G. T.

AU - Roache, E.

AU - Rulten, Cameron B

AU - Sadeh, I.

AU - Sembroski, G. H.

AU - Shahinyan, Karlen

AU - Tyler, J.

AU - Wakely, S. P.

AU - Weiner, O. M.

AU - Weinstein, A.

AU - Wells, R. M.

AU - Wilcox, P.

AU - Wilhelm, A.

AU - Williams, D. A.

AU - Brisken, W. F.

AU - Pontrelli, P.

PY - 2018/7/20

Y1 - 2018/7/20

N2 - HESS J1943+213 is a very high energy (VHE; >100 GeV) γ-ray source in the direction of the Galactic plane. Studies exploring the classification of the source are converging toward its identification as an extreme synchrotron BL Lac object. Here we present 38 hr of VERITAS observations of HESS J1943+213 taken over 2 yr. The source is detected with a significance of ∼20 standard deviations, showing a remarkably stable flux and spectrum in VHE γ-rays. Multifrequency Very Long Baseline Array (VLBA) observations of the source confirm the extended, jet-like structure previously found in the 1.6 GHz band with the European VLBI Network and detect this component in the 4.6 and 7.3 GHz bands. The radio spectral indices of the core and the jet and the level of polarization derived from the VLBA observations are in a range typical for blazars. Data from VERITAS, Fermi-LAT, Swift-XRT, the FLWO 48″ telescope, and archival infrared and hard X-ray observations are used to construct and model the spectral energy distribution (SED) of the source with a synchrotron self-Compton model. The well-measured γ-ray peak of the SED with VERITAS and Fermi-LAT provides constraining upper limits on the source redshift. Possible contribution of secondary γ-rays from ultra-high-energy cosmic-ray-initiated electromagnetic cascades to the γ-ray emission is explored, finding that only a segment of the VHE spectrum can be accommodated with this process. A variability search is performed across X-ray and γ-ray bands. No statistically significant flux or spectral variability is detected.

AB - HESS J1943+213 is a very high energy (VHE; >100 GeV) γ-ray source in the direction of the Galactic plane. Studies exploring the classification of the source are converging toward its identification as an extreme synchrotron BL Lac object. Here we present 38 hr of VERITAS observations of HESS J1943+213 taken over 2 yr. The source is detected with a significance of ∼20 standard deviations, showing a remarkably stable flux and spectrum in VHE γ-rays. Multifrequency Very Long Baseline Array (VLBA) observations of the source confirm the extended, jet-like structure previously found in the 1.6 GHz band with the European VLBI Network and detect this component in the 4.6 and 7.3 GHz bands. The radio spectral indices of the core and the jet and the level of polarization derived from the VLBA observations are in a range typical for blazars. Data from VERITAS, Fermi-LAT, Swift-XRT, the FLWO 48″ telescope, and archival infrared and hard X-ray observations are used to construct and model the spectral energy distribution (SED) of the source with a synchrotron self-Compton model. The well-measured γ-ray peak of the SED with VERITAS and Fermi-LAT provides constraining upper limits on the source redshift. Possible contribution of secondary γ-rays from ultra-high-energy cosmic-ray-initiated electromagnetic cascades to the γ-ray emission is explored, finding that only a segment of the VHE spectrum can be accommodated with this process. A variability search is performed across X-ray and γ-ray bands. No statistically significant flux or spectral variability is detected.

KW - BL Lacertae objects: individual (HESS J1943+213, VER J1943+213)

KW - astroparticle physics

KW - galaxies: active

KW - galaxies: jets

KW - galaxies: nuclei

KW - gamma rays: galaxies

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