VERITAS Discovery of Very High Energy Gamma-Ray Emission from S3 1227+25 and Multiwavelength Observations

A. Acharyya; C. B. Adams; A. Archer; P. Bangale; W. Benbow; A. Brill; J. L. Christiansen; A. J. Chromey; M. Errando; A. Falcone; Q. Feng; J. P. Finley; G. M. Foote; L. Fortson; A. Furniss; G. Gallagher; W. Hanlon; D. Hanna; O. Hervet; C. E. Hinrichs; J. Hoang; J. Holder; W. Jin; M. N. Johnson; P. Kaaret; M. Kertzman; D. Kieda; T. K. Kleiner; N. Korzoun; F. Krennrich; M. J. Lang; M. Lundy; G. Maier; C. E. McGrath; M. J. Millard; J. Millis; C. L. Mooney; P. Moriarty; R. Mukherjee; S. O'Brien; R. A. Ong; M. Pohl; E. Pueschel; J. Quinn; K. Ragan; P. T. Reynolds; D. Ribeiro; E. Roache; I. Sadeh; A. C. Sadun; L. Saha; M. Santander; G. H. Sembroski; R. Shang; M. Splettstoesser; A. K. Talluri; J. V. Tucci; V. V. Vassiliev; D. A. Williams; S. L. Wong; Talvikki Hovatta; Svetlana G. Jorstad; Sebastian Kiehlmann; Anne Lähteenmäki; Ioannis Liodakis; Alan P. Marscher; Walter Max-Moerbeck; Anthony C.S. Readhead; Rodrigo Reeves; Paul S. Smith; Merja Tornikoski

doi:10.3847/1538-4357/acd2d0

VERITAS Discovery of Very High Energy Gamma-Ray Emission from S3 1227+25 and Multiwavelength Observations

A. Acharyya, C. B. Adams, A. Archer, P. Bangale, W. Benbow, A. Brill, J. L. Christiansen, A. J. Chromey, M. Errando, A. Falcone, Q. Feng, J. P. Finley, G. M. Foote, L. Fortson, A. Furniss, G. Gallagher, W. Hanlon, D. Hanna, O. Hervet, C. E. HinrichsJ. Hoang, J. Holder, W. Jin, M. N. Johnson, P. Kaaret, M. Kertzman, D. Kieda, T. K. Kleiner, N. Korzoun, F. Krennrich, M. J. Lang, M. Lundy, G. Maier, C. E. McGrath, M. J. Millard, J. Millis, C. L. Mooney, P. Moriarty, R. Mukherjee, S. O'Brien, R. A. Ong, M. Pohl, E. Pueschel, J. Quinn, K. Ragan, P. T. Reynolds, D. Ribeiro, E. Roache, I. Sadeh, A. C. Sadun, L. Saha, M. Santander, G. H. Sembroski, R. Shang, M. Splettstoesser, A. K. Talluri, J. V. Tucci, V. V. Vassiliev, D. A. Williams, S. L. Wong, Talvikki Hovatta, Svetlana G. Jorstad, Sebastian Kiehlmann, Anne Lähteenmäki, Ioannis Liodakis, Alan P. Marscher, Walter Max-Moerbeck, Anthony C.S. Readhead, Rodrigo Reeves, Paul S. Smith, Merja Tornikoski

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Abstract

We report the detection of very high energy gamma-ray emission from the blazar S3 1227+25 (VER J1230+253) with the Very Energetic Radiation Imaging Telescope Array System (VERITAS). VERITAS observations of the source were triggered by the detection of a hard-spectrum GeV flare on 2015 May 15 with the Fermi-Large Area Telescope (LAT). A combined 5 hr VERITAS exposure on May 16 and 18 resulted in a strong 13? detection with a differential photon spectral index, "= 3.8 ± 0.4, and a flux level at 9% of the Crab Nebula above 120 GeV. This also triggered target-of-opportunity observations with Swift, optical photometry, polarimetry, and radio measurements, also presented in this work, in addition to the VERITAS and Fermi-LAT data. A temporal analysis of the gamma-ray flux during this period finds evidence of a shortest variability timescale of ? obs = 6.2 ± 0.9 hr, indicating emission from compact regions within the jet, and the combined gamma-ray spectrum shows no strong evidence of a spectral cutoff. An investigation into correlations between the multiwavelength observations found evidence of optical and gamma-ray correlations, suggesting a single-zone model of emission. Finally, the multiwavelength spectral energy distribution is well described by a simple one-zone leptonic synchrotron self-Compton radiation model.

Original language	English (US)
Article number	152
Journal	Astrophysical Journal
Volume	950
Issue number	2
DOIs	https://doi.org/10.3847/1538-4357/acd2d0
State	Published - Jun 1 2023
Externally published	Yes

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Publisher Copyright:
© 2023. The Author(s). Published by the American Astronomical Society.

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Acharyya, A., Adams, C. B., Archer, A., Bangale, P., Benbow, W., Brill, A., Christiansen, J. L., Chromey, A. J., Errando, M., Falcone, A., Feng, Q., Finley, J. P., Foote, G. M., Fortson, L., Furniss, A., Gallagher, G., Hanlon, W., Hanna, D., Hervet, O., ... Tornikoski, M. (2023). VERITAS Discovery of Very High Energy Gamma-Ray Emission from S3 1227+25 and Multiwavelength Observations. Astrophysical Journal, 950(2), Article 152. https://doi.org/10.3847/1538-4357/acd2d0

Acharyya, A, Adams, CB, Archer, A, Bangale, P, Benbow, W, Brill, A, Christiansen, JL, Chromey, AJ, Errando, M, Falcone, A, Feng, Q, Finley, JP, Foote, GM, Fortson, L, Furniss, A, Gallagher, G, Hanlon, W, Hanna, D, Hervet, O, Hinrichs, CE, Hoang, J, Holder, J, Jin, W, Johnson, MN, Kaaret, P, Kertzman, M, Kieda, D, Kleiner, TK, Korzoun, N, Krennrich, F, Lang, MJ, Lundy, M, Maier, G, McGrath, CE, Millard, MJ, Millis, J, Mooney, CL, Moriarty, P, Mukherjee, R, O'Brien, S, Ong, RA, Pohl, M, Pueschel, E, Quinn, J, Ragan, K, Reynolds, PT, Ribeiro, D, Roache, E, Sadeh, I, Sadun, AC, Saha, L, Santander, M, Sembroski, GH, Shang, R, Splettstoesser, M, Talluri, AK, Tucci, JV, Vassiliev, VV, Williams, DA, Wong, SL, Hovatta, T, Jorstad, SG, Kiehlmann, S, Lähteenmäki, A, Liodakis, I, Marscher, AP, Max-Moerbeck, W, Readhead, ACS, Reeves, R, Smith, PS & Tornikoski, M 2023, 'VERITAS Discovery of Very High Energy Gamma-Ray Emission from S3 1227+25 and Multiwavelength Observations', Astrophysical Journal, vol. 950, no. 2, 152. https://doi.org/10.3847/1538-4357/acd2d0

@article{dc6697596a7d42339fe5c3e9132e3b9d,

title = "VERITAS Discovery of Very High Energy Gamma-Ray Emission from S3 1227+25 and Multiwavelength Observations",

abstract = "We report the detection of very high energy gamma-ray emission from the blazar S3 1227+25 (VER J1230+253) with the Very Energetic Radiation Imaging Telescope Array System (VERITAS). VERITAS observations of the source were triggered by the detection of a hard-spectrum GeV flare on 2015 May 15 with the Fermi-Large Area Telescope (LAT). A combined 5 hr VERITAS exposure on May 16 and 18 resulted in a strong 13? detection with a differential photon spectral index, {"}= 3.8 ± 0.4, and a flux level at 9% of the Crab Nebula above 120 GeV. This also triggered target-of-opportunity observations with Swift, optical photometry, polarimetry, and radio measurements, also presented in this work, in addition to the VERITAS and Fermi-LAT data. A temporal analysis of the gamma-ray flux during this period finds evidence of a shortest variability timescale of ? obs = 6.2 ± 0.9 hr, indicating emission from compact regions within the jet, and the combined gamma-ray spectrum shows no strong evidence of a spectral cutoff. An investigation into correlations between the multiwavelength observations found evidence of optical and gamma-ray correlations, suggesting a single-zone model of emission. Finally, the multiwavelength spectral energy distribution is well described by a simple one-zone leptonic synchrotron self-Compton radiation model.",

author = "A. Acharyya and Adams, {C. B.} and A. Archer and P. Bangale and W. Benbow and A. Brill and Christiansen, {J. L.} and Chromey, {A. J.} and M. Errando and A. Falcone and Q. Feng and Finley, {J. P.} and Foote, {G. M.} and L. Fortson and A. Furniss and G. Gallagher and W. Hanlon and D. Hanna and O. Hervet and Hinrichs, {C. E.} and J. Hoang and J. Holder and W. Jin and Johnson, {M. N.} and P. Kaaret and M. Kertzman and D. Kieda and Kleiner, {T. K.} and N. Korzoun and F. Krennrich and Lang, {M. J.} and M. Lundy and G. Maier and McGrath, {C. E.} and Millard, {M. J.} and J. Millis and Mooney, {C. L.} and P. Moriarty and R. Mukherjee and S. O'Brien and Ong, {R. A.} and M. Pohl and E. Pueschel and J. Quinn and K. Ragan and Reynolds, {P. T.} and D. Ribeiro and E. Roache and I. Sadeh and Sadun, {A. C.} and L. Saha and M. Santander and Sembroski, {G. H.} and R. Shang and M. Splettstoesser and Talluri, {A. K.} and Tucci, {J. V.} and Vassiliev, {V. V.} and Williams, {D. A.} and Wong, {S. L.} and Talvikki Hovatta and Jorstad, {Svetlana G.} and Sebastian Kiehlmann and Anne L{\"a}hteenm{\"a}ki and Ioannis Liodakis and Marscher, {Alan P.} and Walter Max-Moerbeck and Readhead, {Anthony C.S.} and Rodrigo Reeves and Smith, {Paul S.} and Merja Tornikoski",

note = "Publisher Copyright: {\textcopyright} 2023. The Author(s). Published by the American Astronomical Society.",

year = "2023",

month = jun,

day = "1",

doi = "10.3847/1538-4357/acd2d0",

language = "English (US)",

volume = "950",

journal = "Astrophysical Journal",

issn = "0004-637X",

publisher = "IOP Publishing Ltd.",

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TY - JOUR

T1 - VERITAS Discovery of Very High Energy Gamma-Ray Emission from S3 1227+25 and Multiwavelength Observations

AU - Acharyya, A.

AU - Adams, C. B.

AU - Archer, A.

AU - Bangale, P.

AU - Benbow, W.

AU - Brill, A.

AU - Christiansen, J. L.

AU - Chromey, A. J.

AU - Errando, M.

AU - Falcone, A.

AU - Feng, Q.

AU - Finley, J. P.

AU - Foote, G. M.

AU - Fortson, L.

AU - Furniss, A.

AU - Gallagher, G.

AU - Hanlon, W.

AU - Hanna, D.

AU - Hervet, O.

AU - Hinrichs, C. E.

AU - Hoang, J.

AU - Holder, J.

AU - Jin, W.

AU - Johnson, M. N.

AU - Kaaret, P.

AU - Kertzman, M.

AU - Kieda, D.

AU - Kleiner, T. K.

AU - Korzoun, N.

AU - Krennrich, F.

AU - Lang, M. J.

AU - Lundy, M.

AU - Maier, G.

AU - McGrath, C. E.

AU - Millard, M. J.

AU - Millis, J.

AU - Mooney, C. L.

AU - Moriarty, P.

AU - Mukherjee, R.

AU - O'Brien, S.

AU - Ong, R. A.

AU - Pohl, M.

AU - Pueschel, E.

AU - Quinn, J.

AU - Ragan, K.

AU - Reynolds, P. T.

AU - Ribeiro, D.

AU - Roache, E.

AU - Sadeh, I.

AU - Sadun, A. C.

AU - Saha, L.

AU - Santander, M.

AU - Sembroski, G. H.

AU - Shang, R.

AU - Splettstoesser, M.

AU - Talluri, A. K.

AU - Tucci, J. V.

AU - Vassiliev, V. V.

AU - Williams, D. A.

AU - Wong, S. L.

AU - Hovatta, Talvikki

AU - Jorstad, Svetlana G.

AU - Kiehlmann, Sebastian

AU - Lähteenmäki, Anne

AU - Liodakis, Ioannis

AU - Marscher, Alan P.

AU - Max-Moerbeck, Walter

AU - Readhead, Anthony C.S.

AU - Reeves, Rodrigo

AU - Smith, Paul S.

AU - Tornikoski, Merja

PY - 2023/6/1

Y1 - 2023/6/1

N2 - We report the detection of very high energy gamma-ray emission from the blazar S3 1227+25 (VER J1230+253) with the Very Energetic Radiation Imaging Telescope Array System (VERITAS). VERITAS observations of the source were triggered by the detection of a hard-spectrum GeV flare on 2015 May 15 with the Fermi-Large Area Telescope (LAT). A combined 5 hr VERITAS exposure on May 16 and 18 resulted in a strong 13? detection with a differential photon spectral index, "= 3.8 ± 0.4, and a flux level at 9% of the Crab Nebula above 120 GeV. This also triggered target-of-opportunity observations with Swift, optical photometry, polarimetry, and radio measurements, also presented in this work, in addition to the VERITAS and Fermi-LAT data. A temporal analysis of the gamma-ray flux during this period finds evidence of a shortest variability timescale of ? obs = 6.2 ± 0.9 hr, indicating emission from compact regions within the jet, and the combined gamma-ray spectrum shows no strong evidence of a spectral cutoff. An investigation into correlations between the multiwavelength observations found evidence of optical and gamma-ray correlations, suggesting a single-zone model of emission. Finally, the multiwavelength spectral energy distribution is well described by a simple one-zone leptonic synchrotron self-Compton radiation model.

AB - We report the detection of very high energy gamma-ray emission from the blazar S3 1227+25 (VER J1230+253) with the Very Energetic Radiation Imaging Telescope Array System (VERITAS). VERITAS observations of the source were triggered by the detection of a hard-spectrum GeV flare on 2015 May 15 with the Fermi-Large Area Telescope (LAT). A combined 5 hr VERITAS exposure on May 16 and 18 resulted in a strong 13? detection with a differential photon spectral index, "= 3.8 ± 0.4, and a flux level at 9% of the Crab Nebula above 120 GeV. This also triggered target-of-opportunity observations with Swift, optical photometry, polarimetry, and radio measurements, also presented in this work, in addition to the VERITAS and Fermi-LAT data. A temporal analysis of the gamma-ray flux during this period finds evidence of a shortest variability timescale of ? obs = 6.2 ± 0.9 hr, indicating emission from compact regions within the jet, and the combined gamma-ray spectrum shows no strong evidence of a spectral cutoff. An investigation into correlations between the multiwavelength observations found evidence of optical and gamma-ray correlations, suggesting a single-zone model of emission. Finally, the multiwavelength spectral energy distribution is well described by a simple one-zone leptonic synchrotron self-Compton radiation model.

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UR - http://www.scopus.com/inward/citedby.url?scp=85164598425&partnerID=8YFLogxK

U2 - 10.3847/1538-4357/acd2d0

DO - 10.3847/1538-4357/acd2d0

M3 - Article

AN - SCOPUS:85164598425

SN - 0004-637X

VL - 950

JO - Astrophysical Journal

JF - Astrophysical Journal

IS - 2

M1 - 152

ER -

VERITAS Discovery of Very High Energy Gamma-Ray Emission from S3 1227+25 and Multiwavelength Observations

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