Constraints on axionlike particles from VERITAS observations of a flaring radio galaxy in the Perseus cluster

Axion-like particles (ALPs) are hypothetical particles that emerge in numerous theoretical extensions to the Standard Model. Their coupling to electromagnetic field implies that ALPs would mix with photons in the presence of external magnetic fields. As ALP phenomenology is governed by the mass and strength of its coupling, there is a subset of this parameter space in which this mixing would be expected to leave an imprint on the spectra of TeV <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mi>γ</a:mi> </a:math> -ray sources. In 2017, the VERITAS <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:mi>γ</c:mi> </c:math> -ray observatory recorded the second day of a dramatic flare of the radio galaxy NGC 1275, embedded at the center of the Perseus galaxy cluster. This serendipitous locale provides a spatially-extended magnetic field of strength <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:mi mathvariant="script">O</e:mi> <e:mrow> <e:mo stretchy="false">(</e:mo> <e:mn>10</e:mn> <e:mtext> </e:mtext> <e:mtext> </e:mtext> <e:mrow> <e:mi mathvariant="normal">μ</e:mi> <e:mi mathvariant="normal">G</e:mi> </e:mrow> <e:mo stretchy="false">)</e:mo> </e:mrow> </e:math> through which escaping photons traverse, making it an excellent target to study ALPs. We analyze the VERITAS data of NGC 1275’s 2017 flare with the gammapy analysis package. Extensive fitting and modeling are performed to ultimately conduct a likelihood analysis used to search for any evidence of a preference for ALPs and to explore the confidence with which constraints can be set. We adopt the <l:math xmlns:l="http://www.w3.org/1998/Math/MathML" display="inline"> <l:msub> <l:mi>CL</l:mi> <l:mi mathvariant="normal">s</l:mi> </l:msub> </l:math> method for this study for its conservative approach to setting limits in regimes where the search has limited sensitivity. No evidence for the existence of ALPs is found, and no combination of mass and coupling strength can be excluded at or above 95% confidence level. We provide a map showing the strength of our exclusions in the mass and coupling parameter space. The strongest exclusions are found in the mass range <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"> <o:mn>2</o:mn> <o:mo>×</o:mo> <o:msup> <o:mn>10</o:mn> <o:mrow> <o:mo>−</o:mo> <o:mn>7</o:mn> </o:mrow> </o:msup> <o:mtext> </o:mtext> <o:mtext> </o:mtext> <o:mi>eV</o:mi> <o:mo>≲</o:mo> <o:msub> <o:mi>m</o:mi> <o:mi>a</o:mi> </o:msub> <o:mo>≲</o:mo> <o:mn>4</o:mn> <o:mo>×</o:mo> <o:msup> <o:mn>10</o:mn> <o:mrow> <o:mo>−</o:mo> <o:mn>7</o:mn> </o:mrow> </o:msup> <o:mtext> </o:mtext> <o:mtext> </o:mtext> <o:mi>eV</o:mi> </o:math> and at the coupling strength of <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" display="inline"> <q:msub> <q:mi>g</q:mi> <q:mrow> <q:mi>a</q:mi> <q:mi>γ</q:mi> </q:mrow> </q:msub> <q:mo>≳</q:mo> <q:mn>3</q:mn> <q:mrow> <q:mo>×</q:mo> <q:msup> <q:mn>10</q:mn> <q:mrow> <q:mo>−</q:mo> <q:mn>11</q:mn> </q:mrow> </q:msup> <q:mtext> </q:mtext> <q:mtext> </q:mtext> <q:msup> <q:mrow> <q:mi>GeV</q:mi> </q:mrow> <q:mrow> <q:mo>−</q:mo> <q:mn>1</q:mn> </q:mrow> </q:msup> </q:mrow> </q:math> up to 80% confidence level, which are consistent with previous studies. We find the <s:math xmlns:s="http://www.w3.org/1998/Math/MathML" display="inline"> <s:msub> <s:mi>CL</s:mi> <s:mi mathvariant="normal">s</s:mi> </s:msub> </s:math> to be a trustworthy approach, and advocate for its continued usage in future studies. We note that many of the limitations contributing to the limited sensitivity seen by VERITAS in this study will be improved with next-generation <v:math xmlns:v="http://www.w3.org/1998/Math/MathML" display="inline"> <v:mi>γ</v:mi> </v:math> -ray instruments, such as the Cherenkov Telescope Array Observatory.

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Physical review. D/Physical review. D.
Published
2025-11-24
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https://doi.org/10.1103/jydc-npy6
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1
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Dark Matter and Cosmic Phenomena
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article
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article

Constraints on axionlike particles from VERITAS observations of a flaring radio galaxy in the Perseus cluster

R. Shang, A. J. Chromey, S. Feldman, W. Hanlon et al.
1 citations
Physical review. D/Physical review. D.
Dark Matter and Cosmic Phenomena
1.87
article

Constraints on axionlike particles from VERITAS observations of a flaring radio galaxy in the Perseus cluster

R. Shang, A. J. Chromey, S. Feldman, W. Hanlon, A. K. Talluri, D. Tak, T. K. Kleiner, A. K. Pandey, R. Mukherjee, P. Rabinowitz, Zoë A. Hughes, M. Kherlakian, Jooyun Woo, C. B. Adams, L. Fortson, N. Korzoun, M. J. Lang, M. Lundy, E. Pueschel, R. A. Ong, W. Benbow, J. V. Tucci, O. Hervet, Wei Ning, I. Sadeh, D. Kieda, D. Ribeiro, Janeth Valverde, J. Quinn, S. Kundu, A. Furniss, P. Bangale, J. T. Bartkoske, Y. Chen, P. Moriarty, C. E. Hinrichs, Q. Feng, T. B. Humensky, T. Yoshikoshi, S. Kumar, J. Holder, P. Kaaret, K. Ragan, C. B. Rulten, M. Errando, M. Meyer, D. A. Williams, L. Saha, P. T. Reynolds, M. Iskakova, A. Duerr, M. Escobar Godoy, S. Filbert, W. Jin, S. L. Wong, Juan Escudero, J. L. Christiansen, M. Pohl, F. Krennrich, G. H. Sembroski, A. Archer, M. Kertzman, M. Santander, V. V. Vassiliev, E. Roache
article en
1 citations

Abstract

Axion-like particles (ALPs) are hypothetical particles that emerge in numerous theoretical extensions to the Standard Model. Their coupling to electromagnetic field implies that ALPs would mix with photons in the presence of external magnetic fields. As ALP phenomenology is governed by the mass and strength of its coupling, there is a subset of this parameter space in which this mixing would be expected to leave an imprint on the spectra of TeV <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mi>γ</a:mi> </a:math> -ray sources. In 2017, the VERITAS <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:mi>γ</c:mi> </c:math> -ray observatory recorded the second day of a dramatic flare of the radio galaxy NGC 1275, embedded at the center of the Perseus galaxy cluster. This serendipitous locale provides a spatially-extended magnetic field of strength <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:mi mathvariant="script">O</e:mi> <e:mrow> <e:mo stretchy="false">(</e:mo> <e:mn>10</e:mn> <e:mtext> </e:mtext> <e:mtext> </e:mtext> <e:mrow> <e:mi mathvariant="normal">μ</e:mi> <e:mi mathvariant="normal">G</e:mi> </e:mrow> <e:mo stretchy="false">)</e:mo> </e:mrow> </e:math> through which escaping photons traverse, making it an excellent target to study ALPs. We analyze the VERITAS data of NGC 1275’s 2017 flare with the gammapy analysis package. Extensive fitting and modeling are performed to ultimately conduct a likelihood analysis used to search for any evidence of a preference for ALPs and to explore the confidence with which constraints can be set. We adopt the <l:math xmlns:l="http://www.w3.org/1998/Math/MathML" display="inline"> <l:msub> <l:mi>CL</l:mi> <l:mi mathvariant="normal">s</l:mi> </l:msub> </l:math> method for this study for its conservative approach to setting limits in regimes where the search has limited sensitivity. No evidence for the existence of ALPs is found, and no combination of mass and coupling strength can be excluded at or above 95% confidence level. We provide a map showing the strength of our exclusions in the mass and coupling parameter space. The strongest exclusions are found in the mass range <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"> <o:mn>2</o:mn> <o:mo>×</o:mo> <o:msup> <o:mn>10</o:mn> <o:mrow> <o:mo>−</o:mo> <o:mn>7</o:mn> </o:mrow> </o:msup> <o:mtext> </o:mtext> <o:mtext> </o:mtext> <o:mi>eV</o:mi> <o:mo>≲</o:mo> <o:msub> <o:mi>m</o:mi> <o:mi>a</o:mi> </o:msub> <o:mo>≲</o:mo> <o:mn>4</o:mn> <o:mo>×</o:mo> <o:msup> <o:mn>10</o:mn> <o:mrow> <o:mo>−</o:mo> <o:mn>7</o:mn> </o:mrow> </o:msup> <o:mtext> </o:mtext> <o:mtext> </o:mtext> <o:mi>eV</o:mi> </o:math> and at the coupling strength of <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" display="inline"> <q:msub> <q:mi>g</q:mi> <q:mrow> <q:mi>a</q:mi> <q:mi>γ</q:mi> </q:mrow> </q:msub> <q:mo>≳</q:mo> <q:mn>3</q:mn> <q:mrow> <q:mo>×</q:mo> <q:msup> <q:mn>10</q:mn> <q:mrow> <q:mo>−</q:mo> <q:mn>11</q:mn> </q:mrow> </q:msup> <q:mtext> </q:mtext> <q:mtext> </q:mtext> <q:msup> <q:mrow> <q:mi>GeV</q:mi> </q:mrow> <q:mrow> <q:mo>−</q:mo> <q:mn>1</q:mn> </q:mrow> </q:msup> </q:mrow> </q:math> up to 80% confidence level, which are consistent with previous studies. We find the <s:math xmlns:s="http://www.w3.org/1998/Math/MathML" display="inline"> <s:msub> <s:mi>CL</s:mi> <s:mi mathvariant="normal">s</s:mi> </s:msub> </s:math> to be a trustworthy approach, and advocate for its continued usage in future studies. We note that many of the limitations contributing to the limited sensitivity seen by VERITAS in this study will be improved with next-generation <v:math xmlns:v="http://www.w3.org/1998/Math/MathML" display="inline"> <v:mi>γ</v:mi> </v:math> -ray instruments, such as the Cherenkov Telescope Array Observatory.

Physical review. D/Physical review. D.Vol. 112(10)
University College Dublin (IE), DePauw University (US), University of Iowa (US), University of Minnesota (US), Seoul National University (KR), California Polytechnic State University (US), University of California, Los Angeles (US), University of Alabama (US), Iowa State University (US), University of Potsdam (DE), University of Southern Denmark (DK), University of California, Santa Cruz (US), Ollscoil na Gaillimhe – University of Galway (IE), Durham University (GB), Washington University in St. Louis (US), Purdue University West Lafayette (US), University of Utah (US), University of Minnesota System (US), University of California System (US), Munster Technological University (IE), Center for Astrophysics Harvard & Smithsonian (US), Indiana University Indianapolis (US), McGill University (CA), Indiana University – Purdue University Indianapolis (US), University of Maryland, College Park (US), The University of Tokyo (JP), Columbia University (US), University of Maryland, Baltimore County (US), University of Delaware (US), Ruhr University Bochum (DE), Barnard College (US)
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