What determines the γ-ray luminosities of classical novae?

ABSTRACT Classical novae in the Milky Way have now been well-established as high-energy GeV $\gamma$-ray sources. In novae with main-sequence companions, this emission is believed to result from shocks internal to the nova ejecta, as a later fast wind collides with an earlier slow outflow. To test this model and constrain the $\gamma$-ray production mechanism, we present a systematic study of a sample of recent Galactic novae, comparing their $\gamma$-ray properties ($\gamma$-ray luminosity and duration) with their outflow velocities, peak V-band magnitudes, and the decline times of their optical light curves ($t_2$). We uniformly estimate distances in a luminosity-independent manner, using spectroscopic reddening estimates combined with three-dimensional Galactic dust maps. Across our sample, $\gamma$-ray luminosities ($>$100 MeV) vary by three orders of magnitude, spanning $10^{34}{{-}}10^{37}$ erg s$^{-1}$. Novae with larger velocity of the fast outflow (or larger differential between the fast and slow outflow) have larger $\gamma$-ray luminosities, but are detectable for a shorter duration. The optical and $\gamma$-ray fluxes are correlated, consistent with substantial thermal emission in the optical from shock-heated gas. Across six novae with $\gamma$-ray and infrared light curves, evidence for dust formation appears soon after the end of the detected $\gamma$-ray emission. Dusty and non-dusty novae appear to have similar $\gamma$-ray luminosities, though novae that have more material processed by the shocks may be more likely to form dust. We find that the properties of the $\gamma$-ray emission in novae depend heavily on the ejecta properties, and are consistent with expectations for internal shocks.

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Publication Details

Journal
Monthly Notices of the Royal Astronomical Society
Published
2025-12-26
DOI
https://doi.org/10.1093/mnras/staf2270
Primary Topic
Astrophysical Phenomena and Observations
Type
article
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0.00

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article

What determines the γ-ray luminosities of classical novae?

Peter Craig, L. A. G. Monard, Jhih-Ling Fan, O. Garde et al.
Monthly Notices of the Royal Astronomical Society
Astrophysical Phenomena and Observations
article

What determines the γ-ray luminosities of classical novae?

Peter Craig, L. A. G. Monard, Jhih-Ling Fan, O. Garde, Jay Strader, E. Aydi, A. Kawash, Joan Guarro Fló, F. Walter, Brian D. Metzger, C. Boussin, Kwan-Lok Li, D. A. H. Buckley, Luca Izzo, Laura B. Chomiuk, S. Charbonnel, Evangelia Tremou, N. Thomas, Arash Bahramian, K. V. Sokolovsky, F. -J. Hambsch, Justin Dee Linford, Koji Mukai, Ashley Stone, Konstantin Belyakov, J L Sokoloski, Marina Orio, Atticus Chong
article en

Abstract

ABSTRACT Classical novae in the Milky Way have now been well-established as high-energy GeV $\gamma$-ray sources. In novae with main-sequence companions, this emission is believed to result from shocks internal to the nova ejecta, as a later fast wind collides with an earlier slow outflow. To test this model and constrain the $\gamma$-ray production mechanism, we present a systematic study of a sample of recent Galactic novae, comparing their $\gamma$-ray properties ($\gamma$-ray luminosity and duration) with their outflow velocities, peak V-band magnitudes, and the decline times of their optical light curves ($t_2$). We uniformly estimate distances in a luminosity-independent manner, using spectroscopic reddening estimates combined with three-dimensional Galactic dust maps. Across our sample, $\gamma$-ray luminosities ($>$100 MeV) vary by three orders of magnitude, spanning $10^{34}{{-}}10^{37}$ erg s$^{-1}$. Novae with larger velocity of the fast outflow (or larger differential between the fast and slow outflow) have larger $\gamma$-ray luminosities, but are detectable for a shorter duration. The optical and $\gamma$-ray fluxes are correlated, consistent with substantial thermal emission in the optical from shock-heated gas. Across six novae with $\gamma$-ray and infrared light curves, evidence for dust formation appears soon after the end of the detected $\gamma$-ray emission. Dusty and non-dusty novae appear to have similar $\gamma$-ray luminosities, though novae that have more material processed by the shocks may be more likely to form dust. We find that the properties of the $\gamma$-ray emission in novae depend heavily on the ejecta properties, and are consistent with expectations for internal shocks.

Monthly Notices of the Royal Astronomical SocietyVol. 546(3)
West Virginia University (US), Texas Tech University (US), University of Illinois Urbana-Champaign (US), American Association of Variable Star Observers (US), National Radio Astronomy Observatory (US), Geophysical Survey (RU), Astronomical Observatory of Capodimonte (IT), Krankenhaus Düren (DE), Parallax Research (United States) (US), Bundesdeutsche Arbeitsgemeinschaft für Veränderliche Sterne (DE), South African Radio Astronomy Observatory (ZA), Casa di cura Pierangeli (IT), Astrophysics Science Division (US), Time Domain (United States) (US), Flatiron Health (United States) (US), Hôpital de la Tour (CH), Osservatorio Astronomico di Padova (IT), International Centre for Radio Astronomy Research (AU), Bronberg Observatory (ZA), Stichting tot Steun VCVGZ (NL), United States Air Force Academy (US), Flatiron Institute (US), Stony Brook University (US), Columbia University (US), University of Maryland, Baltimore County (US), Michigan State University (US), National Cheng Kung University (TW)
National Science Foundation, National Aeronautics and Space Administration, Gordon and Betty Moore Foundation, Ohio State University, Michigan State University, Villum Fonden, Space Telescope Science Institute, Flatiron Health, National Research Foundation, Nuclear Safety and Security Commission, Ministerstwo Edukacji i Nauki, Ministério da Ciência, Tecnologia, Inovações e Comunicações, College of Engineering, Michigan State University, University of North Carolina at Chapel Hill, Center for Cosmology and Astroparticle Physics, Ohio State University
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