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Title: Possible Detection of Gamma-Rays from Epsilon Eridani

Abstract

We use the Fermi Large Area Telescope gamma-ray observatory to search for gamma-ray emission from four nearby, debris disk-hosting main-sequence stars: τ Ceti, ϵ Eridani, Fomalhaut, and Vega. For three stars (τ Ceti, Fomalhaut, and Vega), we establish upper limits that are consistent with theoretical expectations. For epsilon Eridani, we find a possible spatially coincident source with a soft energy spectrum of dN/dE ~ E -3.6. However, at this stage we are unable to rule out that this emission is due to a more extended feature in the diffuse background. In the interpretation that the emission is due to epsilon Eridani, the >100 MeV gamma-ray luminosity is ~10 27 erg s -1 ≃ 3 × 10 -7 L , which is ~10 10 times the gamma-ray luminosity from the disk of the quiet Sun. We find ≲2σ evidence of source variability over a ~7 yr timescale. In the interpretation that the gamma-ray emission is from epsilon Eridani itself, we consider two possible models: (1) cosmic-ray collisions with solid bodies in the debris disk, which extends out ~60 au from the host star, and (2) emission from the stellar activity. For the former model, assuming a total disk mass consistent withmore » infrared measurements, we find that the size distribution of bodies is steeper than expected for a collisional cascade state. Finally, if confirmed as being associated with ϵ Eridani, this would be the first indication of gamma-ray emission from the vicinity of a main-sequence star other than the Sun.« less

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [3];  [4];  [5]; ORCiD logo [6]; ORCiD logo [7]
  1. Texas A & M Univ., College Station, TX (United States). Dept. of Physics and Astronomy, Mitchell Inst. for Fundamental Physics and Astronomy
  2. Texas A & M Univ., College Station, TX (United States). Dept. of Physics and Astronomy, Mitchell Inst. for Fundamental Physics and Astronomy
  3. Stanford Univ., CA (United States). Dept. of Physics and Kavli Inst. for Particle Astrophysics and Cosmology
  4. Stanford Univ., CA (United States). Dept. of Physics and Kavli Inst. for Particle Astrophysics and Cosmology
  5. Univ. of California, Irvine, CA (United States). Dept. of Physics and Astronomy
  6. Naval Research Lab. (NRL), Washington, DC (United States). Space Science Division
  7. KTH Royal Inst. of Technology, Stockholm (Sweden); Univ. of Iceland, Reykjavik (Iceland). Science Inst.
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1532464
Grant/Contract Number:  
AC02-76SF00515
Resource Type:
Accepted Manuscript
Journal Name:
The Astrophysical Journal (Online)
Additional Journal Information:
Journal Name: The Astrophysical Journal (Online); Journal Volume: 878; Journal Issue: 1; Journal ID: ISSN 1538-4357
Publisher:
Institute of Physics (IOP)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; gamma rays: stars; protoplanetary disks

Citation Formats

Riley, Alexander H., Strigari, Louis E., Porter, Troy A., Blandford, Roger D., Murgia, Simona, Kerr, Matthew, and Jóhannesson, Guðlaugur. Possible Detection of Gamma-Rays from Epsilon Eridani. United States: N. p., 2019. Web. doi:10.3847/1538-4357/ab1a3c.
Riley, Alexander H., Strigari, Louis E., Porter, Troy A., Blandford, Roger D., Murgia, Simona, Kerr, Matthew, & Jóhannesson, Guðlaugur. Possible Detection of Gamma-Rays from Epsilon Eridani. United States. doi:10.3847/1538-4357/ab1a3c.
Riley, Alexander H., Strigari, Louis E., Porter, Troy A., Blandford, Roger D., Murgia, Simona, Kerr, Matthew, and Jóhannesson, Guðlaugur. Thu . "Possible Detection of Gamma-Rays from Epsilon Eridani". United States. doi:10.3847/1538-4357/ab1a3c.
@article{osti_1532464,
title = {Possible Detection of Gamma-Rays from Epsilon Eridani},
author = {Riley, Alexander H. and Strigari, Louis E. and Porter, Troy A. and Blandford, Roger D. and Murgia, Simona and Kerr, Matthew and Jóhannesson, Guðlaugur},
abstractNote = {We use the Fermi Large Area Telescope gamma-ray observatory to search for gamma-ray emission from four nearby, debris disk-hosting main-sequence stars: τ Ceti, ϵ Eridani, Fomalhaut, and Vega. For three stars (τ Ceti, Fomalhaut, and Vega), we establish upper limits that are consistent with theoretical expectations. For epsilon Eridani, we find a possible spatially coincident source with a soft energy spectrum of dN/dE ~ E -3.6. However, at this stage we are unable to rule out that this emission is due to a more extended feature in the diffuse background. In the interpretation that the emission is due to epsilon Eridani, the >100 MeV gamma-ray luminosity is ~1027 erg s-1 ≃ 3 × 10-7 L ⊙, which is ~1010 times the gamma-ray luminosity from the disk of the quiet Sun. We find ≲2σ evidence of source variability over a ~7 yr timescale. In the interpretation that the gamma-ray emission is from epsilon Eridani itself, we consider two possible models: (1) cosmic-ray collisions with solid bodies in the debris disk, which extends out ~60 au from the host star, and (2) emission from the stellar activity. For the former model, assuming a total disk mass consistent with infrared measurements, we find that the size distribution of bodies is steeper than expected for a collisional cascade state. Finally, if confirmed as being associated with ϵ Eridani, this would be the first indication of gamma-ray emission from the vicinity of a main-sequence star other than the Sun.},
doi = {10.3847/1538-4357/ab1a3c},
journal = {The Astrophysical Journal (Online)},
number = 1,
volume = 878,
place = {United States},
year = {2019},
month = {6}
}

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