Spitzer Space Telescope Infrared Observations of the Binary Neutron Star Merger GW170817

V. A. Villar, P. S. Cowperthwaite, E. Berger, P. K. Blanchard, S. Gomez, K. D. Alexander, R. Margutti, R. Chornock, T. Eftekhari, G. G. Fazio, J. Guillochon, J. L. Hora, M. Nicholl, P. K.G. Williams

Research output: Contribution to journalArticle

11 Scopus citations

Abstract

We present Spitzer Space Telescope 3.6 and 4.5 μm observations of the binary neutron star merger GW170817 at 43, 74, and 264 days post-merger. Using the final observation as a template, we uncover a source at the position of GW170817 at 4.5 μm with a brightness of 22.9 0.3 AB mag at 43 days and 23.8 0.3 AB mag at 74 days (the uncertainty is dominated by systematics from the image subtraction); no obvious source is detected at 3.6 μm to a 3σ limit of >23.3 AB mag in both epochs. The measured brightness is dimmer by a factor of about 2-3 times compared to our previously published kilonova model, which is based on UV, optical, and near-infrared data at ≲30 days. However, the observed fading rate and color (m 3.6-m 4.5 0 AB mag) are consistent with our model. We suggest that the discrepancy is likely due to a transition to the nebular phase, or a reduced thermalization efficiency at such late time. Using the Spitzer data as a guide, we briefly discuss the prospects of observing future binary neutron star mergers with Spitzer (in the Laser Interferometer Gravitational-Wave Observatory (LIGO)/Virgo Observing Run 3) and the James Webb Space Telescope (in LIGO/Virgo Observing Run 4 and beyond).

Original languageEnglish (US)
Article numberL11
JournalAstrophysical Journal Letters
Volume862
Issue number1
DOIs
StatePublished - Jul 20 2018

Keywords

  • gravitational waves
  • infrared: general
  • stars: neutron

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Villar, V. A., Cowperthwaite, P. S., Berger, E., Blanchard, P. K., Gomez, S., Alexander, K. D., Margutti, R., Chornock, R., Eftekhari, T., Fazio, G. G., Guillochon, J., Hora, J. L., Nicholl, M., & Williams, P. K. G. (2018). Spitzer Space Telescope Infrared Observations of the Binary Neutron Star Merger GW170817. Astrophysical Journal Letters, 862(1), [L11]. https://doi.org/10.3847/2041-8213/aad281