{
  "id": "1805.08192",
  "version": "v1",
  "published": "2018-05-21T17:23:46.000Z",
  "updated": "2018-05-21T17:23:46.000Z",
  "title": "Spitzer Space Telescope Infrared Observations of the Binary Neutron Star Merger GW170817",
  "authors": [
    "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",
    "B. D. Metzger",
    "M. Nicholl",
    "P. K. G. Williams"
  ],
  "comment": "6 pages, 2 figures, submitted to ApJL",
  "categories": [
    "astro-ph.HE"
  ],
  "abstract": "We present Spitzer Space Telescope 3.6 and 4.5 micron 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 micron 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 micron to a 3-sigma 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-IR 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 LIGO/Virgo Observing Run 3) and the James Webb Space Telescope (in LIGO/Virgo Observing Run 4 and beyond).",
  "revisions": [
    {
      "version": "v1",
      "updated": "2018-05-21T17:23:46.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "binary neutron star merger gw170817",
      "spitzer space telescope infrared observations",
      "ab mag"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 6,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}