The Panchromatic Afterglow of GW170817: The full uniform dataset, modeling, comparison with previous results and implications

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Abstract

We present the full panchromatic afterglow light curve data of GW170817, including new radio data as well as archival optical and X-ray data, between 0.5 and 940 days post-merger. By compiling all
archival data, and reprocessing a subset of it, we have evaluated the impact of differences in data processing or flux determination methods used by different groups, and attempted to mitigate these
differences to provide a more uniform dataset. Simple power-law fits to the uniform afterglow light curve indicate at 0.86±0.04 rise, at −1.92±0.12 decline, and a peak occurring at 155±4 days. The afterglow is optically thin throughout its evolution, consistent with a single spectral index (−0.584±0.002) across all epochs. This gives a precise and updated estimate of the electron power-law index, p = 2.168±0.004.
By studying the diffuse X-ray emission from the host galaxy, we place a conservative upper limit on the hot ionized ISM density, <0.01 cm−3, consistent with previous afterglow studies. Using the late-time afterglow data we rule out any long-lived neutron star remnant having magnetic field strength between 1010.4 G and 1016 G. Our fits to the afterglow data using an analytical model that includes VLBI proper motion from Mooley et al., and a structured jet model that ignores the proper motion, indicates that the proper motion measurement needs to be considered while seeking an accurate estimate of the viewing angle.
Keywords: gravitational waves — stars: neutron — radio continuum: stars — X-rays: stars — infrared: stars

Bibliographical metadata

Original languageEnglish
JournalAstrophysical Journal
Publication statusAccepted/In press - 23 Aug 2021