The optical afterglow of the short gamma-ray burst associated with GW170817

By J. Lyman, G. Lamb, A. Levan, Ilya Mandel, N. Tanvir, S. Kobayashi, B. Gompertz, J. Hjorth, A. Fruchter, T. Kangas and 26 more. Nature Astronomy, 2018

212 citations recorded by the source corpus.

The binary neutron star merger GW170817 was the first multi-messenger event observed in both gravitational and electromagnetic waves1,2. The electromagnetic signal began approximately two seconds post-merger with a weak, short burst of gamma rays3, which was followed over the next hours and days by the ultraviolet, optical and near-infrared emission from a radioactively powered kilonova4–11. Later, non-thermal rising X-ray and radio emission was observed12,13. The low luminosity of the gamma rays and the rising non-thermal flux from the source at late times could indicate that we are outside the opening angle of the beamed relativistic jet. Alternatively, the emission could be arising from a cocoon of material formed from the interaction between a jet and the merger ejecta13–15. Here we present late-time optical detections and deep near-infrared limits on the emission from GW170817 at 110 days post-merger. Our new observations are at odds with expectations of late-time emission from kilonova models, being too bright and blue16,17. Instead, the emission arises from the interaction between the relativistic ejecta of GW170817 and the interstellar medium. We show that this emission matches the expectations of a Gaussian-structured relativistic jet, which would have launched a high-luminosity, short gamma-ray burst to an aligned observer. However, other jet structure or cocoon models can also match current data—the future evolution of the afterglow will directly distinguish the origin of the emission. Late-time optical and near-infrared observations of the binary neutron star merger GW170817 are at odds with kilonova models but match a Gaussian-structured relativistic jet, which would have launched a high-luminosity short gamma-ray burst to an aligned observer.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/55d5138c638a67d7294a0268557f2dc8fad5bdff

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Citations in the corpus

The outflow structure of GW170817 from late-time broad-band observations (2018, background): “The broadband spectrum, from radio to optical (Lyman et al. 2018) to hard X-rays (Figure 2), can be fit with a simple power-law model with spectral index β=0.575±0.010 and no intrinsic absorption.”
Rates of compact object coalescences (2021, background): “…(Abbott et al., 2017a), followed by the observation of a kilonova (Abbott et al., 2017c; Kasen et al., 2017; Metzger, 2019), and finally a broad-spectrum (radio through optical to X-ray) afterglow (Mooley et al., 2018; Lyman et al., 2018; Troja et al., 2017) following the NS-NS merger GW17017.”
The evolution of the X-ray afterglow emission of GW 170817 / GRB 170817A in XMM-Newton observations (2018, methodology): “The X-ray spectrum expected if the cooling frequency has transitioned below the X-ray band (between the earlier Chandra observation and our XMM-Newton epoch) has a photon index of 2.1 and predicts an optical flux that is inconsistent with that observed by HST at almost the same epoch.”
Gamma-Ray Burst Afterglows in the Multimessenger Era: Numerical Models and Closure Relations (2019, background): “At this point, the afterglow began steadily increasing in brightness at all wavelengths for ∼160 days (Haggard et al. 2017; Hallinan et al. 2017; D’Avanzo et al. 2018; Lyman et al. 2018; Margutti et al. 2018; Mooley et al. 2018c; Ruan et al. 2018; Troja et al. 2018a).”
A Decline in the X-Ray through Radio Emission from GW170817 Continues to Support an Off-axis Structured Jet (2018, methodology): “Relative to our detection in 2018 January with mF606W= 26.60±0.25 mag (Margutti et al. 2018), and the 2017 December detection from Lyman et al. (2018) with mF606W= 26.44±0.14 mag, the new limit is indicative of declining or flat optical brightness.”
Binary Neutron Star Mergers: Mass Ejection, Electromagnetic Counterparts, and Nucleosynthesis (2018, background): “A synchrotron remnant has been detected in X-ray, optical, and radio bands for GW170817 (Haggard et al. 2017; Hallinan et al. 2017; Margutti et al. 2017, 2018; Mooley et al. 2018a; Troja et al. 2017; Alexander et al. 2018; Dobie et al. 2018; Lyman et al. 2018; Ruan et al. 2018).”