The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. V. Rising X-Ray Emission from an Off-axis Jet

Margutti, R.; Berger, E.; Fong, W.; Guidorzi, C.; Alexander, K. D.; Metzger, Brian D.; Blanchard, P. K.; Cowperthwaite, P. S.; Chornock, R.; Eftekhari, T.; Nicholl, M.; Villar, V. Ashley; Williams, Peter K. G.; Annis, J.; Brown, D. A.; Chen, H.; Doctor, Z.; Frieman, Joshua A.; Holz, D. E.; Šako, M.; Soares-Santos, M.

doi:10.3847/2041-8213/aa9057

Cited by 426 publications

(427 citation statements)

References 53 publications

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“…We first note that the light curves are not well described by a power law, indicating minimal contribution from a GRB optical afterglow over the timescale of our observations. This is consistent with modeling of the afterglow based on X-ray and radio observations (Margutti et al 2017;Alexander et al 2017).…”

Section: Light Curvessupporting

confidence: 73%

The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. II. UV, Optical, and Near-infrared Light Curves and Comparison to Kilonova Models

Cowperthwaite

Berger

Villar

et al. 2017

ApJ

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826

581

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We present UV, optical, and near-infrared (NIR) photometry of the first electromagnetic counterpart to a gravitational wave source from Advanced Laser Interferometer Gravitational-wave Observatory (LIGO)/Virgo, the binary neutron star merger GW170817. Our data set extends from the discovery of the optical counterpart at 0.47-18.5 days post-merger, and includes observations with the Dark Energy Camera (DECam), Gemini-South/ FLAMINGOS-2 (GS/F2), and the Hubble Space Telescope (HST). The spectral energy distribution (SED) inferred from this photometry at 0.6 days is well described by a blackbody model with » T 8300 K, a radius of »Ŕ 4.5 10 14 cm (corresponding to an expansion velocity of » v c 0.3 ), and a bolometric luminosity of »Ĺ 5 10 bol 41 erg s −1 . At 1.5 days we find a multi-component SED across the optical and NIR, and subsequently we observe rapid fading in the UV and blue optical bands and significant reddening of the optical/ NIR colors. Modeling the entire data set, we find that models with heating from radioactive decay of 56 Ni, or those with only a single component of opacity from r-process elements, fail to capture the rapid optical decline and red optical/NIR colors. Instead, models with two components consistent with lanthanide-poor and lanthanide-rich ejecta provide a good fit to the data; the resulting "blue" component has » . These ejecta masses are broadly consistent with the estimated r-process production rate required to explain the Milky Way r-process abundances, providing the first evidence that binary neutron star (BNS) mergers can be a dominant site of r-process enrichment.

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Section: Light Curvessupporting

confidence: 73%

The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. II. UV, Optical, and Near-infrared Light Curves and Comparison to Kilonova Models

Cowperthwaite

Berger

Villar

et al. 2017

ApJ

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826

581

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“…The properties of the wide-jet model are consistent with Alexander et al (2017b), Granot et al (2017), Margutti et al (2017), and Troja et al (2017b). However, the two distinct models, discussed in this Letter, show that there is significant degeneracy between the afterglow parameters (for a more detailed study of the afterglow parameter space, see Granot et al 2017).…”

Section: Modeling the Broadband Afterglowsupporting

confidence: 73%

“…This behavior is inconsistent with known X-ray afterglows. When the X-ray afterglow was detected with Chandra (Haggard et al 2017b;Margutti et al 2017;Troja et al 2017b), the luminosity of~- was still 2.6 dex fainter than that of any GRB with detected X-ray afterglow. This faintness of the afterglow is also reflected in the very low energy release at γ-rays, g E ,iso .…”

Section: Grb 170817a In the Context Of Other Sgrbsmentioning

confidence: 99%

“…Although the chance coincidence of finding both transients quasi-contemporaneous and in the same region of the sky is very small, the credible region of the γ-ray localization had a size of ∼1100deg 2 (90% confidence; Blackburn et al 2017). To firmly establish the connection between GRB 170817A and GW170817 by detecting the afterglow of the GRB in the X-ray and radio bands, numerous groups carried out large follow-up campaigns to very deep limits, but without success (e.g., Alexander et al 2017a;Bannister et al 2017;Cenko et al 2017;De et al 2017;Deller et al 2017;Evans et al 2017a;Kaplan et al 2017;Margutti et al 2017;Resmi et al 2017;Sugita et al 2017). It was not until nine days after GW170817 that a brightening X-ray source was detected at the position of AT2017gfo (Troja et al 2017a).…”

Section: Introductionmentioning

confidence: 99%

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ALMA and GMRT Constraints on the Off-axis Gamma-Ray Burst 170817A from the Binary Neutron Star Merger GW170817

Kim

Schulze

Resmi

et al. 2017

ApJL

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Binary neutron-star mergers (BNSMs) are among the most readily detectable gravitational-wave (GW) sources with the Laser Interferometer Gravitational-wave Observatory (LIGO). They are also thought to produce short γ-ray bursts (SGRBs) and kilonovae that are powered by r-process nuclei. Detecting these phenomena simultaneously would provide an unprecedented view of the physics during and after the merger of two compact objects. Such a Rosetta Stone event was detected by LIGO/Virgo on 2017 August 17 at a distance of ∼44Mpc. We monitored the position of the BNSM with Atacama Large Millimeter/submillimeter Array (ALMA) at 338.5 GHz and the Giant Metrewave Radio Telescope (GMRT) at 1.4 GHz, from 1.4 to 44 days after the merger. Our observations rule out any afterglow more luminous than´--3 10 erg s Hz 26 1 1 in these bands, probing >2-4 dex fainter than previous SGRB limits. We match these limits, in conjunction with public data announcing the appearance of X-ray and radio emission in the weeks after the GW event, to templates of off-axis afterglows. Our broadband modeling suggests that GW170817 was accompanied by an SGRB and that the γ-ray burst (GRB) jet, powered byẼ 10 AG,iso 50 erg, had a half-opening angle of~ 20 , and was misaligned by~ 41 from our line of sight. The data are also consistent with a more collimated jet:Ẽ 10 AG,iso 51 erg, q q ~ 5 , 17. This is the most conclusive detection of an off-axis GRB afterglow and the first associated with a BNSM-GW event to date. We use the viewing angle estimates to infer the initial bulk Lorentz factor and true energy release of the burst.

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“…Recent observations with Chandra revealed that the X-ray afterglow continued to increase unexpectedly until ∼110days post merger (Margutti et al 2017;Troja et al 2017;Ruan et al 2018). Ruan et al (2018) further found that the radio emission brightened at approximately the same rate as that of the X-ray emission, which indicates that they share a common origin (see also Mooley et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Continued Brightening of the Afterglow of GW170817/GRB 170817A as Being Due to a Delayed Energy Injection

Huang

et al. 2018

ApJL

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The brightness of the multi-wavelength afterglow of GRB 170817A is increasing unexpectedly even ∼160 days after the associated gravitational burst. Here we suggest that the brightening can be caused by a late-time energy injection process. We use an empirical expression to mimic the evolution of the injection luminosity, which consists of a power-law rising phase and a power-law decreasing phase. It is found that the power-law indices of the two phases are 0.92 and −2.8, respectively, with the peak time of the injection being ∼110days. The energy injection could be due to some kind of accretion, with the total accreted mass being ∼0.006M e . However, normal fall-back accretion, which usually lasts for a much shorter period, cannot provide a natural explanation. Our best-fit decay index of −2.8 is also at odds with the expected value of −5/3 for normal fall-back accretion. Noting that the expansion velocities of the kilonova components associated with GW170817 are 0.1-0.3 c, we argue that there should also be some ejecta with correspondingly lower velocities during the coalescence of the double neutron star (NS) system. They are bound by the gravitational well of the remnant central compact object and might be accreted at a timescale of about 100 days, providing a reasonable explanation for the energy injection. Detailed studies on the long-lasting brightening of GRB 170817A thus may provide useful information on matter ejection during the merger process of binary neutron stars.

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The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. V. Rising X-Ray Emission from an Off-axis Jet

Cited by 426 publications

References 53 publications

The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. II. UV, Optical, and Near-infrared Light Curves and Comparison to Kilonova Models

The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. II. UV, Optical, and Near-infrared Light Curves and Comparison to Kilonova Models

ALMA and GMRT Constraints on the Off-axis Gamma-Ray Burst 170817A from the Binary Neutron Star Merger GW170817

Continued Brightening of the Afterglow of GW170817/GRB 170817A as Being Due to a Delayed Energy Injection

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