2014-2015 Multiple Outbursts of 15P/Finlay

TL;DR

This study documents multiple outbursts of comet 15P/Finlay in 2014-2015, analyzing their physical properties, dust ejection, and comparing their energy to other notable comet events, suggesting a common underlying mechanism.

Contribution

First detailed analysis of 15P/Finlay's outbursts, including dust properties, ejection speeds, and energy estimates, linking them to similar cometary phenomena.

Findings

Dust particles ejected at speeds of ~570 m/s

Estimated dust mass ejected per outburst: 10^8-10^9 kg

Outbursts occur >1.5 times annually, injecting ~10 kg/s of dust

Abstract

Multiple outbursts of a Jupiter-family comet, 15P/Finlay, occurred from late 2014 to early 2015. We conducted an observation of the comet after the first outburst and subsequently witnessed another outburst on 2015 January 15.6-15.7. The gas, consisting mostly of C2 and CN, and dust particles expanded at speeds of 1,110 +/- 180 m/s and 570 +/- 40 m/s at a heliocentric distance of 1.0 AU. We estimated the maximum ratio of solar radiation pressure with respect to the solar gravity beta_max = 1.6 +/- 0.2, which is consistent with porous dust particles composed of silicates and organics. We found that 10^8-10^9 kg of dust particles (assumed to be 0.3 micron - 1 mm) were ejected through each outburst. Although the total mass is three orders of magnitude smaller than that of the 17P/Holmes event observed in 2007, the kinetic energy per unit mass (104 J/kg) is equivalent to the estimated values of 17P/Holmes and 332P/2010 V1 (Ikeya-Murakami), suggesting that the outbursts were caused by a similar physical mechanism. From a survey of cometary outbursts on the basis of voluntary reports, we conjecture that 15P/Finlay-class outbursts occur >1.5 times annually and inject dust particles from Jupiter-family comets and Encke-type comets into interplanetary space at a rate of ~10 kg/s or more.