The Sporadic Activity of (6478) Gault: A YORP-driven Event?

Kleyna, Jan; Hainaut, Olivier; Meech, К. J.; Hsieh, Henry H.; Fitzsimmons, A.; Micheli, M.; Keane, J. V.; Denneau, L.; Tonry, J.; Heinze, A.; Bhatt, B. C.; Sahu, D. K.; Koschny, D.; Smith, K.; Ebeling, H.; Weryk, Robert; Flewelling, H.; Wainscoat, R. J.

doi:10.3847/2041-8213/ab0f40

Cited by 48 publications

(80 citation statements)

References 29 publications

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“…with large macroporosity. As a main conclusion, our analysis definitely rules out the spin-barrier classical value of about 2 hours, as claimed by Kleyna et al (2019).…”

Section: Rotation and Spin-barrier Critical Periodsupporting

confidence: 83%

“…No firm estimate of Gault's rotation period was available until cometary activity was first discovered on 2019 Jan 5 (Smith & Denneau 2019). Subsequent photometric follow up to obtain an accurate lightcurve of the object did not lead to any conclusive result, likely due to the masking effect of dust in the coma (Kleyna et al 2019;Ye, et al 2019;Man-To et al 2019;Jewitt et al 2019;Sanchez et al 2019). Based on a Lomb-Scargle and ANOVA lightcurve analysis, Kleyna et al (2019) recently proposed for Gault a rotation period about 2 hours, which implied a density of about 2.7 g cm −3 as for a typical S-type asteroid.…”

Section: Introductionmentioning

confidence: 98%

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Spinning and colour properties of the active asteroid (6478) Gault

Carbognani

Buzzoni

2020

Monthly Notices of the Royal Astronomical Society

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We report on accurate BVR c observations of (6478) Gault, a 5-6 km diameter inner main-belt asteroid in the Phocaea family, notable for its sporadic, comet-like ejection of dust. This curious behavior has been mainly interpreted as reconfigurations after YORP spin-up, although merging of a contact binary system cannot be fully excluded. We collected optical observations along the 2019 March-April period, at orbital phase angles between 12 • − 21 • , to search for direct evidence of asteroid quick spinning rotation. A prevailing period value of 3.34±0.02 hours is supported by our and other photometric observations. In the YORP spin-up hypothesis, this period points to a bulk density ρ ≈ 1 g/cm 3 . The mean colors are B − V = +0.82 ±0.3 , V − R c = +0.28 ±0.06 and B − R c = +1.11 ±0.4 , but we have observed a strong bluer color during the April session, with about ∆(B − V) ∼ 0.35 ± 0.09 mag. This color change can be due to asteroid rotation and support the hypothesis that there is a bluer surface under the Gault's dust, as indicated by spectroscopic observations made on 2019 March 31 and April 8 by Marsset et al. (2019).

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“…with large macroporosity. As a main conclusion, our analysis definitely rules out the spin-barrier classical value of about 2 hours, as claimed by Kleyna et al (2019).…”

Section: Rotation and Spin-barrier Critical Periodsupporting

confidence: 83%

Section: Introductionmentioning

confidence: 98%

Spinning and colour properties of the active asteroid (6478) Gault

Carbognani

Buzzoni

2020

Monthly Notices of the Royal Astronomical Society

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“…(d∼100 µm) derived from morphological analysis of the tails (Jewitt et al 2019;Kleyna et al 2019;Moreno et al 2019;Ye et al 2019b), implying that they do not contain a preponderance of Rayleigh scatterers.…”

Section: Possible Origins For Spectral Variabilitymentioning

confidence: 99%

Active Asteroid (6478) Gault: A Blue Q-type Surface below the Dust?

Marsset¹,

DeMeo²,

Şonka³

et al. 2019

ApJL

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We present near-infrared spectroscopy of the sporadically active asteroid (6478) Gault collected on the 3 m NASA/Infrared Telescope Facility observatory in late 2019 March/early April. Long-exposure imaging with the 0.5 m NEEMO T05 telescope and previously published data simultaneously monitored the asteroid activity, providing context for our measurements. We confirm Gault is a silicate-rich (Qor S-type) object likely linked to the (25) Phocaea collisional family. The asteroid exhibits substantial spectral variability over the 0.75-2.45 µm wavelength range, from unusual blue (s =-13.5±1.1% µm −1 ) to typical red (s =+9.1±1.2% µm −1 ) spectral slope, that does not seem to correlate with activity. Spectral comparisons with samples of ordinary chondrite meteorites suggest that the blue color relates to the partial loss of the asteroid dust regolith, exposing a fresh, dust-free material at its surface. The existence of asteroids rotating close to rotational break-up limit and having similar spectral properties as Gault further supports this interpretation. Future spectroscopic observations of Gault, when the tails dissipate, will help further testing of our proposed hypothesis.

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“…The index is typically q ∼ 3.5 (Jewitt et al 2016, Ishiguro et al 2016a, Kim et al 2017, Moreno et al 2012) although smaller (e.g. q = 1.7, Kleyna et al 2019) and larger indices (e.g. q = 3.8, Ishiguro et al 2016b) have been reported.…”

Section: Observationsmentioning

confidence: 99%

Disintegrating Inbound Long-period Comet C/2019 J2

Jewitt

Luu

2019

ApJL

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We present observations of the disintegrating long-period comet C/2019 J2 (Palomar) taken to determine the nature of the object and the cause of its demise.The data are consistent with break-up of a sub-kilometer nucleus into a debris cloud of mass ∼ 10 9 kg, peaking on UT 2019 May 24±12. This is ∼56 days before perihelion and at a heliocentric distance of ∼1.9 AU. We consider potential mechanisms of disintegration. Tidal disruption is ruled-out, because the comet has not passed within the Roche sphere of any planet. Impact disruption is implausible, because the comet orbit is highly inclined (inclination 105.1 • ) and disruption occurred far above the ecliptic, where asteroids are rare. The back-pressure generated by sublimation (0.02 to 0.4 N m −2 ) is orders of magnitude smaller than the reported compressive strength (30 to 150 N m −2 ) of cometary material and, therefore, is of no importance. The depletion of volatiles by sublimation occurs too slowly to render the nucleus inactive on the timescale of infall. However, we find that the e-folding timescale for spin-up of the nucleus by the action of sublimation torques is shorter than the infall time, provided the nucleus radius is r n < 0.4 km. Thus, the disintegration of C/2019 J2 is tentatively interpreted as the rotational disruption of a sub-kilometer nucleus caused by outgassing torques.

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The Sporadic Activity of (6478) Gault: A YORP-driven Event?

Cited by 48 publications

References 29 publications

Spinning and colour properties of the active asteroid (6478) Gault

Spinning and colour properties of the active asteroid (6478) Gault

Active Asteroid (6478) Gault: A Blue Q-type Surface below the Dust?

Disintegrating Inbound Long-period Comet C/2019 J2

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