A Dark Asteroid Family in the Phocaea Region

Novaković, Bojan; Tsirvoulis, Georgios; Granvik, Mikael; Todovic, Ana

doi:10.3847/1538-3881/aa6ea8

Cited by 26 publications

(21 citation statements)

References 45 publications

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“…Even if 70% of the Phocaea asteroids observed by WISE with W3<W3lim are in category 1, when we take into account the biases we find It is possible this difference in the Phocaea population is not diagnostic of a problem in our NEO albedo model. Consider that Novakovic et al (2017) found a small dark asteroid family in the Phocaea region that, by its orbital position near an escape route, could potentially dominate the Phoceas' flux to the NEO population. This situation may make it possible for Phocaea-derived NEOs to not be representative of the overall Phocaea population.…”

Section: Validity Testsmentioning

confidence: 99%

Debiased albedo distribution for Near Earth Objects

Morbidelli

Delbò

Granvik

et al. 2020

Icarus

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We extend the most recent orbital -absolute magnitude Near Earth Object (NEO) model (Granvik et al., 2018) to provide a statistical description of NEO geometric albedos. Our model is calibrated on NEOWISE albedo data for the NEO population and reproduces these data very well once a simple model for the NEOWISE observational biases is applied. The results are consistent with previous estimates. There are ~1,000 NEOs with diameter D>1km and the mean albedo to convert absolute magnitude into diameter is 0.147. We don't find any statistically significant evidence that the albedo distribution of NEOs depends on NEO size. Instead, we find evidence that the disruption of NEOs at small perihelion distances found in Granvik et al. (2016) occurs preferentially for dark NEOs. The interval between km-sized bodies striking the Earth should occur on average once every 750,000 years. Low and high albedo NEOs are well mixed in orbital space, but a trend remains with higher albedo objects being at smaller semimajor axes and lower albedo objects more likely found at larger semimajor axes.

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Section: Validity Testsmentioning

confidence: 99%

Debiased albedo distribution for Near Earth Objects

Morbidelli

Delbò

Granvik

et al. 2020

Icarus

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“…Gault is likely between 2-10 km in diameter, as estimated from our HG model. This number is calculated using the canonical relation D = 1329p 1/2 V 10 −H/5 , where p V = 0.03-0.6 is the geometric albedo of the Phocaea asteroids (Novaković et al 2017). The albedo of Gault is not known.…”

Section: Activity Mechanismmentioning

confidence: 99%

Multiple Outbursts of Asteroid (6478) Gault*

Kelley

Bodewits

et al. 2019

ApJL

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Main-belt asteroid (6478) Gault unexpectedly sprouted two tails in late 2018 and early 2019, identifying it as a new active asteroid. Here we present observations obtained by the 1.2-m Zwicky Transient Facility survey telescope that provide detailed time-series coverage of the onset and evolution of Gault's activity. Gault exhibited two brightening events, with the first one starting on 2018 Oct. 18±5 days and a second one starting on 2018 Dec. 24±1 days. The amounts of mass released are 2 × 10 7 kg and 1 × 10 6 kg, respectively. Based on photometric measurements, each event persisted for about a month. Gault's color has not changed appreciably over time, with a pre-outburst color of g PS1 − r PS1 = 0.50 ± 0.04 and g PS1 − r PS1 = 0.46 ± 0.04 during the two outbursts. Simulations of dust dynamics shows that the ejecta consists of dust grains of up to 10 µm in size that are ejected at low velocities below 1 m s −1 regardless of particle sizes. This is consistent with non-sublimationdriven ejection events. The size distribution of the dust exhibits a broken power-law, with particles at 10-20 µm following a power-law of −2.5 to −3.0, while larger particles follow a steeper slope of −4.0. The derived properties can be explained by either rotational excitation of the nucleus or a merger of a near-contact binary, with the latter scenario to be statistically more likely.

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“…Broadband colors of Gault showed that this object is more similar to C-type asteroids than S-types (Jewitt et al 2019;Ye et al 2019). Furthermore, Kleyna et al (2019) found that Gault is also dynamically linked with the low-albedo Tamara family, a recently discovered asteroid family residing in the Phocaea region (Novaković et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Physical Characterization of Active Asteroid (6478) Gault

Sanchez

Reddy

Thirouin

et al. 2019

ApJL

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Main belt asteroid (6478) Gault has been dynamically linked with two overlapping asteroid families: Phocaea, dominated by S-type asteroids, and Tamara, dominated by low-albedo C-types. This object has recently become an interesting case for study after images obtained in late 2018 revealed that it was active and displaying a comet-like tail. Previous authors have proposed that the most likely scenarios to explain the observed activity on Gault were rotational excitation or merger of near-contact binaries. Here we use new photometric and spectroscopic data of Gault to determine its physical and compositional properties. Lightcurves derived from the photometric data showed little variation over three nights of observations, which prevented us from determining the rotation period of the asteroid. Using WISE observations of Gault and the near-Earth Asteroid Thermal Model (NEATM) we determined that this asteroid has a diameter <6 km. Near-infrared spectroscopic data obtained with the Infrared Telescope Facility showed a spectrum similar to that of S-complex asteroids, and a surface composition consistent with H chondrite meteorites. These results favor a compositional affinity between Gault and asteroid (25) Phocaea, and rules out a compositional link with the Tamara family. From the spectroscopic data we found no evidence of fresh material that could have been exposed during the outburst episodes.

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A Dark Asteroid Family in the Phocaea Region

Cited by 26 publications

References 45 publications

Debiased albedo distribution for Near Earth Objects

Debiased albedo distribution for Near Earth Objects

Multiple Outbursts of Asteroid (6478) Gault*

Physical Characterization of Active Asteroid (6478) Gault

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