The heart of the swarm: K2 photometry and rotational characteristics of 56 Jovian Trojan asteroids

Szabó, Gy. M.; Pál, András; Kiss, Cs.; Kiss, L. L.; Molnár, L.; Hanyecz, O.; Plachy, E.; Sárneczky, K.; Szabo, Robert M.

doi:10.1051/0004-6361/201629401

Cited by 39 publications

(59 citation statements)

References 39 publications

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“…The campaign ended earlier than expected because the on-board storage filled up faster than anticipated because of the unusually poor data compression 1 . A similar study about Jovian Trojan asteroids observed by the K2 mission will be published in a related paper (Szabó et al 2016).…”

Section: Introductionmentioning

confidence: 80%

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Uninterrupted optical light curves of main-belt asteroids from the K2 mission

Szabo

Pál

Sárneczky

et al. 2016

A&A

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Context. Because the second reaction wheel failed, a new mission was conceived for the otherwise healthy Kepler space telescope. In the course of the K2 mission, the telescope is staring at the plane of the Ecliptic. Thousands of solar system bodies therefore cross the K2 fields and usually cause additional noise in the highly accurate photometric data. Aims. We here follow the principle that some person's noise is another person's signal and investigate the possibility of deriving continuous asteroid light curves. This is the first such endeavor. In general, we are interested in the photometric precision that the K2 mission can deliver on moving solar system bodies. In particular, we investigate space photometric optical light curves of main-belt asteroids. Methods. We studied the K2 superstamps that cover the fields of M35, and Neptune together with Nereid, which were observed in the long-cadence mode (29.4 min sampling). Asteroid light curves were generated by applying elongated apertures. We used the Lomb-Scargle method to determine periodicities that are due to rotation. Results. We derived K2 light curves of 924 main-belt asteroids in the M35 field and 96 in the path of Neptune and Nereid. The light curves are quasi-continuous and several days long. K2 observations are sensitive to longer rotational periods than typical ground-based surveys. Rotational periods are derived for 26 main-belt asteroids for the first time. The asteroid sample is dominated by faint objects (>20 mag). Owing to the faintness of the asteroids and the high density of stars in the M35 field, only 4.0% of the asteroids with at least 12 data points show clear periodicities or trends that signal a long rotational period, as opposed to 15.9% in the less crowded Neptune field. We found that the duty cycle of the observations had to reach ∼60% to successfully recover rotational periods.

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Section: Introductionmentioning

confidence: 80%

“…The track is approximated with a linear curve. The details of the method are described in Szabó et al (2016). In Fig.…”

Section: Photometrymentioning

confidence: 99%

Uninterrupted optical light curves of main-belt asteroids from the K2 mission

Szabo

Pál

Sárneczky

et al. 2016

A&A

Self Cite

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“…acknowledges support from NASA through grant number HST-GO-15143 from the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555. Ryan et al (2017) (bigger red dots) and Szabó et al (2017) (smaller blue dots). We excluded three cases with inconsistent period determinations (see the main text), leaving 53 objects.…”

Section: Caveats and Outlookmentioning

confidence: 95%

Very Slow Rotators from Tidally Synchronized Binaries

Nesvorný

Vokrouhlický

Bottke

et al. 2020

ApJL

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A recent examination of K2 lightcurves indicates that ∼15% of Jupiter Trojans have very slow rotation (spin periods P s > 100 h). Here we consider the possibility that these bodies formed as equal-size binaries in the massive outer disk at ∼20-30 au. Prior to their implantation as Jupiter Trojans, tight binaries tidally evolved toward a synchronous state with P s ∼ P b , where P b is the binary orbit period. They may have been subsequently dissociated by impacts and planetary encounters with at least one binary component retaining its slow rotation. Surviving binaries on Trojan orbits would continue to evolve by tides and spin-changing impacts over 4.5 Gyr. To explain the observed fraction of slow rotators, we find that at least ∼15-20% of outer disk bodies with diameters 15 < D < 50 km would have to form as equal-size binaries with 12 a b /R 30, where a b is the binary semimajor axis and R = D/2. The mechanism proposed here could also explain very slow rotators found in other small body populations.

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“…1). Moreover, recent results from Kepler-K2 continuous observations spanning weeks show that there are substantially more slow-rotators among faint main belt asteroids and Jupiter Trojans than ground-based studies have shown (Szabó et al 2016(Szabó et al , 2017Molnár et al 2017). Observations from the ground are naturally burdened with selection bias, absent when observing for long time spans from space.…”

Section: Observing and Modelling Biases In Asteroid Studiesmentioning

confidence: 99%

Photometric survey, modelling, and scaling of long-period and low-amplitude asteroids

Marciniak

Bartczak

Müller

et al. 2018

A&A

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Context. The available set of spin and shape modelled asteroids is strongly biased against slowly rotating targets and those with low lightcurve amplitudes. This is due to the observing selection effects. As a consequence, the current picture of asteroid spin axis distribution, rotation rates, radiometric properties, or aspects related to the object's internal structure might be affected too. Aims. To counteract these selection effects, we are running a photometric campaign of a large sample of main belt asteroids omitted in most previous studies. Using least chi-squared fitting we determined synodic rotation periods and verified previous determinations. When a dataset for a given target was sufficiently large and varied, we performed spin and shape modelling with two different methods to compare their performance. Methods. We used the convex inversion method and the non-convex SAGE algorithm, applied on the same datasets of dense lightcurves. Both methods search for the lowest deviations between observed and modelled lightcurves, though using different approaches. Unlike convex inversion, the SAGE method allows for the existence of valleys and indentations on the shapes based only on lightcurves. Results. We obtain detailed spin and shape models for the first five targets of our sample: (159) Aemilia, (227) Philosophia, (329) Svea, (478) Tergeste, and (487) Venetia. When compared to stellar occultation chords, our models obtained an absolute size scale and major topographic features of the shape models were also confirmed. When applied to thermophysical modelling, they provided a very good fit to the infrared data and allowed their size, albedo, and thermal inertia to be determined. Conclusions. Convex and non-convex shape models provide comparable fits to lightcurves. However, some non-convex models fit notably better to stellar occultation chords and to infrared data in sophisticated thermophysical modelling (TPM). In some cases TPM showed strong preference for one of the spin and shape solutions. Also, we confirmed that slowly rotating asteroids tend to have higher-than-average values of thermal inertia, which might be caused by properties of the surface layers underlying the skin depth.

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The heart of the swarm: K2 photometry and rotational characteristics of 56 Jovian Trojan asteroids

Cited by 39 publications

References 39 publications

Uninterrupted optical light curves of main-belt asteroids from the K2 mission

Uninterrupted optical light curves of main-belt asteroids from the K2 mission

Very Slow Rotators from Tidally Synchronized Binaries

Photometric survey, modelling, and scaling of long-period and low-amplitude asteroids

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