Europlanet Science Congress 2020
Virtual meeting
21 September – 9 October 2020
Europlanet Science Congress 2020
Virtual meeting
21 September – 9 October 2020

Oral presentations and abstracts

SB8

In the recent years there were several attempts to obtain asteroid light curves from large surveys, both observed from the ground and space. These surveys are originally dedicated to other kind of science, like detection of microlensing events, or are transient surveys (e.g. the Zwicky Transient Factory). From space the GAIA mission and surveys dedicated to exoplanet research are the most successful in this respect. E.g. the Kepler/K2 and the Transiting Exoplanet Survey Satellite (TESS) space missions have already produced a large number of asteroid light curves, and still has an enormous potential to provide rotation characteristics for additional objects from the main belt to the transneptunian region. Recent results from TESS clearly indicate that this kind of light curve observations will supersede most ground based measurements in terms of accuracy. Surveys aimed at observing the thermal emission of asteroids (e.g. NEOWISE) continue to provide important physical properties (size and albedo), not available otherwise. This EPSC 2020 session aims to summarise the results achieved in the last years using data from big surveys, discuss how these data changed our understanding of the physical properties of asteroids both as individual objects and as populations, what the challenges and possible solutions are in data reduction, what we can expect from current and upcoming missions with similar scales in the big data era, and how the role of dedicated observations of individual targets will change in the future. Papers discussing all aspects of small body surveys are welcomed, with a special emphasis on recent light curve survey results.

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Conveners: Rene Duffard, Csaba Kiss, András Pál | Co-conveners: Joseph Masiero, Sarah Sonnett

Session assets

Session summary

Chairperson: Csaba Kiss
Space Surveys: GAIA
EPSC2020-100ECP
Toni Santana-Ros, Alberto Cellino, Adriano Campo-Bagatin, Paula Benavidez, Alvaro Alvarez-Candal, and Paolo Tanga

Binary asteroids are of special importance in planetary science as they provide direct measurements of the body's bulk mass and density. The main way to discover these systems is by detecting their mutual events in the lightcurves. There are almost 400 asteroids with satellites known as of writing this. Gaia Data Release 2 (Gaia DR2) contains sparse disk-integrated brightness measurements for more than 14.000 asteroids spanned over 22 months of observations. We have studied these data to detect multiple asteroid system candidates. For this work we have used the inversion genetic algorithm which provides best fit solutions for asteroids' spin and shape parameters. In order to cope with the limited viewing geometries of a large majority of asteroids, we have upgraded the inversion algorithm to combine Gaia DR2 with other ground-based data such as the Lowell Observatory photometric database. In the near future we envisage a great increase on the number of multiple asteroid discovery by analysing the data of large sky surveys. Particularly interesting will be the analysis of Gaia DR3 (expected for H2 2021) which will contain data for more than 100.000 asteroids.

How to cite: Santana-Ros, T., Cellino, A., Campo-Bagatin, A., Benavidez, P., Alvarez-Candal, A., and Tanga, P.: Asteroid multiplicity detection in Gaia DR2, Europlanet Science Congress 2020, online, 21 September–9 Oct 2020, EPSC2020-100, https://doi.org/10.5194/epsc2020-100, 2020

EPSC2020-555
Paolo Tanga, Federica Spoto, Ferreira Joao, and Machado Pedro

Gaia DR2, validating the debiasing of asteroid astrometry by orbit improvement

The optimal exploitation of asteroid astrometry is seminal at many tasks such as the monitoring of impact risks by potentially hazardous asteroids, and the measurement of subtle dynamical effects. These can include, most notably, the Yarkovsky thermal recoil force or perturbations due to other asteroids.

The Gaia mission has published astrometry with very high accuracy for 14.099 asteroids in the Data Release 2 (DR2), and about 10 times more are coming in DR3 (end 2021). The level of accuracy of Gaia is unprecedented, reaching 1 mas or better for each epoch, but it deserves unprecedented care to be exploited.
 
In particular, most archival data (astrometry available at the Minor Planet Center) are the result of a calibration with respect to pre-Gaia catalogues, that are often affected by local systematic errors. Such errors have different possible sources. They can be the result of the tiling of the celestial sphere by a imaging device, whose field of view presents some residual distortion in its astrometric reduction. There can also be effects related to the coupling of two different catalogs, distant in time, used to derive proper motions. Eventually, the adopted reference frame can also introduce other effects.

As it has been documented several times in literature such systematic bias, that can vary on spatial scales of a few degrees or less, can also be function of other parameters, such as the magnitude range considered (different bias affect stars of different brightness). 

To take into account these effects and apply the required corrections, we developed a completely new bias correction computation around on the position of single asteroid observations, instead of the classical approach of computing corrections on fixed grid for each catalogue. Despite being much more time-consuming, our approach allows us to reach a full flexibility on effects related to the field of view size of single surveys, magnitude limit and also epoch-dependent variations. We also implement corrections to the reference frame rotation detected for bright stars (V<12) in Gaia DR2 (Lindegren 2020) necessary to obtain a full consistency.

After having completed the debiasing of astrometry archived at MPC for all asteroids in Gaia DR2, we have run an orbit improvement procedure for all of them, that also exploits a refined error model. We illustrate here the results of our processing, in particular investigating the improvement in the ephemeris uncertainty, and the perfomance of the debiasing.
 

How to cite: Tanga, P., Spoto, F., Joao, F., and Pedro, M.: Gaia DR2: orbit improvement based on new debiasing of asteroid astrometry, Europlanet Science Congress 2020, online, 21 September–9 Oct 2020, EPSC2020-555, https://doi.org/10.5194/epsc2020-555, 2020

Space Surveys: K2 and TESS
EPSC2020-855ECP
Csilla Kalup, László Molnár, Csaba Kiss, Gyula M. Szabó, and András Pál

The Kepler space telescope collected continuous photometry of several Jovian Trojan asteroids in the Solar System during its K2 mission. We extracted light curves 43 new targets from K2 Campaigns 11-19 using our own photometric package developed for moving objects in the Kepler images which, together with the 56 asteroids from Campaign 6, brings the total sample size up to 99 asteroids. We calculated rotational frequencies and amplitudes for each object and their distributions, and we derived statistics on the binary fraction and possible compositions of these asteroids. We find and excess of very slow rotators (>100 hours) and a possible dichotomy in the period distribution. When compared to other space-based photometric results, we find that the distribution of Hilda rotation periods detected with K2 shows the same possible dichotomy, but the large sample of main-belt asteroids measured with the TESS space telescope does not.

The excess of slow rotators corroborates with an outward origin, with synchronized binaries migrating inwareds from the Kuiper belt, and some of them dissociating along the way, creating very slowly rotating single objects. Both a low critical density limit and comparison with strengthless ellipsoid models indicate that none of the objects exceed the density of icy objects, further strengthening an inward migration scenario.

We estimate a binary fraction of at least 21% based on the number of high-amplitude, long-period objects, in agreement with earlier results. Large photometric amplitudes are prevalent over the entire period range, and we cannot fit all objects with a strengtless model in rotational equilibrium.

We highlight a few individual objects as well. (99306) 2001 SC101 is the only asteroid observed in to Campaigns, from different sides of the Sun, and we find clear differences in the light curve shape. (13062) Podarkes is the principal body of a proposed small family: we detect a rotation period of 245 hr which puts it into the very slow rotator group. Finally, we present the first continuous light curve of (11351) Leucus, one of the targets of the Lucy spacecraft, and confirm that it also rotates exceedingly slowly, with a period of 445 hr.

How to cite: Kalup, C., Molnár, L., Kiss, C., Szabó, G. M., and Pál, A.: Slow rotators and binary candidates among the Jovian Trojans with K2, Europlanet Science Congress 2020, online, 21 September–9 Oct 2020, EPSC2020-855, https://doi.org/10.5194/epsc2020-855, 2020

EPSC2020-536
Csaba Kiss, Viktória Kecskeméthy, Róbert Szakáts, András Pál, László Molnár, Krisztián Sárneczky, József Vinkó, Róbert Szabó, Gyula M. Szabó, Gábor Marton, and László L. Kiss

Due to their faintness light curves of transneptunian objects (TNOs) in most cases are difficult to obtain, and therefore the number of TNOs with known rotational properties (at least rotation period) are rather limited. As it was shown for other small body populations, long-term, 1-3-month monitoring of small bodies revealed many targets with long rotation periods. These measurements significantly increased the number of slow rotators (P > 24h) for Jovian Trojans (Szabó et al., 2017), Hildas (Szabó et al., 2020) and Centaurs (Marton et al., 2020) using Kepler/K2 measurements, and also for main belt asteroids (Pál et al., 2020) using the TESS space telescope. Here we report on Kepler/K2 measurements of 70 TNOs, collected over the whole length of the K2 mission, in Campaigns 3-19. Our data notably increases the number of TNOs with known rotational properties. We compare these characteristics with those of other small body populations in the Solar system.

Figure 1: Light curve of (50000) Quaoar obtained from the K2 measurements, folded with the canonical P = 8.84 h period (Ortiz et al., 2003, left), and with the newly determined P = 8.88h rotation period (right). 

References: 

- Marton, G., et al., 2020, Icarus, 345, 113721 
- Ortiz, J.L., et al., 2003, A&A, 409, L13
- Pál, A., et al., 2020, ApJS, 247, 26 
- Szabó, Gy. et al., 2017, A&A, 599, A44 
- Szabó, Gy. et al., 2020, ApJS, 247, 34

How to cite: Kiss, C., Kecskeméthy, V., Szakáts, R., Pál, A., Molnár, L., Sárneczky, K., Vinkó, J., Szabó, R., Szabó, G. M., Marton, G., and Kiss, L. L.: Rotational properites of transneptunian objects from the K2 mission, Europlanet Science Congress 2020, online, 21 September–9 Oct 2020, EPSC2020-536, https://doi.org/10.5194/epsc2020-536, 2020

EPSC2020-810
Gyula Szabo, Csaba Kiss, Róbert Szakáts, András Pál, László Molnár, Krisztián Sárneczky, József Vinkó, Róbert Szabó, Gábor Marton, and László Kiss

We identified 125 individual light curves of Hilda asteroids observed by the K2 mission. We found that despite of the mixed taxonomies, the Hilda group highly resembles the Trojans in the distribution of rotation periods and amplitudes, and even the LR group (mostly C- and X-type) Hildas follow this rule. Contrary to the Main Belt, the Hilda group lacks the very fast rotators. The ratio of extremely slow rotators (P > 100 hr) is a surprising 18%, which is unique in the solar system. The occurrence rate of asteroids with multiple periods (4%) and asteroids with three maxima in the light curves (5%) can be signs of a high rate of binarity, which we can estimate as 25% within the Hilda group. 

Based on our extraction of 10 thousand full asteroid light curves from the first year observations by TESS (P\'al et al. 2020) we can compare the distribution of rotation period and shape asphericity in the most populated asteroid families overall in the Main Belt. We reveal internal structure of some asteroid families in respect to rotation statistics and signs of rotation properties evolving with age.

How to cite: Szabo, G., Kiss, C., Szakáts, R., Pál, A., Molnár, L., Sárneczky, K., Vinkó, J., Szabó, R., Marton, G., and Kiss, L.: Rotation properties in the Hilda and Main-Belt asteroid families observed by K2 and TESS, Europlanet Science Congress 2020, online, 21 September–9 Oct 2020, EPSC2020-810, https://doi.org/10.5194/epsc2020-810, 2020

EPSC2020-697
András Pál, Róbert Szakáts, and Csaba Kiss

By analyzing the full-frame images acquired during the first year of the TESS mission, rotation characteristics of nearly ten thousand light curves of bright asteroids were determined with a good accuracy. The continuation of this space-borne mission with its second year on the Northern Hemisphere is just ending by the summer of 2020, allowing us to extend the database. In this presentation we report the results of the initial analysis of the new data set, focusing on the similarities and differences in observational artefacts (and constraints) and the recent development of the processing pipeline. 

How to cite: Pál, A., Szakáts, R., and Kiss, C.: Towards the second data release of TESS asteroid photometry, Europlanet Science Congress 2020, online, 21 September–9 Oct 2020, EPSC2020-697, https://doi.org/10.5194/epsc2020-697, 2020

EPSC2020-420ECP
Malena Rice and Greg Laughlin

In recent years, the observed orbital geometry of extreme trans-Neptunian objects (TNOs) has provided tantalizing evidence predicting the existence of an as-yet undiscovered “Planet Nine.” Combined with orbit stability models, these observations permit a detailed prediction of Planet Nine's properties, with a shrinking parameter space as more of these rare objects are discovered. I will present the first results from a new survey utilizing light curve data from the Transiting Exoplanet Survey Satellite (TESS) to search for TNOs at distances 70-800 au, with a magnitude limit V~22. This survey leverages an innovative new pipeline designed to extract the locations, magnitudes, and 27-day orbital arcs of undiscovered outer solar system objects, including both Planet Nine and the population of extreme trans-Neptunian objects pertinent to the Planet Nine theory, using a blind shift-stacking search along all plausible outer solar system orbits. Together with the extensive sky coverage of the TESS survey, this search will place stringent constraints upon the as-yet undiscovered TNO population, with great potential to either discover Planet Nine or almost entirely rule out its existence.

How to cite: Rice, M. and Laughlin, G.: Surveying the Trans-Neptunian Solar System with TESS, Europlanet Science Congress 2020, online, 21 September–9 Oct 2020, EPSC2020-420, https://doi.org/10.5194/epsc2020-420, 2020