# Summary of K2 Program GO16059

Title: Physical studies of asteroids with Kepler

PI: Marciniak, Anna (Adam Mickiewicz University)
CoIs: Szabo, Robert; Szakats, Robert; Kiss, Csaba; Mueller, Thomas G

As it has been demonstrated in some recent papers, the Kepler Space Telescope in the K2 mission is an excellent tool to observe asteroids and obtain accurate lightcurves even if the targets are relatively fast-moving main belt asteroids (Szabo et al., 2015, 2016a) or Jovian Trojans (Szabo et al., 2016b).  

While in the case of trans-Neptunian bodies the lightcurve information is available for a limited sample only (see e.g. Kiss et al., 2015), the general spin characteristics of main belt asteroids are relatively well know due to their proximity and relatively short (~few years) orbital periods that allows us to observe these bodies at various spin axis aspect angles during their motion around the Sun. The sufficient orbital phase coverage also allows us to apply lightcurve inversion techniques to obtain detailed shape models for these targets (Kaasalainen et al., 2002). 

In this proposal our goal is to obtain lightcurves of slowly rotating asteroids with low amplitudes, to decrease the strong selection effects in spin and shape studies of asteroids. Currently spin and shape models are mainly available for targets with relatively short rotation periods and substantial elongations of their shapes that results in a biased sample of asteroids with known physical properties (Marciniak et al. 2015). Consequently, our knowledge on spin vs. diameter, the internal cohesion and strength or the non-gravitational effects are biased, too. Data from asteroids observed in the K2 mission can substantially increase the data pool for asteroids omitted in previous studies, enabling continuous observations of targets with periods of the order of days. 

We also investigate small asteroids with spin axes close to the ecliptic plane. Some studies suggest their non-existence due to non-gravitational YORP effect (Durech et al. 2016). However, such lack can be a selection effect, because such targets often display very small amplitudes when viewed pole-on. Kepler/K2 data will allow us to decide whether the low amplitude of these targets are due to close to pole-on configurations.  

We propose to observe a set of main belt asteroids for which additional high-quality lightcurve data obtained with K2 would enable us to obtain spin and shape models for the first time. Some of the targets, (203) Pompeja, (566) Stereoskopia and (308) Polyxo have rotation periods close to 12h or 24h and have small, <0.1 mag lightcurve amplitudes. These targets are difficult to observe from ground due to daily gaps and aliases, and would require coordinated observations from many observing sites, typically flawed by weather conditions. The Kepler Space Telescope is able to perform these observations alone. (525) Adelaide is a target with highly inclined spin axis and strongly variable amplitudes, sometimes being as low as 0.02 mag. Obtaining full, composite lightcurve of this P=19.967 h target would be very difficult from the ground, as the period exceeds the length of the average observing night. In practice, only continuous data from a space-based observatory can provide meaningful data for this target. (437) Rhodia is a very slow rotator with a period of ~56 hours, and variable, usually very low amplitudes. A sufficiently long, continuous measurement of this target would allow us to determine the orientation of its (likely) multiple spin axes.  

All our 14 targets will spend enough time on silicon (typically ~5 days) that a sufficient light curve coverage can be guaranteed. 

References:

- Durech et al., 2016, A&A, 587, A48
- Kaasalainen, et al., 2002, "Asteroid Models from Disk-integrated Data", in Asteroids III, Univ. of Arizona Press
- Kiss, Cs. et al., "Trans-Neptunian objects with K2: targeting our own Solar System", 2015, K2 White Paper
- Marciniak et al., 2015, P&SS, 118, 256
- Szabo, R., et al., 2015, AJ, 149, 112
- Szabo, R., et al., 2016a, arXiv:1609.02759, A&A, accepted
- Szabo, Gy.M., et al., 2016b, arXiv:1609.02760, A&A, accepted

# Targets requested by this program that have been observed (71)
EPIC ID, RA (J2000) [deg], Dec (J2000) [deg], magnitude, Investigation IDs
200199835, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199836, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199837, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199838, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199839, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199840, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199841, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199842, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199843, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199844, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199845, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199846, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199847, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199848, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199849, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199850, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199851, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199852, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199853, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199854, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199855, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199856, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199857, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199858, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199859, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199860, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199861, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199862, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199863, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199864, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199865, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199866, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199867, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199868, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199869, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199870, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199871, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199872, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199873, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199874, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199875, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199876, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199877, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199878, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199879, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199880, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199881, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199882, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199883, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199884, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199885, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199886, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199887, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199888, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199889, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199890, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199891, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199892, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199893, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199894, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199895, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199896, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199897, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199898, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199899, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199900, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199901, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199902, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199903, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199904, , , , GO16059_LC|Hekate-LC-SSO_TILE
200199905, , , , GO16059_LC|Hekate-LC-SSO_TILE