PUSHING THE LIMITS: K2 OBSERVATIONS OF THE TRANS-NEPTUNIAN OBJECTS 2002 GV31 and (278361) 2007 JJ43

We present the first photometric observations of trans-Neptunian objects (TNOs) taken with the Kepler space telescope, obtained during the course of the K2 ecliptic survey. Two faint objects have been monitored in specifically designed pixel masks that were centered on the stationary points of the objects, when their daily motion was the slowest. In the design of the experiment, only the apparent path of these objects were retrieved from the detectors, i. e., the costs in terms of Kepler pixels were minimized. Because of the faintness of the targets, we employ specific reduction techniques and co-added images. We measure rotational periods and amplitudes in the unfiltered Kepler band as follows: for (278361) 2007 JJ(43) and 2002 GV(31), we get P-rot = 12.097 hr and P-rot = 29.2 hr with 0.10 and 0.35 mag for the total amplitudes, respectively. Future space missions, such as TESS and PLATO, are not well suited to this kind of observation. Therefore, we encourage including the brightest TNOs around their stationary points in each observing campaign to exploit this unique capability of the K2 Mission-and therefore to provide unbiased rotational, shape, and albedo characteristics of many objects.