# Summary of K2 Program GO16062

Title: A Search for Transiting Objects Orbiting White Dwarf Stars

PI: Redfield, Seth (Wesleyan University)
CoIs: Farihi, Jay; Gaensicke, Boris Teddy; Cauley, Paul Wilson; Veras, Dimitri

Science Goals and Objectives: Given their small size, white dwarf stars present a very intriguing sample to monitor for transiting objects. Indeed, K2 observed the first such example in Campaign 1: WD1145+017 (Vanderburg et al. 2015), which we have followed-up on with high resolution spectroscopy (Redfield et al. 2016). Several researchers have explored the possibility of detecting very small objects, even down to exoasteroids, around white dwarf stars (e.g., Di Stefano et al. 2010, Agol 2011, Loeb & Moaz 2013). The transit of an Earth-sized planet would cause a full eclipse of the host star, and therefore would be easy to detect, however, it would be very short, on the order of seconds to minutes, and would therefore require short cadence observations. The size of the host star also makes any followup observations of the exoplanet significantly easier (e.g., transmission spectroscopy of the planetary atmosphere [e.g., Redfield et al. 2008, Jensen et al. 2013]). Regardless of the relative ease of follow-up observations, the atmospheric measurements of a planet around such an evolved star, would provide critical information regarding the composition and formation of such objects (Veras & Gaensicke 2015). I propose a sample of "bright" (V < 18 mag) white dwarf stars, in which we would be able to detect objects as small as asteroids (i.e., ~500 km) and in periods that range from hours to months, including the intriguing periods in the habitable zone from 4-32 hours.

Estimate of the Number of Targets: Given the sparse distribution of relatively bright white dwarfs, we estimate the total number of targets to be about 30 (based on the numbers proposed in previous campaigns).

Methodology: Given the similarity in size between the host star and even small planetary objects, the transit depth will be substantial, and possibly even total. The detected debris disks around white dwarfs (Kilic & Redfield 2007) and evidence of planetesimal accretion onto white dwarfs (Farihi et al. 2010; Xu et al. 2014) indicates that there may be planetary material in close orbits. The first planets detected were around a compact object, a pulsar (Wolszczan & Frail 1992). Additionally, N-body simulations of planetary systems through stellar evolution indicate it is possible to return significant mass objects back very close to the white dwarf (Veras & Gaensicke 2015), so it is likely for white dwarfs to host planets. Any object in the habitable zone (4-32 hours) will be easily detected with scores of transits in a single K2 campaign. Due to the shortness of any transit, these observations should be taken in short cadence. Even if a single transit is detected, follow-up observations can be done from the ground. While a search from the ground is possible, it suffers from severe aliasing with Earth's rotation. However, a followup campaign on known targets is quite straightforward. At Wesleyan University, we are conducting a ground-based search with our 0.6-meter telescope. However, the observations are limited to 1-2 8-hour epochs, making it difficult to definitively rule-out a transiting signal with periods in the habitable zone range, and extremely limited coverage of longer periods.

Relevance of Proposed Research to this Solicitation: A detection of an object transiting a white dwarf would be significant finding for many areas of astrophysics (e.g., stellar evolution, planetary migration, planet formation, atmospheric characterization), and in line with the objectives of the original Kepler mission, to identify planet candidates. This work identifies a sample of K2 targets, which are directly related to the original Kepler mission of planet discovery, and directly tied to Objective 1.6 in the NASA 2014 Strategic Plan.

# Targets requested by this program that have been observed (207)
EPIC ID, RA (J2000) [deg], Dec (J2000) [deg], magnitude, Investigation IDs
211401770, 137.385305, 11.667261, 18.055, GO16016_LC|GO16046_LC|GO16062_LC
211408253, 136.670557, 11.766945, 18.803, GO16016_LC|GO16046_LC|GO16062_LC
211426122, 132.775505, 12.032722, 17.084, GO16062_LC
211448269, 134.269361, 12.374054, 18.414, GO16016_LC|GO16046_LC|GO16062_LC
211450528, 131.324417, 12.408112, 18.335, GO16016_LC|GO16046_LC|GO16062_LC
211452383, 130.78035, 12.436169, 17.152, GO16016_LC|GO16062_LC
211480256, 135.961062, 12.854133, 19.153, GO16016_LC|GO16046_LC|GO16062_LC
211493869, 130.546078, 13.051918, 18.525, GO16016_LC|GO16046_LC|GO16062_LC
211494257, 130.232165, 13.058194, 17.219, GO16016_LC|GO16046_LC|GO16062_LC|GO16016_SC|GO16062_SC
211501588, 133.526048, 13.161737, 19.445, GO16016_LC|GO16062_LC
211506443, 134.592138, 13.230278, 19.237, GO16016_LC|GO16046_LC|GO16062_LC
211514591, 130.269617, 13.344401, 17.939, GO16016_LC|GO16046_LC|GO16062_LC
211519519, 130.081385, 13.413783, 18.862, GO16016_LC|GO16046_LC|GO16062_LC
211520086, 137.151562, 13.421919, 18.91, GO16016_LC|GO16046_LC|GO16062_LC
211525077, 129.911118, 13.493058, 19.188, GO16016_LC|GO16046_LC|GO16062_LC
211533336, 135.797914, 13.608934, 17.84, GO16016_LC|GO16046_LC|GO16062_LC
211537203, 133.789755, 13.662897, 19.449, GO16016_LC|GO16062_LC
211540647, 135.851958, 13.710961, 18.975, GO16016_LC|GO16046_LC|GO16062_LC
211541742, 133.902625, 13.726538, 18.347, GO16016_LC|GO16046_LC|GO16062_LC
211548364, 136.011823, 13.819749, 16.671, GO16016_LC|GO16046_LC|GO16062_LC
211589375, 137.366473, 14.395343, 18.448, GO16016_LC|GO16046_LC|GO16062_LC
211601001, 133.101749, 14.55237, 17.848, GO16016_LC|GO16062_LC
211606609, 136.694052, 14.628477, 17.556, GO16016_LC|GO16046_LC|GO16062_LC
211606711, 136.132575, 14.629857, 18.406, GO16016_LC|GO16046_LC|GO16062_LC
211606904, 134.051737, 14.632518, 19.367, GO16016_LC|GO16062_LC
211606929, 134.051728, 14.632829, 19.417, GO16062_LC
211614588, 133.948778, 14.737648, 18.54, GO16016_LC|GO16046_LC|GO16062_LC
211629697, 130.225591, 14.952495, 18.391, GO16016_LC|GO16046_LC|GO16062_LC|GO16016_SC
211636579, 137.08775, 15.050177, 17.933, GO16016_LC|GO16046_LC|GO16062_LC
211640386, 135.910944, 15.103145, 18.032, GO16016_LC|GO16046_LC|GO16062_LC|GO16016_SC
211656471, 133.092009, 15.322164, 19.955, GO16062_LC
211656785, 136.182689, 15.326475, 19.055, GO16016_LC|GO16046_LC|GO16062_LC
211683825, 139.011892, 15.697272, 18.403, GO16016_LC|GO16046_LC|GO16062_LC
211684712, 136.46963, 15.709441, 18.963, GO16016_LC|GO16046_LC|GO16062_LC
211695695, 137.237009, 15.858019, 19.183, GO16016_LC|GO16046_LC|GO16062_LC
211695719, 138.673877, 15.858429, 18.615, GO16016_LC|GO16046_LC|GO16062_LC
211695991, 135.389282, 15.862004, 15.922, GO16016_LC|GO16046_LC|GO16062_LC
211705006, 131.880483, 15.981081, 18.739, GO16016_LC|GO16046_LC|GO16062_LC
211708367, 130.331192, 16.025831, 18.049, GO16016_LC|GO16062_LC
211719918, 134.078957, 16.18438, 15.733, GO16016_LC|GO16046_LC|GO16062_LC|GO16065_LC|GO16901_LC
211729535, 137.791217, 16.318759, 18.376, GO16016_LC|GO16046_LC|GO16062_LC
211731069, 131.864445, 16.340238, 18.838, GO16016_LC|GO16046_LC|GO16062_LC
211736653, 136.482246, 16.419323, 19.072, GO16016_LC|GO16046_LC|GO16062_LC
211737660, 135.885417, 16.433625, 16.866, GO16016_LC|GO16046_LC|GO16062_LC|GO16065_LC
211738911, 135.400474, 16.451142, 17.424, GO16016_LC|GO16046_LC|GO16062_LC
211745108, 130.282051, 16.539361, 17.373, GO16016_LC|GO16046_LC|GO16062_LC
211746828, 133.661901, 16.563885, 17.822, GO16016_LC|GO16062_LC
211751631, 136.223022, 16.630865, 18.293, GO16016_LC|GO16046_LC|GO16062_LC
211752966, 135.548929, 16.649368, 19.097, GO16016_LC|GO16046_LC|GO16062_LC
211755392, 133.849449, 16.683052, 18.757, GO16016_LC|GO16046_LC|GO16062_LC
211756756, 136.43103, 16.702801, 18.346, GO16016_LC|GO16046_LC|GO16062_LC
211802985, 135.753533, 17.358884, 18.436, GO16016_LC|GO16046_LC|GO16062_LC
211805660, 130.998198, 17.397257, 17.031, GO16016_LC|GO16062_LC
211808335, 132.69796, 17.433889, 14.773, GO16016_LC|GO16046_LC|GO16062_LC
211810912, 131.886419, 17.471975, 19.065, GO16016_LC|GO16046_LC|GO16062_LC
211813146, 136.376294, 17.503157, 18.545, GO16016_LC|GO16046_LC|GO16062_LC|GO16016_SC
211821355, 133.075712, 17.620285, 19.48, GO16016_LC|GO16062_LC
211826551, 136.858447, 17.693311, 18.23, GO16016_LC|GO16046_LC|GO16062_LC
211830319, 130.605271, 17.747428, 16.501, GO16062_LC
211834988, 133.258557, 17.811972, 17.615, GO16016_LC|GO16046_LC|GO16062_LC
211853072, 132.755449, 18.060922, 18.343, GO16016_LC|GO16046_LC|GO16062_LC
211855381, 132.529085, 18.092514, 19.055, GO16016_LC|GO16046_LC|GO16062_LC
211858409, 134.45672, 18.134199, 17.207, GO16016_LC|GO16046_LC|GO16062_LC|GO16901_LC
211865815, 133.671447, 18.236747, 19.308, GO16016_LC|GO16046_LC|GO16062_LC
211877268, 134.037188, 18.39734, 19.047, GO16016_LC|GO16046_LC|GO16062_LC
211880860, 132.925713, 18.44813, 18.888, GO16016_LC|GO16062_LC
211902739, 133.930089, 18.767042, 17.557, GO16016_LC|GO16046_LC|GO16062_LC
211904631, 136.231074, 18.794965, 19.29, GO16016_LC|GO16062_LC
211904936, 136.20829, 18.799626, 17.295, GO16016_LC|GO16046_LC|GO16062_LC
211906915, 129.732325, 18.829588, 19.142, GO16016_LC|GO16046_LC|GO16062_LC
211908265, 136.604207, 18.849494, 19.369, GO16016_LC|GO16046_LC|GO16062_LC
211908662, 132.906114, 18.855436, 17.995, GO16016_LC|GO16062_LC|GO16901_LC
211909921, 130.441913, 18.874441, 18.91, GO16016_LC|GO16046_LC|GO16062_LC
211916160, 134.20139, 18.968032, 18.981, GO16016_LC|GO16046_LC|GO16062_LC|GO16016_SC
211918437, 133.981642, 19.001286, 19.874, GO16016_LC|GO16062_LC
211918500, 130.415559, 19.002148, 17.952, GO16016_LC|GO16046_LC|GO16062_LC
211922919, 133.110174, 19.067462, 19.703, GO16016_LC|GO16062_LC
211923589, 133.877905, 19.077044, 16.542, GO16062_LC|GO16901_LC
211923593, 133.877748, 19.077087, 16.36, GO16016_LC|GO16046_LC|GO16062_LC
211932489, 134.035153, 19.212617, 19.774, GO16016_LC|GO16062_LC
211932844, 137.473875, 19.218448, 17.942, GO16016_LC|GO16046_LC|GO16062_LC
211934173, 129.691108, 19.237999, 18.229, GO16016_LC|GO16039_LC|GO16062_LC
211935603, 137.568098, 19.258751, 18.665, GO16016_LC|GO16046_LC|GO16062_LC
211936871, 132.607689, 19.277636, 18.523, GO16016_LC|GO16046_LC|GO16062_LC
211957499, 131.562063, 19.587582, 18.365, GO16016_LC|GO16046_LC|GO16062_LC
211968416, 131.643349, 19.75138, 16.998, GO16016_LC|GO16046_LC|GO16062_LC|GO16016_SC|GO16062_SC
211997512, 135.827394, 20.213045, 16.952, GO16016_LC|GO16046_LC|GO16062_LC|GO16901_LC
211997837, 134.907731, 20.218247, 17.837, GO16016_LC|GO16046_LC|GO16062_LC
212015915, 127.005028, 20.519144, 18.555, GO16016_LC|GO16046_LC|GO16062_LC
212020650, 136.592078, 20.597541, 18.383, GO16016_LC|GO16046_LC|GO16062_LC
212021097, 127.525712, 20.605436, 19.835, GO16016_LC|GO16062_LC
212030588, 133.978919, 20.764769, 18.864, GO16016_LC|GO16046_LC|GO16062_LC
212032453, 135.814174, 20.795493, 17.769, GO16016_LC|GO16046_LC|GO16062_LC
212036995, 128.001118, 20.871258, 16.999, GO16016_LC|GO16046_LC|GO16062_LC
212044913, 127.098223, 21.010001, 19.116, GO16016_LC|GO16062_LC
212047071, 135.584501, 21.046366, 18.764, GO16016_LC|GO16046_LC|GO16062_LC
212050004, 137.56848, 21.098383, 16.496, GO16016_LC|GO16046_LC|GO16062_LC|GO16065_LC
212072946, 133.010177, 21.510131, 18.483, GO16016_LC|GO16046_LC|GO16062_LC|GO16016_SC
212080404, 132.652203, 21.648463, 18.652, GO16016_LC|GO16046_LC|GO16062_LC
212080588, 133.320798, 21.651623, 18.311, GO16016_LC|GO16046_LC|GO16062_LC
212081298, 135.840421, 21.664419, 18.434, GO16016_LC|GO16046_LC|GO16062_LC
212086411, 136.501469, 21.759607, 18.194, GO16016_LC|GO16046_LC|GO16062_LC
212090116, 137.313454, 21.829098, 18.198, GO16016_LC|GO16046_LC|GO16062_LC|GO16016_SC
212101462, 136.506327, 22.049726, 18.33, GO16016_LC|GO16046_LC|GO16062_LC|GO16016_SC
212109222, 136.098071, 22.202799, 18.343, GO16016_LC|GO16046_LC|GO16062_LC|GO16016_SC
212112843, 133.472938, 22.274722, 16.788, GO16016_LC|GO16046_LC|GO16062_LC|GO16065_LC
212114029, 133.262751, 22.298724, 18.943, GO16016_LC|GO16046_LC|GO16062_LC
212153568, 135.742594, 23.111165, 17.426, GO16016_LC|GO16046_LC|GO16062_LC
212157560, 133.589889, 23.199131, 19.194, GO16016_LC|GO16046_LC|GO16062_LC
212168788, 135.081229, 23.457786, 18.289, GO16016_LC|GO16046_LC|GO16062_LC|GO16016_SC
212171707, 134.807011, 23.528269, 16.57, GO16016_LC|GO16046_LC|GO16062_LC
212171731, 130.447097, 23.528807, 18.785, GO16016_LC|GO16046_LC|GO16062_LC
212173115, 134.219366, 23.561608, 18.68, GO16016_LC|GO16046_LC|GO16062_LC
212173448, 129.892956, 23.569284, 16.726, GO16046_LC|GO16062_LC
212179850, 135.099571, 23.731451, 18.872, GO16016_LC|GO16046_LC|GO16062_LC
212181664, 134.982843, 23.780281, 18.665, GO16016_LC|GO16046_LC|GO16062_LC
212182185, 131.275478, 23.795315, 17.719, GO16016_LC|GO16046_LC|GO16062_LC|GO16016_SC
212186531, 133.524264, 23.912798, 18.845, GO16016_LC|GO16046_LC|GO16062_LC
212193168, 132.926723, 24.090277, 16.067, GO16016_LC|GO16062_LC
212197411, 131.742296, 24.211153, 18.608, GO16016_LC|GO16046_LC|GO16062_LC
212200453, 134.34457, 24.302776, 17.839, GO16016_LC|GO16046_LC|GO16062_LC
212200935, 134.957055, 24.316251, 19.28, GO16016_LC|GO16062_LC
212214571, 133.845915, 24.756276, 18.78, GO16016_LC|GO16046_LC|GO16062_LC
212227927, 130.388665, 25.284739, 17.454, GO16016_LC|GO16046_LC|GO16062_LC
228682341, 127.1694489, 21.5208492, 18.11, GO16016_LC|GO16046_LC|GO16062_LC
228682373, 130.0553741, 18.7239799, 18.02, GO16016_LC|GO16046_LC|GO16062_LC
228682383, 130.7643127, 16.1220493, 18.43, GO16016_LC|GO16046_LC|GO16062_LC
228682385, 130.9767609, 17.5720291, 18.31, GO16016_LC|GO16046_LC|GO16062_LC
228682387, 131.1430359, 14.9304504, 18.82, GO16016_LC|GO16046_LC|GO16062_LC
228682413, 132.8969116, 16.3103199, 17.19, GO16016_LC|GO16046_LC|GO16062_LC
228682416, 133.3305054, 18.8956909, 17.31, GO16016_LC|GO16046_LC|GO16062_LC
228682419, 133.5581207, 18.8899002, 17.73, GO16016_LC|GO16046_LC|GO16062_LC
228682422, 135.6152344, 12.86833, 17.06, GO16016_LC|GO16046_LC|GO16062_LC
228682423, 135.9700165, 19.6121006, 16.37, GO16016_LC|GO16046_LC|GO16062_LC|GO16065_LC
228682429, 137.0964355, 12.7844296, 17.33, GO16016_LC|GO16046_LC|GO16062_LC
228682478, 130.1159973, 13.3360996, 18.3, GO16016_LC|GO16046_LC|GO16062_LC|GO16016_SC
251277107, 140.276847, 14.126877, 18.249, GO16016_LC|GO16046_LC|GO16062_LC
251282015, 138.91531, 14.64857, 18.176, GO16016_LC|GO16046_LC|GO16062_LC
251286299, 140.660274, 15.115234, 18.28, GO16016_LC|GO16046_LC|GO16062_LC
251293962, 139.736414, 15.970807, 18.432, GO16016_LC|GO16046_LC|GO16062_LC|GO16016_SC
251296369, 140.407959, 16.227348, 17.641, GO16016_LC|GO16062_LC
251310701, 140.079086, 17.689807, 18.467, GO16016_LC|GO16046_LC|GO16062_LC
251312609, 139.539905, 17.871168, 18.624, GO16016_LC|GO16062_LC
251315896, 139.86251, 18.164012, 18.924, GO16016_LC|GO16046_LC|GO16062_LC
251317338, 140.502955, 18.287334, 17.904, GO16016_LC|GO16062_LC
251318460, 139.378123, 18.386049, 18.373, GO16016_LC|GO16046_LC|GO16062_LC
251318875, 139.199411, 18.422875, 18.74, GO16016_LC|GO16046_LC|GO16062_LC
251322279, 140.985449, 18.711842, 18.376, GO16008_LC|GO16016_LC|GO16046_LC|GO16062_LC
251325703, 140.745478, 18.997036, 19.074, GO16016_LC|GO16046_LC|GO16062_LC
251335557, 139.637145, 19.885305, 18.913, GO16062_LC
251335876, 139.329751, 19.910696, 16.763, GO16016_LC|GO16046_LC|GO16062_LC|GO16089_LC|GO16096_LC
251340170, 139.478819, 20.268262, 17.871, GO16016_LC|GO16046_LC|GO16062_LC
251340172, 138.992455, 20.268371, 16.922, GO16016_LC|GO16046_LC|GO16062_LC|GO16065_LC
251341655, 139.774236, 20.387971, 17.502, GO16016_LC|GO16046_LC|GO16062_LC
251344281, 141.021882, 20.596246, 14.75, GO16016_LC|GO16051_LC|GO16062_LC|GO16089_LC|GO16096_LC|GO16051_SC|GO16062_SC
251345204, 141.141578, 20.672228, 17.627, GO16016_LC|GO16062_LC
251345209, 139.994218, 20.672554, 17.357, GO16016_LC|GO16046_LC|GO16062_LC
251347348, 140.808283, 20.855522, 19.71, GO16016_LC|GO16062_LC
251347595, 139.604698, 20.875795, 18.652, GO16016_LC|GO16046_LC|GO16062_LC
251354912, 140.913432, 21.483332, 16.507, GO16016_LC|GO16046_LC|GO16062_LC|GO16065_LC
251355286, 140.98255, 21.514412, 19.365, GO16016_LC|GO16062_LC
251355548, 138.159719, 21.535057, 17.935, GO16016_LC|GO16046_LC|GO16062_LC
251357781, 139.37376, 21.726037, 18.954, GO16016_LC|GO16062_LC
251357953, 138.945438, 21.741208, 18.805, GO16016_LC|GO16046_LC|GO16062_LC|GO16016_SC
251359879, 139.300732, 21.907213, 18.268, GO16016_LC|GO16062_LC
251360267, 137.654925, 21.937943, 17.237, GO16016_LC|GO16046_LC|GO16062_LC
251364086, 137.440468, 22.238818, 18.807, GO16016_LC|GO16046_LC|GO16062_LC
251384067, 138.068281, 23.745184, 17.67, GO16016_LC|GO16062_LC
251398020, 136.657225, 24.667454, 16.978, GO16016_LC|GO16046_LC|GO16062_LC|GO16016_SC|GO16062_SC
251399174, 135.820951, 24.735312, 17.743, GO16016_LC|GO16046_LC|GO16062_LC
251400062, 135.263044, 24.788588, 19.933, GO16016_LC|GO16062_LC
251809151, , , , GO16016_LC|GO16046_LC|GO16062_LC|GO16016_SC
251809152, , , , GO16016_LC|GO16046_LC|GO16062_LC|GO16016_SC
251809153, , , , GO16016_LC|GO16046_LC|GO16062_LC|GO16016_SC
251809154, , , , GO16016_LC|GO16046_LC|GO16062_LC
251809155, , , , GO16016_LC|GO16046_LC|GO16062_LC
251809156, , , , GO16016_LC|GO16046_LC|GO16062_LC
251809158, , , , GO16016_LC|GO16046_LC|GO16062_LC
251809159, , , , GO16016_LC|GO16046_LC|GO16062_LC
251809160, , , , GO16016_LC|GO16046_LC|GO16062_LC
251809161, , , , GO16016_LC|GO16046_LC|GO16062_LC
251809162, , , , GO16016_LC|GO16046_LC|GO16062_LC
251809163, , , , GO16016_LC|GO16046_LC|GO16062_LC
251809164, , , , GO16016_LC|GO16046_LC|GO16062_LC
251809165, , , , GO16016_LC|GO16046_LC|GO16062_LC
251809166, , , , GO16016_LC|GO16046_LC|GO16062_LC
251809167, , , , GO16016_LC|GO16046_LC|GO16062_LC
251809169, , , , GO16016_LC|GO16046_LC|GO16062_LC
251809171, , , , GO16016_LC|GO16046_LC|GO16062_LC
251809177, , , , GO16016_LC|GO16046_LC|GO16062_LC
251809178, , , , GO16016_LC|GO16046_LC|GO16062_LC
251809180, , , , GO16016_LC|GO16046_LC|GO16062_LC
251809185, , , , GO16016_LC|GO16019_LC|GO16046_LC|GO16062_LC
251809186, , , , GO16016_LC|GO16046_LC|GO16062_LC
251809189, , , , GO16016_LC|GO16046_LC|GO16062_LC
251809191, , , , GO16016_LC|GO16046_LC|GO16062_LC
251809193, , , , GO16016_LC|GO16062_LC
251809195, , , , GO16016_LC|GO16046_LC|GO16062_LC
251809197, , , , GO16016_LC|GO16046_LC|GO16062_LC
251809204, , , , GO16016_LC|GO16046_LC|GO16062_LC
251809226, , , , GO16016_LC|GO16062_LC
251809227, , , , GO16016_LC|GO16062_LC
251809232, , , , GO16016_LC|GO16062_LC
251809234, , , , GO16016_LC|GO16062_LC
251809273, , , , GO16062_LC
251809274, , , , GO16062_LC
251809275, , , , GO16062_LC