# Summary of K2 Program GO14046

Title: Eclipses, transits and variability of white dwarf stars with the K2 Mission

PI: Burleigh, Matt R. (University of Leicester)
CoIs: Belardi, Claudia; Holberg, Jay B; Barstow, Martin Adrian; Braker, Ian Peter

Matt Burleigh(1)(PI), Jay Holberg(2)(Co-I), Martin Barstow(1)(Co-I), Ian Braker(1) & Claudia Belardi(1)(Graduate Students)

(1) Dept. Physics and Astronomy, University of Leicester, UK.
(2) Lunar and Planetary Laboratory, Sonnett Space Sciences Bld., University of Arizona, Tucson, AZ 85721, USA

The small size of a white dwarf (WD) star (approx. 1 Earth radii) implies that any sub-stellar or gas giant companion at suitable orbital inclination will completely eclipse it, while terrestrial bodies smaller than the Moon, including asteroids, will still produce transits that are detectable in high signal/noise light-curves. 

Whether such planets actually exist around WDs is an open question. Those caught within the expanding envelope of an AGB star will be destroyed. However, the presence of debris disks around a few % of WDs (Farihi et al. 2011, Barber et al. 2012), and accreted metals in the photospheres of a surprisingly large fraction of such stars (approx. 25% at circa 1 Gyr, Zuckerman et al.2003) demonstrates that surviving asteroids and terrestrial planets must be perturbed into orbits that take them close to the central WD, where they are tidally disrupted. Even so, it appears dynamically difficult, though not impossible, to perturb them into stable, circularised orbits within the WD HZ. Alternatively, 2nd generation planets may be created from material ejected after the AGB phase. 

The Kepler 2 mission is an ideal opportunity to search the HZs of a statistically significant (1000 to 1500) sample of WDs for terrestrial planets. Any discovery would provide vital data and a significant challenge to dynamicists and theoreticians, just as the unexpected discovery of hot Jupiters did in the 1990s. A single detection would then open the exciting possibility of studying the atmosphere of a nearby terrestrial world through spectroscopy with JWST (Loeb & Maoz 2013). 

A Kepler survey of WDs opens up other serendipitous science than just the exciting, but perhaps tantalising prize of a terrestrial planet. Besides pulsating WDs, which can be studied in exquisite detail with high cadence mode observations, other variable examples will be discovered. Recently, Beuermann et al.(2013) discovered the first eclipsing, detached WD + brown dwarf (BD) system, and Casewell et al.(2012) found probably the lowest mass close companion to a white dwarf (25 - 30 Jupiter masses). Both BDs likely survived common envelope evolution, but what is the lowest mass object that can do so, and will it be revealed through eclipses of the WD?

This survey will also reveal the full population of optically variable WDs at accuracies undetectable from the Earth. We have detected low level variability in circa 50% of the WDs in the Kepler and K2 Campaign 0 fields. These could be due to star spots or accretion of dust from disrupted asteroids onto poles of low level magnetic WDs. It is likely more unexpected variables await discovery.

The total eclipse of an Earth-sized WD by a Jovian or BD sized companion in a few hour orbit will last around 5 mins. In a 30 min long cadence (LC) observation this will be diluted to 17%. An eclipse by an Earth terrestrial companion in the HZ would last approximately 2.5 min, diluted to circa 8% in a LC datapoint. These can be compared to the expected Kepler 2 mission sensitivity at magnitude 19.0 of circa 50,000ppm(5%). Even at this faint magnitude, the Jovian sized object would be comfortably visible at 3 sigma confidence in a single datapoint, while the Earth-sized object would also be detectable, especially if many such eclipses/transits are observed and suitably phase-folded.

We estimate that our target list will be made up of 177, 17 and 242 WDs (campaigns 14, 15 and 16), that have been spectroscopically identified or are deemed to have a 60% or greater probability of being a WD (Fusillo et al. 2015), and which are brighter than Kepler Magnitude 19.5 from the McCook & Sion and SDSS catalogues.

# Targets requested by this program that have been observed (165)
EPIC ID, RA (J2000) [deg], Dec (J2000) [deg], magnitude, Investigation IDs
201613723, 165.589668, 2.256308, 19.431, GO14016_LC|GO14046_LC
201631096, 166.495901, 2.524423, 18.317, GO14016_LC|GO14046_LC|GO14062_LC|GO14016_SC
201634969, 166.253388, 2.584651, 18.783, GO14016_LC|GO14046_LC|GO14062_LC
201644501, 166.455178, 2.731244, 18.878, GO14016_LC|GO14046_LC|GO14062_LC
201703729, 165.684386, 3.703003, 18.569, GO14016_LC|GO14046_LC|GO14062_LC
201719996, 166.247355, 3.979986, 19.497, GO14016_LC|GO14046_LC
201730127, 166.769858, 4.152947, 17.235, GO14046_LC|GO14001_LC
210282465, 166.76577, 4.09537, 17.1, GO14016_LC|GO14046_LC|GO14062_LC|GO14016_SC|GO14062_SC
248407521, 162.302712, -0.148571, 18.246, GO14016_LC|GO14046_LC|GO14062_LC
248413871, 162.307617, 0.100055, 19.463, GO14016_LC|GO14046_LC|GO14062_LC
248414370, 161.826303, 0.121795, 17.332, GO14016_LC|GO14046_LC|GO14062_LC|GO14062_SC
248414962, 162.348911, 0.146094, 19.275, GO14016_LC|GO14046_LC
248426757, 162.443492, 0.609764, 17.54, GO14016_LC|GO14046_LC|GO14062_LC
248428008, 162.476839, 0.65873, 19.02, GO14016_LC|GO14046_LC|GO14062_LC
248429573, 156.349081, 0.718279, 17.92, GO14016_LC|GO14046_LC|GO14062_LC
248433277, 156.721318, 0.852928, 19.001, GO14016_LC|GO14046_LC|GO14062_LC
248433650, 158.703862, 0.867064, 19.073, GO14016_LC|GO14046_LC|GO14062_LC
248433686, 157.676808, 0.868146, 17.231, GO14016_LC|GO14046_LC|GO14062_LC|GO14062_SC
248439241, 156.173832, 1.078663, 17.68, GO14016_LC|GO14046_LC|GO14062_LC
248440910, 162.75821, 1.140753, 17.91, GO14016_LC|GO14046_LC|GO14062_LC
248446356, 157.992759, 1.348257, 18.585, GO14016_LC|GO14046_LC|GO14062_LC
248453399, 163.688172, 1.590425, 18.86, GO14016_LC|GO14046_LC|GO14062_LC
248453426, 159.350499, 1.591353, 18.529, GO14016_LC|GO14046_LC|GO14062_LC
248454038, 156.536999, 1.610699, 18.73, GO14016_LC|GO14046_LC|GO14062_LC|GO14016_SC
248460269, 157.400765, 1.836293, 17.492, GO14016_LC|GO14046_LC|GO14062_LC|GO14062_SC
248460728, 157.703153, 1.85276, 19.402, GO14046_LC
248462523, 160.372252, 1.910748, 18.494, GO14016_LC|GO14046_LC|GO14062_LC
248466564, 159.657169, 2.041474, 18.227, GO14016_LC|GO14046_LC|GO14062_LC
248468138, 157.290868, 2.098246, 14.313, GO14016_LC|GO14046_LC|GO14062_LC|GO14016_SC|GO14062_SC
248469194, 157.472206, 2.136798, 19.001, GO14016_LC|GO14046_LC|GO14019_LC|GO14062_LC|GO14016_SC
248474603, 158.081071, 2.316306, 16.667, GO14016_LC|GO14041_LC|GO14046_LC|GO14062_LC|GO14016_SC|GO14062_SC
248497132, 160.944737, 3.055114, 19.204, GO14016_LC|GO14046_LC|GO14062_LC
248498792, 160.838205, 3.108451, 18.049, GO14016_LC|GO14046_LC|GO14062_LC
248500910, 161.278822, 3.170616, 19.083, GO14016_LC|GO14046_LC|GO14062_LC|GO14016_SC
248505080, 159.844275, 3.296458, 19.048, GO14016_LC|GO14046_LC|GO14062_LC|GO14016_SC
248508124, 165.071513, 3.394467, 17.841, GO14016_LC|GO14046_LC|GO14062_LC|GO14016_SC
248511748, 157.724584, 3.514318, 18.886, GO14016_LC|GO14046_LC|GO14062_LC|GO14016_SC
248513530, 160.703944, 3.565382, 17.634, GO14016_LC|GO14089_LC|GO14046_LC
248519839, 157.093041, 3.737939, 17.437, GO14016_LC|GO14046_LC|GO14062_LC|GO14062_SC
248522846, 159.314011, 3.824928, 18.987, GO14016_LC|GO14046_LC|GO14062_LC
248523380, 159.487663, 3.839912, 18.749, GO14016_LC|GO14024_LC|GO14046_LC|GO14024_SC
248523392, 158.052315, 3.84016, 18.983, GO14016_LC|GO14046_LC|GO14062_LC
248524686, 159.390925, 3.87543, 17.859, GO14016_LC|GO14046_LC|GO14062_LC
248530218, 153.56042, 4.026923, 16.738, GO14016_LC|GO14046_LC|GO14062_LC|GO14065_LC|GO14062_SC
248532028, 154.579111, 4.074254, 19.274, GO14016_LC|GO14046_LC|GO14062_LC
248532749, 156.605005, 4.092864, 17.565, GO14016_LC|GO14046_LC|GO14062_LC
248537421, 155.177815, 4.217457, 18.018, GO14016_LC|GO14046_LC|GO14062_LC
248545116, 153.883777, 4.418761, 17.988, GO14016_LC|GO14046_LC|GO14062_LC
248551477, 161.366861, 4.583972, 19.481, GO14046_LC
248556699, 154.178916, 4.721588, 18.685, GO14016_LC|GO14046_LC|GO14062_LC
248563865, 161.561464, 4.923248, 19.199, GO14016_LC|GO14046_LC|GO14062_LC
248569787, 160.065081, 5.072968, 18.403, GO14016_LC|GO14046_LC|GO14062_LC
248573839, 155.802622, 5.177644, 17.723, GO14016_LC|GO14046_LC|GO14062_LC|GO14016_SC|GO14062_SC
248578252, 156.809906, 5.29615, 18.893, GO14016_LC|GO14046_LC|GO14062_LC
248580640, 156.355905, 5.358589, 17.688, GO14016_LC|GO14046_LC|GO14062_LC
248581476, 154.735942, 5.380167, 19.315, GO14016_LC|GO14046_LC
248581555, 154.770168, 5.382291, 18.326, GO14016_LC|GO14046_LC|GO14019_LC
248584439, 163.767577, 5.45889, 17.522, GO14016_LC|GO14046_LC|GO14062_LC|GO14016_SC
248588851, 155.836676, 5.57942, 16.331, GO14016_LC|GO14096_LC|GO14051_LC|GO14089_LC|GO14080_LC|GO14046_LC|GO14051_SC|GO14080_SC
248597896, 155.067138, 5.822043, 18.318, GO14016_LC|GO14046_LC|GO14062_LC
248599783, 160.080297, 5.869449, 19.371, GO14016_LC|GO14046_LC|GO14062_LC
248601252, 164.600344, 5.905086, 19.258, GO14016_LC|GO14046_LC|GO14062_LC
248602701, 160.97848, 5.941483, 18.861, GO14016_LC|GO14046_LC|GO14062_LC
248603516, 159.821266, 5.961589, 19.472, GO14016_LC|GO14046_LC|GO14062_LC
248606906, 158.522215, 6.046606, 16.416, GO14016_LC|GO14046_LC|GO14062_LC|GO14062_SC
248608148, 159.890781, 6.077192, 18.493, GO14016_LC|GO14046_LC|GO14062_LC
248624594, 163.349067, 6.493419, 19.201, GO14016_LC|GO14046_LC|GO14062_LC
248628269, 160.218401, 6.588829, 19.349, GO14016_LC|GO14046_LC
248634592, 164.087204, 6.746097, 18.348, GO14016_LC|GO14046_LC|GO14062_LC
248635938, 162.416822, 6.779755, 19.508, GO14016_LC|GO14046_LC|GO14062_LC
248635955, 155.609552, 6.780263, 19.283, GO14016_LC|GO14046_LC|GO14062_LC
248637190, 163.369576, 6.81157, 19.434, GO14016_LC|GO14046_LC|GO14062_LC
248650425, 158.643, 7.132468, 18.603, GO14016_LC|GO14046_LC|GO14062_LC
248659526, 154.506321, 7.356818, 16.754, GO14046_LC
248660813, 158.605641, 7.389513, 19.156, GO14016_LC|GO14046_LC|GO14062_LC
248661794, 161.139475, 7.412866, 18.186, GO14016_LC|GO14046_LC|GO14062_LC|GO14016_SC
248663488, 158.919961, 7.454663, 18.261, GO14016_LC|GO14046_LC|GO14062_LC
248663697, 153.899341, 7.460197, 19.105, GO14016_LC|GO14046_LC|GO14062_LC
248669978, 161.474447, 7.619067, 19.144, GO14016_LC|GO14046_LC|GO14062_LC
248678645, 154.153366, 7.830919, 18.656, GO14016_LC|GO14046_LC|GO14062_LC
248682887, 161.33209, 7.932435, 19.42, GO14016_LC|GO14089_LC|GO14046_LC
248685601, 156.963157, 7.998743, 18.411, GO14016_LC|GO14046_LC
248701815, 154.298307, 8.376452, 18.977, GO14016_LC|GO14046_LC|GO14062_LC
248705247, 155.27791, 8.456893, 17.872, GO14016_LC|GO14046_LC|GO14062_LC|GO14016_SC
248706244, 163.964535, 8.479521, 17.06, GO14016_LC|GO14046_LC|GO14062_LC|GO14062_SC
248707316, 162.761145, 8.504168, 19.224, GO14016_LC|GO14046_LC
248713178, 154.500103, 8.63906, 16.48, GO14016_LC|GO14046_LC|GO14062_LC|GO14062_SC
248713228, 153.965145, 8.640726, 19.495, GO14016_LC|GO14046_LC
248715682, 160.328744, 8.694389, 17.151, GO14016_LC|GO14046_LC|GO14062_LC|GO14016_SC|GO14062_SC
248717202, 162.023237, 8.728712, 19.542, GO14046_LC
248718843, 159.897456, 8.766421, 17.612, GO14016_LC|GO14046_LC|GO14062_LC
248726003, 160.923082, 8.932843, 17.351, GO14016_LC|GO14024_LC|GO14046_LC|GO14062_LC|GO14016_SC|GO14024_SC|GO14062_SC
248742853, 161.443509, 9.307011, 18.209, GO14016_LC|GO14046_LC|GO14062_LC
248743219, 157.495167, 9.315215, 18.459, GO14016_LC|GO14046_LC|GO14062_LC
248744229, 161.443074, 9.341123, 19.341, GO14016_LC|GO14046_LC
248744955, 163.615097, 9.358002, 17.801, GO14016_LC|GO14046_LC|GO14062_LC
248748936, 157.160956, 9.449415, 18.729, GO14016_LC|GO14046_LC|GO14062_LC|GO14016_SC
248750313, 156.272664, 9.482777, 17.354, GO14016_LC|GO14046_LC|GO14062_LC|GO14016_SC|GO14062_SC
248753592, 157.493227, 9.559278, 17.905, GO14016_LC|GO14046_LC|GO14062_LC
248754831, 160.228947, 9.587581, 18.102, GO14016_LC|GO14046_LC|GO14062_LC
248755999, 157.849654, 9.616023, 18.744, GO14016_LC|GO14046_LC|GO14062_LC|GO14016_SC
248760544, 155.931944, 9.726817, 17.637, GO14016_LC|GO14046_LC|GO14062_LC|GO14016_SC
248760850, 157.649852, 9.733519, 18.682, GO14016_LC|GO14046_LC|GO14062_LC
248764081, 162.198879, 9.811406, 17.953, GO14016_LC|GO14046_LC|GO14062_LC|GO14016_SC
248764651, 155.95589, 9.824913, 19.049, GO14016_LC|GO14046_LC|GO14062_LC
248767533, 154.198396, 9.89285, 17.983, GO14016_LC|GO14046_LC|GO14062_LC
248767795, 160.151646, 9.899594, 18.676, GO14016_LC|GO14046_LC|GO14062_LC
248770462, 164.704769, 9.963881, 18.205, GO14016_LC|GO14046_LC|GO14062_LC
248771179, 162.370085, 9.983218, 17.473, GO14016_LC|GO14046_LC|GO14001_LC|GO14062_LC|GO14062_SC
248774665, 160.082093, 10.066797, 17.094, GO14016_LC|GO14046_LC
248775854, 163.467191, 10.097357, 19.102, GO14016_LC|GO14046_LC|GO14062_LC
248776437, 154.830027, 10.112039, 18.42, GO14016_LC|GO14046_LC|GO14062_LC
248778135, 163.963786, 10.154626, 18.773, GO14016_LC|GO14046_LC|GO14062_LC|GO14016_SC
248784059, 160.588515, 10.298676, 18.142, GO14016_LC|GO14046_LC|GO14062_LC
248785736, 161.708048, 10.339507, 18.688, GO14016_LC|GO14046_LC|GO14062_LC|GO14016_SC
248788064, 162.341569, 10.395493, 17.73, GO14016_LC|GO14046_LC
248790743, 163.669736, 10.461302, 18.939, GO14016_LC|GO14046_LC|GO14062_LC
248792048, 163.285468, 10.493919, 18.464, GO14016_LC|GO14046_LC|GO14062_LC
248804379, 160.769444, 10.781662, 19.259, GO14016_LC|GO14046_LC
248817394, 157.228763, 11.097379, 15.43, GO14016_LC|GO14046_LC|GO14062_LC|GO14062_SC
248821672, 154.465251, 11.200473, 18.45, GO14016_LC|GO14046_LC|GO14062_LC
248829364, 157.215925, 11.391174, 18.127, GO14016_LC|GO14046_LC|GO14062_LC|GO14016_SC
248833121, 163.143818, 11.482274, 18.627, GO14016_LC|GO14046_LC|GO14062_LC
248833732, 163.646476, 11.497381, 18.617, GO14016_LC|GO14046_LC|GO14062_LC
248841922, 154.95696, 11.696847, 18.942, GO14016_LC|GO14046_LC|GO14062_LC
248845621, 161.485788, 11.792908, 19.17, GO14016_LC|GO14046_LC|GO14062_LC
248847931, 162.278352, 11.853336, 18.979, GO14016_LC|GO14046_LC|GO14019_LC|GO14062_LC
248852659, 164.291396, 11.974845, 17.935, GO14016_LC|GO14046_LC|GO14062_LC
248855947, 157.641723, 12.058361, 17.421, GO14016_LC|GO14046_LC|GO14062_LC|GO14062_SC
248856078, 157.859124, 12.061226, 17.919, GO14016_LC|GO14046_LC|GO14062_LC
248860199, 161.586279, 12.163733, 17.719, GO14016_LC|GO14046_LC|GO14062_LC|GO14016_SC
248860933, 165.298301, 12.182773, 18.266, GO14016_LC|GO14046_LC|GO14062_LC
248862231, 165.582346, 12.214978, 18.241, GO14016_LC|GO14046_LC|GO14062_LC
248863169, 163.729545, 12.238126, 17.176, GO14016_LC|GO14046_LC|GO14062_LC|GO14016_SC|GO14062_SC
248877141, 158.043481, 12.592193, 18.681, GO14016_LC|GO14046_LC|GO14062_LC
248885981, 157.551183, 12.830734, 17.832, GO14016_LC|GO14046_LC|GO14062_LC
248891097, 159.645406, 12.978538, 17.021, GO14016_LC|GO14046_LC|GO14019_LC|GO14062_LC|GO14016_SC|GO14062_SC
248891537, 159.167549, 12.990752, 17.715, GO14016_LC|GO14046_LC|GO14062_LC
248894930, 162.505668, 13.087332, 19.136, GO14016_LC|GO14046_LC
248898715, 158.419851, 13.199883, 19.331, GO14016_LC|GO14046_LC|GO14019_LC
248900749, 160.753044, 13.265122, 19.116, GO14016_LC|GO14046_LC
248902546, 160.714226, 13.320636, 18.78, GO14016_LC|GO14046_LC|GO14062_LC|GO14016_SC
248908390, 159.042408, 13.503519, 18.995, GO14016_LC|GO14046_LC|GO14062_LC
248914597, 159.528218, 13.707077, 19.05, GO14046_LC
251457051, 158.080292, 5.433444, 19.1, GO14016_LC|GO14046_LC|GO14062_LC|GO14016_SC
251457052, 161.6614, 12.8478, 18.9, GO14016_LC|GO14046_LC|GO14062_LC|GO14016_SC
251457053, 160.6439, 12.47448, 18.9, GO14016_LC|GO14046_LC|GO14062_LC|GO14016_SC
251457054, 162.3128, -0.118406, 19.0, GO14016_LC|GO14046_LC|GO14062_LC|GO14016_SC
251457056, 156.457133, 0.6517, 16.1, GO14016_LC|GO14046_LC|GO14062_LC|GO14062_SC
251457059, 161.147, 1.704118, 17.6, GO14016_LC|GO14046_LC|GO14062_LC|GO14062_SC
251457062, 160.5694, 12.52032, 18.5, GO14016_LC|GO14046_LC|GO14062_LC
251457065, 164.0916, 5.706318, 18.6, GO14016_LC|GO14046_LC|GO14062_LC
251457067, 159.2584, 3.446688, 18.7, GO14016_LC|GO14046_LC|GO14062_LC
251457068, 157.7258, 1.379383, 18.8, GO14016_LC|GO14046_LC|GO14062_LC
251457069, 160.8492, 4.292681, 18.8, GO14016_LC|GO14046_LC|GO14062_LC
251457070, 162.4046, 12.80774, 18.8, GO14016_LC|GO14046_LC|GO14062_LC
251457076, 156.0577, 1.590721, 19.0, GO14016_LC|GO14046_LC|GO14062_LC
251457077, 158.5436, 10.09502, 19.1, GO14016_LC|GO14046_LC|GO14062_LC
251457078, 156.4799, 1.996308, 19.2, GO14016_LC|GO14046_LC|GO14062_LC
251457079, 161.4473, 8.986471, 19.2, GO14016_LC|GO14046_LC|GO14062_LC|GO14062_SC
251457081, 164.7305, 11.411167, 19.3, GO14016_LC|GO14046_LC
251457083, 158.084125, 1.2075, 19.3, GO14016_LC|GO14046_LC|GO14062_LC
251457084, 158.079917, 13.334222, 19.4, GO14016_LC|GO14046_LC
251457085, 157.329042, 2.189444, 19.5, GO14016_LC|GO14046_LC|GO14062_LC
251457118, 155.12604, 5.262861, 19.2, GO14046_LC