# Summary of K2 Program GO13011

Title: Rotation and activity of brown dwarfs in Taurus

PI: Scholz, Aleks (University of St Andrews)
CoIs: Kostov, Veselin; Stelzer, Beate; Jayawardhana, Ray; Melnikov, Stanislav; Eisloeffel, Jochen

Rotation is a fundamental parameter in the formation and evolution of stars. Young stars have orders of magnitude less angular momentum per unit mass than the cloud cores from which they have formed, indicating that efficient rotational braking occurs in the first few million years, due to binary and planet formation as well as interaction between star and disk. Subsequently stars spin up due to pre-main sequence contraction over ~100 million years. On longer timescales, the spin of stars is controlled by winds powered by stellar magnetic fields. Thus, the rotation is linked to key elements in the evolution of stars. 

In contrast to most other parameters of low-mass stars, the rotation period is a quantity that can be measured with very high accuracy in many objects. Period measurements are routinely done by photometric monitoring and measuring the periodic flux modulation caused by cool magnetic spots co-rotating with the stars. The rotation periods provide highly relevant constraints on our understanding of magnetic activity and angular momentum exchange between stars and their disks. For comprehensive reviews on this topic, see Herbst et al. (2007) and Bouvier et al. (2014).

For FGK stars, our best spindown models succesfully reproduce the observed periods in open clusters with known age and distance. These models take into account disk locking, contraction, wind braking, as well as core-envelope decoupling. So far, however, the models fail to explain the rotational evolution of the fully convective very low mass stars (M<0.3 Msol) and brown dwarfs (M<0.08 Msol). Over the past decade, we have carried out groundbreaking observational work to characterise the rotational behaviour of these VLM objects. In a series of papers we have published more than hundred rotation periods for objects below the 0.3 Msol boundary (Scholz & Eisloeffel 2004a, b, 2005, 2007; Scholz, Eisloeffel, Mundt 2009; Scholz et al. 2011). It has turned out that VLM objects retain high rotation rates for at least a gigayear, brown dwarfs for much longer. This is puzzling, as there is also evidence for large-scale magnetic fields and strong magnetic activity in VLM stars (Morin et al. 2011). The fast rotation of VLM objects may be a result of inefficient angular momentum transport due to a change in magnetic field topology and/or the increasingly neutral stellar atmospheres. At this point, however, this remains speculative.

The current rotational database is very sparse in the mass domain below 0.3 Msol, which precludes further empirical tests of the ideas outlined above. Almost no periods are available for objects with M<0.1Msol and ages >10 Myr. Most periods for young brown dwarfs are in distant regions with little chance of detailed follow-up. K2 offers a unique chance to remedy the situation and to study the rotation of very low mass stars and brown dwarfs as a function of age. We have already published the first brown dwarf rotation period from campaign 2 for the 10 Myr old UpSco association (Scholz et al. 2015). We are currently in the process of analysing data from campaign 4 and 5, which contain The field covers large parts of the Pleiades (age 100 Myr), the Hyades (age 600 Myr), and Praesepe (age 600 Myr), three of the classical benchmark clusters. In addition, a paper with rotation periods and activity diagnostics for field M dwarfs from campaign 0-4 is close to being submitted (Stelzer et al. 2016). In campaign 13 we get another chance to pursue this project, when the K2 field includes the young brown dwarfs in the Taurus association (age 1-2 Myr), and again the Hyades, in total about 100 target for our science goals. Here we propose to study their rotation and activity using K2 and to continue our successful project.

# Targets requested by this program that have been observed (60)
EPIC ID, RA (J2000) [deg], Dec (J2000) [deg], magnitude, Investigation IDs
210540496, 67.51739, 16.068888, 15.236, GO13018_LC|GO13011_LC|GO13077_LC
210552148, 66.919769, 16.248719, 13.814, GO13008_LC|GO13064_LC|GO13018_LC|GO13011_LC|GO13023_LC|GO13077_LC|GO13073_LC
210640966, 66.445925, 17.544606, 14.553, GO13008_LC|GO13064_LC|GO13018_LC|GO13011_LC|GO13023_LC|GO13077_LC|GO13073_LC|GO13090_LC|GO13902_LC|GO13904_LC
210644048, 66.346458, 17.587503, 16.27, GO13011_LC|GO13902_LC|GO13904_LC
210674207, 66.590457, 18.000294, 14.599, GO13008_LC|GO13064_LC|GO13123_LC|GO13018_LC|GO13011_LC|GO13023_LC|GO13077_LC|GO13073_LC|GO13090_LC|GO13902_LC|GO13904_LC|GO13023_SC
210718930, 65.986159, 18.638931, 14.608, GO13008_LC|GO13064_LC|GO13018_LC|GO13011_LC|GO13023_LC|GO13077_LC|GO13073_LC|GO13902_LC|GO13904_LC
210742017, 66.127462, 18.986894, 15.149, GO13008_LC|GO13064_LC|GO13018_LC|GO13011_LC|GO13023_LC|GO13077_LC|GO13073_LC|GO13090_LC|GO13902_LC|GO13904_LC
210743724, 66.424322, 19.013215, 13.8, GO13008_LC|GO13049_LC|GO13064_LC|GO13123_LC|GO13018_LC|GO13011_LC|GO13023_LC|GO13077_LC|GO13073_LC|GO13090_LC|GO13902_LC|GO13904_LC
210754620, 66.087286, 19.180739, 14.397, GO13008_LC|GO13064_LC|GO13018_LC|GO13011_LC|GO13023_LC|GO13077_LC|GO13073_LC|GO13902_LC|GO13904_LC
210772187, 66.902001, 19.445683, 14.363, GO13008_LC|GO13064_LC|GO13123_LC|GO13018_LC|GO13011_LC|GO13002_LC|GO13023_LC|GO13077_LC|GO13073_LC|GO13090_LC
210828490, 65.409687, 20.302828, 15.003, GO13008_LC|GO13064_LC|GO13018_LC|GO13011_LC|GO13023_LC|GO13077_LC|GO13073_LC|GO13090_LC
210834592, 65.441108, 20.395727, 18.572, GO13008_LC|GO13064_LC|GO13011_LC|GO13077_LC|GO13073_LC
210835057, 65.434833, 20.402943, 17.794, GO13008_LC|GO13064_LC|GO13011_LC|GO13077_LC|GO13073_LC
210871016, 66.904524, 20.944139, 14.418, GO13008_LC|GO13064_LC|GO13018_LC|GO13011_LC|GO13006_LC|GO13077_LC|GO13073_LC
210878579, 65.797414, 21.058949, 14.166, GO13008_LC|GO13064_LC|GO13123_LC|GO13018_LC|GO13011_LC|GO13023_LC|GO13077_LC|GO13073_LC|GO13090_LC
210899231, 65.122451, 21.378697, 14.281, GO13008_LC|GO13064_LC|GO13123_LC|GO13018_LC|GO13011_LC|GO13023_LC|GO13077_LC|GO13073_LC|GO13090_LC
247548866, 68.924331, 22.569885, 15.459, GO13117_LC|GO13009_LC|GO13011_LC
247573157, 68.359223, 22.75815, 13.277, GO13117_LC|GO13009_LC|GO13011_LC
247575958, 68.289405, 22.780195, 14.482, GO13117_LC|GO13009_LC|GO13011_LC
247581233, 68.964299, 22.819986, 16.933, GO13029_LC|GO13022_LC|GO13009_LC|GO13011_LC|GO13042_LC
247585465, 68.100646, 22.852333, 17.698, GO13117_LC|GO13009_LC|GO13011_LC|GO13016_LC|GO13082_LC
247588169, 68.925159, 22.872963, 12.835, GO13117_LC|GO13009_LC|GO13011_LC|GO13016_LC|GO13082_LC|GO13118_LC
247591534, 68.990035, 22.899303, 16.646, GO13117_LC|GO13009_LC|GO13011_LC|GO13118_LC
247592919, 68.986864, 22.909994, 12.746, GO13117_LC|GO13009_LC|GO13011_LC|GO13016_LC|GO13002_LC|GO13082_LC|GO13119_LC|GO13118_LC
247600777, 69.16224, 22.969973, 15.057, GO13117_LC|GO13009_LC|GO13011_LC|GO13118_LC
247604448, 69.043281, 22.998896, 15.088, GO13117_LC|GO13009_LC|GO13011_LC|GO13118_LC
247630187, 68.78545, 23.194407, 16.985, GO13117_LC|GO13009_LC|GO13011_LC|GO13016_LC|GO13118_LC
247735103, 66.939085, 23.956757, 16.348, GO13009_LC|GO13011_LC
247739445, 67.598562, 23.986942, 16.377, GO13009_LC|GO13011_LC
247748412, 68.097078, 24.050383, 13.726, GO13117_LC|GO13009_LC|GO13011_LC|GO13016_LC
247766994, 67.849228, 24.181384, 13.212, GO13117_LC|GO13123_LC|GO13009_LC|GO13011_LC|GO13016_LC|GO13002_LC|GO13121_LC|GO13004_LC|GO13119_LC|GO13004_SC
247791556, 68.258238, 24.350002, 15.914, GO13117_LC|GO13009_LC|GO13011_LC|GO13016_LC|GO13082_LC
247794491, 68.209439, 24.369879, 15.305, GO13117_LC|GO13009_LC|GO13011_LC
247794636, 68.074424, 24.370829, 13.065, GO13117_LC|GO13009_LC|GO13011_LC|GO13016_LC|GO13002_LC
247802333, 71.666134, 24.423925, 12.148, GO13011_LC
247820507, 67.348912, 24.549997, 13.069, GO13117_LC|GO13009_LC|GO13011_LC|GO13016_LC|GO13002_LC|GO13121_LC|GO13086_LC|GO13082_LC|GO13119_LC|GO13005_LC
247820821, 67.49795, 24.552181, 17.396, GO13117_LC|GO13009_LC|GO13011_LC|GO13016_LC
247842020, 67.715473, 24.696531, 18.248, GO13117_LC|GO13009_LC|GO13011_LC|GO13016_LC|GO13002_LC|GO13082_LC
247843485, 67.714122, 24.706208, 12.951, GO13117_LC|GO13123_LC|GO13009_LC|GO13011_LC|GO13016_LC|GO13121_LC|GO13082_LC|GO13058_LC|GO13119_LC
247915927, 71.113051, 25.204557, 16.803, GO13117_LC|GO13009_LC|GO13011_LC|GO13016_LC|GO13118_LC
247927319, 71.416127, 25.284621, 11.77, GO13117_LC|GO13011_LC
247932205, 70.165802, 25.318367, 13.294, GO13117_LC|GO13009_LC|GO13011_LC|GO13016_LC|GO13002_LC|GO13118_LC
247950452, 68.428815, 25.446394, 16.03, GO13009_LC|GO13011_LC
247953586, 68.013725, 25.468836, 16.223, GO13117_LC|GO13009_LC|GO13011_LC|GO13016_LC|GO13082_LC
247968420, 70.451043, 25.575138, 15.063, GO13117_LC|GO13009_LC|GO13011_LC|GO13042_LC|GO13118_LC
247989075, 67.993577, 25.724997, 13.004, GO13117_LC|GO13123_LC|GO13009_LC|GO13011_LC|GO13016_LC|GO13082_LC
247989931, 70.352685, 25.731396, 18.265, GO13117_LC|GO13009_LC|GO13011_LC
247991214, 69.7665, 25.740671, 18.092, GO13117_LC|GO13009_LC|GO13011_LC|GO13042_LC
248015397, 70.294936, 25.919903, 18.758, GO13117_LC|GO13009_LC|GO13011_LC|GO13042_LC
248018652, 67.73828, 25.9443, 15.903, GO13029_LC|GO13022_LC|GO13009_LC|GO13011_LC|GO13042_LC|GO13042_SC
248021602, 70.267713, 25.965429, 13.491, GO13117_LC|GO13123_LC|GO13009_LC|GO13011_LC|GO13016_LC|GO13082_LC
248023915, 69.503499, 25.982563, 13.066, GO13117_LC|GO13009_LC|GO13011_LC
248029954, 69.947849, 26.027994, 18.808, GO13117_LC|GO13009_LC|GO13011_LC|GO13042_LC|GO13002_LC|GO13086_LC
248030407, 69.937014, 26.03133, 15.896, GO13117_LC|GO13009_LC|GO13011_LC|GO13016_LC|GO13002_LC|GO13086_LC|GO13082_LC
248044306, 67.530184, 26.139109, 16.415, GO13029_LC|GO13022_LC|GO13009_LC|GO13011_LC|GO13042_LC|GO13042_SC
248051303, 69.56192, 26.194427, 16.61, GO13117_LC|GO13009_LC|GO13011_LC|GO13042_LC
248053986, 68.468574, 26.215237, 17.287, GO13009_LC|GO13011_LC
248058354, 68.436051, 26.250147, 17.316, GO13117_LC|GO13009_LC|GO13011_LC
248060724, 68.282542, 26.268509, 18.111, GO13117_LC|GO13009_LC|GO13011_LC
248075421, 71.685242, 26.385154, 11.999, GO13117_LC|GO13011_LC