We report the discovery by the HATSouth survey of HATS-6b, an extrasolar planet transiting a V = 15.2 mag, i = 13.7 mag M1V star with a mass of 0.57 M-circle dot and a radius of 0.57 R-circle dot HATS-6b has a period of P = 3.3253 d, mass of M-p = 0.32 M-J, radius of R-p = 1.00 R-J, and zero-albedo equilibrium temperature of T-eq = 712.8 +/- 5.1 K. HATS-6 is one of the lowest mass stars known to host a close-in gas giant planet, and its transits are among the deepest of any known transiting planet system. We discuss the follow-up opportunities afforded by this system, noting that despite the faintness of the host star, it is expected to have the highest K-band S/N transmission spectrum among known gas giant planets with T-eq < 750 K. In order to characterize the star we present a new set of empirical relations between the density, radius, mass, bolometric magnitude, and V-, J-, H-and K-band bolometric corrections for main sequence stars with M < 0.80 M-circle dot, or spectral types later than K5. These relations are calibrated using eclipsing binary components as well as members of resolved binary systems. We account for intrinsic scatter in the relations in a self-consistent manner. We show that from the transit-based stellar density alone it is possible to measure the mass and radius of a similar to 0.6 M-circle dot star to similar to 7 and similar to 2% precision, respectively. Incorporating additional information, such as the V - K color, or an absolute magnitude, allows the precision to be improved by up to a factor of two.

The field of the globular cluster NGC 6362 was monitored between 1995 and 2009 in a search for variable stars. BV light curves were obtained for 69 periodic variable stars including 34 known RR Lyr stars, 10 known objects of other types and 25 newly detected variable stars. Among the latter we identified 18 proper-motion members of the cluster: seven detached eclipsing binaries (DEBs), six SX Phe stars, two W UMa binaries, two spotted red giants, and a very interesting eclipsing binary composed of two red giants - the first example of such a system found in a globular cluster. Five of the DEBs are located at the turnoff region, and the remaining two are redward of the lower main sequence. Eighty-four objects from the central 9 x 9 arcmin (2) of the cluster were found in the region of cluster blue stragglers. Of these 70 are proper motion (PM) members of NGC 6362 (including all SX Phe and two W UMa stars), and five are field stars. The remaining nine objects lacking PM information are located at the very core of the cluster, and as such they are likely genuine blue stragglers.

Exoplanets of a few Earth masses can be now detected around nearby low-mass stars using Doppler spectroscopy. In this Letter, we investigate the radial velocity variations of Kapteyn's star, which is both a sub-dwarf M-star and the nearest halo object to the Sun. The observations comprise archival and new HARPS (High Accuracy Radial velocity Planet Searcher), High Resolution Echelle Spectrometer (HIRES) and Planet Finder Spectrograph (PFS) Doppler measurements. Two Doppler signals are detected at periods of 48 and 120 d using likelihood periodograms and a Bayesian analysis of the data. Using the same techniques, the activity indices and archival All Sky Automated Survey (ASAS-3) photometry show evidence for low-level activity periodicities of the order of several hundred days. However, there are no significant correlations with the radial velocity variations on the same time-scales. The inclusion of planetary Keplerian signals in the model results in levels of correlated and excess white noise that are remarkably low compared to younger G, K and M dwarfs. We conclude that Kapteyn's star is most probably orbited by two super-Earth mass planets, one of which is orbiting in its circumstellar habitable zone, becoming the oldest potentially habitable planet known to date. The presence and long-term survival of a planetary system seem a remarkable feat given the peculiar origin and kinematic history of Kapteyn's star. The detection of super-Earth mass planets around halo stars provides important insights into planet-formation processes in the early days of the Milky Way.

The field of the globular cluster M12 (NGC 6218) was monitored between 1995 and 2009 in a search for variable stars. BV light curves were obtained for thirty-six periodic or likely periodic variable stars. Thirty-four of these are new detections. Among the latter we identified twenty propermotion members of the cluster: six detached or semi-detached eclipsing binaries, five contact binaries, five SX Phe pulsators, and three yellow stragglers. Two of the eclipsing binaries are located in the turnoff region, one on the lower main sequence and the remaining three among the blue stragglers. Two contact systems are blue stragglers, and the remaining three reside in the turnoff region. In the blue straggler region a total of 103 objects were found, of which 42 are proper motion members of M12, and another four are field stars. 55 of the remaining objects are located within two core radii from the center of the cluster, and as such they are likely genuine blue stragglers. We also report the discoveries of a radial color gradient of M12, and the shortest period among contact systems in globular clusters in general.

We present precise Doppler observations of WASP-47, a transiting planetary system featuring a hot Jupiter with both inner and outer planetary companions. This system has an unusual architecture and also provides a rare opportunity to measure planet masses in two different ways: the Doppler method, and the analysis of transit-timing variations (TTV). Based on the new Doppler data, obtained with the Planet Finder Spectrograph on the Magellan/Clay 6.5 m telescope, the mass of the hot Jupiter is 370 +/- 29 M-circle plus. This is consistent with the previous Doppler determination as well as the TTV determination. For the inner planet WASP-47e, the Doppler data lead to a mass of 12.2 +/- 3.7 M-circle plus, in agreement with the TTV-based upper limit of < 22 M-circle plus (95% confidence). For the outer planet WASP-47d, the Doppler mass constraint of 10.4 +/- 8.4 M-circle plus is consistent with the TTV-based measurement of 15.2(-7.6)(+6.7) M-circle plus.

We use photometric and spectroscopic observations of the detached eclipsing binaries V40 and V41 in the globular cluster NGC 6362 to derive masses, radii, and luminosities of the component stars. The orbital periods of these systems are 5.30 and 17.89 days, respectively. The measured masses of the primary and secondary components (M-p, M-s) are (0.8337 +/- 0.0063, 0.7947 +/- 0.0048) M-circle dot for V40 and (0.8215 +/- 0.0058, 0.7280 +/- 0.0047) M-circle dot for V41. The measured radii (R-p, R-s) are (1.3253 +/- 0.0075, 0.997 +/- 0.013) R-circle dot for V40 and (1.0739 +/- 0.0048, 0.7307 +/- 0.0046) R-circle dot for V41. Based on the derived luminosities, we find that the distance modulus of the cluster is 14.74 +/- 0.04 mag-in good agreement with 14.72 mag obtained from color-magnitude diagram (CMD) fitting. We compare the absolute parameters of component stars with theoretical isochrones in mass-radius and mass-luminosity diagrams. For assumed abundances [Fe/H] = -1.07, [alpha/Fe] = 0.4, and Y = 0.25 we find the most probable age of V40 to be 11.7 +/- 0.2 Gyr, compatible with the age of the cluster derived from CMD fitting (12.5 +/- 0.5 Gyr). V41 seems to be markedly younger than V40. If independently confirmed, this result will suggest that V41 belongs to the younger of the two stellar populations recently discovered in NGC 6362. The orbits of both systems are eccentric. Given the orbital period and age of V40, its orbit should have been tidally circularized some +/- 7 Gyr ago. The observed eccentricity is most likely the result of a relatively recent close stellar encounter.

The field of the globular cluster NGC 3201 was monitored between 1998 and 2009 in a search for variable stars. BV light curves were obtained for 152 periodic or likely periodic variables, fifty-seven of which are new detections. Thirty-seven newly detected variables are proper motion members of the cluster. Among them we found seven detached or semi-detached eclipsing binaries, four contact binaries, and eight SX Phe pulsators. Four of the eclipsing binaries are located in the turnoff region, one on the lower main sequence and the remaining two slightly above the subgiant branch. Two contact systems are blue stragglers, and another two reside in the turnoff region. In the blue straggler region a total of 266 objects were found, of which 140 are proper motion (PM) members of NGC 3201, and another nineteen are field stars. Seventy-eight of the remaining objects for which we do not have PM data are located within the half-light radius from the center of the cluster, and most of them are likely genuine blue stragglers. Four variable objects in our field of view were found to coincide with X-ray sources: three chromospherically active stars and a quasar at a redshift z approximate to 0.5.

We report the discovery and characterization of a new M-dwarf binary, with component masses and radii of M-1 = 0.244(-0.003)(+0.003) M-circle dot, R-1 = 0.261(-0.009)(+0.006) R-circle dot, M-2 = 0.179(-0.001)(+0.002) M-circle dot, R-2 = 0.218(-0.011)(+0.007) R-circle dot, and orbital period of similar to 4.1 d. The M-dwarf binary HATS551-027 (LP 837-20) was identified as an eclipsing binary by the HATSouth survey, and characterized by a series of high-precision photometric observations of the eclipse events, and spectroscopic determinations of the atmospheric parameters and radial velocity orbits. HATS551-027 is one of few systems with both stellar components lying in the fully convective regime of very low mass stars, and can serve as a test for stellar interior models. The radius of HATS551-027A is consistent with models to 1 sigma, whilst HATS551-027B is inflated by 9 per cent at 2s significance. We measure the effective temperatures for the two stellar components to be T-eff,T- (1) = 3190 +/- 100 K and T-eff, (2) = 2990 +/- 110 K; both are slightly cooler than theoretical models predict, but consistent with other M-dwarfs of similar masses that have previously been studied. We also measure significant Ha emission from both components of the binary system, and discuss this in the context of the correlation between stellar activity and the discrepancies between the observed and model temperatures.

In an effort to measure the masses of planets discovered by the NASA K2 mission, we have conducted precise Doppler observations of five stars with transiting planets. We present the results of a joint analysis of these new data and previously published Doppler data. The first star, an M dwarf known as K2-3 or EPIC 201367065, has three transiting planets ("b," with radius 2.1 R-circle plus; "c," 1.7 R-circle plus; and "d," 1.5 R-circle plus). Our analysis leads to the mass constraints: M-b = 8.1(-1.9)(+2.0) M-circle plus and M-c < 4.2 M-circle plus (95% confidence). The mass of planet d is poorly constrained because its orbital period is close to the stellar rotation period, making it difficult to disentangle the planetary signal from spurious Doppler shifts due to stellar activity. The second star, a G dwarf known as K2-19 or EPIC 201505350, has two planets ("b," 7.7 R-circle plus; and "c," 4.9 R-circle plus) in a 3:2 mean-motion resonance, as well as a shorter-period planet ("d," 1.1 R-circle plus). We find M-b = 28.5(-5.0)(+5.4) M-circle plus, M-c = 25.6(-7.1)(+7.1) M-circle plus and M-d < 14.0 M-circle plus (95% conf.). The third star, a G dwarf known as K2-24 or EPIC 203771098, hosts two transiting planets ("b," 5.7 R-circle plus; and "c," 7.8 R-circle plus) with orbital periods in a nearly 2: 1 ratio. We find M-b = 19.8(-4.4)(+4.5) M-circle plus and M-c = 26.0(-6.1)(+5.8) M-circle plus. The fourth star, a G dwarf known as EPIC 204129699, hosts a hot Jupiter for which we measured the mass to be 1.857(-0.081)(+0.081) M-Jup . The fifth star, a G dwarf known as EPIC 205071984, contains three transiting planets ("b," 5.4 R-circle plus; "c," 3.5 R-circle plus; and "d," 3.8 R-circle plus), the outer two of which have a nearly 2: 1 period ratio. We find M-b = 21.1(-5.9)(+5.9) M-circle plus, M-c < 8.1 M-circle plus (95% conf.) and M-d < 35 M-circle plus (95% conf.).

We report the discovery of HATS-15 b and HATS-16 b, two massive transiting extrasolar planets orbiting evolved (similar to 10 Gyr) main-sequence stars. The planet HATS-15 b, which is hosted by a G9 V star (V = 14.8 mag), is a hot Jupiter with mass of 2.17 +/- 0.15 M-J and radius of 1.105 +/- 0.040 R-J, and it completes its orbit in about 1.7 days. HATS-16 b is a very massive hot Jupiter with mass of 3.27 +/- 0.19 M-J and radius of 1.30 +/- 0.15 R-J; it orbits around its G3 V parent star (V = 13.8 mag) in similar to 2.7 days. HATS-16 is slightly active and shows a periodic photometric modulation, implying a rotational period of 12 days, which is unexpectedly short given its isochronal age. This fast rotation might be the result of the tidal interaction between the star and its planet.