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.

We report on the discovery and characterization of the transiting planet K2-39b (EPIC 206247743b). With an orbital period of 4.6 days, it is the shortest-period planet orbiting a subgiant star known to date. Such planets are rare, with only a handful of known cases. The reason for this is poorly understood but may reflect differences in planet occurrence around the relatively high-mass stars that have been surveyed, or may be the result of tidal destruction of such planets. K2-39 (EPIC 206247743) is an evolved star with a spectroscopically derived stellar radius and mass of 3.88(-0.42)(+0.48) R-circle dot and 1.53(-0.13)(+0.13) M-circle dot, respectively, and a very close-in transiting planet, with a/R-* = 3.4. Radial velocity (RV) follow-up using the HARPS, FIES, and PFS instruments leads to a planetary mass of 50.3(-9.4)(+9.7) M-circle plus. In combination with a radius measurement of 8.3 +/- 1.1, this results in a mean planetary density of 0.50(-0.17)(+0.29) g cm(-3). We furthermore discover a long-term RV trend, which may be caused by a long-period planet or stellar companion. Because K2-39b has a short orbital period, its existence makes it seem unlikely that tidal destruction is wholly responsible for the differences in planet populations around subgiant and main-sequence stars. Future monitoring of the transits of this system may enable the detection of period decay and constrain the tidal dissipation rates of subgiant stars.

The field of the globular cluster NGC 362 was monitored between 1997 and 2015 in a search for variable stars. BV light curves were obtained for 151 periodic or likely periodic variable stars, over a hundred of which are new detections. Twelve newly detected variable stars are proper-motion members of the cluster: two SX Phe and two RR Lyr pulsators, one contact binary, three detached or semi-detached eclipsing binaries, and four spotted variable stars. The most interesting objects among these are the binary blue straggler V20 with an asymmetric light curve, and the 8.1 d semidetached binary V24 located on the red giant branch of NGC 362, which is a Chandra X-ray source. We also provide substantial new data for 24 previously known variable stars.

We present a new precision radial velocity (RV) data set that reveals multiple planets orbiting the stars in the similar to 360 au, G2+G2 "twin" binary HD 133131AB. Our six years of high-resolution echelle observations from MIKE and five years from the Planet Finder Spectrograph (PFS) on the Magellan telescopes indicate the presence of two eccentric planets around HD 133131A with minimum masses of 1.43 +/- 0.03 and 0.63 +/- 0.15 M-J at 1.44 +/- 0.005 and 4.79 +/- 0.92 au, respectively. Additional PFS observations of HD 133131B spanning five years indicate the presence of one eccentric planet of minimum mass 2.50 +/- 0.05 M-J at 6.40 +/- 0.59 au, making it one of the longest-period planets detected with RV to date. These planets are the first to be reported primarily based on data taken with the PFS on Magellan, demonstrating the instrument's precision and the advantage of long-baseline RV observations. We perform a differential analysis between the Sun and each star, and between the stars themselves, to derive stellar parameters and measure a suite of 21 abundances across a wide range of condensation temperatures. The host stars are old (likely similar to 9.5 Gyr) and metal-poor ([Fe/ H] similar to -0.30), and we detect a similar to 0.03 dex depletion in refractory elements in HD 133131A versus B (with standard errors similar to 0.017). This detection and analysis adds to a small but growing sample of binary "twin" exoplanet host stars with precise abundances measured, and represents the most metal-poor and likely oldest in that sample. Overall, the planets around HD 133131A and B fall in an unexpected regime in planet mass-host star metallicity space and will serve as an important benchmark for the study of long-period giant planets.