Context. The abundances of a-elements are a powerful diagnostic of the star formation history and chemical evolution of a galaxy. Sulphur. being moderately volatile, can be reliably measured in the interstellar medium (ISM) of damped Ly-alpha galaxies and extragalactic H-II regions. Measurements in stars of different metallicity in our Galaxy can then be readily compared to the abundances in external galaxies. Such a comparison is not possible for Si or Ca that suffer depletion onto dust in the ISM. Furthermore, studying sulphur is interesting because it probes nucleosynthetic conditions that are very different from those of Oar Mg. In this context measurements in star clusters are a reliable tracers of the Galactic evolution of sulphur.

Passing stars can perturb the Oort Cloud, triggering comet showers and potentially extinction events on Earth. We combine velocity measurements for the recently discovered, nearby, low- mass binary system WISE J072003.20084651.2 (" Scholz's star") to calculate its past trajectory. Integrating the Galactic orbits of this 0.15 Me binary system and the Sun, we find that the binary passed within only 52+ 23 - 14 kAU ( 0.25+ 0.11 - 0.07 pc) of the Sun 70+ 15 - 10 kya ( 1s uncertainties), i. e., within the outer Oort Cloud. This is the closest known encounter of a star to our solar system with a well- constrained distance and velocity. Previous work suggests that flybys within 0.25 pc occur infrequently ( 0.1 Myr- 1). We show that given the low mass and high velocity of the binary system, the encounter was dynamically weak. Using the best available astrometry, our simulations suggest that the probability that the star penetrated the outer Oort Cloud is 98%, but the probability of penetrating the dynamically active inner Oort Cloud (< 20 kAU) is 10- 4. While the flyby of this system likely caused negligible impact on the flux of longperiod comets, the recent discovery of this binary highlights that dynamically important Oort Cloud perturbers may be lurking among nearby stars.

Context. The severe crowding towards the Galactic plane suggests that the census of nearby stars in that direction may be incomplete. Recently, Scholz reported a new M9 object at an estimated distance d similar or equal to 7 pc (WISE J072003.20-084651.2; hereafter WISE J0720) at Galactic latitude b = 2.3 degrees.

So far, roughly 40 quasars with redshifts greater than z = 6 have been discovered(1-8). Each quasar contains a black hole with a mass of about one billion solar masses (10(9) M-circle dot)(2,6,7,9-13). The existence of such black holes when the Universe was less than one billion years old presents substantial challenges to theories of the formation and growth of black holes and the coevolution of black holes and galaxies(14). Here we report the discovery of an ultraluminous quasar, SDSS J010013.02+280225.8, at redshift z = 6.30. It has an optical and near-infrared luminosity a few times greater than those of previously known z > 6 quasars. On the basis of the deep absorption trough(15) on the blue side of the Lyman-alpha emission line in the spectrum, we estimate the proper size of the ionized proximity zone associated with the quasar to be about 26 million light years, larger than found with other z > 6.1 quasars with lower luminosities(16). We estimate (on the basis of a near-infrared spectrum) that the black hole has a mass of similar to 1.2 x 10(10) M-circle dot, which is consistent with the 1.3 x 10(10) M-circle dot derived by assuming an Eddington-limited accretion rate.

We describe the new spectroscopic data reduction pipeline for the multi-object MMT/Magellan Infrared Spectrograph. The pipeline is implemented in IDL as a stand-alone package and is publicly available in both stable and development versions. We describe novel algorithms for sky subtraction and correction for telluric absorption. We demonstrate that our sky subtraction technique reaches the Poisson limit set by the photon statistics. Our telluric correction uses a hybrid approach by first computing a correction function from an observed stellar spectrum, and then differentially correcting it using a grid of atmosphere transmission models for the target airmass value. The pipeline provides a sufficient level of performance for real time reduction and thus enables data quality control during observations. We reduce an example dataset to demonstrate the high data reduction quality.

We report the discovery of a substellar companion to 2MASS J02192210-3925225, a young M6. candidate member of the Tucana-Horologium association (30-40 Myr). This L4 gamma companion has been discovered with seeing-limited direct imaging observations; at a 4 '' separation (160 AU) and a modest contrast ratio, it joins the very short list of young low-mass companions amenable to study without the aid of adaptive optics, enabling its characterization with a much wider suite of instruments than is possible for companions uncovered by highcontrast imaging surveys. With a model-dependent mass of 12-15 M-Jup, it straddles the boundary between the planet and brown dwarf mass regimes. We present near-infrared spectroscopy of this companion and compare it to various similar objects uncovered in the last few years. The J0219-3925 system falls in a sparsely populated part of the host mass versus mass ratio diagram for binaries; the dearth of known similar companions may be due to observational biases in previous low-mass companion searches.

Context. The DANCe survey provides photometric and astrometric (position and proper motion) measurements for approximately 2 million unique sources in a region encompassing similar to 80 deg(2) centered on the Pleiades cluster.

Context. Messier 35 (NGC 2168) is an important young nearby cluster. Its age, richness and relative proximity make it an ideal target for stellar evolution studies. The Kepler K2 mission recently observed it and provided a high accuracy photometric time series of a large number of sources in this area of the sky. Identifying the cluster's members is therefore of high importance to optimize the interpretation and analysis of the Kepler K2 data.

We report the results of spectrophotometric observations of the massive star MN18 revealed via discovery of a bipolar nebula around it with the Spitzer Space Telescope. Using the optical spectrum obtained with the Southern African Large Telescope, we classify this star as B1 Ia. The evolved status of MN18 is supported by the detection of nitrogen overabundance in the nebula, which implies that it is composed of processed material ejected by the star. We analysed the spectrum of MN18 by using the code CMFGEN, obtaining a stellar effective temperature of approximate to 21 kK. The star is highly reddened, E(B - V) approximate to 2 mag. Adopting an absolute visual magnitude of M-V = -6.8 +/- 0.5 (typical of B1 supergiants), MN18 has a luminosity of log L/L-circle dot approximate to 5.42 +/- 0.30, a mass-loss rate of approximate to(2.8-4.5) x 10(-7) M-circle dot yr(-1), and resides at a distance of approximate to 5.6-(+1.5)(1.2) kpc. We discuss the origin of the nebula around MN18 and compare it with similar nebulae produced by other blue supergiants in the Galaxy (Sher 25, HD 168625, [SBW2007] 1) and the Large Magellanic Cloud (Sk-69 degrees 202). The nitrogen abundances in these nebulae imply that blue supergiants can produce them from the main-sequence stage up to the pre-supernova stage. We also present a K-band spectrum of the candidate luminous blue variable MN56 (encircled by a ring-like nebula) and report the discovery of an OB star at approximate to 17 arcsec from MN18. The possible membership of MN18 and the OB star of the star cluster Lynga 3 is discussed.

The existence of black holes with masses of about one billion solar masses in quasars at redshifts z > 6 presents significant challenges to theories of the formation and growth of black holes and the black hole/galaxy co-evolution in the early Universe. Here we report a recent discovery of an ultra-luminous quasar at redshift z = 6.30, which has an observed optical and near-infrared luminosity a few times greater than those of previously known z > 6 quasars. With near-infrared spectroscopy, we obtain a black hole mass of about 12 billion solar masses, which is well consistent with the mass derived by assuming an Eddington-limited accretion. This ultra-luminous quasar with at z > 6 provides a unique laboratory to the study of the mass assembly and galaxy formation around the most massive black holes at cosmic dawn. It raises further challenges to the black hole/galaxy co-evolution in the epoch of cosmic reionization because the black hole needs to grow much faster than the host galaxy.