Context. VISTA Variables in the Vía Láctea (VVV) is one of the six ESO Public Surveys operating on the new 4-m Visible and Infrared Survey Telescope for Astronomy (VISTA). VVV is scanning the Milky Way bulge and an adjacent section of the disk, where star formation activity is high. One of the principal goals of the VVV Survey is to find new star clusters of different ages. Aims. In order to trace the early epochs of star cluster formation we concentrated our search in the directions to those of known star formation regions, masers, radio, and infrared sources. Methods. The disk area covered by VVV was visually inspected using the pipeline processed and calibrated K S -band tile images for stellar overdensities. Subsequently, we examined the composite JHK S and Z JK S color images of each candidate. PSF photometry of 15 × 15 arcmin fields centered on the candidates was then performed on the Cambridge Astronomy Survey Unit reduced images. After statistical field-star decontamination, color-magnitude and color-color diagrams were constructed and analyzed. Results. We report the discovery of 96 new infrared open clusters and stellar groups. Most of the new cluster candidates are faint and compact (with small angular sizes), highly reddened, and younger than 5 Myr. For relatively well populated cluster candidates we derived their fundamental parameters such as reddening, distance, and age by fitting the solar-metallicity Padova isochrones to the color-magnitude diagrams.

We report the discovery of three very late T dwarfs in the UKIRT Infrared Deep Sky Survey (UKIDSS) Third Data Release: ULAS J101721.40+011817.9 (ULAS1017), ULAS J123828.51+095351.3 (ULAS1238) and ULAS J133553.45+113005.2 (ULAS1335). We detail optical and near‐infrared (NIR) photometry for all three sources, and mid‐IR photometry for ULAS1335. We use NIR spectra of each source to assign spectral types T8p (ULAS1017), T8.5 (ULAS1238) and T9 (ULAS1335) to these objects. ULAS1017 is classed as a peculiar T8 (T8p) due to appearing as a T8 dwarf in the J band, whilst exhibiting H‐ and K‐band flux ratios consistent with a T6 classification. Through comparison to BT‐Settl model spectra we estimate that ULAS1017 has 750 K ≲Teff≲ 850 K, and 5.0 ≲ log g(cm s−2) ≲ 5.5, assuming solar metallicity. This estimate for gravity is degenerate with varying metallicity. We estimate that ULAS1017 has an age of 1.6–15 Gyr, a mass of 33–70MJ and lies at a distance of 31–54 pc. We do not estimate atmospheric parameters for ULAS1238 due to a lack of K‐band photometry. We extend the unified scheme of Burgasser et al. to the type T9 and suggest the inclusion of the WJ index to replace the now saturated J‐band indices. We propose ULAS1335 as the T9 spectral type standard. ULAS1335 is the same spectral type as ULAS J003402.77−005206.7 and CFBDS J005910.90−011401.3. We argue that given the similarity of the currently known >T8 dwarfs to the rest of the T dwarf sequence, the suggestion of the Y0 spectral class for these objects is premature. Comparison of model spectra with that of ULAS1335 suggest a temperature below 600 K, possibly combined with low gravity and/or high metallicity. We find ULAS1335 to be extremely red in NIR to mid‐IR colours, with H−[4.49]= 4.34 ± 0.04. This is the reddest NIR to mid‐IR colour yet observed for a T dwarf. The NIR to mid‐IR spectral energy distribution of ULAS1335 further supports Teff < 600 K, and we estimate Teff∼ 550–600 K for ULAS1335. We estimate that ULAS1335 has an age of 0.6–5.3 Gyr, a mass of 15–31MJ and lies at a distance of 8–12 pc.

Aims. In this work we present chromospheric activity indices, kinematics, radial-velocities, and rotational velocities for more than 850 FGK-type dwarfs and subgiant stars in the southern hemisphere and test how best to calibrate and measure S -indices from echelle spectra. Methods. We measured our parameters using the high-resolution and high-S /N FEROS echelle spectra acquired for this purpose. Results. We confirm the bimodal distribution of chromospheric activities for such stars and highlight the role that the more active K-dwarfs play in biasing the number of active stars. We show that the age-activity relationship does appear to continue to ages older than the Sun if we simply compare main sequence stars and subgiant stars with an offset of around 2.5 Gyr between the peaks of both distributions. Also we show evidence of an increased spin-down timescale for cool K dwarfs compared with earlier F and G type stars. We highlight that activities drawn from low-resolution spectra (R < 2500) significantly increase the rms scatter when calibrating onto common systems of measurements like the Mt. Wilson system. Also we show that older and widely used catalogues of activities in the south appear to be offset compared to more recent works at the ∼0.1 dex level in log R HK through calibrator drift. In addition, we show how kinematics can be used to preselect inactive stars for future planet search projects. We see the well known trend between projected rotational velocity and activity, however we also find a correlation between kinematic space velocity and chromospheric activity. It appears that after the Vaughan-Preston gap there is a quick step function in the kinematic space motion towards a significantly broader spread in velocities. We speculate on reasons for this correlation and provide some model scenarios to describe the bimodal activity distribution through magnetic saturation, residual low level gas accretion, or accretion by the star of planets or planetesimals. Finally, we provide a new empirical measurement for the disk-heating law, using the latest age-activity relationships to reconstruct the age-velocity distribution for local disk stars. We find a value of 0.337 ± 0.045 for the exponent of this power law (i.e. σ tot ∝ t 0.337 ), in excellent agreement with those found using isochrone fitting methods and with theoretical disk-heating models.

Context. The ESO public survey VISTA variables in the Vía Láctea (VVV) started in 2010. VVV targets 562 sq. deg in the Galactic bulge and an adjacent plane region and is expected to run for about five years. Aims. We describe the progress of the survey observations in the first observing season, the observing strategy, and quality of the data obtained. Methods. The observations are carried out on the 4-m VISTA telescope in the ZY JHK s filters. In addition to the multi-band imaging the variability monitoring campaign in the K s filter has started. Data reduction is carried out using the pipeline at the Cambridge Astronomical Survey Unit. The photometric and astrometric calibration is performed via the numerous 2MASS sources observed in each pointing. Results. The first data release contains the aperture photometry and astrometric catalogues for 348 individual pointings in the ZY JHK s filters taken in the 2010 observing season. The typical image quality is ∼0. 9−1. 0. The stringent photometric and image quality requirements of the survey are satisfied in 100% of the JHK s images in the disk area and 90% of the JHK s images in the bulge area. The completeness in the Z and Y images is 84% in the disk, and 40% in the bulge. The first season catalogues contain 1.28 × 10 8 stellar sources in the bulge and 1.68 × 10 8 in the disk area detected in at least one of the photometric bands. The combined, multi-band catalogues contain more than 1.63 × 10 8 stellar sources. About 10% of these are double detections because of overlapping adjacent pointings. These overlapping multiple detections are used to characterise the quality of the data. The images in the JHK s bands extend typically ∼4 mag deeper than 2MASS. The magnitude limit and photometric quality depend strongly on crowding in the inner Galactic regions. The astrometry for K s = 15−18 mag has rms ∼ 35−175 mas. Conclusions. The VVV Survey data products offer a unique dataset to map the stellar populations in the Galactic bulge and the adjacent plane and provide an exciting new tool for the study of the structure, content, and star-formation history of our Galaxy, as well as for investigations of the newly discovered star clusters, star-forming regions in the disk, high proper motion stars, asteroids, planetary nebulae, and other interesting objects.

We have searched the Wide‐field Infrared Survey Explorer first data release for widely separated (≤10 000 au) late T dwarf companions to Hipparcos and Gliese stars. We have discovered a new binary system containing a K‐band suppressed T8p dwarf WISEP J142320.86+011638.1 and the mildly metal poor ([Fe/H] =−0.38 ± 0.06) primary BD +01° 2920 (HIP 70319), a G1 dwarf at a distance of 17.2 pc. This new benchmark has Teff= 680 ± 55 K and a mass of 20–50MJup. Its spectral properties are well modelled except for known discrepancies in the Y and K bands. Based on the well‐determined metallicity of its companion, the properties of BD +01° 2920B imply that the currently known T dwarfs are dominated by young low‐mass objects. We also present an accurate proper motion for the T8.5 dwarf WISEP J075003.84+272544.8.