The Orion cloud complex presents a variety of star formation mechanisms and properties and is still one of the most intriguing targets for star formation studies. We present VISTA/VIRCAM near-infrared observations of the L1630N star-forming region, including the stellar clusters NGC 2068 and NGC 2071 in the Orion molecular cloud B, and discuss them in combination with Spitzer data. We select 186 young stellar object (YSO) candidates in the region on the basis of multi-color criteria, confirm the YSO nature of the majority of them using published spectroscopy from the literature, and use this sample to investigate the overall star formation properties in L1630N. The K-band luminosity function of L1630N is remarkably similar to that of the Trapezium cluster, i.e., it presents a broad peak in the range 0.3-0.7M_{sun}_ and a fraction of substellar objects of ~20%. The fraction of YSOs still surrounded by disk/envelopes is very high (~85%) compared to other star-forming regions of similar age (1-2Myr), but includes some uncertain corrections for diskless YSOs. Yet, a possibly high disk fraction, together with the fact that 1/3 of the cloud mass has a gas surface density above the threshold for star formation (~129M_{sun}_/pc^2^), points toward a still ongoing star formation activity in L1630N. The star formation efficiency (SFE), star formation rate (SFR), and density of star formation of L1630N are within the ranges estimated for Galactic star-forming regions by the Spitzer "core to disk" and "Gould's Belt" surveys. However, the SFE and SFR are lower than the average value measured in the Orion A cloud and, in particular, lower than that in the southern regions of L1630. This might suggest different star formation mechanisms within the L1630 cloud complex.
The VVV Survey data delivered in this part of ESO Data Release 2 (DR2) are based on the VISTA/VIRCAM images that were acquired up to September 30, 2011, and processed by the Cambridge Astronomical Survey Unit (CASU). This "VVV_CAT" data release contains the single-epoch band-merged (Z, Y, J, H, Ks) catalogues associated with the VVV tile images that have already been released in the part of DR2 identified as Batch 2 of the "VVV' collection in the ESO archive. VVV_CAT contains 348 tile catalogues.
Variability is examined in over 2.6 million stars covering 11 square degrees of the core of the Sagittarius dwarf spheroidal galaxy (Sgr dSph) from Visible and Infrared Survey Telescope for Astronomy Z-band observations. Generally, pulsation on the Sgr dSph giant branches appears to be excited by the internal {kappa} mechanism. Pulsation amplitudes appear identical between red and asymptotic (red giant branch/asymptotic giant branch) giant stars, and between unreddened carbon and oxygen-rich stars at the same luminosity. The lack of correlation between infrared excess and variability among oxygen-rich stars indicates that pulsations do not contribute significantly to wind driving in oxygen-rich stars in the Sgr dSph, though the low amplitudes of these stars mean this may not apply elsewhere. The dust-enshrouded carbon stars have the highest amplitudes of the stars we observe. Only in these stars does an external {kappa}-mechanism-driven pulsation seem likely, caused by variations in their more opaque carbon-rich molecules or dust. This may allow pulsation driving of winds to be effective in carbon stars. Variability can be simplified to a power law (A{prop.to}L/T_2_), as in other systems. In total, we identify 3026 variable stars (with rms variability of {delta}Z>~0.015mag), of which 176 are long-period variables associable with the upper giant branches of the Sgr dSph. We also identify 324 candidate RR Lyrae variables in the Sgr dSph and 340 in the outer Galactic bulge.
The VVV survey targets the galactic bulge and a piece of the adjacent plane in Z, Y, J, H, and Ks. The total area of this survey is 520 square degrees and contains 355 open and 33 globular clusters. The VVV is multi-epoch in nature in order to detect a large number of variable objects and will provide > 100 carefully spaced observations for each tile. 5-sigma detection limits are Z=21.9, Y=21.2, J=20.2, H=18.2, Ks=18.1. These will be used to create a 3-dimensional map of the Bulge from well-understood distance indicators such as RR Lyrae stars. Other science drivers include the ages of stellar populations, globular cluster evolution, as well as the stellar initial mass function. The VVV Survey data delivered in this part of ESO Data Release 1 (DR1) includes the VISTA/VIRCAM paw-print and tile images that were acquired until September 30, 2010, and processed by the Cambridge Astronomical Survey Unit (CASU). This VVV_CAT data release contains the single-epoch band-merged (Z,Y,J,H,Ks) catalogues associated with the VVV tile images that have already been released in the part of DR1 identified as VVV in the ESO archive. VVV_CAT contains 269 tile catalogues.
The NIR photometric data of minor planets observed by the VISTA-VHS survey. This survey uses Y, J, H, and Ks filters for imaging the entire sky of the southern hemisphere. A total of 39947 Solar System objects were detected in the VISTA VHS Data Release 3. The detections found include: 52 NEAs, 325 Mars Crossers, 515 Hungaria asteroids, 38428 Main Belt asteroids, 146 Cybele asteroid, 147 Hilda asteroids, 270 Trojans, 13 comets, 12 Kuiper Belt objects, and Neptune with its 4 satellites. About 34998 of these objects were imaged with at least two different filters.
We present the deepest near-infrared (ZJKs) photometry yet obtained of the Sagittarius dwarf spheroidal (Sgr dSph), using Visible and Infrared Survey Telescope for Astronomy (VISTA) to survey 11 square degrees centred on its core. We list locations and ZJKs-band magnitudes for over 2.9 million sources in the field. We discuss the isolation of the Sgr dSph from the foreground and Galactic Bulge populations, identify the Sgr dSph's horizontal branch in the near-infrared for the first time and map the density of the galaxy's stars. We present isochrones for the Sgr dSph and Bulge populations. These are consistent with the previously reported properties of the Sgr dSph core: namely that it is dominated by a population between [Fe/H]~-1dex and solar, with a significant [{alpha}/Fe] versus [Fe/H] gradient. While strong contamination from the Galactic Bulge prevents accurate measurement of the (Galactic) north side of the Sgr dSph, the dwarf galaxy can be well approximated by a roughly ovaloid projection of characteristic size 4{deg}x2{deg}, beyond which the projected stellar density is less than half that of the region surrounding the core. The galaxy's major axis is perpendicular to the Galactic Plane, as in previous studies. We find slight evidence to confirm a metallicity gradient in the Sgr dSph and use isochrones to fit a distance of 24.3+/-2.3kpc. We were unable to fully constrain the metallicity distribution of the Sgr dSph due to the Bulge contamination and strong correlation of [{alpha}/Fe] with metallicity; however, we find that metal-poor stars ([Fe/H]<~-1) make up <~29% of the Sgr dSph's upper red giant branch population. The Bulge population is best fitted by a younger population with [Fe/H] {approx} 0 and [{alpha}/Fe] {approx} 0 or slightly higher. We find no evidence for a split, peanut- or X-shaped Bulge population in this line of sight (l=5.6+/-~1{deg}, b=-14.1+/-~3{deg}).
Recent surveys indicate that planets in binary systems are more abunda- nt than previously thought, which is in agreement with theoretical work on disc dynamics and planet formation in binaries. So far, most observational surveys, however, have focused on short-period planets in binaries, thus little is known about the occurrence rates of planets on longer periods (>10au). In order to measure the abundance and physical characteristics of wide-orbit giant exoplanets in binary systems, we have designed the 'VIsual Binary Exoplanet survey with Sphere' (VIBES) to search for planets in visual binaries. It uses the SPHERE instrument at VLT to search for planets in 23 visual binary and four visual triple systems with ages of <145Myr and distances of <150pc. We used the IRDIS dual-band imager on SPHERE to acquire high-contrast images of the sample targets. For each binary, the two components were observed at the same time with a coronagraph masking only the primary star. For the triple star, the tight components were treated as a single star for data reduction. This enabled us to effectively search for companions around 50 individual stars in binaries and four binaries in triples. We derived upper limits of <13.7% for the frequency of sub-stellar companions around primaries in visual binaries, <26.5% for the fraction of sub-stellar companions around secondaries in visual binaries, and an occurrence rate of <9.0% for giant planets and brown dwarfs around either component of visual binaries. We have combined our observations with literature measurements to astrometrically confirm, for the first time, that 20 binaries and two triple systems, which were previously known, are indeed physically bound. Finally, we discovered a third component of the binary HD 121336. The upper limits we derived are compatible with planet formation through the core accretion and the gravitational instability processes in binaries. These limits are also in line with limits found for single star and circumbinary planet search surveys.
The results of a BVR photometry observations are presented for multiple stars visual subsystems (table2.dat). The objects (table1.dat) were observed in 1996 with the 60 cm and 1 m telescopes at Maidanak Observatory (Uzbekistan) by aperture and scanning photometers. The positional parameters and physical relation of visual subsystems are also given (table4.dat).
Astrophysical parameters (MK class, colour excess, absolute magnitude, distance, effective temperature, mass and age) are derived from calibrations of the uvbybeta indices for the members of 253 double stars with O or B type primaries and faint secondaries. The photometric spectral classification is compared to the MK classes and the agreement is very good. The derived data together with spectroscopic and JHKL data indicate that these stars are likely to be members of physical systems. For 90% of the physical pairs the projected separations between the components is less than 25,000 AU. A majority of the physical secondaries are late type stars and 50% of them are contracting towards the zero-age main-sequence (ZAMS).
With the aim of contributing to the understanding of the disk formation process in Be stars, we pursued a one-year spectroscopic observing campaign of the Be star {mu} Centauri in the L-band, using VLT/ISAAC. We present the nine near-IR spectra we obtained in an epoch of relative photometric quiescence prior to an outburst of {Delta}V=0.4 magnitude. Visual estimates during the epoch of our L-band spectroscopy are also presented for the first time, together with the unpublished complete visual light curve between the years 1998 and 2014. We observe significant and monotonic changes in emission line strength of Bracket-{alpha} and Pfund-{gamma} lines relative to Humphreys lines, and also in the continuum slope. We interpret these observed changes in terms of important changes to the column density of the line emitting regions, moving from an optically thin to an optically thick stage just prior to a major outburst. For each observing date, we provide estimates for the column density and relative extension of the line emitting region. If the changes observed toward the end of our observing campaign were related to mass-loss changes from the central star, they would correspond to an increase in a factor of two in the mass of the disk in the innermost region. If related to the visual outburst observed one month later, the variability observed in our spectra would be the first detection of the early disk formation process in the L-band.
