The catalog is a collection of spectrophotometric measurements obtained with rotating grating scanners attached to various telescopes at the Kitt Peak National, Mount Wilson, and Palomar Observatories. The observations were made during the 1970s and early 1980s, both individually and jointly, by S.J. Adelman, D.M. Pyper, S.N. Shore, and R.E. White. All measurements were calibrated with the fluxes of Alpha Lyrae (Vega) as presented by Hayes and Latham (1975ApJ...197..593H). There are 1134 observations concerning 207 individual stars.
We report the discovery of a large, dynamically cold, coeval stellar stream that is currently traversing the immediate solar neighborhood at a distance of only 100pc. The structure was identified in a wavelet decomposition of the 3D velocity space of all stars within 300pc of the Sun. Its members form a highly elongated structure with a length of at least 400pc, while its vertical extent measures only about 50pc. Stars in the stream are not isotropically distributed but instead form two parallel lanes with individual local overdensities, that may correspond to a remnant core of a tidally disrupted cluster or OB association. Its members follow a very well-defined main sequence in the observational Hertzsprung-Russel diagram and also show a remarkably low 3D velocity dispersion of only 1.3km/s. These findings strongly suggest a common origin as a single coeval stellar population. An extrapolation of the present-day mass function indicates a total mass of at least 2000M_{sun}_, making it larger than most currently known clusters or associations in the solar neighborhood. We estimated the age of the stream to be around 1 Gyr based on a comparison with a set of isochrones and giant stars in our member selection and find a mean metallicity of [Fe/H]=-0.04. This structure may very well represent the Galactic disk counterpart to the prominent stellar streams observed in the Milky Way halo. As such, it constitutes a new valuable probe to constrain the Galaxy's mass distribution.
We present a spectroscopic analysis of five stellar streams ("A", "B", "Cr", "Cp" and "D") as well as the extended star cluster, EC4, which lies within Stream "C", all discovered in the halo of M31 from our Canada-France-Hawaii Telescope/MegaCam survey. These spectroscopic results were initially serendipitous, making use of our existing observations from the DEep Imaging Multi-Object Spectrograph mounted on the Keck II telescope, and thereby emphasizing the ubiquity of tidal streams that account for ~70 per cent of the M31 halo stars in the targeted fields. Subsequent spectroscopy was then procured in Stream "C" and Stream "D" to trace the velocity gradient along the streams. Nine metal-rich ([Fe/H]~-0.7) stars at v_hel_=-349.5km/s, {sigma}_v,corr_~5.1+/-2.5km/s are proposed as a serendipitous detection of Stream "Cr", with follow-up kinematic identification at a further point along the stream. Seven metal-poor ([Fe/H]~-1.3) stars confined to a narrow, 15km/s velocity bin centred at v_hel_=-285.6, {sigma}_v,corr_=4.3^+1.7^_-1.4_km/s represent a kinematic detection of Stream "Cp", again with follow-up kinematic identification further along the stream. For the cluster EC4, candidate member stars with average [Fe/H]~-1.4, are found at v_hel_=-282 suggesting it could be related to Stream "Cp". No similarly obvious cold kinematic candidate is found for Stream "D", although candidates are proposed in both of two spectroscopic pointings along the stream (both at ~-400km/s). Spectroscopy near the edge of Stream "B" suggests a likely kinematic detection at v_hel_~-330, {sigma}_v,corr_~6.9km/s, while a candidate kinematic detection of Stream "A" is found (plausibly associated to M33 rather than M31) with v_hel_~-170, {sigma}_v,corr_=12.5km/s. The low dispersion of the streams in kinematics, physical thickness and metallicity makes it hard to reconcile with a scenario whereby these stream structures as an ensemble are related to the giant southern stream. We conclude that the M31 stellar halo is largely made up of multiple kinematically cold streams.
Recent studies have made the community aware of the importance of accounting for scattered light when examining low-surface-brightness galaxy features such as thick discs. In our past studies of the thick discs of edge-on galaxies in the Spitzer Survey of Stellar Structure in Galaxies - the S4G - we modelled the point spread function as a Gaussian. In this paper we re- examine our results using a revised point spread function model that accounts for extended wings out to more than 2.5arcmin. We study the 3.6micron images of 141 edge-on galaxies from the S4G and its early-type galaxy extension. Thus, we more than double the samples examined in our past studies. We decompose the surface-brightness profiles of the galaxies perpendicular to their mid-planes assuming that discs are made of two stellar discs in hydrostatic equilibrium. We decompose the axial surface- brightness profiles of galaxies to model the central mass concentration - described by a Sersic function - and the disc - described by a broken exponential disc seen edge-on. Our improved treatment fully confirms the ubiquitous occurrence of thick discs. The main difference between our current fits and those presented in our previous papers is that now the scattered light from the thin disc dominates the surface brightness at levels below ~26mag/arcsec^2^. We stress that those extended thin disc tails are not physical, but pure scattered light. This change, however, does not drastically affect any of our previously presented results: 1) Thick discs are nearly ubiquitous. They are not an artefact caused by scattered light as has been suggested elsewhere. 2) Thick discs have masses comparable to those of thin discs in low-mass galaxies - with circular velocities vc<120km/s - whereas they are typically less massive than the thin discs in high-mass galaxies. 3) Thick discs and central mass concentrations seem to have formed at the same epoch from a common material reservoir. 4) Approximately 50% of the up-bending breaks in face-on galaxies are caused by the superposition of a thin and a thick disc where the scale-length of the latter is the largest.
In our previous work we found that high-quality light curves, such as those obtained by Kepler, may be used to measure stellar surface gravity via granulation-driven light curve "flicker" (F_8_). Here, we update and extend the relation originally presented by Bastien et al. (2013Natur.500..427B) after calibrating F_8_ against a more robust set of asteroseismically derived surface gravities. We describe in detail how we extract the F_8_ signal from the light curves, including how we treat phenomena, such as exoplanet transits and shot noise, that adversely affect the measurement of F_8_. We examine the limitations of the technique, and, as a result, we now provide an updated treatment of the F_8_-based log g error. We briefly highlight further applications of the technique, such as astrodensity profiling or its use in other types of stars with convective outer layers. We discuss potential uses in current and upcoming space-based photometric missions. Finally, we supply F_8_-based log g values, and their uncertainties, for 27628 Kepler stars not identified as hosts of transiting planets, with 4500K<T_eff_<7150K, 2.5<logg<4.6, K_p_<=13.5, and overall photometric amplitudes <10 parts per thousand.
We apply the twin method to determine parallaxes to 232 545 stars of the RAVE survey using the parallaxes of Gaia DR1 as a reference. To search for twins in this large data set, we apply the t-student stochastic neighbour embedding projection that distributes the data according to their spectral morphology on a two-dimensional map. From this map, we choose the twin candidates for which we calculate a {chi}^2^ to select the best sets of twins. Our results show a competitive performance when compared to other model-dependent methods relying on stellar parameters and isochrones. The power of the method is shown by finding that the accuracy of our results is not significantly affected if the stars are normal or peculiar since the method is model free. We find twins for 60 per cent of the RAVE sample that are not contained in Tycho-Gaia Astrometric Solution (TGAS) or that have TGAS uncertainties that are larger than 20 per cent. We could determine parallaxes with typical errors of 28 per cent. We provide a complementary data set for the RAVE stars not covered by TGAS, or that have TGAS uncertainties which are larger than 20 per cent, with model-free parallaxes scaled to the Gaia measurements.
We present results from a 5 night wide-field time-series photometric survey that detects variable field stars. We find that the fraction of stars whose light curves show variations depends on color and magnitude, reaching 17% for the brightest stars in this survey (V~4) for which the photometric precision is best. The fraction of stars found to be variable is relatively high at colors bluer than the Sun and relatively low at colors similar to the Sun and increases again for stars redder than the Sun. We present light curves for a sample of the pulsating and eclipsing variables. Most of the stars identified as pulsating variables have low amplitudes ({Delta}V=0.01-0.05), relatively blue colors, and multiple periods. There are 13 stars we identify as either SX Phoenicis or {delta} Scuti stars. These classes represent a significant contribution to the total number of blue variables found in this survey. Another 17 stars are identified as eclipsing variables, which have a wide range in color, magnitude, and amplitude. Two variable giants are observed, and both show night-to-night ~1% variations. We present data for 222 variables in total, most of which are not classified. Implications of surveys for stellar variability and interferometry are briefly discussed. On 2000 March 16-20 UT we observed a time series of images in V and one or two images each in UBRI toward two 59'x59' fields using the NOAO Mosaic Camera at the Kitt Peak 0.9 m telescope.
We report the results of a diffraction-limited, photometric variability study of the central 5"x5" of the Galaxy conducted over the past 10-years using speckle imaging techniques on the W.M. Keck I 10 m telescope. Within our limiting magnitude of m_K_<16mag for images made from a single night of data, we find a minimum of 15K[2.2um]-band variable stars out of 131 monitored stars. The only periodic source in our sample is the previously identified variable IRS 16SW, for which we measure an orbital period of 19.448+/-0.002-days.
The Table "stars.dat" contains the catalogue of variable stars discovered and/or observed for the 12 low-extinction fields towards the galactic bulge, with the IAG/USP Meridian Circle. The first column of the catalog indicates the star label, formed by a name that identifies the window (see Table 1) and a sequential number that indicates the position of the object in the corresponding database. The following columns display successively the mean right ascension, the mean declination, their standard deviations (in seconds and in arcseconds, respectively) (J2000); the mean magnitude observed (m_{Val}), the difference between the maximum and the minimum magnitude value observed, the number of observations, a estimative for the period, if possible, or a indication "NF" when the stars show periodic characteristics but we aren't able to found a period, or "NC" when the star can be aperiodic or have few observations. The next column have the tentative classification and the last are the remarks about the previous known variables. Finding charts will be available upon request from the authors.
A catalog of central velocity dispersion measurements is presented, current through 1993 September. The catalog includes 2474 measurements of 1563 (*) galaxies. A standard set of 86 galaxies is defined, consisting of galaxies with at least three reliable concordant measurements. It is suggested that future studies observe some of these standard galaxies so that different studies can be normalised to a consistent system. All measurements are reduced to a normalized system using these standards. (*) Actually 1562 galaxies.