839 research outputs found
Binary Star Database (BDB): New Developments and Applications
Binary star DataBase (BDB) is the database of binary/multiple systems of
various observational types. BDB contains data on physical and positional
parameters of 260,000 components of 120,000 stellar systems of multiplicity 2
to more than 20, taken from a large variety of published catalogues and
databases. We describe the new features in organization of the database,
integration of new catalogues and implementation of new possibilities available
to users. The development of the BDB index-catalogue, Identification List of
Binaries (ILB), is discussed. This star catalogue provides cross-referencing
between most popular catalogues of binary stars.Comment: 5 pages, 1 figur
Prospecting in ultracool dwarfs : Measuring the metallicities of mid- and late-m dwarfs
© 2014. The American Astronomical Society. All rights reserved.Metallicity is a fundamental parameter that contributes to the physical characteristics of a star. The low temperatures and complex molecules present in M dwarf atmospheres make it difficult to measure their metallicities using techniques that have been commonly used for Sun-like stars. Although there has been significant progress in developing empirical methods to measure M dwarf metallicities over the last few years, these techniques have been developed primarily for early- to mid-M dwarfs. We present a method to measure the metallicity of mid- to late-M dwarfs from moderate resolution (R ∼ 2000) K-band (≃ 2.2 μm) spectra. We calibrate our formula using 44 wide binaries containing an F, G, K, or early-M primary of known metallicity and a mid- to late-M dwarf companion. We show that similar features and techniques used for early-M dwarfs are still effective for late-M dwarfs. Our revised calibration is accurate to ∼0.07 dex for M4.5-M9.5 dwarfs with -0.58 <[Fe/H] <+0.56 and shows no systematic trends with spectral type, metallicity, or the method used to determine the primary star metallicity. We show that our method gives consistent metallicities for the components of M+M wide binaries. We verify that our new formula works for unresolved binaries by combining spectra of single stars. Lastly, we show that our calibration gives consistent metallicities with the Mann et al. study for overlapping (M4-M5) stars, establishing that the two calibrations can be used in combination to determine metallicities across the entire M dwarf sequence.Peer reviewe
Stellar Variability in the Globular Cluster Terzan 5
We present the results of a search for variability in and near the core of
the metal-rich, obscured globular cluster Terzan 5, using NICMOS on HST. This
extreme cluster has approximately solar metallicity and a central density that
places it in the upper few percent of all clusters. It is estimated to have the
highest interaction rate of any galactic globular cluster. The large extinction
towards Terzan 5 and the severe stellar crowding near the cluster center
present a substantial observational challenge. Using time series analysis we
discovered two variable stars in this cluster. The first is a RRab Lyrae
variable with a period of ~0.61 days, a longer period than that of field stars
with similar high metallicities. This period is, however, shorter than the
average periods of RR Lyraes found in the metal-rich globular clusters NGC
6441, NGC 6388 and 47 Tuc. The second variable is a blue star with a 7-hour
period sinusoidal variation and a likely orbital period of 14 hours. This star
is probably an eclipsing blue straggler, or (less likely) the infrared
counterpart to the low mass X-ray binary known in Terzan 5. Due to the extreme
crowding and overlapping Airy profile of the IR PSF, we fall short of our
original goal of detecting CVs via Palpha emission and detecting variable
infrared emission from the location of the binary MSP in Terzan 5.Comment: 17 pages including 12 figures. Accepted for publication in Ap
A Cross-Match of 2MASS and SDSS. II. Peculiar L Dwarfs, Unresolved Binaries, and the Space Density of T Dwarf Secondaries
We present the completion of a program to cross-correlate the SDSS Data
Release 1 and 2MASS Point Source Catalog in search for extremely red L and T
dwarfs. The program was initiated by Metchev and collaborators, who presented
the findings on all newly identified T dwarfs in SDSS DR1, and estimated the
space density of isolated T0--T8 dwarfs in the solar neighbourhood. In the
current work we present most of the L dwarf discoveries. Our red-sensitive (z-J
> 2.75 mag) cross-match proves to be efficient in detecting peculiarly red L
dwarfs, adding two new ones, including one of the reddest known L dwarfs. Our
search also nets a new peculiarly blue L7 dwarf and, surprisingly, two M8
dwarfs. We further broaden our analysis to detect unresolved binary L or T
dwarfs through spectral template fitting to all L and T dwarfs presented here
and in the earlier work by Metchev and collaborators. We identify nine probable
binaries, six of which are new and eight harbour likely T dwarf secondaries. We
combine this result with current knowledge of the mass ratio distribution and
frequency of substellar companions to estimate an overall space density of
0.005--0.05 pc^{-3} for individual T0--T8 dwarfs.Comment: Accepted by Ap
Planetary Candidates Observed by Kepler, III: Analysis of the First 16 Months of Data
New transiting planet candidates are identified in sixteen months (May 2009 -
September 2010) of data from the Kepler spacecraft. Nearly five thousand
periodic transit-like signals are vetted against astrophysical and instrumental
false positives yielding 1,091 viable new planet candidates, bringing the total
count up to over 2,300. Improved vetting metrics are employed, contributing to
higher catalog reliability. Most notable is the noise-weighted robust averaging
of multi-quarter photo-center offsets derived from difference image analysis
which identifies likely background eclipsing binaries. Twenty-two months of
photometry are used for the purpose of characterizing each of the new
candidates. Ephemerides (transit epoch, T_0, and orbital period, P) are
tabulated as well as the products of light curve modeling: reduced radius
(Rp/R*), reduced semi-major axis (d/R*), and impact parameter (b). The largest
fractional increases are seen for the smallest planet candidates (197% for
candidates smaller than 2Re compared to 52% for candidates larger than 2Re) and
those at longer orbital periods (123% for candidates outside of 50-day orbits
versus 85% for candidates inside of 50-day orbits). The gains are larger than
expected from increasing the observing window from thirteen months (Quarter 1--
Quarter 5) to sixteen months (Quarter 1 -- Quarter 6). This demonstrates the
benefit of continued development of pipeline analysis software. The fraction of
all host stars with multiple candidates has grown from 17% to 20%, and the
paucity of short-period giant planets in multiple systems is still evident. The
progression toward smaller planets at longer orbital periods with each new
catalog release suggests that Earth-size planets in the Habitable Zone are
forthcoming if, indeed, such planets are abundant.Comment: Submitted to ApJS. Machine-readable tables are available at
http://kepler.nasa.gov, http://archive.stsci.edu/kepler/results.html, and the
NASA Exoplanet Archiv
Getting Ready for LISA: The Data, Support and Preparation Needed to Maximize US Participation in Space-Based Gravitational Wave Science
The NASA LISA Study Team was tasked to study how NASA might support US
scientists to participate and maximize the science return from the Laser
Interferometer Space Antenna (LISA) mission. LISA is gravitational wave
observatory led by ESA with NASA as a junior partner, and is scheduled to
launch in 2034. Among our findings: LISA science productivity is greatly
enhanced by a full-featured US science center and an open access data model. As
other major missions have demonstrated, a science center acts as both a locus
and an amplifier of research innovation, data analysis, user support, user
training and user interaction. In its most basic function, a US Science Center
could facilitate entry into LISA science by hosting a Data Processing Center
and a portal for the US community to access LISA data products. However, an
enhanced LISA Science Center could: support one of the parallel independent
processing pipelines required for data product validation; stimulate the high
level of research on data analysis that LISA demands; support users unfamiliar
with a novel observatory; facilitate astrophysics and fundamental research;
provide an interface into the subtleties of the instrument to validate
extraordinary discoveries; train new users; and expand the research community
through guest investigator, postdoc and student programs. Establishing a US
LISA Science Center well before launch can have a beneficial impact on the
participation of the broader astronomical community by providing training,
hosting topical workshops, disseminating mock catalogs, software pipelines, and
documentation. Past experience indicates that successful science centers are
established several years before launch; this early adoption model may be
especially relevant for a pioneering mission like LISA.Comment: 93 pages with a lovely cover page thanks to Bernard Kelly and
Elizabeth Ferrar
Low-mass Tertiary Companions to Spectroscopic Binaries. I. Common Proper Motion Survey for Wide Companions Using 2MASS
We report the first results of a multi-epoch search for wide (separations greater than a few tens of AU), low-mass tertiary companions of a volume-limited sample of 118 known spectroscopic binaries within 30 pc of the Sun, using the Two Micron All Sky Survey Point Source Catalog and follow-up observations with the KPNO and CTIO 4 m telescopes. Note that this sample is not volume complete but volume limited, and, thus, there is incompleteness in our reported companion rates. We are sensitive to common proper motion companions with separations from roughly 200 AU to 10,000 AU (~10ˮ → ~ 10'). From 77 sources followed-up to date, we recover 11 previously known tertiaries, 3 previously known candidate tertiaries, of which 2 are spectroscopically confirmed and 1 rejected, and 3 new candidates, of which 2 are confirmed and 1 rejected. This yields an estimated wide tertiary fraction of 19.5^(+5.2)_(–3.7)%. This observed fraction is consistent with predictions set out in star formation simulations where the fraction of wide, low-mass companions to spectroscopic binaries is >10%
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