718 research outputs found
G 112-29 (=NLTT 18149), a Very Wide Companion to GJ 282 AB with a Common Proper Motion, Common Parallax, Common Radial Velocity and Common Age
We have made a search for common proper motion (CPM) companions to the wide
binaries in the solar vicinity. We found that the binary GJ 282AB has a very
distant CPM companion (NLTT 18149) at a separation s=1.09 \arcdeg. Improved
spectral types and radial velocities are obtained, and ages determined for the
three components. The Hipparcos trigonometric parallaxes and the new radial
velocities and ages turn out to be very similar for the three stars, and
provide strong evidence that they form a physical system. At a projected
separation of 55733AU from GJ 282AB, NLTT 18149 ranks among the widest physical
companions known.Comment: 13 pages, 3 figures, submmited to Ap
HI aperture synthesis and optical observations of the pair of galaxies NGC 6907 and 6908
NGC 6908, a S0 galaxy situated in direction of NGC 6907, was only recently
recognized as a distinct galaxy, instead of only a part of NGC 6907. We present
21 cm radio synthesis observations obtained with the GMRT and optical images
and spectroscopy obtained with the Gemini North telescope of this pair of
interacting galaxies. From the radio observations we obtained the velocity
field and the HI column density map of the whole region containing the NGC
6907/8 pair, and by means of the Gemini multi-object spectroscopy we obtained
high quality photometric images and resolution spectra sampling the
two galaxies. By comparing the rotation curve of NGC 6907 obtained from the two
opposite sides around the main kinematic axis, we were able to distinguish the
normal rotational velocity field from the velocity components produced by the
interaction between the two galaxies. Taking into account the rotational
velocity of NGC 6907 and the velocity derived from the absorption lines for NGC
6908, we verified that the relative velocity between these systems is lower
than 60 km s. The emission lines observed in the direction of NGC 6908,
not typical of S0 galaxies, have the same velocity expected for the NGC 6907
rotation curve. Some of them, superimposed on the absorption profiles, which
reinforces the idea that they were not formed in NGC 6908. Finally, the HI
profile exhibits details of the interaction, showing three components: one for
NGC 6908, another for the excited gas in the NGC 6907 disk and a last one for
the gas with higher relative velocities left behind NGC 6908 by dynamical
friction, used to estimate the time when the interaction started in years ago.Comment: 11 pages, 5 tables, 13 figures. Corrected typos. Accepted for
publication in MNRAS. The definitive version will be available at
http://www.blackwell-synergy.co
M2K: I. A Jovian mass planet around the M3V star HIP79431
Doppler observations from Keck Observatory reveal the presence of a planet
with Msini of 2.1 Mjup orbiting the M3V star HIP79431. This is the sixth giant
planet to be detected in Doppler surveys of M dwarfs and it is one of the most
massive planets discovered around an M dwarf star. The planet has an orbital
period of 111.7 days and an orbital eccentricity of 0.29. The host star is
metal rich, with an estimated [Fe/H] = +0.4. This is the first planet to emerge
from our new survey of 1600 M-to-K dwarf stars.Comment: 5 figure
On the Reported Death of the MACHO Era
We present radial velocity measurements of four wide halo binary candidates
from the sample in Chaname & Gould (2004; CG04) which, to date, is the only
sample containing a large number of such candidates. The four candidates that
we have observed have projected separations >0.1 pc, and include the two widest
binaries from the sample, with separations of 0.45 and 1.1 pc. We confirm that
three of the four CG04 candidates are genuine, including the one with the
largest separation. The fourth candidate, however, is spurious at the 5-sigma
level. In the light of these measurements we re-examine the implications for
MACHO models of the Galactic halo. Our analysis casts doubt on what MACHO
constraints can be drawn from the existing sample of wide halo binaries.Comment: 6 Pages, 4 Figures, Accepted for MNRAS Letter
Use of waveform lidar and hyperspectral sensors to assess selected spatial and structural patterns associated with recent and repeat disturbance and the abundance of sugar maple (Acer saccharum Marsh.) in a temperate mixed hardwood and conifer forest.
Abstract
Waveform lidar imagery was acquired on September 26, 1999 over the Bartlett Experimental Forest (BEF) in New Hampshire (USA) using NASA\u27s Laser Vegetation Imaging Sensor (LVIS). This flight occurred 20 months after an ice storm damaged millions of hectares of forestland in northeastern North America. Lidar measurements of the amplitude and intensity of ground energy returns appeared to readily detect areas of moderate to severe ice storm damage associated with the worst damage. Southern through eastern aspects on side slopes were particularly susceptible to higher levels of damage, in large part overlapping tracts of forest that had suffered the highest levels of wind damage from the 1938 hurricane and containing the highest levels of sugar maple basal area and biomass. The levels of sugar maple abundance were determined through analysis of the 1997 Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) high resolution spectral imagery and inventory of USFS Northern Research Station field plots. We found a relationship between field measurements of stem volume losses and the LVIS metric of mean canopy height (r2 = 0.66; root mean square errors = 5.7 m3/ha, p \u3c 0.0001) in areas that had been subjected to moderate-to-severe ice storm damage, accurately documenting the short-term outcome of a single disturbance event
Characterization of the Benchmark Binary NLTT 33370
We report the confirmation of the binary nature of the nearby, very low-mass
system NLTT 33370 with adaptive optics imaging and present resolved
near-infrared photometry and integrated light optical and near-infrared
spectroscopy to characterize the system. VLT-NaCo and LBTI-LMIRCam images show
significant orbital motion between 2013 February and 2013 April. Optical
spectra reveal weak, gravity sensitive alkali lines and strong lithium 6708
Angstrom absorption that indicate the system is younger than field age.
VLT-SINFONI near-IR spectra also show weak, gravity sensitive features and
spectral morphology that is consistent with other young, very low-mass dwarfs.
We combine the constraints from all age diagnostics to estimate a system age of
~30-200 Myr. The 1.2-4.7 micron spectral energy distribution of the components
point toward T_eff=3200 +/- 500 K and T_eff=3100 +/- 500 K for NLTT 33370 A and
B, respectively. The observed spectra, derived temperatures, and estimated age
combine to constrain the component spectral types to the range M6-M8.
Evolutionary models predict masses of 113 +/- 8 M_Jup and 106 +/- 7 M_Jup from
the estimated luminosities of the components. KPNO-Phoenix spectra allow us to
estimate the systemic radial velocity of the binary. The Galactic kinematics of
NLTT 33370AB are broadly consistent with other young stars in the Solar
neighborhood. However, definitive membership in a young, kinematic group cannot
be assigned at this time and further follow-up observations are necessary to
fully constrain the system's kinematics. The proximity, age, and late-spectral
type of this binary make it very novel and an ideal target for rapid, complete
orbit determination. The system is one of only a few model calibration
benchmarks at young ages and very low-masses.Comment: 25 pages, 3 tables, 13 figures, accepted for publication in The
Astrophysical Journa
An inner ring and the micro lensing toward the Bulge
All current Bulge-Disk models for the inner Galaxy fall short of reproducing
self-consistently the observed micro-lensing optical depth by a factor of two
(). We show that the least mass-consuming way to increase the
optical depth is to add density roughly half-way the observer and the highest
micro-lensing-source density. We present evidence for the existence of such a
density structure in the Galaxy: an inner ring, a standard feature of barred
galaxies. Judging from data on similar rings in external galaxies, an inner
ring can contribute more than 50% of a pure Bulge-Disk model to the
micro-lensing optical depth. We may thus eliminate the need for a small viewing
angle of the Bar. The influence of an inner ring on the event-duration
distribution, for realistic viewing angles, would be to increase the fraction
of long-duration events toward Baade's window. The longest events are expected
toward the negative-longitude tangent point at -22\degr . A properly
sampled event-duration distribution toward this tangent point would provide
essential information about viewing angle and elongation of the over-all
density distribution in the inner Galaxy.Comment: 9 pages, 7(15) figs, LaTeX, AJ (accepted
The Solar Neighborhood. XXXIX. Parallax Results from the CTIOPI and NOFS Programs: 50 New Members of the 25 Parsec White Dwarf Sample
We present 114 trigonometric parallaxes for 107 nearby white dwarf (WD)
systems from both the Cerro Tololo Inter-American Observatory Parallax
Investigation (CTIOPI) and the U. S. Naval Observatory Flagstaff Station (NOFS)
parallax programs. Of these, 76 parallaxes for 69 systems were measured by the
CTIOPI program and 38 parallaxes for as many systems were measured by the NOFS
program. A total of 50 systems are confirmed to be within the 25 pc horizon of
interest. Coupled with a spectroscopic confirmation of a common proper motion
companion to a Hipparcos star within 25 pc as well as confirmation parallax
determinations for two WD systems included in the recently released Tycho Gaia
Astrometric Solution (TGAS) catalog, we add 53 new systems to the 25 pc WD
sample a 42% increase. Our sample presented here includes four strong
candidate halo systems, a new metal-rich DAZ WD, a confirmation of a recently
discovered nearby short-period (P = 2.85 hr) double degenerate, a WD with a new
astrometric pertubation (long period, unconstrained with our data), and a new
triple system where the WD companion main-sequence star has an astrometric
perturbation (P 1.6 yr).Comment: 32 pages, 12 figures. Figure 4 in the manuscript is a representative
set of plots - plots for all WDs presented here are available
(allfits_photo.pdf, allfits_photo_DQ.pdf, and allfits_photo_DZ.pdf). Accepted
for publication in The Astronomical Journa
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