5,173 research outputs found
Burglary project
This report outlines the process and findings from an innovative project for students. This work was part of the curriculum and involved students working with West Yorkshire Police as part of the safer Leeds project in designing and making a film for students n crime prevention and personal safety in Leed
New Brown Dwarfs and an Updated Initial Mass Function in Taurus
I have performed a search for young low-mass stars and brown dwarfs (BDs) in
2 regions encompassing a total area of 4 deg^2 in the Taurus star-forming
region, discovering 15 new members of Taurus. In addition, I present 7 new
members outside of these areas from the initial stage of a survey of all of
Taurus. These 22 objects exhibit spectral types of M4.5-M9.25 and masses of
0.3-0.015 M_sun according to the theoretical evolutionary models of Baraffe and
Chabrier, 7 of which are likely to be BDs. Emission in H(alpha), He I, Ca II,
[O I], and [S II] and excess emission in optical and near-IR bands among some
of these objects suggest the presence of accretion, outflows, and circumstellar
disks. The results from the 4 deg^2 survey have been combined with previous
studies of Taurus to arrive at an IMF for a total area of 12.4 deg^2. As in the
previous IMFs for Taurus, the updated IMF peaks at a higher mass (0.8 M_sun)
than the mass functions in IC 348 and Orion (0.1-0.2 M_sun). Meanwhile, the
deficit of BDs in Taurus appears to be less significant (x1.4-1.8) than found
in earlier studies (x2) because of a slightly higher BD fraction in the new IMF
for Taurus and a lower BD fraction in the new spectroscopic IMF for the
Trapezium from Slesnick and coworkers. The spatial distribution of the low-mass
stars and BDs discovered in the two new survey areas closely matches that of
the more massive members. Thus, on the degree size scales (~3 pc) probed to
date, there is no indication that BDs form through ejection.Comment: 35 pages, The Astrophysical Journal, 2004, v617 (December 20
Dusty Cometary Globules in W5
We report the discovery of four dusty cometary tails around low mass stars in
two young clusters belonging to the W5 star forming region. Fits to the
observed emission profiles from 24 micron observations with the Spitzer Space
Telescope give tail lifetimes < 30 Myr, but more likely < 5 Myr. This result
suggests that the cometary phase is a short lived phenomenon, occurring after
photoevaporation by a nearby O star has removed gas from the outer disk of a
young low mass star (see also Balog et al. 2006; Balog et al. 2008).Comment: 11 pages, 3 figures. Accepted for publication to ApJ Letter
Combined ultraviolet studies of astronomical sources
Topics addressed include: Cygnus Loop; P Cygni profiles in dwarf novae; YY Gem; nova shells; HZ Herculis; activity cycles in cluster giants; Alpha Ori; metal deficient giant stars; ultraviolet spectra of symbiotic stars detected by the Very Large Array; time variability in symbiotic stars; blue galaxies; and quasistellar objects with X-ray spectra
Anisotropic KPZ growth in 2+1 dimensions: fluctuations and covariance structure
In [arXiv:0804.3035] we studied an interacting particle system which can be
also interpreted as a stochastic growth model. This model belongs to the
anisotropic KPZ class in 2+1 dimensions. In this paper we present the results
that are relevant from the perspective of stochastic growth models, in
particular: (a) the surface fluctuations are asymptotically Gaussian on a
sqrt(ln(t)) scale and (b) the correlation structure of the surface is
asymptotically given by the massless field.Comment: 13 pages, 4 figure
The TAOS Project: Upper Bounds on the Population of Small KBOs and Tests of Models of Formation and Evolution of the Outer Solar System
We have analyzed the first 3.75 years of data from TAOS, the Taiwanese
American Occultation Survey. TAOS monitors bright stars to search for
occultations by Kuiper Belt Objects (KBOs). This dataset comprises 5e5
star-hours of multi-telescope photometric data taken at 4 or 5 Hz. No events
consistent with KBO occultations were found in this dataset. We compute the
number of events expected for the Kuiper Belt formation and evolution models of
Pan & Sari (2005), Kenyon & Bromley (2004), Benavidez & Campo Bagatin (2009),
and Fraser (2009). A comparison with the upper limits we derive from our data
constrains the parameter space of these models. This is the first detailed
comparison of models of the KBO size distribution with data from an occultation
survey. Our results suggest that the KBO population is comprised of objects
with low internal strength and that planetary migration played a role in the
shaping of the size distribution.Comment: 18 pages, 16 figures, Aj submitte
Conductance tomography of conductive filaments in intrinsic silicon-rich silica RRAM
We present results from an imaging study of filamentary conduction in silicon suboxide resistive RAM devices. We used a conductive atomic force microscope to etch through devices while measuring current, allowing us to produce tomograms of conductive filaments. To our knowledge this is the first report of such measurements in an intrinsic resistance switching material
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