225 research outputs found
Approach for power scaling solid-state lasers with intracavity motion
Solid-state lasers are typically limited by adverse thermal effects within the gain medium. In this paper we describe a new method for dramatically reducing thermal effects in an end-pumped solid-state laser by incorporating a rotating intracavity periscope in the resonator to spatially separate the lasing and thermal processes. In contrast to previous examples of moving solid-state lasers our approach keeps the gain medium stationary simplifying the heat removal arrangement. This scheme has been applied to a Nd:YAG laser yielding an output power of 120 W at 1.064 µm, limited by available pump power. Analysis suggests that scaling to much higher power is feasible with the appropriate laser design
Prospecting Period Measurements with LSST - Low Mass X-ray Binaries as a Test Case
The Large Synoptic Survey Telescope (LSST) will provide for unbiased sampling
of variability properties of objects with mag 24. This should allow for
those objects whose variations reveal their orbital periods (), such
as low mass X-ray binaries (LMXBs) and related objects, to be examined in much
greater detail and with uniform systematic sampling. However, the baseline LSST
observing strategy has temporal sampling that is not optimised for such work in
the Galaxy. Here we assess four candidate observing strategies for measurement
of in the range 10 minutes to 50 days. We simulate multi-filter
quiescent LMXB lightcurves including ellipsoidal modulation and stochastic
flaring, and then sample these using LSST's operations simulator (OpSim) over
the (mag, ) parameter space, and over five sightlines sampling a range
of possible reddening values. The percentage of simulated parameter space with
correctly returned periods ranges from 23 %, for the current baseline
strategy, to 70 % for the two simulated specialist strategies. Convolving
these results with a distribution, a modelled Galactic spatial
distribution and reddening maps, we conservatively estimate that the most
recent version of the LSST baseline strategy will allow determination
for 18 % of the Milky Way's LMXB population, whereas strategies that do
not reduce observations of the Galactic Plane can improve this dramatically to
32 %. This increase would allow characterisation of the full binary
population by breaking degeneracies between suggested distributions
in the literature. Our results can be used in the ongoing assessment of the
effectiveness of various potential cadencing strategies.Comment: Replacement after addressing minor corrections from the referee -
mainly improvements in clarificatio
Nanoparticleâ Based Targeting and Detection of Microcavities
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/136015/1/adhm201600883.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/136015/2/adhm201600883_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/136015/3/adhm201600883-sup-0001-S1.pd
The Blanco DECam Bulge Survey (BDBS) VIII: Chemo-kinematics in the southern Galactic bulge from 2.3 million red clump stars with Gaia DR3 proper motions
The Blanco DECam Bulge Survey (BDBS) provides near-ultraviolet to
near-infrared photometry for ~250 million unique stars. By combining BDBS
photometry with the latest Gaia astrometry, we characterize the chemo-dynamics
of red clump stars across the BDBS footprint, using an unprecedented sample
size and sky coverage. We construct a sample of ~2.3 million red clump giants
in the bulge with photometric metallicities, BDBS photometric distances, and
proper motions. We study the kinematics of the red clump stars as a function of
sky position and metallicity, by investigating proper motion rotation curves,
velocity dispersions, and proper motion correlations across the southern
Galactic bulge. We find that metal-poor red clump stars exhibit lower rotation
amplitudes, at ~29 km s kpc^{-1}. The peak of the angular velocity is
~39 km s^{-1} kpc^{-1} for [Fe/H] ~ -0.2 dex, exhibiting declining rotation at
higher [Fe/H]. The velocity dispersion is higher for metal-poor stars, while
metal-rich stars show a steeper gradient with Galactic latitude, with a maximum
dispersion at low latitudes along the bulge minor axis. Only metal-rich stars
([Fe/H] >~ -0.5 dex) show clear signatures of the bar in their kinematics,
while the metal-poor population exhibits isotropic motions with an axisymmetric
pattern around Galactic longitude l = 0. This work reports the largest sample
of bulge stars with distance, metallicity, and astrometry and shows clear
kinematic differences with metallicity. The global kinematics over the bulge
agrees with earlier studies. However, we see striking changes with increasing
metallicity and for the first time, see kinematic differences for stars with
[Fe/H]>-0.5, suggesting that the bar itself may have kinematics that depends on
metallicity.Comment: 12 pages, Accepted for publication in A&
The thermal emission of the exoplanets WASP-1b and WASP-2b
We present a comparative study of the thermal emission of the transiting
exoplanets WASP-1b and WASP-2b using the Spitzer Space Telescope. The two
planets have very similar masses but suffer different levels of irradiation and
are predicted to fall either side of a sharp transition between planets with
and without hot stratospheres. WASP-1b is one of the most highly irradiated
planets studied to date. We measure planet/star contrast ratios in all four of
the IRAC bands for both planets (3.6-8.0um), and our results indicate the
presence of a strong temperature inversion in the atmosphere of WASP-1b,
particularly apparent at 8um, and no inversion in WASP-2b. In both cases the
measured eclipse depths favor models in which incident energy is not
redistributed efficiently from the day side to the night side of the planet. We
fit the Spitzer light curves simultaneously with the best available radial
velocity curves and transit photometry in order to provide updated measurements
of system parameters. We do not find significant eccentricity in the orbit of
either planet, suggesting that the inflated radius of WASP-1b is unlikely to be
the result of tidal heating. Finally, by plotting ratios of secondary eclipse
depths at 8um and 4.5um against irradiation for all available planets, we find
evidence for a sharp transition in the emission spectra of hot Jupiters at an
irradiation level of 2 x 10^9 erg/s/cm^2. We suggest this transition may be due
to the presence of TiO in the upper atmospheres of the most strongly irradiated
hot Jupiters.Comment: 10 pages, submitted to Ap
Monitoring observations of SMC X-1's excursions (MOOSE)-II: A new excursion accompanies spin-up acceleration
SMC X-1 is a high-mass X-ray binary showing superorbital modulation with an
unstable period. Previous monitoring shows three excursion events in
1996--1998, 2005--2007, and 2014--2016. The superorbital period drifts from >60
days to <40 days and then evolves back during an excursion. Here we report a
new excursion event of SMC X-1 in 2020--2021, indicating that the superorbital
modulation has an unpredictable, chaotic nature. We trace the spin-period
evolution and find that the spin-up rate accelerated one year before the onset
of this new excursion, which suggests a possible inside-out process connecting
the spin-up acceleration and the superorbital excursion. This results in a
deviation of the spin period residual, similar to the behaviour of the first
excursion in 1996--1998. In further analysis of the pulse profile evolution, we
find that the pulsed fraction shows a long-term evolution and may be connected
to the superorbital excursion. These discoveries deepen the mystery of SMC X-1
because they cannot be solely interpreted by the warped disc model. Upcoming
pointed observations and theoretical studies may improve our understanding of
the detailed accretion mechanisms taking place.Comment: 7 pages, 3 figures, Accepted for publication in MNRA
Blanco DECam Bulge Survey (BDBS) IV: Metallicity Distributions and Bulge Structure from 2.6 Million Red Clump Stars
We present photometric metallicity measurements for a sample of 2.6 million
bulge red clump stars extracted from the Blanco DECam Bulge Survey (BDBS).
Similar to previous studies, we find that the bulge exhibits a strong vertical
metallicity gradient, and that at least two peaks in the metallicity
distribution functions appear at b < -5. We can discern a metal-poor ([Fe/H] ~
-0.3) and metal-rich ([Fe/H] ~ +0.2) abundance distribution that each show
clear systematic trends with latitude, and may be best understood by changes in
the bulge's star formation/enrichment processes. Both groups exhibit asymmetric
tails, and as a result we argue that the proximity of a star to either peak in
[Fe/H] space is not necessarily an affirmation of group membership. The
metal-poor peak shifts to lower [Fe/H] values at larger distances from the
plane while the metal-rich tail truncates. Close to the plane, the metal-rich
tail appears broader along the minor axis than in off-axis fields. We also
posit that the bulge has two metal-poor populations -- one that belongs to the
metal-poor tail of the low latitude and predominantly metal-rich group, and
another belonging to the metal-poor group that dominates in the outer bulge. We
detect the X-shape structure in fields with |Z| > 0.7 kpc and for stars with
[Fe/H] > -0.5. Stars with [Fe/H] < -0.5 may form a spheroidal or "thick bar"
distribution while those with [Fe/H] > -0.1 are strongly concentrated near the
plane.Comment: 26 pages, 22 figures, accepted for publication in MNRAS; the full
data table is very long so only a stub table has been provided here; the full
electronic table will be provided through MNRAS upon publication, but early
access to the full table will be granted upon request to the author
Stakeholder Theory and Marketing: Moving from a Firm-Centric to a Societal Perspective
This essay is inspired by the ideas and research examined in the special section on “Stakeholder Marketing” of the Journal of Public Policy & Marketing in 2010. The authors argue that stakeholder marketing is slowly coalescing with the broader thinking that has occurred in the stakeholder management and ethics literature streams during the past quarter century. However, the predominant view of stakeholders that many marketers advocate is still primarily pragmatic and company centric. The position advanced herein is that stronger forms of stakeholder marketing that reflect more normative, macro/societal, and network-focused orientations are necessary. The authors briefly explain and justify these characteristics in the context of the growing “prosociety” and “proenvironment” perspectives—orientations that are also in keeping with the public policy focus of this journal. Under the “hard form” of stakeholder theory, which the authors endorse, marketing managers must realize that serving stakeholders sometimes requires sacrificing maximum profits to mitigate outcomes that would inflict major damage on other stakeholders, especially society
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