4,290 research outputs found
Albert Jackson (1844-1901)
Albert Jackson was a leader in Savannah\u27s African-American community. He was a native of Savannah, and resided in the city for most of his life. He was active in the business community, and in many organizations that helped the. Albert Jackson was married twice, first to Jennette Bullock then to Mary Scott. He had four children, three sons and a daughter. He died in 1901 after a prolonged illness, and is buried in Laurel Grove Cemetery.https://digitalcommons.georgiasouthern.edu/sav-bios-lane/1087/thumbnail.jp
Hands-On TAROT: Intercontinental use of the TAROT for Education and Public Outreach
The TAROT telescope has for primary goal the search for the prompt optical
counterpart of Cosmic Gamma-Ray Bursts. It is a completely autonomous 25cm
telescope installed near Nice (France), able to point any location of the sky
within 1-2 seconds. The control, scheduling, and data processing activities are
completely automated, so the instrument is completely autonomous. In addition
to its un-manned modes, we added recently the possibility to remotely control
the telescope, as a request of the "Hands-On Universe" (HOU) program for
exchange of time within automatic telescopes for the education and public
outreach. To this purpose we developed a simple control interface. A webcam was
installed to visualize the telescope. Access to the data is possible through a
web interface. The images can be processed by the HOU software, a program
specially suited for use within the classroom. We experienced these feature
during the open days of the University of California Berkeley and the Astronomy
Festival of Fleurance (France). We plan a regular use for an astronomy course
of the Museum of Tokyo, as well as for French schools. Not only does Hands-On
TAROT gives the general public an access to professional astronomy, but it is
also a more general tool to demonstrate the use of a complex automated system,
the techniques of data processing and automation. Last but not least, through
the use of telescopes located in many countries over the globe, a form of
powerful and genuine cooperation between teachers and children from various
countries is promoted, with a clear educational goal.Comment: 4 pages, Based on a demonstration presented at the ADASS X
Conference, Boston, MA, USA, October 2000, to appear in ASP Conf. Serie
The complex environment of the bright carbon star TX Psc as probed by spectro-astrometry
Context: Stars on the asymptotic giant branch (AGB) show broad evidence of
inhomogeneous atmospheres and circumstellar envelopes. These have been studied
by a variety of methods on various angular scales. In this paper we explore the
envelope of the well-studied carbon star TX Psc by the technique of
spectro-astrometry. Aims: We explore the potential of this method for detecting
asymmetries around AGB stars. Methods:We obtained CRIRES observations of
several CO v=1 lines near 4.6 m and HCN lines near 3 m in
2010 and 2013. These were then searched for spectro-astrometric signatures. For
the interpretation of the results, we used simple simulated observations.
Results: Several lines show significant photocentre shifts with a clear
dependence on position angle. In all cases, tilde-shaped signatures are found
where the positive and negative shifts (at PA 0deg) are associated with blue
and weaker red components of the lines. The shifts can be modelled with a
bright blob 70 mas to 210 mas south of the star with a flux of several percent
of the photospheric flux. We estimate a lower limit of the blob temperature of
1000 K. The blob may be related to a mass ejection as found for AGB stars or
red supergiants. We also consider the scenario of a companion object.
Conclusions: Although there is clear spectro-astrometric evidence of a rather
prominent structure near TX Psc, it does not seem to relate to the other
evidence of asymmetries, so no definite explanation can be given. Our data thus
underline the very complex structure of the environment of this star, but
further observations that sample the angular scales out to a few hundred
milli-arcseconds are needed to get a clearer picture
A modern study of HD166734: a massive supergiant system
Aims. HD166734 is an eccentric eclipsing binary system composed of two
supergiant O-type stars, orbiting with a 34.5-day period. In this rare
configuration for such stars, the two objects mainly evolve independently,
following single-star evolution so far. This system provides a chance to study
the individual parameters of two supergiant massive stars and to derive their
real masses. Methods. An intensive monitoring was dedicated to HD166734.We
analyzed mid- and high-resolution optical spectra to constrain the orbital
parameters of this system. We also studied its light curve for the first time,
obtained in the VRI filters. Finally, we disentangled the spectra of the two
stars and modeled them with the CMFGEN atmosphere code in order to determine
the individual physical parameters. Results. HD166734 is a O7.5If+O9I(f)
binary. We confirm its orbital period but we revise the other orbital
parameters. In comparison to what we found in the literature, the system is
more eccentric and, now, the hottest and the most luminous component is also
the most massive one. The light curve exhibits only one eclipse and its
analysis indicates an inclination of 63.0{\deg} 2.7{\deg}. The
photometric analysis provides us with a good estimation of the luminosities of
the stars, and therefore their exact positions in the Hertzsprung-Russell
diagram. The evolutionary and the spectroscopic masses show good agreement with
the dynamical masses of 39.5 Msun for the primary and 33.5 Msun for the
secondary, within the uncertainties. The two components are both enriched in
helium and in nitrogen and depleted in carbon. In addition, the primary also
shows a depletion in oxygen. Their surface abundances are however not different
from those derived from single supergiant stars, yielding, for both components,
an evolution similar to that of single stars.Comment: 13 pages, 13 figures, A&A accepte
Catching the fish - Constraining stellar parameters for TX Psc using spectro-interferometric observations
Stellar parameter determination is a challenging task when dealing with
galactic giant stars. The combination of different investigation techniques has
proven to be a promising approach. We analyse archive spectra obtained with the
Short-Wavelength-Spectrometer (SWS) onboard of ISO, and new interferometric
observations from the Very Large Telescope MID-infrared Interferometric
instrument (VLTI/MIDI) of a very well studied carbon-rich giant: TX Psc. The
aim of this work is to determine stellar parameters using spectroscopy and
interferometry. The observations are used to constrain the model atmosphere,
and eventually the stellar evolutionary model in the region where the tracks
map the beginning of the carbon star sequence. Two different approaches are
used to determine stellar parameters: (i) the 'classic' interferometric
approach where the effective temperature is fixed by using the angular diameter
in the N-band (from interferometry) and the apparent bolometric magnitude; (ii)
parameters are obtained by fitting a grid of state-of-the-art hydrostatic
models to spectroscopic and interferometric observations. We find a good
agreement between the parameters of the two methods. The effective temperature
and luminosity clearly place TX Psc in the carbon-rich AGB star domain in the
H-R-diagram. Current evolutionary tracks suggest that TX Psc became a C-star
just recently, which means that the star is still in a 'quiet' phase compared
to the subsequent strong-wind regime. This is in agreement with the C/O ratio
being only slightly larger than 1.Comment: 11 pages, 9 figures, 5 table
Coplanar stripline antenna design for optically detected magnetic resonance on semiconductor quantum dots
We report on the development and testing of a coplanar stripline antenna that
is designed for integration in a magneto-photoluminescence experiment to allow
coherent control of individual electron spins confined in single self-assembled
semiconductor quantum dots. We discuss the design criteria for such a structure
which is multi-functional in the sense that it serves not only as microwave
delivery but also as electrical top gate and shadow mask for the single quantum
dot spectroscopy. We present test measurements on hydrogenated amorphous
silicon, demonstrating electrically detected magnetic resonance using the
in-plane component of the oscillating magnetic field created by the coplanar
stripline antenna necessary due to the particular geometry of the quantum dot
spectroscopy. From reference measurements using a commercial electron spin
resonance setup in combination with finite element calculations simulating the
field distribution in the structure, we obtain an average magnetic field of
~0.2mT at the position where the quantum dots would be integrated into the
device. The corresponding pi-pulse time of ~0.3us fully meets the requirements
set by the high sensitivity optical spin read-out scheme developed for the
quantum dot
Influence of body water distribution on skin thickness: measurements using high-frequency ultrasound
Origin of anomalous breakdown of Bloch's rule in the Mott-Hubbard insulator MnTe
We reinvestigate the pressure dependence of the crystal structure and
antiferromagnetic phase transition in MnTe by the rigorous and reliable
tool of high pressure neutron powder diffraction. First-principles density
functional theory calculations are carried out in order to gain microscopic
insight. The measured N\'eel temperature of MnTe is found to show unusually
large pressure dependence of K GPa. This gives rise to large
violation of Bloch's rule given by , to a value of -6.0 0.1 for
MnTe. The ab-initio calculation of the electronic structure and the
magnetic exchange interactions in MnTe, for the measured crystal structures
at different pressures, gives the pressure dependence of the Ne\'el
temperature, to be -5.61, in close agreement with experimental
finding. The microscopic origin of this behavior turns to be dictated by the
distance dependence of the cation-anion hopping interaction strength
How disruptions to our morning routines harm daily productivity, and what we can do about it
Advice for managers and employees on how to minimise disruptions to much-needed morning rituals - by Shawn T. McClean, Joel Koopman, Junhyok Yim, and Anthony C. Klot
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