204 research outputs found
DIRECT Distances to Nearby Galaxies Using Detached Eclipsing Binaries and Cepheids. V. Variables in the Field M31F
We undertook a long term project, DIRECT, to obtain the direct distances to
two important galaxies in the cosmological distance ladder -- M31 and M33 --
using detached eclipsing binaries (DEBs) and Cepheids. While rare and difficult
to detect, DEBs provide us with the potential to determine these distances with
an accuracy better than 5%. The extensive photometry obtained in order to
detect DEBs provides us with good light curves for the Cepheid variables. These
are essential to the parallel project to derive direct Baade-Wesselink
distances to Cepheids in M31 and M33. For both Cepheids and eclipsing binaries,
the distance estimates will be free of any intermediate steps.
As a first step in the DIRECT project, between September 1996 and October
1997 we obtained 95 full/partial nights on the F. L. Whipple Observatory 1.2 m
telescope and 36 full nights on the Michigan-Dartmouth-MIT 1.3 m telescope to
search for DEBs and new Cepheids in the M31 and M33 galaxies. In this paper,
fifth in the series, we present the catalog of variable stars found in the
field M31F [(\alpha,\delta)= (10.\arcdeg10, 40.\arcdeg72), J2000.0]. We have
found 64 variable stars: 4 eclipsing binaries, 52 Cepheids and 8 other
periodic, possible long period or non-periodic variables. The catalog of
variables, as well as their photometry and finding charts, is available via
anonymous ftp and the World Wide Web. The complete set of the CCD frames is
available upon request.Comment: submitted to the Astronomical Journal, 31 pages, 18 figures; paper
and data available at ftp://cfa-ftp.harvard.edu/pub/kstanek/DIRECT/ and
through WWW at http://cfa-www.harvard.edu/~kstanek/DIRECT
DIRECT Distances to Nearby Galaxies Using Detached Eclipsing Binaries and Cepheids. III. Variables in the Field M31C
We undertook a long term project, DIRECT, to obtain the direct distances to
two important galaxies in the cosmological distance ladder -- M31 and M33 --
using detached eclipsing binaries (DEBs) and Cepheids. While rare and difficult
to detect, DEBs provide us with the potential to determine these distances with
an accuracy better than 5%. The extensive photometry obtained in order to
detect DEBs provides us with good light curves for the Cepheid variables. These
are essential to the parallel project to derive direct Baade-Wesselink
distances to Cepheids in M31 and M33. For both Cepheids and eclipsing binaries,
the distance estimates will be free of any intermediate steps.
As a first step in the DIRECT project, between September 1996 and October
1997 we obtained 95 full/partial nights on the F. L. Whipple Observatory 1.2 m
telescope and 36 full nights on the Michigan-Dartmouth-MIT 1.3 m telescope to
search for DEBs and new Cepheids in the M31 and M33 galaxies. In this paper,
third in the series, we present the catalog of variable stars, most of them
newly detected, found in the field M31C [(alpha,delta)=(11.10, 41.42) deg,
J2000.0}]. We have found 115 variable stars: 12 eclipsing binaries, 35 Cepheids
and 68 other periodic, possible long period or non-periodic variables. The
catalog of variables, as well as their photometry and finding charts, is
available via anonymous ftp and the World Wide Web. The complete set of the CCD
frames is available upon request.Comment: submitted to the Astronomical Journal, 39 pages, 27 figures; paper
and data available at ftp://cfa-ftp.harvard.edu/pub/kstanek/DIRECT/ and
through WWW at http://cfa-www.harvard.edu/~kstanek/DIRECT
Resolving the nature of electronic excitations in resonant inelastic x-ray scattering
The study of elementary bosonic excitations is essential toward a complete
description of quantum electronic solids. In this context, resonant inelastic
X-ray scattering (RIXS) has recently risen to becoming a versatile probe of
electronic excitations in strongly correlated electron systems. The nature of
the radiation-matter interaction endows RIXS with the ability to resolve the
charge, spin and orbital nature of individual excitations. However, this
capability has been only marginally explored to date. Here, we demonstrate a
systematic method for the extraction of the character of excitations as
imprinted in the azimuthal dependence of the RIXS signal. Using this novel
approach, we resolve the charge, spin, and orbital nature of elastic
scattering, (para-)magnon/bimagnon modes, and higher energy dd excitations in
magnetically-ordered and superconducting copper-oxide perovskites (Nd2CuO4 and
YBa2Cu3O6.75). Our method derives from a direct application of scattering
theory, enabling us to deconstruct the complex scattering tensor as a function
of energy loss. In particular, we use the characteristic tensorial nature of
each excitation to precisely and reliably disentangle the charge and spin
contributions to the low energy RIXS spectrum. This procedure enables to
separately track the evolution of spin and charge spectral distributions in
cuprates with doping. Our results demonstrate a new capability that can be
integrated into the RIXS toolset, and that promises to be widely applicable to
materials with intertwined spin, orbital, and charge excitations
Generic phase diagram of "electron-doped" T' cuprates
We investigated the generic phase diagram of the electron doped
superconductor, Nd2-xCexCuO4, using films prepared by metal organic
decomposition. After careful oxygen reduction treatment to remove interstitial
Oap atoms, we found that the Tc increases monotonically from 24 K to 29 K with
decreasing x from 0.15 to 0.00, demonstrating a quite different phase diagram
from the previous bulk one. The implication of our results is discussed on the
basis of tremendous influence of Oap "impurities" on superconductivity and also
magnetism in T' cuprates. Then we conclude that our result represents the
generic phase diagram for oxygen-stoichiometric Nd2-xCexCuO4.Comment: 12 pages, 4 figures; International Symposium on Superconductivity
(ISS) 200
Data on the fungal species consumed by mammal species in Australia
The data reported here support the manuscript Nuske et al. (2017). Searches were made for quantitative data on the occurrence of fungi within dietary studies of Australian mammal species. The original location reported in each study was used as the lowest grouping variable within the dataset. To standardise the data and compare dispersal events from populations of different mammal species that might overlap, data from locations were further pooled and averaged across sites if they occurred within 100 km of a random central point. Three locations in Australia contained data on several (>7) mycophagous mammals, all other locations had data on 1–3 mammal species. Within these three locations, the identity of the fungi species was compared between mammal species’ diets. A list of all fungi species found in Australian mammalian diets is also provide along with the original reference and fungal synonym names
Chandra detection of diffuse X-ray emission from the globular cluster Terzan 5
Terzan 5, a globular cluster (GC) prominent in mass and population of compact
objects, is searched for diffuse X-ray emission, as proposed by several models.
We analyzed the data of an archival Chandra observation of Terzan 5 to search
for extended diffuse X-ray emission outside the half-mass radius of the GC. We
removed detected point sources from the data to extract spectra from diffuse
regions around Terzan 5. The Galactic background emission was modeled by a
2-temperature thermal component, which is typical for Galactic diffuse
emission.
We detected significant diffuse excess emission above the particle background
level from the whole field-of-view. The surface brightness appears to be peaked
at the GC center and decreases smoothly outwards. After the subtraction of
particle and Galactic background, the excess spectrum of the diffuse emission
between the half-mass radius and 3' can be described by a power-law model with
photon index = 0.90.5 and a surface flux of F =
(1.170.16) 10 erg s cm sr in the 1--7 keV
band. We estimated the contribution from unresolved point sources to the
observed excess to be negligible. The observations suggest that a purely
thermal origin of the emission is less likely than a non-thermal scenario.
However, from simple modeling we cannot identify a clearly preferred scenario.Comment: 6 pages, 4 figures, accepted for publication by A&
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