11,419 research outputs found
The Near-Infrared Photometric Properties of Bright Giants in the Central Regions of the Galactic Bulge
Images recorded through broad (J, H, K), and narrow (CO, and 2.2micron
continuum) band filters are used to investigate the photometric properties of
bright (K < 13.5) stars in a 6 x 6 arcmin field centered on the SgrA complex.
The giant branch ridgelines in the (K, J-K) and (K, H-K) color-magnitude
diagrams are well matched by the Baade's Window (BW) M giant sequence if the
mean extinction is A_K ~ 2.8 mag. Extinction measurements for individual stars
are estimated using the M_K versus infrared color relations defined by M giants
in BW, and the majority of stars have A_K between 2.0 and 3.5 mag. The
extinction is locally high in the SgrA complex, where A_K ~ 3.1 mag.
Reddening-corrected CO indices, CO_o, are derived for over 1300 stars with J,
H, and K brightnesses, and over 5300 stars with H and K brightnesses. The
distribution of CO_o values for stars with K_o between 11.25 and 7.25 can be
reproduced using the M_K versus CO_o relation defined by M giants in BW. The
data thus suggest that the most metal-rich giants in the central regions of the
bulge and in BW have similar photometric properties and 2.3micron CO strengths.
Hence, it appears that the central region of the bulge does not contain a
population of stars that are significantly more metal-rich than what is seen in
BW.Comment: 29 pages, including 14 figure
Comparison of charge modulations in LaBaCuO and YBaCuO
A charge modulation has recently been reported in (Y,Nd)BaCuO
[Ghiringhelli {\em et al.} Science 337, 821 (2013)]. Here we report Cu
edge soft x-ray scattering studies comparing the lattice modulation associated
with the charge modulation in YBaCuO with that associated with
the well known charge and spin stripe order in LaBaCuO.
We find that the correlation length in the CuO plane is isotropic in both
cases, and is \AA for LaBaCuO and \AA for YBaCuO. Assuming weak inter-planar correlations of
the charge ordering in both compounds, we conclude that the order parameters of
the lattice modulations in LaBaCuO and
YBaCuO are of the same order of magnitude.Comment: 3 pages, 2 figure
Two-mirror Schwarzschild aplanats. Basic relations
It is shown that the theory of aplanatic two-mirror telescopes developed by
Karl Schwarzschild in 1905 leads to the unified description both the prefocal
and the postfocal systems. The class of surfaces in the ZEMAX optical program
has been properly extended to ascertain the image quality in exact
Schwarzschild aplanats. A comparison of Schwarzschild aplanats with approximate
Ritchey-Chretien and Gregory-Maksutov aplanatic telescopes reveals a noticeable
advantage of the former at fast focal ratio of the system.Comment: 19 page
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