5,044 research outputs found
Upper limits on the Polarized Isotropic Stochastic Gravitational-Wave Background from Advanced LIGO-Virgo's First Three Observing Runs
Parity violation is expected to generate an asymmetry between the amplitude
of left and right-handed gravitational-wave modes which leads to a circularly
polarized stochastic gravitational-wave background (SGWB). Due to the three
independent baselines in the LIGO-Virgo network, we focus on the amplitude
difference in strain power characterized by Stokes' parameters and do
maximum-likelihood estimation to constrain the polarization degree of SGWB. Our
results indicate that there is no evidence for the circularly polarized SGWB in
the data. Furthermore, by modeling the SGWB as a power-law spectrum, we place
upper limit on the normalized energy density
at confidence level
after marginalizing over the polarization degree and spectral index.Comment: 6 pages, 4 figures and 2 tables; some clarifications added, version
accepted for publication in JCA
An update of the catalog of radial velocity standard stars from the APOGEE DR17
We present an updated catalog of 46,753 radial velocity (RV) standard stars
selected from the APOGEE DR17. These stars cover the Northern and Southern
Hemispheres almost evenly, with 62% being red giants and 38% being
main-sequence stars. These RV standard stars are stable on a baseline longer
than 200 days (54% longer than one year and 10% longer than five years) with a
median stability better than 215 m s. The average observation number of
those stars are 5 and each observation is required to have
spectral-to-noise-ratio (SNR) greater than 50 and RV measurement error smaller
than 500 m s. Based on the new APOGEE RV standard star catalog, we have
checked the RV zero points (RVZPs) for current large-scale stellar
spectroscopic surveys including RAVE, LAMOST, GALAH and Gaia. By carefully
analysis, we estimate their mean RVZP to be km s, km
s (for LRS), km s and km s,
respectively, for the four surveys. In the RAVE, LAMOST (for MRS), GALAH and
Gaia surveys, RVZP exhibits systematic trend with stellar parameters (mainly
[Fe/H], , log , and ).
The corrections of those small but clear RVZPs are of vital importances for
these massive spectroscopic surveys in various studies that require extremely
high radial velocity accuracies.Comment: 10 pages, 7 figures, 2 tables, accepted by RAA; full table can be
accessed from https://nadc.china-vo.org/res/r101244
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