ausblenden:
Schlagwörter:
General Relativity and Quantum Cosmology, gr-qc,Astrophysics, Cosmology and Extragalactic Astrophysics, astro-ph.CO, Astrophysics, High Energy Astrophysical Phenomena, astro-ph.HE, Astrophysics, Instrumentation and Methods for Astrophysics, astro-ph.IM
Zusammenfassung:
We employ gravitational-wave radiometry to map the gravitational waves
stochastic background expected from a variety of contributing mechanisms and
test the assumption of isotropy using data from Advanced LIGO's first observing
run. We also search for persistent gravitational waves from point sources with
only minimal assumptions over the 20 - 1726 Hz frequency band. Finding no
evidence of gravitational waves from either point sources or a stochastic
background, we set limits at 90% confidence. For broadband point sources, we
report upper limits on the gravitational wave energy flux per unit frequency in
the range $F(f, \Theta) < (0.1 - 56) \times 10^{-8}$ erg cm$^{-2}$ s$^{-1}$
Hz$^{-1}$ (f/25 Hz)$^{\alpha-1}$ depending on the sky location $\Theta$ and the
spectral power index $\alpha$. For extended sources, we report upper limits on
the fractional gravitational wave energy density required to close the Universe
of $\Omega(f,\Theta) < (0.39-7.6) \times 10^{-8}$ sr$^{-1}$ (f/25 Hz)$^\alpha$
depending on $\Theta$ and $\alpha$. Directed searches for narrowband
gravitational waves from astrophysically interesting objects (Scorpius X-1,
Supernova 1987 A, and the Galactic Center) yield median frequency-dependent
limits on strain amplitude of $h_0 <$ (6.7, 5.5, and 7.0) $\times 10^{-25}$
respectively, at the most sensitive detector frequencies between 130 - 175 Hz.
This represents a mean improvement of a factor of 2 across the band compared to
previous searches of this kind for these sky locations, considering the
different quantities of strain constrained in each case.