Results from an extended Falcon all-sky survey for continuous gravitational waves

We present the results of an all-sky search for continuous gravitational wave signals with frequencies in the 200–600 Hz range and frequency derivative (spindown) from $-1\times {10}^{-8}$ through $1.11\times {10}^{-9}\mathrm{Hz}/\mathrm{s}$. Together with the results from [ Phys. Rev. Lett. 123, 101101 (2019)], this search completes the all-sky survey for frequencies between 20 to 600 Hz on O1 data. It also demonstrates the scalability of our search on a parameter space 26 times larger than previously considered. The results presented here complement the LIGO O2 data results [ Phys. Rev. Lett. 123, 171101 (2019), Phys. Rev. D 100, 024004 (2019)] with comparable when not better sensitivity and do not rely on data with irregularities in the noise-subtraction procedure. We establish strict upper limits which hold for worst-case signal parameters and dedicated upper limits for generic $\approx 0$ spindown signals, such as those expected from boson condensates around black holes.

Figure 1

O1 upper limits. The dimensionless strain (vertical axis) is plotted against signal frequency. Looking at the right side of the plot, the upper (yellow) curve shows worst-case upper limits, the next lower curve (purple) shows the population average proxy, followed by the black curve showing best-case upper limits (circularly polarized signals). The worst-case and best-case upper limits are maximized over sky and all intrinsic signal parameters for each frequency band displayed. For completeness we include Falcon results in the frequency range 20–200 Hz from [1].

Figure 2

Range of the search for neutron stars spinning down solely due to gravitational radiation. This is a superposition of two contour plots. The grey solid lines are contours of the maximum distance at which a neutron star could be detected as a function of gravitational wave frequency $f$ and its derivative $\dot{f}$. The dashed lines are contours of the corresponding ellipticity $\epsilon (f,\dot{f})$. The fine dotted line marks the maximum spindown searched. Together these quantities tell us the maximum range of the search in terms of various populations [14, 17].

Figure 3

Comparison of the Falcon O1 (population-average) upper limits (purple curve with many spikes, especially below 100 Hz) and the LIGO-Virgo collaboration results [24] (yellow curve, with spikes extending downward near 100 Hz). The dimensionless strain (vertical axis) is plotted against signal frequency.

Figure 4

Reprinted figure with permission from B. P. Abbott et al. (LIGO Scientific Collaboration and Virgo Collaboration), All-sky search for continuous gravitational waves from isolated neutron stars using Advanced LIGO O2 data, [24]. Copyright (2019) by the American Physical Society.