Searches for Continuous Gravitational Waves from Supernova Remnants in the first part of the LIGO-Virgo-KAGRA Fourth Observing run

Abstract

We present results from directed searches for continuous gravitational waves from a sample of 15 nearby supernova remnants, likely hosting young neutron star candidates, using data from the first eight months of the fourth observing run (O4) of the LIGO-Virgo-KAGRA Collaboration. The analysis employs five pipelines: four semi-coherent methods -- the Band-Sampled-Data directed pipeline, Weave and two Viterbi pipelines (single- and dual-harmonic) -- and PyStoch, a cross-correlation-based pipeline. These searches cover wide frequency bands and do not assume prior knowledge of the targets' ephemerides. No evidence of a signal is found from any of the 15 sources. We set 95\% confidence-level upper limits on the intrinsic strain amplitude, with the most stringent constraints reaching $\sim 4 \times 10^{-26}$ near 300 Hz for the nearby source G266.2$-$1.2 (Vela Jr.). We also derive limits on neutron star ellipticity and $r$-mode amplitudes for the same source, with the best constraints reaching $\lesssim 10^{-7}$ and $\lesssim 10^{-5}$, respectively, at frequencies above 400 Hz. These results represent the most sensitive wide-band directed searches for continuous gravitational waves from supernova remnants to date.

Figures (13)

• Figure 1: Parameter space covered by each of the 5 pipelines for G266.2$-$1.2 (Vela Jr.).
• Figure 2: Upper Limits for the source G266.2$-$1.2 (Vela Jr.) obtained for the pipelines assuming the single harmonic emission scenario. The dual harmonic results for the same source are shown in Fig. \ref{['fig:viterbi1f2fUL']}.
• Figure 3: Equatorial ellipticity (left) and $r$-mode amplitude $\alpha$ (right) with 95% confidence for all the BSD targets. Filled circles show the ellipticity or $r$-mode amplitude computed using the minimum estimated source distance $D_{\min}$. Shaded regions indicate the full range of values obtained when varying the source distance from $D_{\min}$ to $D_{\max}$ (see Table \ref{['tab:targets']}). The limits are derived from the upper limits curves in Fig. \ref{['fig:BSD_ULall']}.
• Figure 4: Equatorial ellipticity (left) and $r$-mode amplitude $\alpha$ (right) with 95% confidence for all targets studied in the PyStoch search. The filled circles indicate the minimum $\epsilon^{95\%}$ for each SNR, and the shaded regions span the full range of ellipticity values obtained by varying the distance between $D_{\min}$ and $D_{\max}$ (see Table \ref{['tab:targets']}).
• Figure 5: Equatorial ellipticity (left) and $r$-mode amplitude $\alpha$ (right) with 95% confidence for all the SHV targets. The filled circles indicate the minimum $\epsilon^{95\%}$ and $\alpha^{95\%}$ for each SNR, and the shaded regions span the full range of ellipticity and $r$-mode amplitude values obtained by varying the distance between $D_{\min}$ and $D_{\max}$ (see Table \ref{['tab:targets']}).