arXiv subjects

K. Wette

Publications and source records attributed to K. Wette.

7 recordsLinked to original sources

arXiv2026

The G347.3-0.5 outlier from O3: a follow-up case study for continuous gravitational-wave candidates

We report a multi-pipeline follow-up study of the continuous gravitational-wave (CW) outlier identified by the Ming et al. Einstein@Home directed search for the young supernova remnant G347.3-0.5 (containing the central compact object RXJ1713.7-3946). The outlier was initially identified in LIGO data from the O3a observing run and followed up with the addition of O3b and O4a data by the Einstein@Home pipeline, with O4a producing weaker evidence. Here, we show extended data quality checks and results from three pipelines that have independently investigated this outlier, including the newly released O4b data set. We can robustly recover the outlier in O3, while we find no evidence for a related standard CW signal in O4a (consistent with Ming et al.) and O4b data. This work serves as a useful test case for future multi-pipeline follow-ups of CW candidates that aim to investigate their astrophysical or noise nature, and it is therefore an important step in preparation for the first CW detection.

gr-qc↗

arXiv2018

Implementing a semicoherent search for continuous gravitational waves using optimally-constructed template banks

All-sky surveys for isolated continuous gravitational waves present a significant data-analysis challenge. Semicoherent search methods are commonly used to efficiently perform the computationally-intensive task of searching for these weak signals in the noisy data of gravitational-wave detectors such as LIGO and Virgo. We present a new implementation of a semicoherent search method, Weave, that for the first time makes full use of a parameter-space metric to generate banks of search templates at the correct resolution, combined with optimal lattices to minimize the required number of templates and hence the computational cost of the search. We describe the implementation of Weave and associated design choices, and characterize its behavior using semi-analytic models.

astro-ph.IM↗

arXiv2018

Reduced order modelling in searches for continuous gravitational waves - I. Barycentering time delays

The frequencies and phases of emission from extra-solar sources measured by Earth-bound observers are modulated by the motions of the observer with respect to the source, and through relativistic effects. These modulations depend critically on the source's sky-location. Precise knowledge of the modulations are required to coherently track the source's phase over long observations, for example, in pulsar timing, or searches for continuous gravitational waves. The modulations can be modelled as sky-location and time-dependent time delays that convert arrival times at the observer to the inertial frame of the source, which can often be the Solar system barycentre. We study the use of reduced order modelling for speeding up the calculation of this time delay for any sky-location. We find that the time delay model can be decomposed into just four basis vectors, and with these the delay for any sky-location can be reconstructed to sub-nanosecond accuracy. When compared to standard routines for time delay calculation in gravitational wave searches, using the reduced basis can lead to speed-ups of 30 times. We have also studied components of time delays for sources in binary systems. Assuming eccentricities $< 0.25$ we can reconstruct the delays to within 100s of nanoseconds, with best case speed-ups of a factor of 10, or factors of two when interpolating the basis for different orbital periods or time stamps. In long-duration phase-coherent searches for sources with sky-position uncertainties, or binary parameter uncertainties, these speed-ups could allow enhancements in their scopes without large additional computational burdens.

astro-ph.HE↗

arXiv2017

The very-faint X-ray binary IGR J17062-6143: a truncated disk, no pulsations and a possible outflow

We present a comprehensive X-ray study of the neutron star low-mass X-ray binary IGR J17062-6143, which has been accreting at low luminosities since its discovery in $2006$. Analysing NuSTAR, XMM-Newton and Swift observations, we investigate the very faint nature of this source through three approaches: modelling the relativistic reflection spectrum to constrain the accretion geometry, performing high-resolution X-ray spectroscopy to search for an outflow, and searching for the recently reported millisecond X-ray pulsations. We find a strongly truncated accretion disk at $77^{+22}_{-18}$ gravitational radii ($\sim 164$ km) assuming a high inclination, although a low inclination and a disk extending to the neutron star cannot be excluded. The high-resolution spectroscopy reveals evidence for oxygen-rich circumbinary material, possibly resulting from a blueshifted, collisionally-ionised outflow. Finally, we do not detect any pulsations. We discuss these results in the broader context of possible explanations for the persistent faint nature of weakly accreting neutron stars. The results are consistent with both an ultra-compact binary orbit and a magnetically truncated accretion flow, although both cannot be unambigiously inferred. We also discuss the nature of the donor star and conclude that it is likely a CO or O-Ne-Mg white dwarf, consistent with recent multi-wavelength modelling.

astro-ph.HE↗

arXiv2017

A Deep Pulse Search in Eleven Low Mass X-Ray Binaries

We present a systematic coherent X-ray pulsation search in eleven low mass X-ray binaries (LMXBs). We select a relatively broad variety of LMXBs, including persistent and transient sources and spanning orbital periods between 0.3 and 17 hours. We use about 3.6 Ms of data collected by the Rossi X-Ray Timing Explorer (RXTE) and XMM-Newton and apply a semi-coherent search strategy to look for weak and persistent pulses in a wide spin frequency range. We find no evidence for X-ray pulsations in these systems and consequently set upper limits on the pulsed sinusoidal semi-amplitude between 0.14% and 0.78% for ten outbursting/persistent LMXBs and 2.9% for a quiescent system. These results suggest that weak pulsations might not form in (most) non-pulsating LMXBs.

astro-ph.HE↗

arXiv2009

Sinking of a magnetically confined mountain on an accreting neutron star

We perform ideal-magnetohydrodynamic axisymmetric simulations of magnetically confined mountains on an accreting neutron star, with masses less than ~0.12 solar masses. We consider two scenarios, in which the mountain sits atop a hard surface or sinks into a soft, fluid base. We find that the ellipticity of the star, due to a mountain grown on a hard surface, approaches ~2e-4 for accreted masses greater than ~1.2e-3 solar masses, and that sinking reduces the ellipticity by between 25% and 60%. The consequences for gravitational radiation from low-mass x-ray binaries are discussed.

astro-ph.HE↗

arXiv2008

Searching for gravitational waves from Cassiopeia A with LIGO

We describe a search underway for periodic gravitational waves from the central compact object in the supernova remnant Cassiopeia A. The object is the youngest likely neutron star in the Galaxy. Its position is well known, but the object does not pulse in any electromagnetic radiation band and thus presents a challenge in searching the parameter space of frequency and frequency derivatives. We estimate that a fully coherent search can, with a reasonable amount of time on a computing cluster, achieve a sensitivity at which it is theoretically possible (though not likely) to observe a signal even with the initial LIGO noise spectrum. Cassiopeia A is only the second object after the Crab pulsar for which this is true. The search method described here can also obtain interesting results for similar objects with current LIGO sensitivity.

gr-qc↗