arXiv subjects

Oryna Ivashtenko

Publications and source records attributed to Oryna Ivashtenko.

5 recordsLinked to original sources

arXiv2026

Searching for precessing binary systems with mode-by-mode filtering and marginalization

Nearly all previous binary black hole searches in LIGO--Virgo--KAGRA (LVK) gravitational wave data have assumed that the component spins are aligned with the orbital angular momentum, thereby neglecting spin-precession effects in the waveform, which can lead to potentially missing interesting signals. Precessing searches are challenging, because the extra degrees of freedom due to misaligned spins lead to: $(i)$ a much larger number of templates compared to the aligned-spin configurations, $(ii)$ an increased rate of background triggers. To address this, we develop novel precessing signal template banks using mode-by-mode filtering and marginalization methods. We use the precession harmonic decomposition from Fairhurst et al. (2019) and filter each precessing harmonic separately with the data. We then marginalize over the SNRs from different harmonics in our detection statistic. We also use machine learning methods to improve our search efficiency: $(i)$ we use singular value decomposition together with random forest regressor to reduce redundancy in the dominant precessing-harmonic templates; $(ii)$ we use normalizing flows to generate optimal prior samples for harmonic SNRs for the marginalized statistic. We show that marginalizing (instead of maximizing) over the harmonic mode SNRs increases the search sensitive volume by $\sim 10\%$. Results from searching in LVK data using this framework will be reported in a companion paper.

gr-qc↗

arXiv2025

Sampler-free gravitational wave inference using matrix multiplication

Parameter estimation (PE) for compact binary coalescence (CBC) events observed by gravitational wave (GW) laser interferometers is a core task in GW astrophysics. We present a method to compute the posterior distribution efficiently without relying on stochastic samplers. First, we show how to select sets of intrinsic and extrinsic parameters that efficiently cover the relevant phase space. We then show how to compute the likelihood for all combinations of these parameters using dot products. We describe how to assess and tune the integration accuracy, making the outcome predictable and adaptable to different applications. The low computational cost allows full PE in minutes on a single CPU, with the potential for further acceleration using multiple CPUs or GPUs. We implement this method in the $\texttt{dot-PE}$ package, enabling sensitive searches using the full evidence integral for precessing CBCs and supporting large waveform banks ($\sim10^5$--$10^6$ waveforms), regardless of waveform generation cost.

gr-qc↗

arXiv2025

An Independent Search for Small Long-period Planets in Kepler Data I: Detection Pipeline

The unprecedented photometric precision of Kepler mission allows searching for Earth-like planets. However, it remains difficult to distinguish these low signal-to-noise planets from the false alarms originating from correlated and non-Gaussian noise. It reduces the resulting planetary catalog reliability and makes it hard to measure the occurrence rate of small long-period planets. We aim to obtain a more reliable catalog of small long-period planet candidates from Kepler data and use it to improve their occurrence rate estimate. This work develops an independent search pipeline for small (Kepler Multiple-Event Statistic, MES$\lesssim$12) long-period (50-500 days) planets. It designs and implements a detection statistic that takes into account noise non-Gaussianity and physical prior. For every threshold-crossing event, it runs permutation and injection procedures to calculate the probability of it being caused by a real planet. The provided detection statistic has a tail-less background distribution with a rate of ~1 false alarm per search for MES~7.8. We demonstrate the increase in detection efficiency for MES of ~7.5-9 and $>$4 transits due to the background distribution control. The pipeline was tested to be able to detect most of the faint Confirmed Kepler planets. The pipeline was applied to the entirety of Kepler data and detected ~50 candidate events with a high probability of originating from real planets, which will be presented in our future work.

astro-ph.EP↗

arXiv2022

fBLS -- a fast-folding BLS algorithm

We present fBLS -- a novel fast-folding technique to search for transiting planets, based on the fast-folding algorithm (FFA), which is extensively used in pulsar astronomy. For a given lightcurve with $N$ data points, fBLS simultaneously produces all the binned phase-folded lightcurves for an array of $N_p$ trial periods. For each folded lightcurve produced by fBLS, the algorithm generates the standard BLS periodogram and statistics. The number of performed arithmetic operations is $\mathcal{O}\big(N_p\cdot\log N_p \big)$, while regular BLS requires $\mathcal{O}\big(N_p\cdot N\big)$ operations. fBLS can be used to detect small rocky transiting planets, with periods shorter than one day, a period range for which the computation is extensive. We demonstrate the capabilities of the new algorithm by performing a preliminary fBLS search for planets with ultra-short periods in the Kepler main-sequence lightcurves. In addition, we developed a simplistic signal validation scheme for vetting the planet candidates. This two-stage preliminary search identified all known ultra-short planet candidates and found three new ones.

astro-ph.IM↗

arXiv2019

Origami launcher

The article studies the elastic and locomotive properties of Miura-ori-type paper origami. The mechanics of a single paper crease is studied experimentally, and its non-elastic properties turn out to be crucial. The entire origami construction is then described as a collection of individual creases, its capability to launch small objects is evaluated, and the equation of motion is found. Thus, the height of the launched ball is studied theoretically and experimentally as a function of governing parameters.

cond-mat.soft↗