arXiv subjects

Jessica Planelles-Villalva

Publications and source records attributed to Jessica Planelles-Villalva.

3 recordsLinked to original sources

arXiv2026

Spin-down of the accreting magnetar candidate 4U 0114+65: possible first evidence for a strong coupling regime

4U~0114+65 is a high-mass X-ray binary composed of the B1\,Ia supergiant V*~V662~Cas and one of the slowest known accreting neutron stars, with a spin period of $\sim$9.4 ks. In 2025, its long X-ray pulsations became undetectable in \textit{Swift}/BAT monitoring, motivating a Director's Discretionary Time observation with \textit{XMM-Newton}. We compare this observation with a 2015 \textit{XMM-Newton} observation, when the source was brighter and clearly pulsed, and analyze the long-term spin evolution using \textit{Swift}/BAT data. We performed average and pulse-phase-resolved spectroscopy using the same model as in previous work. The 2025 observation still reveals weak pulsations, with a period of about 9.3 ks, despite their non-detection in \textit{Swift}/BAT. The overall spectral shape remains similar in both epochs, but the luminosity decreased by about one order of magnitude, mainly due to strong suppression of the bulk-motion Comptonization component. Although the absorbing column is higher in 2025, the inferred wind properties remain broadly compatible with those from 2015, suggesting that no major global change in the donor wind is required. Instead, the results point to a substantial reduction in accretion efficiency close to the neutron-star magnetosphere. We propose that 4U~0114+65 may be evolving toward partial centrifugal inhibition in the strong-coupling regime, where the toroidal magnetic-field component is comparable to the poloidal one. If confirmed, this would represent the first observational evidence of this state. Accretion would become progressively less efficient and more intermittent without reaching a fully developed propeller regime. The apparent disappearance of the pulse in long-term hard X-ray monitoring would then result from the lower luminosity and reduced absolute pulsed flux, rather than from the loss of the underlying spin modulation.

astro-ph.HE↗

arXiv2026

Blind Line Search System: BLiSS

The increasing sensitivity and spectral resolution of current and forthcoming X-ray observatories, including \textit{XRISM} and \textit{NewAthena}, are expected to reveal increasing numbers of weak and blended emission lines, motivating reproducible tools for their systematic identification. Existing workflows often rely on manual inspection or source-specific analysis pipelines, making homogeneous analyses of large datasets difficult. To address this need, we present BLiSS (Blind Line Search System), an open-source Python package for the fast, blind detection and characterization of emission-line candidates in one-dimensional X-ray spectra without requiring a prior physical continuum model. BLiSS is intended as an exploratory analysis tool that complements subsequent physical spectral modelling. The package estimates an empirical baseline directly from the observed spectrum, identifies positive excesses, groups them into candidate regions, and characterizes them with Gaussian models. Candidate reliability is estimated by comparison with synthetic spectra using a Gaussian Mixture Model classifier. Finally, optional routines perform a simultaneous multi-Gaussian fit and associate detected features with compatible atomic transitions. The methodology implemented in BLiSS has already enabled published spectroscopic studies and is presented here as a documented, modular, and publicly available software package. Its performance is demonstrated using \textit{Chandra}/HETGS and \textit{XRISM}/Resolve observations of the high-mass X-ray binary Vela X-1, one of the best-studied X-ray sources. BLiSS recovers the principal emission features reported in previous studies while providing a fast, reproducible, and instrument-independent workflow for exploratory line searches.

astro-ph.IM↗

arXiv2025

Cyclical accretion regime change in the slow X-ray pulsar 4U 0114+65 observed with Chandra

4U 0114+65 is a high-mass X-ray binary system formed by the luminous supergiant B1Ia, known as V{*} V662 Cas, and one of the slowest rotating neutron stars (NS) with a spin period of about 2.6 hours. This fact provides a rare opportunity to study interesting details of the accretion within each individual pulse of the compact object. In this paper, we analyze 200 ks of Chandra grating data, divided into 9 uninterrupted observations around the orbit. The changes in the circumstellar absorption column through the orbit suggest an orbital inclination of $\sim$ $40^{\circ}$ with respect to the observer and a companion mass-loss rate of $\sim$ 8.6 10$^{-7}$ solar masses yr$^{-1}$. The peaks of the NS pulse show a large pulse-to-pulse variability. Three of them show an evolution from a brighter regime to a weaker one. We propose that the efficiency of Compton cooling in this source fluctuates throughout an accumulation cycle. After significant depletion of matter within the magnetosphere, since the settling velocity is $\sim \times$ 2 times lower than the free-fall velocity, the source gradually accumulates matter until the density exceeds a critical threshold. This increase in density triggers a transition to a more efficient Compton cooling regime, leading to a higher mass accretion rate and consequently to an increased brightness.

astro-ph.HE↗