arXiv subjects

G. Sanjurjo-Ferrín

Publications and source records attributed to G. Sanjurjo-Ferrín.

7 recordsLinked to original sources

arXiv2026

Spectral Analysis of the Egress and Ingress Phases of Cen X-3 with XRISM/Resolve

We investigate the phase-resolved X-ray spectral evolution of the high-mass X-ray binary Cen X-3 across eclipse ingress and egress, using two out-of-eclipse intervals as references, to constrain the absorbing material and Fe K emitting regions with high-resolution XRISM/Resolve spectroscopy. We model the spectra with SPEX, including interstellar and local wind absorption, a power-law and blackbody continuum, disk reflection, and Gaussian components for Fe XXV and Fe XXVI. We compare the orbital variation of the absorbing column with a smooth CAK wind model and investigate the variability of the Fe K alpha line width. The local absorbing column varies by nearly two orders of magnitude, from N_H^local = 4.25 x 10^22 cm^-2 during pre-ingress to 5.9 x 10^23 cm^-2 at ingress. The excess ingress absorption cannot be reproduced by a smooth wind model alone, suggesting a localized overdense structure along the line of sight. The Fe K alpha width varies from approximately 510 km s^-1 during pre-ingress to 1400 km s^-1 during egress, with intermediate, statistically indistinguishable values of approximately 900 km s^-1 during ingress and post-egress. Highly ionized Fe XXV and Fe XXVI emission is detected throughout the orbit, although fewer components are resolved during ingress. These diagnostics reveal a complex circumstellar environment with localized dense material and multiple reprocessing regions. The results demonstrate the capability of XRISM/Resolve to probe the geometry and kinematics of accretion environments in eclipsing high-mass X-ray binaries.

astro-ph.HE↗

arXiv2026

Spectroscopic modeling of ionic structure in stellar winds of high-mass X-ray binaries

High-mass X-ray binaries (HMXBs) provide a natural laboratory to study radiatively driven stellar winds under strong external X-ray irradiation. As the compact object moves along its orbit, the wind density and ionization structure vary with orbital phase, leaving characteristic signatures in X-ray emission and absorption features. The amplitude and morphology of this variability depend on the system geometry, including the orbital inclination (via line-of-sight and occultation effects) and the orbital eccentricity (via phase-dependent changes in the orbital separation). We present a computational framework that connects phase-resolved spectroscopic variability to the three-dimensional structure of irradiated winds, and that enables inference of physically meaningful wind--irradiation parameters within a Bayesian setting. We combine photoionization calculations with a parametric wind description and orbital geometry to construct three-dimensional maps of density and ionization. From these maps we compute orbital-phase-dependent diagnostics, accounting for geometric occultation and wind inhomogeneity through a clumping prescription. We then use Bayesian inference to compare model predictions with phase-resolved observables and to quantify parameter constraints and degeneracies. The framework reproduces the main orbital-phase-dependent trends expected for irradiated winds and yields robust constraints on the system ionization balance. While combinations of wind and luminosity parameters are well constrained, individual parameters can remain partially degenerate depending on the orbital configuration and data quality. This modular and computationally efficient approach provides a route to interpret HMXB phase variability in physical terms, and offers a foundation for future extensions toward forward spectral modeling and population-level applications.

astro-ph.HE↗

arXiv2026

A thousand looks at X Persei: X-ray spectroscopy at high time resolution

X Persei is a classical Be/X-ray binary composed of an O9.5III-B0V Be-type star and a neutron star (NS). The NS exhibits coherent pulsations with a spin period of ~837 s, orbiting the Be star with a ~250 d period. X Persei is notable for its exceptionally hard X-ray emission extending beyond 100 keV. Due to the mild eccentricity of the orbit, ~0.11, the orbital separation varies between roughly 35 R_star at periastron and 44 R_star at apastron. In this work, we analyze five targeted observations obtained with the XMM-Newton and Chandra observatories taken over a 10-year time span, with the aim of investigating the structure and variability of the circumstellar disk surrounding the Be star, in particular the presence of over-dense areas known as clumps. We performed spectral and timing analyses, including average and NS spin-resolved spectroscopy for three of the observations, producing individual spectra at intervals as short as 210 s, corresponding to different epochs of the NS spin, resulting in approximately 1200 spectra. This detailed analysis aimed at resolving emission-line features otherwise diluted in averaged spectra and the evolution of continuum components along the NS spin. The observed spectra are accurately modeled by a two-component continuum comprising a high-temperature blackbody and a power-law component. Phase-resolved spectroscopy reveals transient Fe K alpha emission linked to clumps in the circumstellar disk during high-density epochs, with an 8-9% prevalence. Dips in the X-ray light curve are tied to clump passages. The disk-density modeling, based solely on X-ray data, suggests a compact and dense disk, with a radial density exponent alpha of 2.4-3.3, and a high inner disk density, rho_0 ~ (6-20) x 10^-10 g cm^-3, in agreement with previous studies conducted in the optical and infrared bands.

astro-ph.HE↗

arXiv2026

Iron line diagnostics of the stellar wind in X1908+075

Aims. X1908+075 is a supergiant X-ray binary (SgXB) composed of an evolved OB star and a neutron star (NS) in a 4.4-day orbit. We aim to characterize the stellar wind, constrain the system geometry, and investigate the origin and variability of the Fe K$α$ fluorescence line. Methods. We analyzed three Chandra HETGS observations at different orbital phases. The continuum was modeled with a bulk motion Comptonization (Bmc) model including partial-covering absorption. We performed a blind line search with Monte Carlo simulations accounting for the look-elsewhere effect. The orbital modulation of $N_{\rm H}$ was modeled through particle swarm optimization to constrain the inclination and donor mass-loss rate. Results. Fe K$α$ emission is detected in all observations and remains significant after correcting for multiple trials (global $p < 0.005$). Tentative features include a Compton shoulder and Fe K$β$ emission, indicating dense reprocessing material. No highly ionized Fe XXV or Fe XXVI lines are confirmed. The Fe K$α$ flux correlates with the continuum flux, while its equivalent width anticorrelates with both $N_{\rm H}$ and orbital phase, opposite to the canonical curve of growth seen in many HMXBs. Line broadening reaches velocities of $\sim3000$ km s$^{-1}$. Modeling of the $N_{\rm H}$ variability yields an inclination $i = 46 \pm 3^\circ$ and a donor mass-loss rate $\dot{M}_{\rm W} = (9.1 \pm 1.6) \times 10^{-7}\,M_\odot\,{\rm yr}^{-1}$. Conclusions. X1908+075 is a classical wind-fed SgXB in the direct accretion regime. The observed continuum and line variability reflect the complex density and ionization structure of the stellar wind.

astro-ph.HE↗

arXiv2026

High-resolution X-ray spectroscopy of Cen X-3 with XMM-Newton

The spectral analysis of two XMM-Newton observations of the high-mass X-ray binary system Cen X-3 is presented. In particular, it is focused on the eclipse and out-of-eclipse spectra in order to compare the properties of the environment around the compact object. The high-resolution spectra obtained from the reflection grating spectrometer on board XMM-Newton was analysed focusing on studying eclipse and out-of-eclipse spectra separately. Several continuum models were explored in SPEX for which we studied the properties of emitting and absorbing matter depending on the emission and absorption lines identified in the spectra. It was found that the X-ray continuum is heavily absorbed by a neutral gas and photoionised matter. Emission lines from Si v, Mg xii, Mg xi, and Ne x were detected in the eclipse spectrum. In particular, H-like lines of Mg and Ne with a significance greater than 5 sigma in the eclipse spectrum and 3 sigma in the out-of-eclipse spectrum. But in the out-of-eclipse spectrum any absorption lines, if any, were detected with a significance less than 2 sigma. RGS light curve showed dips in the out-of-eclipse spectrum which are not due to an increase in the column absorption but may be produced by instabilities in the accretion stream. On the other hand, the level of counts above 20 was compatible with the X-ray background. A simple local continuum model was used to describe the He-like triplet of Ne and the derived values of R and G ratio parameters pointed out that the UV photospheric field should be important at the line production site and an electron density greater than 10(12) cm-3. As a consequence, a hybrid plasma may be present in the binary system.

astro-ph.HE↗

arXiv2024

GX 301-2 pre-periastron and apastron flares with MAXI

The bright high-mass X-ray binary GX 301-2 exhibits two periodic flare episodes along its orbit which are produced when the neutron star is close to the apastron and periastron passages. Time-resolved spectra were extracted and several models applied to describe all of them. The best description was obtained with a blackbody continuum modified by the Fe K-shell absorption edge, absorbed by a large column density on the order of $10^{23}$ cm$^{-2}$ and, if present, a Fe K$α$ fluorescent emission line. Three of the nine apastron flares were as bright as the pre-periastron flare and two of them coincided with spin-up episodes of the neutron star. This fact points to the presence of a transient disc around the neutron star as it passes through the apastron that increases the accretion process. The size of emitting region on the neutron star surface showed some variability but quite consistent with a hot spot.

astro-ph.HE↗

arXiv2022

Cen x-3 as seen by MAXI during six years

The aim of this work is to study both light curve and orbital phase spectroscopy of this source taking advantage of the MAXI/GSC observation strategy. We have investigated the spectral and light curve properties of the X-ray emission from Cen X-3 along the binary orbit. These studies allow delimiting the stellar wind properties and its interactions with the compact object. A timing analysis of light curves in different energy bands was carried out. From the analysis of the light curve, we have estimated the orbital period of the binary system and also found possible QPOs around a superorbital period of $P_\mathrm{superorb} = 220\pm 5$ days. Both orbital phase-averaged and phase-resolved spectra were extracted and analysed in the 2.0-20.0 keV energy range. We have defined and compared the high and low states spectra with the averaged spectrum. Two models have described spectra satisfactorily, a partial absorbed Comptonization of cool photons on hot electrons plus a power law and a partial absorbed blackbody plus a power law, both modified by adding Gaussian lines. The radius of the blackbody emitting area has been determined and the high value of the X-ray luminosity in the averaged spectrum indicates that the accretion mode is not only due to the stellar wind.

astro-ph.HE↗