arXiv subjects

Maria Jose Bustamante-Rosell

Publications and source records attributed to Maria Jose Bustamante-Rosell.

3 recordsLinked to original sources

arXiv2026

A Foundation for Gravitational-Wave Population Inference within the LISA Global Fit

Population inference in gravitational-wave astronomy allows us to connect individual detections to the astrophysics of compact objects and their environments. Current approaches employed for population inference with LIGO-Virgo-KAGRA data approximate evaluation of the hierarchical population likelihood via post-processing of individual-event posteriors. However, the case of the Laser Interferometer Space Antenna (LISA) will be more complex for two main reasons: the transdimensional "global fit" approach to LISA data analysis which models all signals and noise simultaneously, and the presence of both individually-resolved signals and the unresolved stochastic ``Galactic foreground" arising from the Galactic binary population, which induces a circular dependence between the resolved and unresolved systems and our ability to detect the former. These challenges are not without opportunity; LISA's data will contain every mHz compact binary in the Milky Way -- either individually or within the Galactic foreground -- with great potential for Galactic and stellar astrophysics. We therefore propose an alternative approach: direct evaluation of the full hierarchical population likelihood within the LISA global fit. We develop a statistical formalism for joint inference of individually-resolved gravitational-wave sources, an unresolved stochastic foreground, and a shared, underlying astrophysical population, present PELARGIR, a prototype GPU-accelerated population inference module for the LISA global fit, demonstrate the formalism and PELARGIR via a toy model analysis, and lay out a roadmap towards an astrophysically-motivated LISA global fit with embedded population inference. While we apply the formalism here to the population of LISA Galactic binaries, it is applicable across the gravitational-wave spectrum with use cases in pulsar timing and next-generation terrestrial observatories.

astro-ph.IM↗

arXiv2024

Ground-based and JWST Observations of SN 2022pul: II. Evidence from Nebular Spectroscopy for a Violent Merger in a Peculiar Type-Ia Supernova

We present an analysis of ground-based and JWST observations of SN~2022pul, a peculiar "03fg-like" (or "super-Chandrasekhar") Type Ia supernova (SN Ia), in the nebular phase at 338d post explosion. Our combined spectrum continuously covers 0.4--14 $μ$m and includes the first mid-infrared spectrum of an 03fg-like SN Ia. Compared to normal SN Ia 2021aefx, SN 2022pul exhibits a lower mean ionization state, asymmetric emission-line profiles, stronger emission from the intermediate-mass elements (IMEs) argon and calcium, weaker emission from iron-group elements (IGEs), and the first unambiguous detection of neon in a SN Ia. Strong, broad, centrally peaked [Ne II] line at 12.81 $μ$m was previously predicted as a hallmark of "violent merger'' SN Ia models, where dynamical interaction between two sub-$M_{ch}$ white dwarfs (WDs) causes disruption of the lower mass WD and detonation of the other. The violent merger scenario was already a leading hypothesis for 03fg-like SNe Ia; in SN 2022pul it can explain the large-scale ejecta asymmetries seen between the IMEs and IGEs and the central location of narrow oxygen and broad neon. We modify extant models to add clumping of the ejecta to better reproduce the optical iron emission, and add mass in the innermost region ($< 2000$ km s$^{-1}$) to account for the observed narrow [O I]~$λ\lambda6300$, 6364 emission. A violent WD-WD merger explains many of the observations of SN 2022pul, and our results favor this model interpretation for the subclass of 03fg-like SN Ia.

astro-ph.HE↗

arXiv2021

Dynamical analysis of the dark matter and central black hole mass in the dwarf spheroidal Leo I

We measure the central kinematics for the dwarf spheroidal galaxy Leo I using integrated-light measurements and previously published data. We find a steady rise in the velocity dispersion from $300^{\prime\prime}$ into the center. The integrated-light kinematics provide a velocity dispersion of $11.76\pm0.66$ km/s inside $75^{\prime\prime}$. After applying appropriate corrections to crowding in the central regions, we achieve consistent velocity dispersion values using velocities from individual stars. Crowding corrections need to be applied when targeting individual stars in high density stellar environments. From integrated light, we measure the surface brightness profile and find a shallow cusp towards the center. Axisymmetric, orbit-based models measure the stellar mass-to-light ratio, black hole mass and parameters for a dark matter halo. At large radii it is important to consider possible tidal effects from the Milky Way so we include a variety of assumptions regarding the tidal radius. For every set of assumptions, models require a central black hole consistent with a mass $(3.3 \pm 2) \times 10^6\, M_\odot$. The no-black-hole case for any of our assumptions is excluded at over 95% significance, with $6.4<Δχ^2<14$. A black hole of this mass would have significant effect on dwarf galaxy formation and evolution. The dark halo parameters are heavily affected by the assumptions for the tidal radii, with the circular velocity only constrained to be above 30 km/s. Reasonable assumptions for the tidal radius result in stellar orbits consistent with an isotropic distribution in the velocities. These more realistic models only show strong constraints for the mass of the central black hole.

astro-ph.GA↗