arXiv subjects

Samuel Gómez Gómez

Publications and source records attributed to Samuel Gómez Gómez.

4 recordsLinked to original sources

arXiv2026

Can bosenovae deplete the galactic dark matter?

No: neither through the bosenovae of gravitational atoms formed around stars and compact objects, nor through those of boson stars formed in the galactic dark-matter halo. We assume that all the dark matter consists of ultralight bosons with attractive self-interactions, which can be captured in the gravitational potential of astrophysical objects or condense into self-gravitating configurations. When these systems collapse in a bosenova, part of their mass is turned into relativistic radiation that escapes the galaxy. We bound the mass that a single object can eject and sum it over realistic models of the Milky Way and of other types of galaxies. For gravitational atoms, with realistic stellar populations and stellar evolution, the stars of the Milky Way deplete at most $ε^{\rm GA}_\star\simeq3\times10^{-9}$ of its halo, and the pump is equally negligible in other galaxies. The central black hole, Sgr A$^*$, could reach $ε^{\rm GA}\sim10^{-3}$, but only for a boson mass disfavoured by ultrafaint dwarf galaxies and beyond the validity of the perturbative treatment, where only a geometric bound on the dark matter flux is available. For boson stars feeding on the rest of the halo, these would radiate at most $\sim3\times10^{-5}$ of the Milky-Way halo and $0.1\%$ of a DF2-like one.

astro-ph.HE↗

arXiv2026

Can LISA See Inside the Little Red Dots?

The Little Red Dots (LRDs) are compact, broad-line sources that appear to contain accreting black holes (BHs) embedded in dense gas. Proposed models for their central environments (including quasi-stars, radiative BH envelopes and super-Eddington accretion discs) predict gas densities at the radii probed by an extreme-mass-ratio inspiral that differ by many orders of magnitude. We compute the inspiral of a $10$--$30\Msun$ BH for a range of LRD interior models, including environmental effects from the gas, and test with a mismatch criterion whether the resulting waveforms can be distinguished from vacuum and from one another. Dense interiors (Bondi-like free-fall cavities and radiative envelopes) produce measurable deviations from vacuum in essentially every detectable event. Convective quasi-star interiors are measurable for $\MBH\lesssim10^5\Msun$ and $z\lesssim0.6$, while a co-rotating disc leaves no measurable imprint. In favorable cases the models are also mutually distinguishable. None of the 14 JWST LRDs at $z>3.9$ would be detectable with a $10\Msun$ companion, but 30 of 31 LRDs at $z<0.9$ would be if their black holes are $\sim100$ times less massive than their virial estimates, and in many of them the interior's imprint would be measurable. Across the LRD population to $z=6$, a 4-yr LISA mission would yield $0.08$--$0.8$ detectable events for $10^5\Msun$ hosts and $10\Msun$ companions ($1.5$--$15$ for $30\Msun$) if LRD nuclei host inspirals at the rate of ordinary galactic nuclei. In dense clusters, where captures are plunges, this falls to $\lesssim10^{-4}$.

astro-ph.HE↗

arXiv2026

Impact of the axion-like self-interactions in gravitational atoms for LISA

Ultralight bosons with self-interactions, such as axion-like particles, can form astrophysical Bose--Einstein condensates around stars or compact objects, often referred to as gravitational atoms. In this work, we adopt a recently proposed dynamical formation mechanism for these halos and estimate their impact on extreme- and intermediate-mass-ratio inspirals when present around the primary black hole. We show that, for signal-to-noise ratios $\lesssim 100$, LISA can distinguish gravitational waveforms from binaries embedded in such halo overdensities. Our analysis indicates that LISA can probe boson masses $m_\mathrm{dm}\sim10^{-17}$--$10^{-15}\,\mathrm{eV}$ and decay constants $f_a\sim3 \times 10^{10}$--$6 \times 10^{12}\,\mathrm{GeV}$ using binaries with total masses $M\sim10^4$--$10^5\,M_\odot$, assuming conservative DM densities consistent with the central values of Navarro--Frenk--White profiles. Allowing for higher background densities and different extreme-mass-ratio configurations further extends the accessible parameter space. Moreover, we find that for a binary configuration with $M\sim10^4M_{\odot}$, $ρ_{\rm dm} = 10^4\,\mathrm{GeV/cm^3}$, and signal to noise ratio $\text{SNR} \sim 20$, a particle mass of $m_{dm} = 3.2 \cdot 10^{-15}$ eV and decay constant of $f_a = 1.6 \cdot 10^{11}$ GeV maximize the dephasing due to dynamical friction, enabling the recovery of the particle parameters at the percent level. These results demonstrate that LISA can place constraints on axion-like particle masses and self-interactions without requiring additional couplings to Standard Model fields.

gr-qc↗

arXiv2026

Shaping black hole resonances I. Black hole ringdown as a spectral filtering process

The ringdown of a perturbed black hole (BH) can be described as a superposition of quasinormal modes (QNMs), whose frequencies are determined by the spacetime geometry while their amplitudes depend also on the perturbing source. However, the physical mechanism governing mode excitation remains unclear and is typically treated on a case by case basis. In this work, we show that QNM excitation is governed by a simple spectral rule: each mode is excited according to the Fourier content of the perturbation evaluated at its characteristic frequency. This result follows from the factorization of the excitation coefficients and establishes a direct, quantitative connection between the spectral properties of the perturbation and the resulting ringdown amplitudes. To make this mechanism explicit and controllable, we construct localized perturbations with independently tunable spectral bandwidth and carrier frequency. We demonstrate analytically and numerically that BHs act as resonant spectral filters. We show analytically that the excitation amplitude of each mode equals the weighted spatial Fourier transform of the initial data evaluated at wavenumber $k\simω_n$ so that the filter selectively excites modes whose frequencies lie within the spectral support of the perturbation while suppressing others. Consequently, the excitation is maximized when the dominant perturbation frequency lies close to the real part of the QNM frequency, and we validate this at the percent level with fits to time-domain numerical evolutions. To robustly perform these fits, we have developed a new fitting algorithm, $\mathtt{QNMToolkit}$, which performs ringdown fits over large ensembles of sliding time-domain windows and quantifies the resulting fitting variance.

gr-qc↗