arXiv subjects

F. García

Publications and source records attributed to F. García.

At least 19 recordsLinked to original sources

arXiv2026

Giant radio pulses in the magnetar XTE J1810-197 detected with the IAR's telescopes

[...] We observed XTE J1810-197 between 29 September 2022 and 14 July 2023 with the radio telescopes at the Argentine Institute of Radioastronomy (IAR). We searched for single pulses in time series at a DM range of 100-400 pc cm-3 , with a threshold in signal-to-noise ratio (S/N) of 8. [...] We found 249 giant pulses at a DM mean value of 178.8$\pm$0.1 pc cm-3 . We measured peak flux densities up to 119 Jy, and fluences up to 58 Jy ms. We fitted a power law distribution to the flux density, obtaining an index of -4.0$\pm$0.3. We observed a maximum rate of approximately 15 pulses per hour on 20 February 2023, followed by an abrupt disappearance of transient radio emission, indicating a transition to a less active state. The brightest single pulses are limited to a $\sim$2$\%$ of the rotational phase and have similar fluence values to the reported intermediate FRB-like bursts of SGR 1935+2154. No significant X-ray activity in the MAXI data was detected during the radio observing period. This is the first study of single radio pulses of a magnetar using IAR data, showing the potential of the upgraded telescopes for investigating the transient radio sky. The properties of the single pulses detected here show the magnetar transient nature and capability to emit high-luminosity pulses. We compared the detected emission to FRB-like bursts and single pulses emitted by SGR 1935+2154. Even though the mechanism producing all the events should be coherent, the luminosity of the events, features on the dynamic spectra, and the difference between being phase confined or not, indicate that XTE J1810-197 presents GP emission, while SGR 1935+2154 only shows normal single pulses or FRB bursts. This could indicate that the conditions for producing each type of event differ.

astro-ph.HE↗

arXiv2025

PSR J0537-6910: Exponential recoveries detected for 12 glitches

Pulsar glitches are unresolved increments of the rotation rate that sometimes trigger an enhancement of the spin-down rate. On occasions, the augmented spin-down decays gradually in an exponential manner, particularly after the largest glitch events. The young pulsar PSR J0537-6910 exhibits the highest known glitching rate, with 60 events detected in nearly 18 years of monitoring. Despite most PSR J0537-6910 glitches being large, only one exponential recovery has been reported, following its first discovered glitch. This is puzzling, as pulsars of similar characteristics typically present significant exponential recoveries. We aim to determine whether this reflects an intrinsic difference in PSR J0537-6910 or a detectability issue, for example due to its high glitch frequency. The full dataset, including recent NICER observations, was systematically searched for exponential relaxations. Each glitch was tested for evidence of a recovery over a broad range of trial timescales. Promising candidates were investigated further by comparing recovery models with and without an exponential term using Bayesian evidence. We discovered six new glitches, bringing the total to 66. Our criteria strongly indicates the presence of 11 previously undetected exponential recoveries. We presente updated glitch and timing solutions. Exponential recoveries are detected only for the largest glitches, though not all of them. The inferred timescales range from 4 to 37 d, with the decaying frequency increment generally below $1\%$ of the total. We find that $\ddotν$ can remain stable across several glitches, with persistent changes associated with only some events. In particular, it tends to be lowest after glitches with exponential recoveries, yielding inter-glitch braking indices between 6 and 9. Following glitches without recoveries, $\ddotν$ is higher, leading to braking indices between 10 and 35.

astro-ph.HE↗

arXiv2025

The hard ultraluminous state of NGC 5055 ULX X-1

We present the results of the first broadband X-ray analysis of the ultraluminous X-ray source NGC 5055 ULX X-1, combining simultaneous data from XMM$-$Newton and NuSTAR missions, with a combined exposure time of $\sim$100 ks across the $0.3-20$ keV energy range. The source exhibits a stable flux across the entire exposure with no detectable pulsations by any instrument on their X-ray light curves, placing pulsed-fraction upper limits of 10% and 32% for XMM$-$Newton and NuSTAR, respectively. The X-ray spectrum is dominated by two thermal components consistent with the emission from an accretion disk, and shows a weak high-energy tail above 10 keV, with no statistical requirement for an additional nonthermal component. The unabsorbed $0.3-20$ keV luminosity is ${\sim}2\times10^{40}$ erg s$^{-1}$, evidencing the ULX nature of the source. The parameters obtained from spectral modeling are consistent with the hard ultraluminous state. Despite the fact that a neutron-star accretor cannot be ruled out by the available data, under the assumption that the compact object in NGC 5055 ULX X-1 is a black hole accreting through a geometrically thick, radiation-pressure-supported disk that drives an optically thick wind, we constrained its putative mass to $11-26$ M$_{\odot}$.

astro-ph.HE↗

arXiv2024

Glitch-induced pulse profile change of PSR J0742-2822 observed from the IAR

The radio pulsar PSR J0742-2822 is known to exhibit rapid changes between different pulse profile states that correlate with changes in its spin-down rate. However, the connection between these variations and the glitch activity of the pulsar remains unclear. We aim to study the evolution of the pulse profile and spin-down rate of PSR J0742-2822 in the period MJD 58810-60149 (November 2019 to July 2023), which includes the glitch on MJD 59839 (September 2022). In particular, we look for pulse profile or spin-down changes associated with the 2022 glitch. We observed PSR J0742-2822 with high cadence from the Argentine Institute of Radio astronomy (IAR) between November 2019 and July 2023. We used standard timing tools to characterize the times of arrival of the pulses and study the pulsar rotation, and particularly, the oscillations of $\dot ν$. We also study the evolution of the pulse profile. For both of them, we compare their behavior before and after the 2022 glitch. With respect to $\dot ν$, we found oscillations diminished in amplitude after the glitch. We found four different components contributing to the pre-glitch $\dot ν$ oscillations, and only one component after the glitch. About the emission, we found the pulse profile has two main peaks. We detected an increase in the $W_{50}$ of the total pulse profile of $\sim$12% after the glitch and we found the amplitude of the trailing peak increased with respect to the amplitude of the leading one after the glitch. We found significant changes in the pulse profile and the spin-down rate of PSR J0742-2822 after its 2022 glitch. These results suggest that there is a strong coupling between the internal superfluid of the neutron star and its magnetosphere, and that pulse profile changes may be led by this coupling instead of being led purely by magnetospheric effects.

astro-ph.HE↗

arXiv2023

Evidence for non-thermal X-ray emission from the double WR colliding-wind binary Apep

Context: Massive colliding-wind binaries (CWBs) can be non-thermal sources. The emission produced in their wind-collision region (WCR) encodes information of both the shocks properties and the relativistic electrons accelerated in them. The recently discovered system Apep, a unique massive system hosting two Wolf-Rayet stars, is the most powerful synchrotron radio emitter among the known CWBs, being an exciting candidate to investigate the non-thermal processes associated with stellar wind shocks. Aims: We intend to break the degeneracy between the relativistic particle population and the magnetic field strength in the WCR of Apep by probing its hard X-ray spectrum, where inverse-Compton (IC) emission is expected to dominate. Methods: We observe Apep with NuSTAR for 60 ks and combine this with a re-analysis of a deep archival XMM-Newton observation to better constrain the X-ray spectrum. We use a non-thermal emission model to derive physical parameters from the results. Results: We detect hard X-ray emission consistent with a power-law component. This is compatible with IC emission produced in the WCR for a magnetic field of 100-160 mG and a fraction of ~1.5e-4 of the total wind kinetic power being converted into relativistic electron acceleration. Conclusions: This is the first time that the non-thermal emission from a CWB is detected both in radio and high energies. This allows us to derive the most robust constraints of the particle acceleration efficiency and magnetic field intensity in a CWB so far, reducing the typical uncertainty of a few orders of magnitude to just within a factor of two. This constitutes an important step forward in our characterisation of the physical properties of CWBs.

astro-ph.HE↗

arXiv2022

Evolution of eccentric high-mass X-ray binaries. The case of GX 301-2

The formation of neutron stars is associated with powerful astrophysical transients such as supernovae. In many cases, asymmetries in the supernova explosions are thought to be responsible for the large observed velocities of neutron stars. We aim to study the complete evolutionary history of one particular eccentric high-mass X-ray binary containing a neutron star, GX 301-2, and characterize the natal kick at the time of neutron star formation. We used the publicly available stellar-evolution code MESA to evolve binaries from their initial stages until the core-collapse scenario. We incorporated a natal kick distribution based on observations to continue the evolution during the X-ray binary phase and search for candidates matching current observations of GX 301-2. We find that the range of initial masses is constrained to be less than around $30$ M$_\odot$ depending on the initial mass ratio, as higher initial masses will most likely end up producing a black hole. In the completely conservative mass-transfer scenario under study, only is an interaction between the stars when the donor is still burning Hydrogen in its core, the so-called Case A of mass transfer, able to produce progenitors for GX 301-2. The natal kick study favours kicks of variable strength, which in turn increases the tilt angle between the orbital angular momentum and the spin of the neutron star. We conclude that only a narrow initial progenitor parameter space is able to produce a binary such as GX 301-2. Additionally, the strength of the natal kick can span a wide range of values, but it can be constrained when considering new data concerning the systemic velocity of the binary. Finally, we derive the fraction of the expected number of binaries such as GX 301-2 in the Galaxy to be $\sim 6 \times 10^{-5}$, implying a really low chance of finding a binary similar to GX 301-2.

astro-ph.SR↗

arXiv2022

Impact of tides on non-coplanar orbits of progenitors of high-mass X-ray binaries

An important stage in the evolution of massive binaries is the formation of a compact object in the system. It is believed that in some cases a momentum kick is imparted to the newly born object, changing the orbital parameters of the binary, such as eccentricity and orbital period, and even acquiring an asynchronous orbit between its components. In this situation, tides play a central role in the evolution of these binaries. In this work we aim to study how the orbital parameters of a massive binary change after the formation of a compact object when the stellar spin of the non-degenerate companion is not aligned with the orbital angular momentum. We used MESA, which we modified to be able to evolve binaries with different values of the inclination between the orbital planes before and just after the formation of the compact object. These modifications to the equations solved by the MESA code are extended to the case of non-solid body rotation. We find that the impact of having different initial inclinations is mostly present in the evolution towards an equilibrium state that is independent of the inclination. If the binary separation is small enough such that the interaction happens when the star is burning hydrogen in its core, this state is reached before the beginning of a mass-transfer phase, while for a wider binary not all conditions characterizing the equilibrium are met. These findings show that including the inclination in the equations of tidal evolution to a binary after a kick is imparted onto a newly born compact object changes the evolution of some parameters, such as the eccentricity and the spin period of the star, depending on how large this inclination is. Moreover, these results can be used to match the properties of observed X-ray binaries to estimate the strength of the momentum kick.

astro-ph.SR↗

arXiv2022

Precise timing and recent advancements with segmented anode PICOSEC Micromegas prototypes

Timing information in current and future accelerator facilities is important for resolving objects (particle tracks, showers, etc.) in extreme large particles multiplicities on the detection systems. The PICOSEC Micromegas detector has demonstrated the ability to time 150\,GeV muons with a sub-25\,ps precision. Driven by detailed simulation studies and a phenomenological model which describes stochastically the dynamics of the signal formation, new PICOSEC designs were developed that significantly improve the timing performance of the detector. PICOSEC prototypes with reduced drift gap size ($\sim$\SI{119}{\micro\metre}) achieved a resolution of 45\,ps in timing single photons in laser beam tests (in comparison to 76\,ps of the standard PICOSEC detector). Towards large area detectors, multi-pad PICOSEC prototypes with segmented anodes has been developed and studied. Extensive tests in particle beams revealed that the multi-pad PICOSEC technology provides also very precise timing, even when the induced signal is shared among several neighbouring pads. Furthermore, new signal processing algorithms have been developed, which can be applied during data acquisition and provide real time, precise timing.

physics.ins-det↗

arXiv2022

Recoil imaging for directional detection of dark matter, neutrinos, and physics beyond the Standard Model

Recoil imaging entails the detection of spatially resolved ionization tracks generated by particle interactions. This is a highly sought-after capability in many classes of detector, with broad applications across particle and astroparticle physics. However, at low energies, where ionization signatures are small in size, recoil imaging only seems to be a practical goal for micro-pattern gas detectors. This white paper outlines the physics case for recoil imaging, and puts forward a decadal plan to advance towards the directional detection of low-energy recoils with sensitivity and resolution close to fundamental performance limits. The science case covered includes: the discovery of dark matter into the neutrino fog, directional detection of sub-MeV solar neutrinos, the precision study of coherent-elastic neutrino-nucleus scattering, the detection of solar axions, the measurement of the Migdal effect, X-ray polarimetry, and several other applied physics goals. We also outline the R&D programs necessary to test concepts that are crucial to advance detector performance towards their fundamental limit: single primary electron sensitivity with full 3D spatial resolution at the $\sim$100 micron-scale. These advancements include: the use of negative ion drift, electron counting with high-definition electronic readout, time projection chambers with optical readout, and the possibility for nuclear recoil tracking in high-density gases such as argon. We also discuss the readout and electronics systems needed to scale-up such detectors to the ton-scale and beyond.

physics.ins-det↗

arXiv2021

Failed-Transition outbursts in Black hole low-mass X-ray binaries

Black hole low-mass X-ray binaries (BH LMXBs) evolve in a similar way during outburst. Based on the X-ray spectrum and variability, this evolution can be divided into three canonical states: low/hard, intermediate and high/soft state. BH LMXBs evolve from the low/hard to the high/soft state through the intermediate state in some outbursts (here called "full outbursts"). However, in other cases, BH LMXBs undergo outbursts in which the source never reaches the high/soft state, here called "Failed-Transition outburst" (FT outbursts). From a sample of 56 BH LMXBs undergoing 128 outbursts, we find that $\sim$36% of these BH LMXBs experienced at least one FT outburst, and that FT outbursts represent $\sim$33% of the outbursts of the sample, showing that these are common events. We compare all the available X-ray data of full and FT outbursts of BH LMXBs from RXTE/PCA, Swift/BAT and MAXI and find that FT and full outbursts cannot be distinguished from their X-ray light curves, HIDs or X-ray variability during the initial 10-60 days after the outburst onset. This suggests that both types of outbursts are driven by the same physical process. We also compare the optical and infrared (O/IR) data of FT and full outbursts of GX 339-4. We found that this system is generally brighter in O/IR bands before an FT outburst, suggesting that the O/IR flux points to the physical process that later leads to a full or an FT outburst. We discuss our results in the context of models that describe the onset and evolution of outbursts in accreting X-ray binaries.

astro-ph.HE↗

arXiv2021

Discovery of millihertz quasi-periodic oscillations in the X-ray binary EXO 0748--676

We report the discovery of millihertz quasi-periodic oscillations (mHz QPOs) from the bursting, high-inclination atoll neutron-star low-mass X-ray binary (NS LMXB) EXO 0748--676 with the Rossi X-ray Time Explorer (RXTE). This class of QPO, originally discovered in three NS LMXBs, has been interpreted as a consequence of a special mode of nuclear burning on the NS surface. Using all the RXTE archival observations of the source, we detected significant ($>3σ$) mHz QPOs in 11 observations. The frequency of the oscillations was between $\sim$ 5 and $\sim$ 13 mHz. We also found a decrease of the QPO frequency with time in two occasions; in one of these the oscillations disappeared with the onset of an X-ray burst, similar to what was reported in other sources. Our analysis of the X-ray colours revealed that EXO 0748--676 was in a soft spectral state when it exhibited the QPOs. This makes EXO 0748--676 the sixth source with mHz oscillations associated to marginally stable burning, and the second one that shows a systematic frequency drift. Our results suggest that the mechanism that produces the drift might always be present if the mHz QPOs are observed in the so-called intermediate state.

astro-ph.HE↗

arXiv2021

Timing performance of a multi-pad PICOSEC-Micromegas detector prototype

The multi-pad PICOSEC-Micromegas is an improved detector prototype with a segmented anode, consisting of 19 hexagonal pads. Detailed studies are performed with data collected in a muon beam over four representative pads. We demonstrate that such a device, scalable to a larger area, provides excellent time resolution and detection efficiency. As expected from earlier single-cell device studies, we measure a time resolution of approximately 25 picoseconds for charged particles hitting near the anode pad centers, and up to 30 picoseconds at the pad edges. Here, we study in detail the effect of drift gap thickness non-uniformity on the timing performance and evaluate impact position based corrections to obtain a uniform timing response over the full detector coverage.

physics.ins-det↗

arXiv2021

PSR J0437-4715: The Argentine Institute of Radioastronomy 2019-2020 Observational Campaign

The Argentine Institute of Radio astronomy (IAR) is equipped with two single-dish 30-m radio antennas capable of performing daily observations of pulsars and radio transients in the southern hemisphere at 1.4 GHz. We aim to contribute to pulsar timing studies related to short time-scale interstellar scintillation and searches for sources of continuous gravitational waves. We performed high-cadence (almost daily) and long-duration observations of the bright millisecond pulsar J0437$-$4715 for over a year, gathering more than 700 hours of good-quality data with timing precision better than 1~$μ$s. We characterize the white and red timing noise in IAR's observations of J0437$-$4715. We quantify the effects of scintillation in this data set and perform single pulsar searches of continuous gravitational waves, setting constraints in the nHz--$μ$Hz frequency range. We demonstrate IAR's potential for performing pulsar monitoring in the 1.4 GHz radio band for long periods of time with a daily cadence. In particular, we conclude that the ongoing observational campaign of the millisecond pulsar J0437$-$4715 can contribute to increase the sensitivity of the existing pulsar timing arrays.

astro-ph.GA↗

arXiv2020

Modeling the Timing Characteristics of the PICOSEC Micromegas Detector

The PICOSEC Micromegas detector can time the arrival of Minimum Ionizing Particles with a sub-25 ps precision. A very good timing resolution in detecting single photons is also demonstrated in laser beams. The PICOSEC timing resolution is determined mainly by the drift field. The arrival time of the signal and the timing resolution vary with the size of the pulse amplitude. Detailed simulations based on GARFIELD++ reproduce the experimental PICOSEC timing characteristics. This agreement is exploited to identify the microscopic physical variables, which determine the observed timing properties. In these studies, several counter-intuitive observations are made for the behavior of such microscopic variables. In order to gain insight on the main physical mechanisms causing the observed behavior, a phenomenological model is constructed and presented. The model is based on a simple mechanism of "time-gain per interaction" and it employs a statistical description of the avalanche evolution. It describes quantitatively the dynamical and statistical properties of the microscopic quantities, which determine the PICOSEC timing characteristics, in excellent agreement with the simulations. In parallel, it offers phenomenological explanations for the behavior of these microscopic variables. The formulae expressing this model can be used as a tool for fast and reliable predictions, provided that the input parameter values (e.g. drift velocities) are known for the considered operating conditions.

physics.ins-det↗

arXiv2020

On the origin of X-ray oxygen emission-lines in obscured AGN

We present the Catalog of High REsolution Spectra of Obscured Sources (CHRESOS) from the XMM-Newton Science Archive. It comprises the emission-line luminosities of H- and He-like transitions from C to Si, and the Fe 3C and Fe 3G L-shell ones. Here, we concentrate on the soft X-ray OVII(f) and OVIII Ly_alpha emission lines to shed light onto the physical processes with which their formation can be related to: active galactic nucleus vs. star forming regions. We compare their luminosity with that of two other important oxygen key lines [OIII]5007A, in the optical, and [OIV]25.89mic, in the IR. We also test OVII(f) and OVIIILy_alpha luminosities against that of continuum bands in the IR and hard X-rays, which point to different ionization processes. We probe into those processes by analyzing photoionization and colisional ionization model predictions upon our lines. We show that both scenarios can explain the formation and observed intensities of OVII(f) and OVIII Ly_alpha. By analyzing the relationships between OVII(f) and OVIII Ly_alpha, and all other observables: [OIII]5007A, [OIV]25.89mic emission lines, and MIR-12mic, FIR-60mic, FIR-100mic, 2-10 keV and 14-195 keV continuum bands, we conclude that the AGN radiation field is mainly responsible of the soft X-ray oxygen excitation.

astro-ph.GA↗

arXiv2020

The high-energy emission from HD~93129A near periastron

We conducted an observational campaign towards one of the most massive and luminous colliding wind binaries in the Galaxy, HD~93129A, close to its periastron passage in 2018. During this time the source was predicted to be in its maximum of high-energy emission. Here we present our data analysis from the X-ray satellites \textit{Chandra} and \textit{NuSTAR} and the $γ$-ray satellite \textit{AGILE}. High-energy emission coincident with HD~93129A was detected in the X-ray band up to $\sim$18~keV, whereas in the $γ$-ray band only upper limits were obtained. We interpret the derived fluxes using a non-thermal radiative model for the wind-collision region. We establish a conservative upper limit for the fraction of the wind kinetic power that is converted into relativistic electron acceleration, $f_\mathrm{NT,e} < 0.02$. In addition, we set a lower limit for the magnetic field in the wind-collision region as $B_\mathrm{WCR} > 0.3$~G. We also argue a putative interpretation of the emission from which we estimate $f_\mathrm{NT,e} \approx 0.006$ and $B_\mathrm{WCR} \approx 0.5$~G. We conclude that multi-wavelength, dedicated observing campaigns during carefully selected epochs are a powerful tool for characterising the relativistic particle content and magnetic field intensity in colliding wind binaries.

astro-ph.HE↗

arXiv2019

Upgraded antennas for pulsar observations in the Argentine Institute of Radio astronomy

The Argentine Institute of Radio astronomy (IAR) is equipped with two single-dish 30mts radio antennas capable of performing daily observations of pulsars and radio transients in the southern hemisphere at 1.4 GHz. We aim to introduce to the international community the upgrades performed and to show that IAR observatory has become suitable for investigations in numerous areas of pulsar radio astronomy, such as pulsar timing arrays, targeted searches of continuous gravitational waves sources, monitoring of magnetars and glitching pulsars, and studies of short time scale interstellar scintillation. We refurbished the two antennas at IAR to achieve high-quality timing observations. We gathered more than $1\,000$ hours of observations with both antennas to study the timing precision and sensitivity they can achieve. We introduce the new developments for both radio telescopes at IAR. We present observations of the millisecond pulsar J0437$-$4715 with timing precision better than 1~$μ$s. We also present a follow-up of the reactivation of the magnetar XTE J1810--197 and the measurement and monitoring of the latest (Feb. 1st. 2019) glitch of the Vela pulsar (J0835--4510). We show that IAR is capable of performing pulsar monitoring in the 1.4 GHz radio band for long periods of time with a daily cadence. This opens the possibility of pursuing several goals in pulsar science, including coordinated multi-wavelength observations with other observatories. In particular, observations of the millisecond pulsar J0437$-$4715 will increase the gravitational wave sensitivity of the NANOGrav array in their current blind spot. We also show IAR's great potential for studying targets of opportunity and transient phenomena such as magnetars, glitches, and fast-radio-burst sources.

astro-ph.IM↗

arXiv2019

Precise Charged Particle Timing with the PICOSEC Detector

The experimental requirements in near future accelerators (e.g. High Luminosity-LHC) has stimulated intense interest in development of detectors with high precision timing capabilities. With this as a goal, a new detection concept called PICOSEC, which is based to a "two-stage" MicroMegas detector coupled to a Cherenkov radiator equipped with a photocathode has been developed. Results obtained with this new detector yield a time resolution of 24\,ps for 150\,GeV muons and 76\,ps for single photoelectrons. In this paper we will report on the performance of the PICOSEC in test beams, as well as simulation studies and modelling of its timing characteristics.

physics.ins-det↗