arXiv subjects

J. Rodriguez

Publications and source records attributed to J. Rodriguez.

At least 19 recordsLinked to original sources

arXiv2026

Early results from the SVOM Observatory Science program

We present the organisation and early results from the Observatory Science program of the Space-based multi-band astronomical Variable Objects Monitor (SVOM), based on data collected between July 2024 and December 2025. Although primarily designed for gamma-ray burst studies, SVOM's wide-field, multi-wavelength instruments enable a broad range of high-energy astrophysical investigations. We summarize the execution and performance of the General Program and Target-of-Opportunity observations, and we describe the frameworks used for serendipitous source detection and monitoring with the ECLAIRs coded-mask instrument. Over this period, SVOM carried out more than a thousand pointed observations and detected several hundred non-GRB high-energy sources, mainly X-ray binaries, as well as blazars, stellar flares, magnetars, and unidentified events. We highlight some key results, including the monitoring of the microquasar Cygnus X-1, the detection of burst oscillations from the Low-Mass X-ray Binary 4U 0614+091, the spectral-state monitoring of Aql X-1, the first SVOM detection of an X-ray blazar flare from 1ES 1959+650, and observations of a stellar flare from HD 22468. These results demonstrate SVOM's strong capabilities for time-domain astrophysics beyond its core GRB program.

astro-ph.HE↗

arXiv2026

SVOM Science User Support at FSC

The SVOM mission, a Sino-French collaboration dedicated to Gamma-Ray Bursts (GRBs) and transient sources, began scientific operations in 2025. This paper describes the ground computing infrastructure and user support tools for SVOM's three observing programs: the Core Program (CP), the General Program (GP), and Targets of Opportunity Program (ToO), the latter two being open to the broader scientific community, provided they collaborate with a mission Co-I. The mission adopts operational roles inspired by Swift, including on-duty scientists such as Burst Advocates (BAs), who validate GRB triggers and coordinate follow-up observations, and Instrument Scientists (IS), who calibrate and validate data for all programs. Users can access observation schedules, public data products, and support tools via the French and Chinese mission centers. The SVOM portal serves as the primary interface for accessing these resources, including a GRB public table, API, and user documentation. This paper serves as a guide for both newcomers and external researchers interested in SVOM scientific operations, focusing on aspects related to the CP.

astro-ph.HE↗

arXiv2026

The SVOM / ECLAIRs Scientific Analysis Pipeline

This paper reports on the scientific pipeline for the analysis of the ECLAIRs data of the SVOM mission. We describe the overall procedure, the different steps and the main algorithms of the data analysis for this hard X-ray coded mask instrument. The pipeline runs in automatic mode at the science center generating standard products but can also be used off-line with specific choices of parameters. Generated data products and preliminary performances are illustrated along with perspectives for future improvements.

astro-ph.HE↗

arXiv2026

Multi-wavelength Study of A Superflare on RS CVn-type Star HD22468 Triggered at Hard X-ray by SVOM

Detection of stellar flares at hard X-ray is still rare at the current stage. A transient was recently detected by the hard X-ray camera, ECLAIRs onboard the SVOM mission at 11:39:01.2UT on 2025, January 09. Simultaneous monitor in the optical band on the ground by SVOM/GWAC and follow-up spectroscopy enable us to confirm that the transient is caused by a superflare on HD~22468, a RS CVn-type star. The bolometric energy released in the flare is estimated to be $\sim7.2\times10^{37}-1.7\times10^{38}\ \mathrm{erg}$. The hard X-ray spectra of the event at the peak can be reproduced by the ``apec'' model of a hot plasma with a temperature of $106^{+27}_{-22}$~MK. In the optical range, the H$\alpha$ emission-line profile obtained at $\sim1.7$ hrs after the trigger shows a bulk blueshift of $-96\pm20\ \mathrm{km\ s^{-1}}$, which can be explained by either a chromospheric evaporation or a prominence eruption. The ejected mass is estimated to be $3.9\times10^{20}$ g for the evaporating plasma, and to be $3.2\times10^{21}\ \mathrm{g}<M_{\mathrm{p}}<8.8\times10^{21}\ \mathrm{g}$ for the erupted prominence.

astro-ph.SR↗

arXiv2026

SVOM discovery of a strong X-ray outburst of the blazar 1ES~1959+650 and multi-wavelength follow-up with the Neil Gehrels Swift observatory

On December 6, 2024, 1ES 1959+650, one of the X-ray brightest blazars known, underwent a high-amplitude X-ray outburst detected by SVOM, the first such discovery with this mission. The source was subsequently monitored with SVOM and Swift from December 2024 to March 2025. We report the detection and multi-wavelength follow-up of this event, and describe the temporal and spectral evolution observed during the campaign. Data from SVOM/MXT, SVOM/ECLAIRs, and Swift/XRT were analyzed with log-parabola models to track flux and spectral variability. The source was detected in a bright state over the 0.3-50 keV range. During the three months of monitoring, the X-ray flux varied significantly, showing episodes of spectral hardening at high flux levels. The spectral curvature evolved more irregularly and did not show a clear trend with flux. A shift of the Spectral Energy Distribution (SED) synchrotron peak to higher energies is seen when the flux increases. This constitutes the first blazar outburst discovered in X-rays by SVOM. The coordinated follow-up with Swift provided continuous coverage of the flare and highlights the strong complementarity of the two missions for time-domain studies of blazars. The flare shows no clear signatures of either Fermi I or Fermi II acceleration, suggesting a mixed Fermi I/II scenario.

astro-ph.HE↗

arXiv2025

Unprecedentedly bright X-ray flaring in Cygnus X-1 observed by INTEGRAL

We study three extraordinarily bright X-ray flares originating from Cyg X-1 seen on 2023 July 10 detected with INTEGRAL. The flares had a duration on the order of only ten minutes each, and within seconds reached a 1-100 keV peak luminosity of $1.1-2.6\times10^{38}$ erg/s. The associated INTEGRAL/IBIS count rate was about ${\sim}$10x higher than usual for the hard state. To our knowledge, this is the first time that such strong flaring has been seen in Cyg X-1, despite the more than 21 years of INTEGRAL monitoring, with almost ${\sim}$20 Ms of exposure, and the similarly deep monitoring with RXTE/PCA that lasted from 1997 to 2012. The flares were seen in all three X-ray and $\gamma$-ray instruments of INTEGRAL. Radio monitoring by the AMI Large Array with observations 6 h before and 40 h after the X-ray flares did not detect a corresponding increase in radio flux. The shape of the X-ray spectrum shows only marginal change during the flares, i.e., photon index and cut-off energy are largely preserved. The overall flaring behavior points toward a sudden and brief release of energy, either due to the ejection of material in an unstable jet or due to the interaction of the jet with the ambient clumpy stellar wind.

astro-ph.HE↗

arXiv2024

Observation of microquasars high-energy emission with INTEGRAL

Microquasars are Black Hole X-ray binaries (BHXB) which can eject material in the form of a bipolar jet, similarly to quasars, but at much smaller scales. Their high-energy emission comes from an accretion disk (~ 1 keV) and from a hot "corona" near the black hole that up-scatters photons from the disk in the hard X-ray domain (1--100 keV). A high-energy component above 150 keV has been detected in bright sources and its precise origin is still unknown: it could come either from Compton scattering of disk photons on coronal relativistic non-thermal electrons (a.k.a hybrid Comptonization), or from the synchrotron emission from the very base of the compact jet. The measurement of polarization above 150 keV can provide valuable insights into the processes at play as we expect higher polarization fraction due to synchrotron emission from the jets (up to 70 % with a very ordered magnetic field). We use the INTEGRAL/IBIS telescope to measure the soft gamma-ray polarization of the Crab Nebula and the BHXB Swift J1727.8-1613.

astro-ph.HE↗

arXiv2022

INTEGRAL study of MAXI J1535-571, MAXI J1820+070 and MAXI J1348-630 outbursts -- I. Detection and polarization properties of the high-energy emission

In black hole X-ray binaries, a non-thermal high-energy component is sometimes detected at energies above 200 keV. The origin of this component is debated and distinct spectral modelizations can lead to different interpretations. High-energy polarimetry measurements with INTEGRAL allow new diagnostics on the physics responsible for the MeV spectral component. In this work, we aim to investigate the high-energy behavior of three bright sources discovered by the MAXI: MAXI J1535-571, MAXI J1820+070 and MAXI J1348-630. We take advantage of their brightness to investigate their soft gamma-ray (0.1-2 MeV) properties with INTEGRAL. We use both spectral and polarimetric approaches to probe their high-energy emission with the aim to bring new constraints on the ~ MeV emission. We first study the spectral characteristics of the sources in the 3-2000 keV using JEM-X, IBIS and SPI with a semi-phenomenological description of the data. We then use IBIS as a Compton telescope in order to evaluate the polarization properties of the sources above 300 keV. A high-energy component is detected during the HIMS and SIMS of MAXI J1535-571, the LHS of MAXI J1820+070 and the LHS of MAXI J1348-630. The components detected in MAXI J1820+070 and MAXI J1348-630 are polarized with a polarization fraction of 26 +/- 9{\deg} and > 56 % in the 300-1000 keV, respectively. With no polarization information for MAXI J1535-571, the component detected could either come from the jets or the corona. In the case of MAXI J1820+070, the extrapolation of the synchrotron spectrum measured in the infrared indicates that the component is likely due to a non-thermal distribution of electrons from a hybrid corona. For MAXI J1348-630, the high fraction of polarization points towards a jets origin, however, we cannot formally conclude without any infrared data giving information on the optically thin part of the synchrotron spectrum.

astro-ph.HE↗

arXiv2022

The spectral-timing analysis of Cygnus X-1 with Insight-HXMT

Cygnus X-1, as the first discovered black hole binary, is a key source for understanding the mechanisms of state transitions, and the scenarios of accretion in extreme gravity fields. We present a spectral-timing analysis of observations taken with the Insight-HXMT mission, focusing on the spectral-state dependent timing properties in the broad energy range of 1--150 keV, thus extending previous RXTE-based studies to both lower and higher energies. Our main results are the following: a) We successfully use a simple empirical model to fit all spectra, confirming that the reflection component is stronger in the soft state than in the hard state; b) The evolution of the total fractional root mean square (rms) depends on the selected energy band and the spectral shape, which is a direct result of the evolution of the power spectral densities (PSDs); c) In the hard/intermediate state, we see clear short-term variability features and a positive correlation between central frequencies of the variability components and the soft photon index $\Gamma_1$, also at energies above 15 keV. The power spectrum is dominated by red noise in the soft state instead. These behaviors can be traced to at least 90 keV; d) The coherence and the phase-lag spectra show different behaviors dependent on different spectral shapes.

astro-ph.HE↗

arXiv2022

Neutral Bremsstrahlung emission in xenon unveiled

We present evidence of non-excimer-based secondary scintillation in gaseous xenon, obtained using both the NEXT-White TPC and a dedicated setup. Detailed comparison with first-principle calculations allows us to assign this scintillation mechanism to neutral bremsstrahlung (NBrS), a process that has been postulated to exist in xenon that has been largely overlooked. For photon emission below 1000 nm, the NBrS yield increases from about 10$^{-2}$ photon/e$^{-}$ cm$^{-1}$ bar$^{-1}$ at pressure-reduced electric field values of 50 V cm$^{-1}$ bar$^{-1}$ to above 3$\times$10$^{-1}$ photon/e$^{-}$ cm$^{-1}$ bar$^{-1}$ at 500 V cm$^{-1}$ bar$^{-1}$. Above 1.5 kV cm$^{-1}$ bar$^{-1}$, values that are typically employed for electroluminescence, it is estimated that NBrS is present with an intensity around 1 photon/e$^{-}$ cm$^{-1}$ bar$^{-1}$, which is about two orders of magnitude lower than conventional, excimer-based electroluminescence. Despite being fainter than its excimeric counterpart, our calculations reveal that NBrS causes luminous backgrounds that can interfere, in either gas or liquid phase, with the ability to distinguish and/or to precisely measure low primary-scintillation signals (S1). In particular, we show this to be the case in the "buffer" and "veto" regions, where keeping the electric field below the electroluminescence (EL) threshold will not suffice to extinguish secondary scintillation. The electric field in these regions should be chosen carefully to avoid intolerable levels of NBrS emission. Furthermore, we show that this new source of light emission opens up a viable path towards obtaining S2 signals for discrimination purposes in future single-phase liquid TPCs for neutrino and dark matter physics, with estimated yields up to 20-50 photons/e$^{-}$ cm$^{-1}$.

physics.ins-det↗

arXiv2021

INTEGRAL Results on Gamma-Ray Bursts and Polarization of Hard X-ray Sources

In this paper we first review the results obtained by the INTEGRAL mission in the domain of Gamma-Ray Bursts (GRBs), thanks to the INTEGRAL Burst Alert System, which is able to deliver near real-time alerts for GRBs detected within the IBIS field of view. More than 120 GRBs have been detected to date and we summarize their properties here. In the second part of this review we focus on the polarimetric results obtained by IBIS and SPI on GRBs and Galactic compact objects.

astro-ph.HE↗

arXiv2021

Clues on jet behavior from simultaneous radio-X-ray fits of GX339-4

Understanding the mechanisms of accretion-ejection during X-ray binaries outbursts has been a problem for several decades. It is still not clear yet what controls the spectral evolution of these objects from the hard to the soft states and then back to the hard states at the end of the outburst, tracing the well-known hysteresis cycle in the hardness-intensity diagram. Moreover, the link between the spectral states and the presence/absence of radio emission is still highly debated. In a series of papers, we developed a model composed of a truncated outer standard accretion disk (SAD, from the solution of Shakura and Sunyaev) and an inner jet emitting disk (JED). In this paradigm, the JED plays the role of the hot corona while simultaneously explaining the presence of a radio jet. Our goal is to apply for the first time direct fitting procedures of the JED-SAD model to the hard states of four outbursts of GX 339-4 observed during the 2000-2010 decade by RXTE, combined with simultaneous or quasi simultaneous ATCA observations. We built JED-SAD model tables usable in Xspec as well as a reflection model table based on the Xillver model. We apply our model to the 452 hard state observations obtained with RXTE/PCA. We were able to correctly fit the X-ray spectra and simultaneously reproduce the radio flux. We show that the functional dependency of the radio emission on the model parameters (mainly the accretion rate and the transition radius between the JED and the SAD) is similar between all the rising phases of the different outbursts of GX 339-4. But it is significantly different from the functional dependency obtained in the decaying phases. This result strongly suggests a change in the radiative and/or dynamical properties of the ejection between the beginning and the end of the outburst. We discuss possible scenarios that could explain these differences.

astro-ph.HE↗

arXiv2021

The INTEGRAL view on Black Hole X-ray Binaries

INTEGRAL is an ESA mission in fundamental astrophysics that was launched in October 2002. It has been in orbit for over 18 years, during which it has been observing the high-energy sky with a set of instruments specifically designed to probe the emission from hard X-ray and soft gamma-ray sources. This paper is devoted to the subject of black hole binaries, which are among the most important sources that populate the high-energy sky. We present a review of the scientific literature based on INTEGRAL data, which has significantly advanced our knowledge in the field of relativistic astrophysics. We briefly summarise the state-of-the-art of the study of black hole binaries, with a particular focus on the topics closer to the INTEGRAL science. We then give an overview of the results obtained by INTEGRAL and by other observatories on a number of sources of importance in the field. Finally, we review the main results obtained over the past 18 years on all the black hole binaries that INTEGRAL has observed. We conclude with a summary of the main contributions of INTEGRAL to the field, and on the future perspectives.

astro-ph.HE↗

arXiv2021

Secure Virtual Mobile Small Cells: A Stepping Stone Towards 6G

As 5th Generation research reaches the twilight, the research community must go beyond 5G and look towards the 2030 connectivity landscape, namely 6G. In this context, this work takes a step towards the 6G vision by proposing a next generation communication platform, which aims to extend the rigid coverage area of fixed deployment networks by considering virtual mobile small cells (MSC) that are created on demand. Relying on emerging computing paradigms such as NFV (Network Function Virtualization) and SDN (Software Defined Networking), these cells can harness radio and networking capability locally reducing protocol signaling latency and overhead. These MSCs constitute an intelligent pool of networking resources that can collaborate to form a wireless network of MSCs providing a communication platform for localized, ubiquitous and reliable connectivity. The technology enablers for implementing the MSC concept are also addressed in terms of virtualization, lightweight wireless security, and energy efficient RF. The benefits of the MSC architecture towards reliable and efficient cell offloading are demonstrated as a use-case.

cs.NI↗

arXiv2021

Time Domain Astronomy with the THESEUS Satellite

THESEUS is a medium size space mission of the European Space Agency, currently under evaluation for a possible launch in 2032. Its main objectives are to investigate the early Universe through the observation of gamma-ray bursts and to study the gravitational waves electromagnetic counterparts and neutrino events. On the other hand, its instruments, which include a wide field of view X-ray (0.3-5 keV) telescope based on lobster-eye focusing optics and a gamma-ray spectrometer with imaging capabilities in the 2-150 keV range, are also ideal for carrying out unprecedented studies in time domain astrophysics. In addition, the presence onboard of a 70 cm near infrared telescope will allow simultaneous multi-wavelegth studies. Here we present the THESEUS capabilities for studying the time variability of different classes of sources in parallel to, and without affecting, the gamma-ray bursts hunt.

astro-ph.IM↗

arXiv2021

Expected disk wind properties evolution along an X-ray Binary outburst

Blueshifted X-ray absorption lines (preferentially from Fe XXV and Fe XXVI present in the 6-8 keV range) indicating the presence of massive hot disk winds in Black Hole (BH) X-ray binaries (XrB) are most generally observed during the soft states. It has been recently suggested that the non-detection of such hot wind signatures in the hard states could be due to the thermal instability of the wind in the ionisation domain consistent with Fe XXV and Fe XXVI. Studying the wind thermal stability requires however a very good knowledge of the spectral shape of the ionizing Spectral Energy Distribution (SED). We discuss in this paper the expected evolution of the disk wind properties during an entire outburst by using the RXTE observations of GX 339-4 during its 2010-2011 outburst. While GX 339-4 never showed signatures of a hot wind in the X-rays, the dataset used is optimal to illustrate our purposes. We compute the corresponding stability curves of the wind using the SED obtained with the Jet-Emitting Disk model. We show that the disk wind can transit from stable to unstable states for Fe XXV and Fe XXVI ions on a day time scale. While the absence of wind absorption features in hard states could be explained by this instability, their presence in soft states seems to require changes of the wind properties (e.g. density) during the spectral transitions between hard and soft states. We propose that these changes could be partly due to the variation of heating power release at the accretion disk surface through irradiation by the central X-ray source. The evolution of the disk wind properties discussed in this paper could be confirmed through the daily monitoring of the spectral transition of a high-inclination BH XrB.

astro-ph.HE↗

arXiv2021

Potential origin of the state-dependent high-energy tail in the black hole microquasar Cygnus X-1 as seen with INTEGRAL

0.1-10 MeV observations of the black hole microquasar Cygnus X-1 have shown the presence of a spectral feature in the form of a power law in addition to the standard black body and Comptonization components observed by INTEGRAL. This so-called "high-energy tail" has recently been shown to be strong in its hard spectral state and interpreted as high-energy part of the emission from a compact jet. This result was, however, obtained from a data set dominated by hard state observations. In the soft state, only upper limits on the presence and hence the potential parameters of a high-energy tail could be derived. Using an extended data set we aim at obtaining better constraints on the properties of this spectral component in both states. We make use of data obtained from 15 years of observations with the INTEGRAL satellite. The data set is separated into the different states and we analyse stacked state-resolved spectra obtained from the X-ray monitors, the gamma-ray imager, and the gamma-ray spectrometer onboard. A high-energy component is detected in both states confirming its earlier detection in the hard state and its suspected presence in the soft state with INTEGRAL. We first characterize the high-energy tail components in the two states through a model-independent, phenomenological analysis. We then apply physical models based on hybrid Comptonization. The spectra are well modeled in all cases, with a similar goodness of the fits. While in the phenomenological approach the high-enery tail has similar indices in both states, the fits with the physical models seem to indicate different properties. We discuss the potential origins of the high-energy components in both states, and favor an interpretation where the part of the high-energy component is due to a compact jet in the hard state and hybrid Comptonization in either a magnetised or non-magnetised corona in the soft state.

astro-ph.HE↗

arXiv2021

New upper bounds for the forgotten index among bicyclic graphs

The forgotten topological index of a graph $G$, denoted by $F(G)$, is defined as the sum of weights $d(u)^{2}+d(v)^{2}$ over all edges $uv$ of $G$ , where $d(u)$ denotes the degree of a vertex $u$. In this paper, we give sharp upper bounds of the F-index (forgotten topological index) over bicyclic graphs, in terms of the order and maximum degree.

math.CO↗