Grupo de Astrofísica de Rayos X

Instituto Argentino de Radioastronomía (IAR-CONICET-CICPBA-UNLP)

RESEARCH TOPICS

X-ray binaries

high-mass and low-mass X-ray binaries; catalogs; accretion/ejection; variability; spectral-timing; quasi-periodic oscillations; highly-absorbed systems; microquasars

Supernova remnants

thermal emission; chemical abundances; shocks; particle-acceleration; synchrotron emission; radio continuum and gamma-ray emission.

Binary Evolution

formation and evolution of high-mass X-ray binaries; connection to sgHMXBs and SFXTs; neutron-star kicks; binary compact-objects progenitors; gravitational wave coalesces.

UNDER CONSTRUCTION

WHAT'S NEW?

A NuSTAR view of SS433. Precessional evolution of the jet-disk system

Fogantini, F. A.; García, Federico; Combi, J.A.; Chaty, S.; Martí, J.; Luque Escamilla, P.L. (MNRAS 513, 4196, July 2022)

We studied the famous microquasar SS433 using 10 NuSTAR observations that span almost 2 precessional cycles of the system. Using a combination of a thermal leptonic jet and relativistic reflection from an accretion disk, we found that the precessional motion of the system successfully explains the modulation seen in several spectral parameters.

NuSTAR and XMM-Newton observations of the binary 4FGL J1405.1-6119. A Gamma-ray emitting microquasar?

Saavedra, Enzo A. ; Fogantini, Federico A. ; Escobar, Gastón J. ; Romero, Gustavo E. ; Combi, Jorge A.; Marcel, Estefania ( A&A - In press. )

We studied the binary 4FGL J1405.1-6119, a high-mass gamma-ray emitter, with NuSTAR and XMM-Newton. We use a parabolic and slightly relativistic lepto-hadronic jet scenario to explain the spectral energy distribution, suggesting that 4FGL J1405.1-6119 could be a supercritical microquasar similar to SS433.

Relativistic X-ray reflection and photoionized absorption in the neutron star low-mass X-ray binary GX 13+1

Saavedra, Enzo A.; García, Federico; Fogantini, Federico A.; Méndez, Mariano ; Combi, Jorge A.; Luque-Escamilla, Pedro L. ; Martí, Josep (MNRAS 522, 3367, July 2023)

We studied the neutron-star binary GX 13+1 with NuSTAR, finding its transition from normal to flaring states. Spectral analysis revealed evidence of relativistic reflection, constraining inner disc radius and magnetic field strength. A hot wind with photo-ionised absorption of Fe and Ni was detected. The study suggests high electron densities in the accretion disk, challenging previous models and impacting our understanding of GX 13+1's physical conditions.

vKompth: A variable Comptonisation model for low-frequency quasi-periodic oscillations in black-hole X-ray binaries
Candela Bellavita, Federico García, Mariano Méndez, Konstantinos Karpouzas (MNRAS 515, 2099, September 2022)

We introduce a dynamic Comptonization model, explaining low-frequency quasi-periodic oscillations in black hole LMXBs. Modeling the accretion disc as a multi-temperature blackbody, we compare it with a spherical blackbody model. Applying our model to BH LMXBs (e.g., MAXI J1438-630, GRS 1915 + 105) shows better fits and compatibility, affirming its ability to reproduce QPO characteristics.

The model is openly available on GitHub.

The evolving properties of the corona of GRS 1915+105: a spectral-timing perspective through variable-Comptonization modelling

García, Federico; Karpouzas, Konstantinos; Méndez, Mariano, Zhang, Liang; Zhang, Yuexin; Belloni, Tomaso; Altamirano, Diego (MNRAS 513, 4196, July 2022)

We explore the role of inverse Compton processes in shaping X-ray spectra in black hole low-mass X-ray binaries, focusing on GRS 1915+105. Our spectral-timing Comptonization model, applied to 398 observations, reveals consistent trends in corona properties over 15 years. Connecting with 15 GHz radio monitoring, we propose disc-corona interactions influencing the radio jet launch.