M. Armas Padilla
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View article: A multiwavelength view of the outflowing short-period X-ray binary UW CrB
A multiwavelength view of the outflowing short-period X-ray binary UW CrB Open
Previous work detected transient ultraviolet outflow features for the short-period (P$_{\mathrm{orb}}{\approx }111$ min), low-mass X-ray binary (LMXB) UW CrB, suggesting the presence of a disc wind in the system. However, because of the tr…
View article: The orbital period and inclination of the neutron star X-ray transient MAXI J1807+132
The orbital period and inclination of the neutron star X-ray transient MAXI J1807+132 Open
The neutron star X-ray transient MAXI J1807+132 underwent outbursts in 2017, 2019, and 2023. We conducted an R -band time series photometry campaign using the Isaac Newton Telescope during the 2022 quiescent state. We detected a periodic v…
View article: The orbital period and inclination of the neutron star X-ray transient MAXI J1807+132
The orbital period and inclination of the neutron star X-ray transient MAXI J1807+132 Open
The neutron star X-ray transient MAXI J1807+132 has undergone outbursts in 2017, 2019, and 2023. We conducted an $R$-band time series photometry campaign using the Isaac Newton Telescope during the 2022 quiescent state. We detected a perio…
View article: XRISM reveals a variable, multi-phase outflow-inflow structure during the X-ray obscured 2024 outburst of the black hole transient V4641 Sgr
XRISM reveals a variable, multi-phase outflow-inflow structure during the X-ray obscured 2024 outburst of the black hole transient V4641 Sgr Open
We report the results of a simultaneous X-ray and optical spectroscopy campaign on the Galactic black hole X-ray binary V4641 Sgr, carried out with XRISM and the Seimei telescope during a low-luminosity phase towards the end of its 2024 ou…
View article: A Multi-wavelength Characterization of the 2023 Outburst of MAXI J1807+132: Manifestations of Disk Instability and Jet Emission
A Multi-wavelength Characterization of the 2023 Outburst of MAXI J1807+132: Manifestations of Disk Instability and Jet Emission Open
Several phenomenological aspects of low-luminosity neutron star transients, such as atolls, remain poorly understood. One such source, MAXI J1807+132, entered its latest outburst in 2023 July. To thoroughly characterize this outburst, we c…
View article: Radio Continuum Studies of Ultracompact and Short Orbital Period X-Ray Binaries
Radio Continuum Studies of Ultracompact and Short Orbital Period X-Ray Binaries Open
We present the radio continuum counterparts to the enigmatic ultracompact X-ray binaries (UCXBs): a black hole or neutron star accreting from a hydrogen-deficient white dwarf donor star with short orbital periods (<80 minutes). For the sam…
View article: Radio Continuum Studies of Ultra-Compact and Short Orbital Period X-Ray Binaries
Radio Continuum Studies of Ultra-Compact and Short Orbital Period X-Ray Binaries Open
We present the radio continuum counterparts to the enigmatic ultra-compact X-ray binaries (UCXBs); a black hole or neutron star accreting from a hydrogen-deficient white dwarf donor star, with short orbital periods ($<$ 80 minutes). For th…
View article: The nature of the X-ray binary transient MAXI J1834–021: Clues from its first observed outburst
The nature of the X-ray binary transient MAXI J1834–021: Clues from its first observed outburst Open
MAXI J1834–021 is a new X-ray transient discovered in February 2023. We analysed the spectral and timing properties of MAXI J1834–021 using NICER , NuSTAR and Swift data collected between March and October 2023. The light curve showed a ma…
View article: On the nature of the X-ray binary transient MAXI J1834-021: clues from its first observed outburst
On the nature of the X-ray binary transient MAXI J1834-021: clues from its first observed outburst Open
MAXI J1834-021 is a new X-ray transient that was discovered in February 2023. We analysed the spectral and timing properties of MAXI J1834-021 using NICER, NuStar and Swift data collected between March and October 2023. The light curve sho…
View article: Revisiting the fundamental parameters for the black hole X-ray transient Swift J1753.5-0127
Revisiting the fundamental parameters for the black hole X-ray transient Swift J1753.5-0127 Open
We present time-resolved Gran Telescopio Canarias optical spectroscopy and William Herschel Telescope $i$-band photometry of the X-ray transient SWIFT J1753.5-0127 in quiescence. The $i$-band light curve is dominated by flickering with an …
View article: Revisiting the fundamental parameters for the black hole X-ray transient Swift J1753.5–0127
Revisiting the fundamental parameters for the black hole X-ray transient Swift J1753.5–0127 Open
We present time-resolved Gran Telescopio Canarias optical spectroscopy and William Herschel Telescope i -band photometry of the X-ray transient SWIFT J1753.5–0127 in quiescence. The i -band light curve is dominated by flickering with an am…
View article: State-dependent signatures of jets and winds in the optical and infrared spectrum of the black hole transient GX 339$-$4
State-dependent signatures of jets and winds in the optical and infrared spectrum of the black hole transient GX 339$-$4 Open
GX 339$-$4 is one of the prototypical black hole X-ray transients, exhibiting recurrent outbursts that allow detailed studies of black hole accretion and ejection phenomena. In this work we present four epochs of optical and near-infrared …
View article: State-dependent signatures of jets and winds in the optical and infrared spectrum of the black hole transient GX 339–4
State-dependent signatures of jets and winds in the optical and infrared spectrum of the black hole transient GX 339–4 Open
GX 339–4 is one of the prototypical black hole X-ray transients, exhibiting recurrent outbursts that allow detailed studies of black hole accretion and ejection phenomena. In this work we present four epochs of optical and near-infrared sp…
View article: Detection of Extended X-Ray Emission around the PeVatron Microquasar V4641 Sgr with XRISM
Detection of Extended X-Ray Emission around the PeVatron Microquasar V4641 Sgr with XRISM Open
A recent report on the detection of very-high-energy gamma rays from V4641 Sagittarii (V4641 Sgr) up to ≈0.8 PeV has made it the second confirmed “PeVatron” microquasar. Here we report on the observation of V4641 Sgr with X-Ray Imaging and…
View article: Assessing the Spatio-Temporal Dynamics of Ecuadorian Andean Peatlands Using Multispectral Indicators and Environmental Modelling
Assessing the Spatio-Temporal Dynamics of Ecuadorian Andean Peatlands Using Multispectral Indicators and Environmental Modelling Open
View article: Evolution of the Accretion Disk and Corona during the Outburst of the Neutron Star Transient MAXI J1807+132
Evolution of the Accretion Disk and Corona during the Outburst of the Neutron Star Transient MAXI J1807+132 Open
Low-mass X-ray binaries with a neutron star as the primary object show a complex array of phenomenology during outbursts. The observed variability in X-ray emission primarily arises from changes in the innermost regions of the accretion di…
View article: Detection of extended X-ray emission around the PeVatron microquasar V4641 Sgr with XRISM
Detection of extended X-ray emission around the PeVatron microquasar V4641 Sgr with XRISM Open
A recent report on the detection of very-high-energy gamma rays from V4641 Sagittarii (V4641 Sgr) up to ~0.8 peta-electronvolt has made it the second confirmed "PeVatron" microquasar. Here we report on the observation of V4641 Sgr with X-R…
View article: Dynamical confirmation of a black hole in the X-ray transient Swift J1727.8−1613
Dynamical confirmation of a black hole in the X-ray transient Swift J1727.8−1613 Open
The X-ray transient Swift J1727.8−1613 ended its 10-month discovery outburst in June of 2024, when it reached an optical brightness comparable to pre-discovery magnitudes. With the aim of performing a dynamical study, we launched an optica…
View article: X-ray observations of the very-faint X-ray transient XMMSL1 J171900.4--353217: A new candidate neutron star low-mass X-ray binary
X-ray observations of the very-faint X-ray transient XMMSL1 J171900.4--353217: A new candidate neutron star low-mass X-ray binary Open
XMMSL1 J171900.4-353217 is a very-faint X-ray transient that was discovered in 2010 March when it exhibited an outburst. We report on 7 observations, obtained with the X-Ray Telescope (XRT) aboard the Neil Gehrels {\it{Swift}} Observatory …
View article: Dynamical confirmation of a black hole in the X-ray transient Swift J1727.8-1613
Dynamical confirmation of a black hole in the X-ray transient Swift J1727.8-1613 Open
The X-ray transient Swift J1727.8-1613 ended its 10-month discovery outburst on June of 2024, when it reached an optical brightness comparable to pre-discovery magnitudes. With the aim of performing a dynamical study, we launched an optica…
View article: Soft-state optical spectroscopy of the black hole MAXI J1305-704
Soft-state optical spectroscopy of the black hole MAXI J1305-704 Open
The X-ray dipper MAXI J1305-704 is a dynamically confirmed black hole (BH) X-ray binary discovered a decade ago. While its only outburst has been studied in detail in X-rays, follow-up at other wavelengths has been scarce. We report here t…
View article: The omnipresent flux-dependent optical dips of the black hole transient Swift J1357.2−0933
The omnipresent flux-dependent optical dips of the black hole transient Swift J1357.2−0933 Open
Swift J1357.2-0933 is a black hole transient that is of particular interest due to the optical recurrent dips found during its first two outbursts (in 2011 and 2017), which lack an obvious X-ray equivalent. We present a study based on fast…
View article: Evidence for inflows and outflows in the nearby black hole transient Swift J1727.8−162
Evidence for inflows and outflows in the nearby black hole transient Swift J1727.8−162 Open
We present 20 epochs of optical spectroscopy obtained with the GTC-10.4m telescope across the bright discovery outburst of the black hole candidate Swift J1727.8−162. The spectra cover the main accretion states and are characterised by the…
View article: Evidence for inflows and outflows in the nearby black hole transient Swift J1727.8-162
Evidence for inflows and outflows in the nearby black hole transient Swift J1727.8-162 Open
We present 20 epochs of optical spectroscopy obtained with the GTC-10.4m telescope across the bright discovery outburst of the black hole candidate Swift J1727.8-162. The spectra cover the main accretion states and are characterised by the…
View article: Fast infrared winds during the radio-loud and X-ray obscured stages of the black hole transient GRS 1915+105
Fast infrared winds during the radio-loud and X-ray obscured stages of the black hole transient GRS 1915+105 Open
The black hole transient GRS 1915+105 entered a new phase of activity in 2018, generally characterised by low X-ray and radio fluxes. This phase has only been interrupted by episodes of strong and variable radio emission, where high levels…
View article: Fast infrared winds during the radio-loud and X-ray obscured stages of the black hole transient GRS 1915+105
Fast infrared winds during the radio-loud and X-ray obscured stages of the black hole transient GRS 1915+105 Open
The black hole transient GRS 1915+105 entered a new phase of activity in 2018, generally characterised by low X-ray and radio fluxes. This phase has been only interrupted by episodes of strong and variable radio emission, during which high…
View article: Evidence for a black hole in the historical X-ray transient A 1524-61 (= KY TrA)
Evidence for a black hole in the historical X-ray transient A 1524-61 (= KY TrA) Open
We present Very Large Telescope spectroscopy, high-resolution imaging, and time-resolved photometry of KY TrA, the optical counterpart to the X-ray binary A 1524-61. We perform a refined astrometry of the field, yielding improved coordinat…
View article: Evidence for a black hole in the historical X-ray transient A 1524-61 (=KY TrA)
Evidence for a black hole in the historical X-ray transient A 1524-61 (=KY TrA) Open
We present VLT spectroscopy, high-resolution imaging and time-resolved photometry of KY TrA, the optical counterpart to the X-ray binary A 1524-61. We perform a refined astrometry of the field, yielding improved coordinates for KY TrA and …
View article: The omnipresent flux-dependent optical dips of the black hole transient Swift J1357.2-0933
The omnipresent flux-dependent optical dips of the black hole transient Swift J1357.2-0933 Open
Swift J1357.2-0933 is a black hole transient of particular interest due to the optical, recurrent dips found during its first two outbursts (in 2011 and 2017), with no obvious X-ray equivalent. We present fast optical photometry during its…
View article: An infrared FWHM–<i>K</i><sub>2</sub> correlation to uncover highly reddened quiescent black holes
An infrared FWHM–<i>K</i><sub>2</sub> correlation to uncover highly reddened quiescent black holes Open
Among the sample of Galactic transient X-ray binaries (SXTs) discovered to date, about 70 have been proposed as likely candidates to host a black hole. Yet, only 19 have been dynamically confirmed. Such a reliable confirmation requires pha…