Person: Luna, Gerardo Juan Manuel
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23/12/1976
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Luna
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Gerardo Juan Manuel
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Publication Discovery of the most luminous quasar of the last 9 Gyr(Astronomical Society of Australia, 2021) Onken, Christopher A.; Lai, Samuel; Wolf, Christian; Lucy, Adrian B.; Hon,Wei Jeat; Tisserand, Patrick; Sokolosk, Jennifer L.; Luna, Gerardo J. M.; Manick, Rajeev; Fan, Xiaohui; Bian, Fuyan; Pérez, Mariana Valeria; Luna, Gerardo Juan ManuelWe report the discovery of a bright (g = 14.5 mag (AB), K = 11.9 mag (Vega)) quasar at redshift z = 0.83 — the optically brightest (unbeamed) quasar at z > 0.4. SMSS J114447.77-430859.3, at a Galactic latitude of b = +18.1◦, was identified by its optical colours from the SkyMapper Southern Survey (SMSS) during a search for symbiotic binary stars. Optical and near-infrared spectroscopy reveals broad Mg II, Hβ, Hα, and Paβ emission lines, from which we measure a black hole mass of log10(MBH/M) = 9.4 ± 0.5. With its high luminosity, Lbol = (4.7 ± 1.0) × 1047 erg s−1 or Mi(z = 2) = −29.74 mag (AB), we estimate an Eddington ratio of ≈ 1.4. As the most luminous quasar known over the last ∼9 Gyr of cosmic history, having a luminosity 8× greater than 3C 273, the source offers a range of potential follow-up opportunities.Publication The Remarkable Spin-down and Ultrafast Outflows of the Highly Pulsed Supersoft Source of Nova Herculis 2021(IOP Publishing, 2021) Drake, Jeremy; Ness, Jan Uwe; Page, Kim L.; Beardmore, Andrew P.; Orio, Marina; Osborne, Julian P.; Mróz, Przemek; Starrfield, Sumner; Banerjee, Dipankar P. K.; Balman, Solen; Darnley, Matt J; Bhargava, Yash; Dewangan, Gulab C.; Singh, Kulinder Pal; Luna, Gerardo Juan ManuelNova Her 2021 (V1674 Her), which erupted on 2021 June 12, reached naked-eye brightness and has been detected from radio to γ-rays. An extremely fast optical decline of 2 magnitudes in 1.2 days and strong Ne lines imply a high-mass white dwarf. The optical pre-outburst detection of a 501.42 s oscillation suggests a magnetic white dwarf. This is the first time that an oscillation of this magnitude has been detected in a classical nova prior to outburst. We report X-ray outburst observations from Swift and Chandra that uniquely show (1) a very strong modulation of supersoft X-rays at a different period from reported optical periods, (2) strong pulse profile variations and the possible presence of period variations of the order of 0.1-0.3 s, and (3) rich grating spectra that vary with modulation phase and show P Cygni-type emission lines with two dominant blueshifted absorption components at ∼3000 and 9000 km s-1 indicating expansion velocities up to 11,000 km s-1. X-ray oscillations most likely arise from inhomogeneous photospheric emission related to the magnetic field. Period differences between reported pre- and post-outburst optical observations, if not due to other period drift mechanisms, suggest a large ejected mass for such a fast nova, in the range 2 10-5-2 10-4 M o˙. A difference between the period found in the Chandra data and a reported contemporaneous post-outburst optical period, as well as the presence of period drifts, could be due to weakly nonrigid photospheric rotation.Publication Transient and asymmetric dust structures in the TeV-bright nova RS Oph revealed by spectropolarimetry(EDP Sciences, 2023) Nikolov, Y.; Luna, Gerardo Juan Manuel; Stoyanov, K. A.; Borisov, G.; Mukai, K.; Sokoloski, J. L.; Avramova Boncheva, A.A long-standing question related to nova eruptions is how these eruptions might lead to dust formation, despite the ostensibly inhospitable environment for dust within the hot, irradiated ejecta. In the novae of systems such as the symbiotic binary RS Ophiuchi (RS Oph), ejecta from the white dwarf collide with pre-existing circumstellar material fed by the wind from the red-giant companion, offering a particularly clear view of some nova shocks and any associated dust production. In this work, we use the spectropolarimetric monitoring of the recurrent nova RS Oph starting two days after its eruption in August 2021 to show that: 1) dust was present in the RS Oph system as early as two days into the 2021 eruption; 2) the spatial distribution of this early dust was asymmetric, with components both aligned with and perpendicular to the orbital plane of the binary; 3) between two and nine days after the start of the eruption, this early dust was gradually destroyed; and 4) dust was again created, aligned roughly with the orbital plane of the binary more than 80 days after the start of the outburst, most likely as a result of shocks that arose as the ejecta interacted with circumbinary material concentrated in the orbital plane. The modeling of X-rays and very-high-energy (GeV and TeV) emission from RS Oph days to months into the 2021 eruption suggests that collisions between the ejecta and the circumbinary material may have led to shock formation in two distinct regions: the polar regions perpendicular to the orbital plane, where collimated outflows have been observed after prior eruptions, and a circumbinary torus in the orbital plane. The observations described here indicate that dust formed in approximately the same two regions, supporting the connection between shocks and dust in novae and revealing a very early onset of asymmetry. The spectropolarimetric signatures of RS Oph in the first week into the 2021 outburst indicate: 1) polarized flux across the Hα emission line and 2) the position angle orientation relative to the radio axis is similar to what is seen from the spectropolarimetric signatures of active galactic nuclei (AGNs)