Simultaneous Heavy Ion Dissociation at Ultrarelativistic Energies

We study the simultaneous dissociation of heavy ultrarelativistic nuclei followed by the forward-backward neutron emission in peripheral collisions at colliders. The main contribution to this particular heavy-ion dissociation process, which can be used as a beam luminosity monitor, is expected to be due to the electromagnetic interaction. The Weizsacker-Williams method is extended to the case of simultaneous excitation of collision partners which is simulated by the RELDIS code. A contribution to the dissociation cross section due to grazing nuclear interactions is estimated within the abrasion model and found to be relatively small.Comment: Talk given at Bologna 2000 Conference - Structure of the Nucleus at the Dawn of the Century, May 29 - June 3, 2000, 4 pages, 2 figure

Constraining ΩM\Omega_M and Dark Energy with Gamma-Ray Bursts

An $E_{\gamma,{\rm jet}}\propto {E'_p}^{1.5}$ relationship with a small scatter for current $\gamma$-ray burst (GRB) data was recently reported, where $E_{\gamma,{\rm jet}}$ is the beaming-corrected $\gamma$-ray energy and $E'_p$ is the $\nu F_\nu$ peak energy in the local observer frame. By considering this relationship for a sample of 12 GRBs with known redshift, peak energy, and break time of afterglow light curves, we constrain the mass density of the universe and the nature of dark energy. We find that the mass density $\Omega_M=0.35\pm^{0.15}_{0.15}$ (at the $1\sigma$ confident level) for a flat universe with a cosmological constant, and the $w$ parameter of an assumed static dark-energy equation of state $w=-0.84\pm^{0.57}_{0.83}$ ($1\sigma$). Our results are consistent with those from type Ia supernovae. A larger sample established by the upcoming {\em Swift} satellite is expected to provide further constraints.Comment: 8 pages including 4 figures, to appear in ApJ Letters, typos correcte

GRB Energetics and the GRB Hubble Diagram: Promises and Limitations

We present a complete sample of 29 GRBs for which it has been possible to determine temporal breaks (or limits) from their afterglow light curves. We interpret these breaks within the framework of the uniform conical jet model, incorporating realistic estimates of the ambient density and propagating error estimates on the measured quantities. In agreement with our previous analysis of a smaller sample, the derived jet opening angles of those 16 bursts with redshifts result in a narrow clustering of geometrically-corrected gamma-ray energies about E_gamma = 1.33e51 erg; the burst-to-burst variance about this value is a factor of 2.2. Despite this rather small scatter, we demonstrate in a series of GRB Hubble diagrams, that the current sample cannot place meaningful constraints upon the fundamental parameters of the Universe. Indeed for GRBs to ever be useful in cosmographic measurements we argue the necessity of two directions. First, GRB Hubble diagrams should be based upon fundamental physical quantities such as energy, rather than empirically-derived and physically ill-understood distance indicators. Second, a more homogeneous set should be constructed by culling sub-classes from the larger sample. These sub-classes, though now first recognizable by deviant energies, ultimately must be identifiable by properties other than those directly related to energy. We identify a new sub-class of GRBs (``f-GRBs'') which appear both underluminous by factors of at least 10 and exhibit a rapid fading at early times. About 10-20% of observed long-duration bursts appear to be f-GRBs.Comment: Accepted to the Astrophysical Journal (20 May 2003). 19 pages, 3 Postscript figure

A search for counterparts to massive X-ray binaries using photometric catalogues

(abridged) INTEGRAL has discovered large numbers of new hard X-ray sources, many of which are believed to be high mass X-ray binaries. However, for a significant fraction, their counterparts remain unidentified. We explore the use of photometric catalogues to find optical counterparts to high mass X-ray binaries. Candidates were selected from 2MASS photometry by means of a reddening free Q parameter. Sufficiently bright candidates were spectroscopically observed. Many of the candidates selected turned out to be moderately reddened late A or early F stars, but our method is able to identify the counterpart to IGR J16207-5129, confirmed by a Chandra localisation. We classify this object as a B0 supergiant. In the field of AX J1820.5-1434, we find a mid or early B-type star, but we cannot confirm it as the counterpart. For AX J1700.2-4220, we do not find any suitable candidate within the ASCA error circle. We classify HD 153295, a marginal candidate to be the counterpart, as B0.5IVe, and find a distance compatible with membership in Sco OB1. We derive a spectral type B0IIIe for HD100199, previously identified as the counterpart to IGR J11305-6256. In the case of IGR J17091-3624, the object associated with a variable radio source in the field is a late F star. The procedure used is able to correctly identify OB stars and, in about one third of the cases, may lead to the localisation of the correct counterpart. However, the majority of INTEGRAL error circles do not contain any suitable optically visible counterpart. Deep infrared searches are going to be necessary in order to locate the counterparts to these sources.Comment: 10 pages, 6 figures; Accepted for publication in Astronomy & Astrophysics (Sept 25th

On the nature of the hard X-ray sources SWIFTJ1907.3-2050, IGRJ12123-5802 and IGRJ19552+0044

The INTEGRAL and Swift hard X-ray surveys have identified a large number of new sources, among which many are proposed as Cataclysmic Variables (CVs). Here we present the first detailed study of three X-ray selected CVs, Swift J1907.3-2050, IGRJ12123-5802, and IGRJ19552+0044 based on XMM-Newton, Suzaku, Swift observations and ground based optical and archival nIR/IR data. Swift J1907.3-2050 is highly variable from hours to months-years at all wavelengths. No coherent X-ray pulses are detected but rather transient features. The X-ray spectrum reveals a multi-temperature optically thin plasma absorbed by complex neutral material and a soft black body component arising from a small area. These characteristics are remarkably similar to those observed in magnetic CVs. A supra-solar abundance of nitrogen could arise from nuclear processed material from the donor star. Swift J1907.3-2050 could be a peculiar magnetic CV with the second longest (20.82 h) binary period. IGRJ12123-5802 is variable in the X-rays on a timescale of ~7.6 h. No coherent pulsations are detected, but its spectral characteristics suggest that it could be a magnetic CV of the Intermediate Polar (IP) type. IGRJ19552+0044 shows two X-ray periods, 1.38 h and 1.69 h and a X-ray spectrum characterized by a multi-temperature plasma with little absorption.We derive a low accretion rate, consistent with a CV below the orbital period gap. Its peculiar nIR/IR spectrum suggests a contribution from cyclotron emission. It could either be a pre-polar or an IP with the lowest degree of asynchronism.Comment: Accepted for publication in MNRAS. 14 pages, 11 figures, 5 table

IGR J17544-2619: A new supergiant fast X-ray transient revealed by optical/infrared observations

One of the most recent discoveries of the INTEGRAL observatory is the existence of a previously unknown population of X-ray sources in the inner arms of the Galaxy. IGR J17544-2619, IGR J16465-4507 and XTE J1739-302 are among these sources. Although the nature of these systems is still unexplained, the investigations of the optical/NIR counterparts of the two last sources, combined with high energy data, have provided evidence of them being highly absorbed high mass X-ray binaries with blue supergiant secondaries and displaying fast X-ray transient behaviour. In this work we present our optical/NIR observations of IGR J17544-2619, aimed at identifying and characterizing its counterpart. We show that the source is a high mass X-ray binary at a distance of 2-4 kpc with a strongly absorbed O9Ib secondary, and discuss the nature of the system.Comment: 7 pages, 4 figures. Accepted for publication in A&

The intriguing nature of the high energy gamma ray source XSSJ12270-4859

The nature of the hard X-ray source XSSJ12270-4859 is still unclear though it was claimed to be a magnetic Cataclysmic Variable. We here present a broad-band X-ray and gamma ray study based on a recent XMM-Newton observation and archival INTEGRAL and RXTE data. From the Fermi/LAT 1-year point source catalogue, we tentatively associate XSSJ12270-4859 with 1FGLJ1227.9-4852, a source of high energy gamma rays with emission up to 10GeV. We complement the study with UV photometry from XMM-Newton and ground-based optical and near-IR photometry. The X-ray emission is highly variable showing flares and intensity dips. The X-ray flares consist of flare-dip pairs. Flares are also detected in the UV range but not the dips. Aperiodic dipping behaviour is also observed during X-ray quiescence but not in the UV. The 0.2-100keV spectrum is featureless and described by a power law model with Gamma=1.7. The 100MeV-10GeV spectrum is instead represented by a power law index of 2.45. The luminosity ratio between 0.1-100GeV and 0.2--100keV is ~0.8, hence the GeV emission is a significant component of the total energy output. Furthermore, the X-ray spectrum does not greatly change during flares, quiescence and the dips seen in quiescence but it hardens during the post-flare dips. Optical photometry reveals a period of 4.32hr likely related to the binary orbit. Near-IR, possibly ellipsoidal, variations are detected. Large amplitude variability on shorter (tens mins) timescales are found to be non-periodic. The observed variability at all wavelengths and the spectral characteristics strongly favour a low-mass atypical low-luminosity X-ray binary and are against a Cataclysmic Variable nature. The association with a Fermi/LAT high energy gamma ray source further strengths this interpretation.Comment: 12 pages, 11 figures, 3 tables; Accepted for publication in Astronomy & Astrophysics Main Journ

Variable broad lines and outflow in the weak blazar PBC J2333.9-2343

Indexación: Scopus; Scielo.Funding text #1 1Instituto de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Gran Bretaña 1111, Playa Ancha, Valparaíso, Chile 2INAF – Istituto di Astrofisica e Planetologia Spaziali di Roma (IAPS-INAF), Via del Fosso del Cavaliere 100, I-00133 Roma, Italy 3INAF – Osservatorio Astronomico di Roma, via Frascati 33, I-00078 Monte Porzio Catone, Italy 4Excellence Cluster Universe, Technische Universität München, Boltzmannstr. 2, D-85748, Garching, Germany 5European Southern Observatory, Karl-Schwarzschild-Str 2, D-85748 Garching b. München, Germany 6Instituto Nacional de Astrofísica, Óptica y Electrónica, Apartado Postal 51-216, 72000 Puebla, México 7Argelander Institute for Astronomy, University of Bonn, Auf dem Hügel 71, D-53121 Bonn, Germany 8International Max Planck Research School of Astronomy and Astrophysics at the Universities of Bonn and Cologne, Auf dem Hügel 69, D-53121 Bonn, Germany 9INAF – Osservatorio di Astrofisica e Scienza dello Spazio, via Gobetti 93/3, I-40129 Bo...View all Funding text #2 We acknowledge the referee, M. Villar Martín, for her comments and suggestions that helped to improve the paper. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester, the NASA/IPAC extragalactic database (NED), the STARLIGHT code, and the IRAF software. Based upon observations carried out at the Observatorio Astronómico Nacional on the Sierra San Pedro Mártir (OAN-SPM), Baja California, México. LHG and FP acknowledge the ASI/INAF agreement number 2013-023-R1, LHG partial support from FONDECYT through grant 3170527, MP from ESSTI under the MoST, and from MINECO through research projects AYA2013-42227-P and AYA2016-76682-C3-1-P (AEI/FEDER, UE), LHG and SC from the Spanish grant AYA2013-42227-P, VC by CONACyT research grant 280789, EFJA from the Collaborative Research Center 956, subproject A1, funded by DFG, and GV from the DFG Cluster of Excellence ‘Origin and Structure of the Universe’ (www.universe-cluster.de).PBC J2333.9-2343 is a peculiar active nucleus with two giant radio lobes and a weak blazarlike nucleus at their centre. In this work we show new optical, ultraviolet (UV), and X-ray data taken from the San Pedro Mártir telescope, the New Technology Telescope, NTT/EFOSC2, and the Swift/XRT satellite. The source is highly variable at all frequencies, in particular the strongest variations are found in the broad Hα component with a flux increase of 61±4 per cent between 2009 and 2016, following the X-ray flux increase of 62±6 per cent between 2010 and 2016. We also detected a broad Hβ component in 2016, making the optical classification change from type 1.9 to type 1.8 in 1 yr. We have also detected a broad component of the [OIII]λ5007 line, which is blue-shifted and of high velocity, suggesting an origin from a highly disturbed medium, possibly an outflow. The line flux variability and broad widths are indicative of a jet that is, at least in part, responsible for the ionization of the broad line region (BLR) and narrow line region (NLR). © 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.https://academic.oup.com/mnras/article-abstract/478/4/4634/4999938?redirectedFrom=fulltex

Potent Antioxidant and Anti-Tyrosinase Activity of Butein and Homobutein Probed by Molecular Kinetic and Mechanistic Studies †

Butein (BU) and homobutein (HB) are bioactive polyhydroxylated chalcones widespread in dietary plants, whose antioxidant properties require mechanistic definition. They were investigated by inhibited autoxidation kinetic studies of methyl linoleate in TritonTM X-100 micelles at pH 7.4, 37 °C. Butein had kinh = (3.0 ± 0.9) × 104 M−1s−1 showing a chain-breaking mechanism with higher antioxidant activity than reference α-tocopherol (kinh = (2.2 ± 0.6) × 104 M−1s−1), particularly concerning the stoichiometry or peroxyl radical trapping n = 3.7 ± 1.1 vs. 2.0 for tocopherol. Homobutein had kinh = (2.8 ± 0.9) × 103 M−1s−1, pairing the relative BDEOH measured by radical equilibration EPR as 78.4 ± 0.2 kcal/mol for BU and estimated as 82.6 kcal/mol for HB. The inhibition of mushroom tyrosinase (mTYR) by HB and BU was also investigated. BU gives a reversible uncompetitive inhibition of monophenolase reaction with KI′ = 9.95 ± 2.69 μM and mixed-type diphenolase inhibition with KI = 3.30 ± 0.75 μM and KI′ = 18.75 ± 5.15 μM, while HB was nearly competitive toward both mono- and diphenolase with respective KI of 2.76 ± 0.70 μM and 2.50 ± 1.56 μM. IC50 values (monophenolase/diphenolase at 1 mM substrate) were 10.88 ± 2.19 μM/15.20 ± 1.25 μM, 14.78 ± 1.05 μM/12.36 ± 2.00 μM, and 33.14 ± 5.03 μM/18.27 ± 3.42 μM, respectively, for BU, HB, and reference kojic acid. Molecular docking studies confirmed the mechanism. Results indicate very potent antioxidant activity for BU and potent anti-tyrosinase activity for both chalcones, which is discussed in relation to bioactivity toward protection from skin disorders and food oxidative spoilage