A magnetic reconnection model for explaining the multi-wavelength emission of the microquasars Cyg X-1 and Cyg X-3

Recent studies have indicated that cosmic ray acceleration by a first-order Fermi process in magnetic reconnection current sheets can be efficient enough in the surrounds of compact sources. In this work, we discuss this acceleration mechanism operating in the core region of galactic black hole binaries (or microquasars) and show the conditions under which this can be more efficient than shock acceleration. In addition, we compare the corresponding acceleration rate with the relevant radiative loss rates obtaining the possible energy cut-off of the accelerated particles and also compute the expected spectral energy distribution (SED) for two sources of this class, namely Cygnus X-1 and Cygnus X-3, considering both leptonic and hadronic processes. The derived SEDs are comparable to the observed ones in the low and high energy ranges. Our results suggest that hadronic non-thermal emission due to photo-meson production may produce the very high energy gamma-rays in these microquasars.Comment: 17 pages and 7 figures. Accepted for publication in the Monthly Notices of the Royal Astronomical Society (MNRAS

Numerical models of neutrino and gamma-ray emission from magnetic reconnection in the core of radio-galaxies

Non-blazar radio-galaxies emitting in the very-high-energy (VHE; >100 GeV) regime offer a unique perspective for probing particle acceleration and emission processes in black hole (BH) accretion-jet systems. The misaligned nature of these sources indicates the presence of an emission component that could be of hadronic origin and located in the core region. Here we consider turbulent magnetic reconnection in the BH accretion flow of radio-galaxies as a potential mechanism for cosmic-ray (CR) acceleration and VHE emission. To investigate if this scenario is able to account for the observed VHE data, we combine three numerical techniques to self-consistently model the accretion flow environment and the propagation of CRs plus electromagnetic cascades within the accretion flow zone. Here we apply our approach to the radio-galaxy Centaurus A and find that injection of CRs consistent with magnetic reconnection power partially reproduce the VHE data, provided that the accretion flow makes no substantial contribution to the radio-GeV components. The associated neutrino emission peaks at $\sim10^{16}$ eV and is two orders of magnitude below the minimum IceCube flux.Comment: To be published in the Proceedings of International Conference on Black Holes as Cosmic Batteries: UHECRs and Multimessenger Astronomy - BHCB2018 12-15 September, 2018, Foz du Iguazu, Brasi

Gravitational waves : a 100-year tool applied to the dark energy problem

Recent observations from type Ia Supernovae and from cosmic microwave background (CMB) anisotropies have revealed that most of the matter of the Universe interacts in a repulsive manner, composing the so-called dark energy constituent of the Universe. Determining the properties of dark energy is one of the most important tasks of modern cosmology and this is the main motivation for this work. The analysis of cosmic gravitational waves (GW) represents, besides the CMB temperature and polarization anisotropies, an additional approach in the determination of parameters that may constrain the dark energy models and their consistence. In recent work, a generalized Chaplygin gas model was considered in a flat universe and the corresponding spectrum of gravitational waves was obtained. In the present work we have added a massless gas component to that model and the new spectrum has been compared to the previous one. The Chaplygin gas is also used to simulate a L-CDM model by means of a particular combination of parameters so that the Chaplygin gas and the L-CDM models can be easily distinguished in the theoretical scenarios here established. We find that the models are strongly degenerated in the range of frequencies studied. This degeneracy is in part expected since the models must converge to each other when some particular combinations of parameters are considered

The Gemini NICI Planet-Finding Campaign: The Frequency of Giant Planets Around Debris Disk Stars

We have completed a high-contrast direct imaging survey for giant planets around 57 debris disk stars as part of the Gemini NICI Planet-Finding Campaign. We achieved median H-band contrasts of 12.4 mag at 0.5" and 14.1 mag at 1" separation. Follow-up observations of the 66 candidates with projected separation < 500 AU show that all of them are background objects. To establish statistical constraints on the underlying giant planet population based on our imaging data, we have developed a new Bayesian formalism that incorporates (1) non-detections, (2) single-epoch candidates, (3) astrometric and (4) photometric information, and (5) the possibility of multiple planets per star to constrain the planet population. Our formalism allows us to include in our analysis the previously known Beta Pictoris and the HR 8799 planets. Our results show at 95% confidence that 5MJup planet beyond 80 AU, and 3MJup planet outside of 40 AU, based on hot-start evolutionary models. We model the population of directly-imaged planets as d^2N/dMda ~ m^alpha a^beta, where m is planet mass and a is orbital semi-major axis (with a maximum value of amax). We find that beta 1.7. Likewise, we find that beta < -0.8 and/or amax < 200 AU. If we ignore the Beta Pic and HR 8799 planets (should they belong to a rare and distinct group), we find that 3MJup planet beyond 10 AU, and beta < -0.8 and/or alpha < -1.5. Our Bayesian constraints are not strong enough to reveal any dependence of the planet frequency on stellar host mass. Studies of transition disks have suggested that about 20% of stars are undergoing planet formation; our non-detections at large separations show that planets with orbital separation > 40 AU and planet masses > 3 MJup do not carve the central holes in these disks.Comment: Accepted to ApJ on June 24, 2013. 67 pages, 17 figures, 12 table

The role of reconnection diffusion in the gravitational collapse of turbulent cloud cores

For a molecular cloud clump to form stars some\ud transport of magnetic flux is required from the\ud denser, inner regions to the outer regions of the\ud cloud, otherwise this can prevent the collapse. Fast\ud magnetic reconnection which takes place in the presence\ud of turbulence can induce a process of reconnection\ud diffusion (RD). Extending earlier numerical\ud studies of reconnection diffusion in cylindrical\ud clouds, we consider more realistic clouds with spherical\ud gravitational potentials and also account for the\ud effects of the gas self-gravity. We demonstrate that\ud within our setup RD is efficient. We have also identified\ud the conditions under which RD becomes strong\ud enough to make an initially subcritical cloud clump\ud supercritical and induce its collapse. Our results indicate\ud that the formation of a supercritical core is\ud regulated by a complex interplay between gravity,\ud self-gravity, the magnetic field strength and nearly\ud transonic and trans-Alfv´enic turbulence, confirming\ud that RD is able to remove magnetic flux from collapsing\ud clumps, but only a few of them become nearly\ud critical or supercritical, sub-Alfv´enic cores, which is\ud consistent with the observations. Besides, we have\ud found that the supercritical cores built up in our simulations\ud develop a predominantly helical magnetic\ud field geometry which is also consistent with observations.\ud Finally, we have evaluated the effective values\ud of the turbulent reconnection diffusion coefficient and found that they are much larger than the numerical\ud diffusion, especially for initially trans-Alfv´enic\ud clouds, ensuring that the detected magnetic flux removal\ud is due to to the action of the RD rather than\ud to numerical diffusivity.Resumo publicado no periódico: Revista Mexicana de Astronomía y Astrofísica. Serie de Conferencias, v. 44, p. 140-141, 2013

Magnetic field components analysis of the SCUPOL 850μm polarization data catalog

We present an extensive analysis of the 850 μm polarization maps of the SCUBA Polarimeter Legacy (SCUPOL) Catalogue produced by Matthews et al., focusing exclusively on the molecular clouds and star-forming regions. For the sufficiently sampled regions, we characterize the depolarization properties and the turbulent-to-mean magnetic field ratio of each region. Similar sets of parameters are calculated from two-dimensional synthetic maps of dustemission polarization produced with three-dimensional magnetohydrodynamics (MHD) numerical simulations scaled to the S106, OMC-2/3, W49, and DR21 molecular cloud polarization maps. For these specific regions, the turbulent MHD regimes retrieved from the simulations, as described by the turbulent Alfv´en and Sonic Mach numbers, are consistent within a factor one to two with the values of the same turbulent regimes estimated from the analysis of Zeeman measurements data provided by Crutcher. Constraints on the values of the inclination angle α of the mean magnetic field with respect to the line of sight are also given. The values obtained from the comparison of the simulations with the SCUPOL data are consistent with the estimates made by using two observational methods provided by other authors. Our main conclusion is that simple, ideal, isothermal, and non-self-gravitating MHD simulations are sufficient in order to describe the large-scale observed physical properties of the envelopes of this set of regions.FAPESP 2007/56302-4Leverhulme Trust Research Project Grant F/00 407/BNFAPESP 2006/50654-3CNPq 306598/2009-4European Research Council (ADG- 2011 ECOGAL)CNPq 300382/ 2008-1CAPES 3400-13-1FAPESP 2011/12909-

Prospect on intergalactic magnetic field measurements with gamma-ray instruments

Observing high-energy gamma-rays from Active Galactic Nuclei (AGN) offers a unique potential to probe extremely tiny values of the intergalactic magnetic field (IGMF), a long standing question of astrophysics, astroparticle physics and cosmology. Very high energy (VHE) photons from blazars propagating along the line of sight interact with the extragalactic background light (EBL) and produce e + e - pairs. Through inverse-Compton interaction, mainly on the cosmic microwave background (CMB), these pairs generate secondary GeV-TeV components accompanying the primary VHE signal. Such secondary components would be detected in the gamma-ray range as delayed ``pair echos'' for very weak IGMF (B < 10-16 G), while they should result in a spatially extended gamma-ray emission around the source for higher IGMF values (B > 10-16 G). Coordinated observations with space (i.e. Fermi) and ground-based gamma-ray instruments, such as the present Cherenkov experiments H.E.S.S., MAGIC and VERITAS, the future Cherenkov Telescope Array (CTA) Observatory, and the wide-field detectors such as HAWC and LHAASO, should allow to analyze and finally detect such echos, extended emission or pair halos, and to further characterize the IGM

Do dense molecular cores with broad emission spectra at |l| ≈ 5.4 ◦ , |b| ≈ 0.4 ◦ trace the Galactic bar? : a multi molecular line study from HOPS

We used NH3(1,1) data from the H2O Southern Galactic Plane Survey (HOPS) between −60◦ < l < −2.7◦ and 3.9◦ < l < 30◦ and |b| < 0.5◦ to identify dense molecular regions/clumps of the MilkyWay Galaxy that are likely to form high-mass stars. We identified ∼500 such clumps and in this paper we report on 14 of these clumps near the Central Molecular Zone that show broad emission spectral lines (with observed velocity widths between 19.8 and 47.6 km/s corresponding to intrinsic velocity widths between 7.1 and 25.2 km/s). We find that these clumps are grouped into three clusters of dense molecular cores centred at l ≈ 5.4◦,−5.4◦ and −10◦. We name them ‘Cluster-1’, ‘Cluster-2’ (also known as ‘Bania’s Clump 1’) and ‘Cluster-3’. We find that the same clumps exhibit broad emission spectra for other molecular lines - NH3(2,2), (3,3) and HC3N(3−2). The anti-symmetry of Cluster-1 and Cluster-2 in the l − b plane, and the large velocity dispersion of each clump in these two clusters suggest that clusters 1 and 2 may be associated with the Galactic bar potential x-1 orbits. Our assessments show that the clumps of these three clusters host hot gases and their emission line broadening are associated with shock heating. We find that Cluster-3 is likely to be undergoing high-mass star formation, as suggested by the presence of emission from H2O maser and radio recombination line (H69α) from HOPS

LLAMA Project

The project LLAMA, acronym of Long Latin\ud American Millimetre Array is very briefly described\ud in this paper. This project is a joint\ud scientific and technological undertaking of Argentina\ud and Brazil on the basis of an equal\ud investment share, whose mail goal is both to\ud install and to operate an observing facility capable\ud of exploring the Universe at millimetre\ud and sub/millimetre wavelengths. This facility\ud will be erected in the argentinean province of\ud Salta, in a site located at 4830m above sea\ud level.Resumo publicado no periódico: Revista Mexicana de Astronomía y Astrofísica. Serie de Conferencias, v. 44, p. 121, 2014

The Schenberg spherical gravitational wave detector: the first commissioning runs

Here we present a status report of the first spherical antenna project equipped with a set of parametric transducers for gravitational detection. The Mario Schenberg, as it is called, started its commissioning phase at the Physics Institute of the University of Sao Paulo, in September 2006, under the full support of FAPESP. We have been testing the three preliminary parametric transducer systems in order to prepare the detector for the next cryogenic run, when it will be calibrated. We are also developing sapphire oscillators that will replace the current ones thereby providing better performance. We also plan to install eight transducers in the near future, six of which are of the two-mode type and arranged according to the truncated icosahedron configuration. The other two, which will be placed close to the sphere equator, will be mechanically non-resonant. In doing so, we want to verify that if the Schenberg antenna can become a wideband gravitational wave detector through the use of an ultra-high sensitivity non-resonant transducer constructed using the recent achievements of nanotechnology