M87 black hole mass and spin estimate through the position of the jet boundary shape break

We propose a new method of estimating a mass of a super massive black hole residing in the center of an active galaxy. The active galaxy M87 offers a convenient test case for the method due to the existence of a large amount of observational data on the jet and ambient environment properties in the central area of the object. We suggest that the observed transition of a jet boundary shape from a parabolic to a conical form is associated with the flow transiting from the magnetically dominated regime to the energy equipartition between plasma bulk motion and magnetic field. By coupling the unique set of observations available for the jet kinematics, environment and boundary profile with our MHD modelling under assumption on the presence of a dynamically important magnetic field in the M87 jet, we estimate the central black hole mass and spin. The method leads us to believe that the M87 super massive black hole has a mass somewhat larger than typically accepted so far.Comment: 10 pages, 1 figure, 3 tables, accepted for publication by MNRA

Dynamics of broadband dispersive Alfven waves

The properties of amplitude modulated broadband Alfven waves is investigated. In particular, the dynamics of circularly polarized dispersive Alfven waves, governed by a derivative nonlinear Schroedinger equation, is analyzed using the Wigner formalism. The modulational instability of random phase dispersive pump Alfven waves is investigated, and it is shown that the spectral broadening gives rise to a new mode structure.Comment: 9 pages, 2 figures, to appear in Phys. Lett.

Discovery of a wandering radio jet base after a large X-ray flare in the blazar Markarian 421

We investigate the location of the radio jet bases ("radio cores") of blazars in radio images, and their stationarity by means of dense very long baseline interferometry (VLBI) observations. In order to measure the position of a radio core, we conducted 12 epoch astrometric observation of the blazar Markarian 421 with the VLBI Exploration of Radio Astrometry at 22 GHz immediately after a large X-ray flare, which occurred in the middle of 2011 September. For the first time, we find that the radio core is not stationary but rather changes its location toward 0.5 mas downstream. This angular scale corresponds to the de-projected length of a scale of $10^5$ Schwarzschild radii (Rs) at the distance of Markarian~421. This radio-core wandering may be a new type of manifestation associated with the phenomena of large X-ray flares.Comment: 6 pages, 4 figures, 1 table, has been published in ApJ Letter

Las guías de uso de medios sociales: regularización periodística y calidad informativa

This paper tackles a first diagnosis of the media bet through usage guides of social networking for journalists in the current outlook of prominence in the audience who decides what, how, when and where they consume information. The goal is focused on determining the reality and perception of the aforementioned guides in the local media of Seville and the role that the journalist plays concerning to concepts such as quality, believability and freedom of expression. We base on qualitative and quantitative techniques to carry out the document analysis, as well as the observation technique that provides the survey (selfadministered, Likerttype questionnaireinstrument). To sum it up, we observe immaturity in the development of these usage guides by Sevillian local media.Este artículo realiza un primer diagnóstico de la apuesta de los medios de comunicación por las guías de uso de redes sociales para periodistas en el panorama actual de protagonismo de la audiencia que decide qué, cómo, cuándo y dónde consume la información. El objetivo se centra en determinar la realidad y percepción de estas guías en los medios locales de Sevilla y el papel que desempeña el periodista en relación a conceptos como la calidad, la credibilidad y la libertad de expresión. Se apoya en técnicas cualitativas y cuantitativas para realizar el análisis documental, así como en la técnica de observación que proporciona la encuesta (instrumentocuestionario autoadministrado de tipo Likert). A modo de conclusión, se observa inmadurez en el desarrollo guías de uso por los medios locales sevillanos

A New Solution to the Plasma Starved Event Horizon Magnetosphere: Application to the Forked Jet in M87

© 2018 ESO. Reproduced with permission from Astronomy & Astrophysics. Content in the UH Research Archive is made available for personal research, educational, and non-commercial purposes only. Unless otherwise stated, all content is protected by copyright, and in the absence of an open license, permissions for further re-use should be sought from the publisher, the author, or other copyright holder.Very Long Baseline Interferometry observations at 86 GHz reveal an almost hollow jet in M87 with a forked morphology. The detailed analysis presented here indicates that the spectral luminosity of the central spine of the jet in M87 is a few percent of that of the surrounding hollow jet 200-400 μ as from the central black hole. Furthermore, recent jet models indicate that a hollow "tubular" jet can explain a wide range of plausible broadband spectra originating from jetted plasma located within ~30 μ as of the central black hole, including the 230 GHz correlated flux detected by the Event Horizon Telescope. Most importantly, these hollow jets from the inner accretion flow have an intrinsic power capable of energizing the global jet out to kiloparsec scales. Thus motivated, this paper considers new models of the event horizon magnetosphere (EHM) in low luminosity accretion systems. Contrary to some models, the spine is not an invisible powerful jet. It is an intrinsically weak jet. In the new EHM solution, the accreted poloidal magnetic flux is weak and the background photon field is weak. It is shown how this accretion scenario naturally results in the dissipation of the accreted poloidal magnetic flux in the EHM not the accumulation of poloidal flux required for a powerful jet. The new solution indicates less large scale poloidal magnetic flux (and jet power) in the EHM than in the surrounding accretion flow and cannot support significant EHM driven jets.Peer reviewe