The jet-disk symbiosis without maximal jets: 1-D hydrodynamical jets revisited

In this work we discuss the recent criticism by Zdziarski of the maximal jet model derived in Falcke & Biermann (1995). We agree with Zdziarski that in general a jet's internal energy is not bounded by its rest-mass energy density. We describe the effects of the mistake on conclusions that have been made using the maximal jet model and show when a maximal jet is an appropriate assumption. The maximal jet model was used to derive a 1-D hydrodynamical model of jets in agnjet, a model that does multiwavelength fitting of quiescent/hard state X-ray binaries and low-luminosity active galactic nuclei. We correct algebraic mistakes made in the derivation of the 1-D Euler equation and relax the maximal jet assumption. We show that the corrections cause minor differences as long as the jet has a small opening angle and a small terminal Lorentz factor. We find that the major conclusion from the maximal jet model, the jet-disk symbiosis, can be generally applied to astrophysical jets. We also show that isothermal jets are required to match the flat radio spectra seen in low-luminosity X-ray binaries and active galactic nuclei, in agreement with other works.Comment: 7 pages, accepted by A&

P1_3 Relativistic Optics

The famous 1970s motion picture Star wars depicts the stars as stretched beams of light passing the view of the Millennium Falcon as it nears the speed of light. Investigations are undertaken into what an interstellar traveller would observe during their journey due to relativistic optics. It is concluded that the traveller would observe a central disc of aberrated radiation, whereby the frequencies are all blue-shifted; the Cosmic Microwave Background Radiation peaks in intensity at λ 530nm, and visible light from stars peaks in the X-ray range (0.20 – 0.35nm)

P1_5 Relativistic Optics Strikes Back

This paper expands upon previous work on relativistic optics by investigating the radiation pressure exerted on a vessel travelling at relativistic speeds toward a Sun-like star. It is concluded that a power of 1.3x1019W is required to keep the vessel moving at =1000 against the radiation pressure

P1_4 Super(conducting) Cars: Levitation

 This article considers using the phenomenon of the Meissner effect in superconductivity to levitate a vehicle above the ground. A model consisting of two parallel wires with opposing currents produces a magnetic field upon which the vehicle levitates. It was found that the power needed to keep the vehicle at 1.75m above the ground was 1.88TW, where 1.75m is the height which minimises the required power. This power is analogous to the overall electrical power consumption of the world, showing that this type of transportation is not feasible with our current technological achievements

P1_6 Golden Delivery

This article investigates the magnitude of the magnetic field gradient required to transport a gold nanoparticle of 1.9nm in diameter through the cardiovascular system. As an upper limit, the gradient calculated to overcome the blood flow velocity in the aorta was calculated by setting the force from the magnetic field gradient to be larger than or equal to the viscous drag from the blood. This yielded a magnetic field gradient of 1.3x1013Tm-1 which is far higher than what is available at present. The effects of such a high magnetic field gradient on the biological processes in the body must also be considered as haemoglobin, for example, contains iron

P1_1 The Fate of the Falling Feline

This article considers the potential energy of a falling cat and explores the maximum height from which the fall can occur without sustaining limb fractures, taking into account the drag due to air resistance. 2.3m was found to be the highest distance from which a cat can fall without fracturing all four of its legs. However, investigations into the typical number of limb fractures sustained indicated that cats are able to fall from greater heights. This is due to the assumptions made; cats have only one bone in their legs and their muscles do not contract upon landing

A jet-dominated model for a broad-band spectral energy distribution of the nearby low-luminosity active galactic nucleus in M94

We have compiled a new multiwavelength spectral energy distribution (SED) for the closest obscured low-ionization emission-line region active galactic nucleus (AGN), NGC 4736, also known as M94. The SED comprises mainly high-resolution (mostly sub-arcsecond, or, at the distance to M94, <23 pc from the nucleus) observations from the literature, archival data, as well as previously unpublished sub-millimetre data from the Plateau de Bure Interferometer (PdBI) and the Combined Array for Research in Millimeter-wave Astronomy, in conjunction with new electronic MultiElement Radio Interferometric Network (e-MERLIN) L-band (1.5 GHz) observations. Thanks to the e-MERLIN resolution and sensitivity, we resolve for the first time a double structure composed of two radio sources separated by ~1 arcsec, previously observed only at higher frequency. We explore this data set, which further includes non-simultaneous data from the Very Large Array, the Gemini telescope, the Hubble Space Telescope and the Chandra X-ray observatory, in terms of an outflow-dominated model. We compare our results with previous trends found for other AGN using the same model (NGC 4051, M81*, M87 and Sgr A*), as well as hard- and quiescent-state X-ray binaries. We find that the nuclear broad-band spectrum of M94 is consistent with a relativistic outflow of low inclination. The findings in this work add to the growing body of evidence that the physics of weakly accreting black holes scales with mass in a rather straightforward fashion.Comment: 18 pages, 7 figure

Revisiting the galactic X-ray binary MAXI J1631-479: Implications for high inclination and a massive black hole

X-ray spectroscopy of galactic black hole binaries serve as a powerful tool to gain an overall understanding of the system. Not only can the properties of the accretion disk be studied in detail, the fundamental properties of the black hole can also be inferred. The pursuit of these objectives also leads to an indirect validation of general relativity in strong field limit. In this work we carry out a comprehensive spectral analysis of the galactic X-ray binary MAXI J1631-479 using data from NICER and NuSTAR observatories. We trace the evolution of the accretion disk properties such as density, ionization, Fe abundance, etc as the source transitions from a disk dominated soft state to a power law dominated hard intermediate state. We provide strong constrains on the spin of the black hole and the inclination of the inner disk. We also use the soft state NICER observations to constrain the black hole mass using distance estimates from optical observations.Comment: 15 pages, 6 figures, 1 table. Accepted in the Astrophysical Journa