The nonapeptide oxytocin is considered beneficial to mental health due to its anxiolytic, prosocial and antistress effects, but evidence for anxiogenic actions of oxytocin in humans has recently ...emerged. Using region-specific manipulations of the mouse oxytocin receptor (Oxtr) gene (Oxtr), we identified the lateral septum as the brain region mediating fear-enhancing effects of Oxtr. These effects emerge after social defeat and require Oxtr specifically coupled to the extracellular signal-regulated protein kinase pathway.
We explore the possibility that a single relativistic shock, where the gas dynamics is coupled with radiation, can fit the light curves of long GRBs. For this, we numerically solve the 1D ...relativistic radiation hydrodynamics equations with a single initial shock. We calculate light curves due to the evolution of this shock in terms of the velocity of the shock, the opacity of the gas, mass density and density of radiated energy. We explore how the variation of each of these parameters provides different features in the light curves. As examples, we include the fitting of two long GRBs.
Abstract
Understanding the Fe
II
emission from active galactic nuclei (AGNs) has been a grand challenge for many decades. The rewards from understanding the AGN spectra would be immense, involving ...both quasar classification schemes such as “Eigenvector 1” and tracing the chemical evolution of the cosmos. Recently, three large Fe
II
atomic data sets with radiative and electron collisional rates have become available. We have incorporated these into the spectral synthesis code
Cloudy
and examined predictions using a new generation of AGN spectral energy distribution (SED), which indicates that the ultraviolet (UV) emission can be quite different depending on the data set utilized. The Smyth et al. data set better reproduces the observed Fe
II
template of the I ZW 1 Seyfert galaxy in the UV and optical regions, and we adopt these data. We consider both thermal and microturbulent clouds and show that a microturbulence of ≈100 km s
−1
reproduces the observed shape and strength of the so-called Fe
II
“UV bump.” Comparing our predictions to the observed Fe
II
template, we derive a typical cloud density of 10
11
cm
−3
and photon flux of 10
20
cm
−2
s
−1
, and show that these largely reproduce the observed Fe
II
emission in the UV and optical. We calculate the
I
(Fe
II
)/
I
(Mg
II
) emission-line intensity ratio using our best-fitting model and obtain log(
I
(Fe
II
)/
I
(Mg
II
)) ∼ 0.7, suggesting many AGNs have a roughly solar Fe/Mg abundance ratio. Finally, we vary the Eddington ratio and SED shape as a step in understanding the Eigenvector 1 correlation.
We present the accretion of collisional dark matter on a supermassive black hole (SMBH) seed. The analysis is based on the numerical solution of the fully coupled system of Einstein–Euler equations ...for spherically symmetric flow, where the dark matter is modelled as a perfect fluid that obeys an ideal gas equation of state. As the black hole actually grows, the accretion rate of dark matter corresponds to the black hole apparent horizon growth rate. We analyse cases with infall velocity as high as 0.5c and an environment density of 100 M⊙ pc−3, which are rather extreme conditions. Being the radial flux the maximum accretion case, our results show that the accretion of an ideal gas, eventually collisional dark matter, does not contribute significantly to SMBH masses. This result favours models predicting SMBHs were formed already with supermasses. We show that despite the fact that we are solving the full general relativistic system, for the parameter space studied our results are surprisingly similar to those obtained using the Bondi formula, which somehow certifies its use as a good approximation of a fully evolving space–time with spherical symmetry at short scales at least for dark matter densities. Additionally, we study the density profile of the gas and find that the presence of SMBHs redistributes the gas near the event horizon with a cuspy profile, whereas beyond a small fraction of a parsec it is not cuspy anymore.
We study numerically the axisymmetric relativistic Bondi-Hoyle accretion of a supersonic ideal gas on to a fixed Schwarzschild background space-time described with horizon penetrating coordinates. We ...verify that a nearly stationary shock cone forms and that the properties of the shock cone are consistent with previous results in Newtonian gravity and former relativistic studies. The fact that the evolution of the gas is tracked on a spatial domain that contains a portion of the inner part of the black hole avoids the need to impose boundary conditions on a time-like boundary as done in the past. Thus, our approach contributes to the solution to the Bondi-Hoyle accretion problem at the length-scale of the accretor in the sense that the gas is genuinely entering the black hole. As an astrophysical application, we study for a set of particular physical parameters, the spectrum of the shock cone vibrations and their potential association with Quasi Periodic Oscillations sources.
Abstract
Future microcalorimeter X-ray observations will resolve spectral features in unmatched detail. Understanding of line formation processes in X-rays deserves much attention. The purpose of ...this paper is to discuss such processes in the presence of a photoionizing source. Line formation processes in one- and two-electron species are broadly categorized into four cases. Case A occurs when the Lyman line optical depths are very small and photoexcitation does not occur. Line photons escape the cloud without any scattering. Case B occurs when the Lyman line optical depths are large enough for photons to undergo multiple scatterings. Case C occurs when a broadband continuum source strikes an optically thin cloud. The Lyman lines are enhanced by induced radiative excitation of the atoms/ions by continuum photons, also known as continuum pumping. A fourth, less studied scenario, where the Case B spectrum is enhanced by continuum pumping, is called Case D. Here, we establish the mathematical foundation of Cases A, B, C, and D in an irradiated cloud with Cloudy. We also show the total X-ray emission spectrum for all four cases within the energy range 0.1–10 keV at the resolving power of XRISM around 6 keV. Additionally, we show that the combined effect of electron scattering and partial blockage of continuum pumping reduces the resonance line intensities. Such reduction increases with column density and can serve as an important tool to measure the column density/optical depth of the cloud.
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