| 1. |
- Raga, Alejandro C., et al.
(författare)
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HIT REGIONS IN HYDROSTATIC BALANCE BETWEEN GAS PRESSURE, RADIATION PRESSURE AND GRAVITY
- 2015
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Ingår i: Revista mexicana de astronomía y astrofísica. - : Universidad Nacional Autonoma de Mexico. - 0185-1101. ; 51:1, s. 27-34
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Tidskriftsartikel (refereegranskat)abstract
- We study the solutions of a modified version of the isothermal Lane-Emden equation, which incorporates the effect of the (owtwards directed) radiation pressure resulting from photoionizations. These solutions are relevant for HIT regions around a cluster with over approximate to 500 O stars, which can photoionize gas out to approximate to 200 root 10 cm(-3)/n(0) pc (where n(0) is the central gas density), where the effects of the self-gravity and the radiation pressure become important. We find that the solutions have a transition from a "gravity dominated" regime (in which the solutions converge at large radii to the non-singular, isothermal sphere solution) to a "radiation pressure dominated" regime (in which the density diverges at a finite radius) for central HIT region densities above n(crit) = 100 cm(-3). We argue that the high central density, radiation pressure dominated solutions will not occur in most astrophysically relevant situations, because of the absence of a possible confining environment with a high enough pressure.
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| 2. |
- Rodriguez, L. F., et al.
(författare)
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Limits to the magnetic field in the planetary nebula NGC 246 from faraday rotation
- 2017
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Ingår i: Revista Mexicana de Astronomia y Astrofisica. - 0185-1101. ; 53:1, s. 45-52
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Tidskriftsartikel (refereegranskat)abstract
- We present radio continuum observations of the linearly polarized extragalactic source J0047-1150, whose line of sight traverses the galactic planetary nebula NGC 246. We determine the position angle of the electric vector at seven frequencies between 1.3 and 1.8 GHz, finding no evidence of Faraday rotation and setting a 4-sigma upper limit to the rotation measure of 9.6 rad m(-2), which implies an upper limit to the average line-of-sight component of the magnetic field in NGC 246 of 1.3 mu G. However, we show that the rotation measure across a source with a dipolar magnetic field morphology practically cancels out. Therefore, if the magnetic field has this morphology, the local values of the magnetic field in NGC 246 could be much larger and will not be evident in a Faraday rotation experiment.
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| 3. |
- Sacahui, J. R., et al.
(författare)
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Study of blazar activity in 10 year fermi-lat data and implications for TeV neutrino expectations
- 2021
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Ingår i: Revista mexicana de astronomía y astrofísica. - : Universidad Nacional Autónoma de México. - 0185-1101. ; 57:2, s. 251-268
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Tidskriftsartikel (refereegranskat)abstract
- Blazars are the most active extragalactic gamma-ray sources. They show sporadic bursts of activity, lasting from hours to months. In this work we present a 10-year analysis of a sample of bright sources detected by Fermi-LAT (100 MeV - 300 GeV). Using 2-week binned light curves (LC) we estimate the duty cycle (DC): fraction of time that the source spends in an active state. The objects show different DC values, with an average of 22.74% and 23.08% when considering (or not) the extragalactic background light (EBL). Additionally, we study the so-called "blazar sequence" trend for the sample of selected blazars in the ten years of data. This analysis constrains a possible counterpart of sub-PeV neutrino emission during the quiescent states, leaving open the possibility to explain the observed IceCube signal during the flaring states.
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