Radio emission of SN1993J. The complete picture: II. Simultaneous fit of expansion and radio light curves

We report on a simultaneous modelling of the expansion and radio light curves of SN1993J. We have developed a simulation code capable of generating synthetic expansion and radio light curves of supernovae by taking into consideration the evolution of the expanding shock, magnetic fields, and relativistic electrons, as well as the finite sensitivity of the interferometric arrays used in the observations. Our software successfully fits all the available radio data of SN 1993J with an standard emission model for supernovae extended with some physical considerations, as an evolution in the opacity of the ejecta material, a radial drop of the magnetic fields inside the radiating region, and a changing radial density profile of the circumstellar medium beyond day 3100 after explosion.Comment: 12 pages, 12 figures, accepted for publication in A&

Multi-wavelength differential astrometry of the S5 polar cap sample

We report on the status of our S5 polar cap astrometry program. Since 1997 we have observed all the 13 radio sources of the complete S5 polar cap sample at the wavelengths of 3.6 cm, 2 cm and 7 mm. Images of the radio sources at 3.6 and 2 cm have already been published reporting morphological changes. Preliminary astrometric analyses have been carried out at three frequencies with precisions in the relative position determination ranging from 80 to 20 microarcseconds. We report also on the combination of our phase-delay global astrometry results with the microarcsecond-precise optical astrometry that will be provided by future space-based instruments.Comment: 2 pages. 1 figure. Proceedings of the 7th European VLBI Network Symposium held in Toledo, Spain on October 12-15, 2004. Editors: R. Bachiller, F. Colomer, J.-F. Desmurs, P. de Vicente (Observatorio Astronomico Nacional), p. 323-324. Needs evn2004.cl

VLBI observations of SN2011dh: imaging of the youngest radio supernova

We report on the VLBI detection of supernova SN2011dh at 22GHz using a subset of the EVN array. The observations took place 14 days after the discovery of the supernova, thus resulting in a VLBI image of the youngest radio-loud supernova ever. We provide revised coordinates for the supernova with milli-arcsecond precision, linked to the ICRF. The recovered flux density is a factor 2 below the EVLA flux density reported by other authors at the same frequency and epoch of our observations. This discrepancy could be due to extended emission detected with the EVLA or to calibration problems in the VLBI and/or EVLA observations.Comment: Letter. Accepted in A&

The population of SNe/SNRs in the starburst galaxy Arp 220. A self-consistent analysis of 20 years of VLBI monitoring

The nearby ultra-luminous infrared galaxy (ULIRG) Arp 220 is an excellent laboratory for studies of extreme astrophysical environments. For 20 years, Very Long Baseline Interferometry (VLBI) has been used to monitor a population of compact sources thought to be supernovae (SNe), supernova remnants (SNRs) and possibly active galactic nuclei (AGNs). Using new and archival VLBI data spanning 20 years, we obtain 23 high-resolution radio images of Arp 220 at wavelengths from 18 cm to 2 cm. From model-fitting to the images we obtain estimates of flux densities and sizes of all detected sources. We detect radio continuum emission from 97 compact sources and present flux densities and sizes for all analysed observation epochs. We find evidence for a LD-relation within Arp 220, with larger sources being less luminous. We find a compact source LF $n(L)\propto L^\beta$ with $\beta=-2.19\pm0.15$, similar to SNRs in normal galaxies. Based on simulations we argue that there are many relatively large and weak sources below our detection threshold. The observations can be explained by a mixed population of SNe and SNRs, where the former expand in a dense circumstellar medium (CSM) and the latter interact with the surrounding interstellar medium (ISM). Nine sources are likely luminous, type IIn SNe. This number of luminous SNe correspond to few percent of the total number of SNe in Arp 220 which is consistent with a total SN-rate of 4 yr$^{-1}$ as inferred from the total radio emission given a normal stellar initial mass function (IMF). Based on the fitted luminosity function, we argue that emission from all compact sources, also below our detection threshold, make up at most 20\% of the total radio emission at GHz frequencies.Comment: Accepted for publication in Astronomy and Astrophysic

Aislamiento de cocaína y benzoilecgonina en muestras de orina por extracciones líquido-líquido y en fase sólida y confirmación por Cromatografía líquida de alta resolución (HPLC)

El consumo ilícito de cocaína se ha incrementado extraordinariamente en los últimos años, por lo que resulta indispensable el desarrollo de metodologías seguras, rápidas y eficientes para su detección. En este trabajo se desarrollo una técnica de HPLC de fase reversa con detector de UV para identificar y cuantificar a la cocaína y la benzoilecgonina, con resultados satisfactorios en los parámetros del control de calidad.Se realizó un estudio de recobrado para el aislamiento de la cocaína y la benzoilecgonina en orina con extracciones liquido liquido y en fase sólida con tres tipos de columnas comerciales (Bond Elut Certify, Extrelut 3 y Supelclean LC-18). Las fracciones obtenidas con la extracción líquido-líquido resultaron muy contaminados, con porcentajes de recobrados bajos (45% y 28% para la cocaína y la benzoilecgonina, respectivamente. En las extracciones en fase sólida para la cocaína resultaron muy eficientes las columnas Supelclean LC-18 (87-102 %) y Extrelut 3 (70-102 %), mientras que para el aislamiento de la benzoilecgonina resultaron más eficiente las columnas Extrelut 3 (86-101 %) y Supelclean LC-18 (73-89%). Las columnas Bond Elut Certify resultaron poco eficientes para el aislamiento de la cocaína (53-79%) y con un recobrado aún mas bajo para su metabolito (2-21% %)

Radio emission of SN1993J: the complete picture. I. Re-analysis of all the available VLBI data

We have performed a complete re-calibration and re-analysis of all the available VLBI observations of supernova SN1993J, following an homogeneous and well-defined methodology. Observations of SN1993J at 69 epochs, spanning 13 years, were performed by two teams, which used different strategies and analysis tools. The results obtained by each group are similar, but their conclusions on the supernova expansion and the shape and evolution of the emitting region differ significantly. From our analysis of the combined set of observations, we have obtained an expansion curve with unprecedented time resolution and coverage. We find that the data from both teams are compatible when analyzed with the same methodology. One expansion index ($m_3 = 0.87 \pm 0.02$) is enough to model the expansion observed at 1.7\,GHz, while two expansion indices ($m_1 = 0.933\pm0.010$ and $m_2 = 0.796\pm0.005$), separated by a break time, $t_{br} = 390\pm30$ days, are needed to model the data, at frequencies higher than 1.7\,GHz, up to day 4000 after explosion. We thus confirm the wavelength dependence of the size of the emitting region reported by one of the groups. We also find that all sizes measured at epochs later than day 4000 after explosion are systematically smaller than our model predictions. We estimate the fractional shell width ($0.31 \pm 0.02$, average of all epochs and frequencies) and the level of opacity to the radio emission by the ejecta. We find evidence of a spectral-index radial gradient in the supernova shell, which is indicative of a frequency-dependent ejecta opacity. Finally, we study the distribution and evolution of the azimuthal anisotropies (hot spots) found around the radio shell during the expansion. These anisotropies have intensities of $\sim 20$% of the mean flux density of the shell, and appear to systematically evolve during the expansion.Comment: 13 pages, 9 figures, accepted for publication in A&

Absolute kinematics of radio source components in the complete S5 polar cap sample. III. First wide-field high-precision astrometry at 15.4 GHz

We report on the first wide-field, high-precision astrometric analysis of the 13 extragalactic radio sources of the complete S5 polar cap sample at 15.4 GHz. We describe new algorithms developed to enable the use of differenced phase delays in wide-field astrometric observations and discuss the impact of using differenced phase delays on the precision of the wide-field astrometric analysis. From this global fit, we obtained estimates of the relative source positions with precisions ranging from 14 to 200 $\mu$as at 15.4 GHz, depending on the angular separation of the sources (from $\sim$1.6 to $\sim$20.8 degrees). These precisions are $\sim$10 times higher than the achievable precisions using the phase-reference mapping technique.Comment: 9 pages, 7 figure

VLBI observations of SN 2008iz: I. Expansion velocity and limits on anisotropic expansion

We present observations of the recently discovered supernova 2008iz in M82 with the VLBI High Sensitivity Array at 22 GHz, the Very Large Array at frequencies of 1.4, 4.8, 8.4, 22 and 43 GHz, and the Chandra X-ray observatory. The supernova was clearly detected on two VLBI images, separated by 11 months. The source shows a ring-like morphology and expands with a velocity of ~23000 km/s. The most likely explosion date is in mid February 2008. The measured expansion speed is a factor of ~2 higher than expected under the assumption that synchrotron self-absorption dominates the light curve at the peak, indicating that this absorption mechanism may not be important for the radio emission. We find no evidence for an asymmetric explosion. The VLA spectrum shows a broken power law, indicating that the source was still optically thick at 1.4 GHz in April 2009. Finally, we report upper limits on the X-ray emission from SN 2008iz and a second radio transient recently discovered by MERLIN observations.Comment: accepted Astronomy & Astrophysics, 9 pages, 8 figures, also available at http://www.mpifr-bonn.mpg.de/staff/abrunthaler/pub.shtm

1.6 GHz VLBI Observations of SN 1979C: almost-free expansion

We report on 1.6 GHz Very-Long-Baseline-Interferometry (VLBI) observations of supernova SN 1979C made on 18 November 2002. We derive a model-dependent supernova size. We also present a reanalysis of VLBI observations made by us on June 1999 and by other authors on February 2005. We conclude that, contrary to our earlier claim of strong deceleration in the expansion, SN 1979C has been undergoing almost-free expansion ($m = 0.91\pm0.09$; $R \propto t^m$) for over 25 years.Comment: 4 pages, 4 figures; submitted to A&A on 14 May 2009. Accepted on 7 Jul 200

Electron cooling and the connection between expansion and flux-density evolution in radio supernovae

Radio supernovae (RSNe) are weak and rare events. Their typical maximum radio luminosities are of the order of only $10^{27}$\,erg\,s$^{-1}$\,Hz$^{-1}$. There are, however, very few cases of relatively bright (and/or close) RSNe, from which the expansion of the shock and the radio light curves at several frequencies have been monitored covering several years. Applying the standard model of radio emission from supernovae, it is possible to relate the defining parameters of the modelled expansion curve to those of the modelled light curves in a simple algebraic way, by assuming an evolution law for the magnetic field and for the energy density of the population of synchrotron-emitting electrons. However, cooling mechanisms of the electrons may affect considerably this connection between light curves and expansion curve, and lead to wrong conclusions on the details of the electron acceleration and/or on the CSM radial density profile. In this paper, we study how electron cooling modifies the flux-density decay rate of RSNe for a set of plausible/realistic values of the magnetic field and for different expansion regimes. We use these results to estimate the magnetic fields of different RSNe observed to date and compare them to those obtained by assuming energy equipartition between particles and magnetic fields. For some of the best monitored RSNe, for which deceleration measurements, optically thin spectral index, and power-law time decay have been observed (SN\,1979C, SN\,1986J, SN\,1993J, and SN\,2008iz), we find self-consistent solutions for the index of the power-law circumstellar density profile ($s=2$ for all cases), the index of the power-law relativistic electron population (rather steep values, $p = 2.3 - 3.0$) and the initial magnetic field (ranging from $\sim 20$ to $> 100$\,G).Comment: 14 pages, 4 figures. Accepted for publication in A&