Spectral index of the H 2O-maser-emitting planetary nebula IRAS 17347-3139
Por:
Gómez J.F., De Gregorio-Monsalvo I., Lovell J.E.J., Anglada G., Miranda L.F., Suárez O., Torrelles J.M., Gómez Y.
Publicada:
1 ene 2005
Resumen:
We present radio-continuum observations of the planetary nebula (PN) IRAS 17347-3139 (one of the only two known to harbour water maser emission), made to derive its spectral index and the turnover frequency of the emission. The spectrum of the source rises in the whole frequency range sampled, from 2.4 to 24.9 GHz, although the spectral index seems to decrease at the highest frequencies (0.79 ± 0.04 between 4.3 and 8.9 GHz, and 0.64 ± 0.06 between 16.1 and 24.9 GHz). This suggests a turnover frequency of around 20 GHz (which is unusual among PNe, whose radio emission usually becomes optically thin at frequencies <10 GHz), and a relatively high emission measure (1.5 × 10 9 cm -6 pc). The radio-continuum emission has increased by a factor of ?1.26 at 8.4 GHz in 13 yr, which can be explained as expansion of the ionized region by a factor of ?1.12 in radius with a dynamical age of ?120 yr and at an expansion velocity of ?5-40km s -1. These radio-continuum characteristics, together with the presence of water maser emission and a strong optical extinction, suggest that IRAS 17347-3139 is one of the youngest PNe known, with a relatively massive progenitor star. © 2005 RAS.
Filiaciones:
Gómez J.F.:
Instituto de Astrofísica de Andalucía, CSIC, Apartado 3004, E-18080 Granada, Spain
Laboratorio de Astrofísica Espacial y Física Fundamental, INTA, Apartado 50727, E-28080 Madrid, Spain
De Gregorio-Monsalvo I.:
Laboratorio de Astrofísica Espacial y Física Fundamental, INTA, Apartado 50727, E-28080 Madrid, Spain
Lovell J.E.J.:
Australia Telescope National Facility, CSIRO, PO Box 76, Epping, NSW 1710, Australia
Anglada G.:
Instituto de Astrofísica de Andalucía, CSIC, Apartado 3004, E-18080 Granada, Spain
Miranda L.F.:
Instituto de Astrofísica de Andalucía, CSIC, Apartado 3004, E-18080 Granada, Spain
Suárez O.:
Laboratorio de Astrofísica Espacial y Física Fundamental, INTA, Apartado 50727, E-28080 Madrid, Spain
Torrelles J.M.:
Instituto de Ciencias del Espacio (CSIC)-IEEC, Gran Capità 2-4, 08034 Barcelona, Spain
UK Astronomy Technology Centre, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, United Kingdom
Gómez Y.:
Centro de Radioastronomia y Astrofísica, UNAM, Apartado Postal 3-72 (Xangari), 58089 Morelia, Michoacán, Mexico
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