sheeny
20-07-2006, 07:59 AM
Found these in this morning's Nature Contents.
Enjoy,
Al.
Letter
Nature 442, 276-278(20 July 2006) | doi:10.1038/nature04893; Received 21 March 2006; Accepted 11 May 2006
An X-ray-emitting blast wave from the recurrent nova RS Ophiuchi
J. L. Sokoloski1 (http://www.nature.com/nature/journal/v442/n7100/abs/nature04893.html#a1), G. J. M. Luna1 (http://www.nature.com/nature/journal/v442/n7100/abs/nature04893.html#a1),2 (http://www.nature.com/nature/journal/v442/n7100/abs/nature04893.html#a2), K. Mukai3 (http://www.nature.com/nature/journal/v442/n7100/abs/nature04893.html#a3) and Scott J. Kenyon1 (http://www.nature.com/nature/journal/v442/n7100/abs/nature04893.html#a1)
Top of page (http://www.nature.com/nature/journal/v442/n7100/abs/nature04893.html#top) Stellar explosions such as novae and supernovae produce most of the heavy elements in the Universe. The onset of a nova is well understood1 as driven by runaway thermonuclear fusion reactions on the surface of a white dwarf in a binary star system; but the structure, dynamics and mass of the ejecta are not well known. In rare cases, the white dwarf is embedded in the wind nebula of a red-giant companion, and the explosion products plough through the nebula and produce X-ray emission. Here we report X-ray observations of such an event, from the eruption of the recurrent nova RS Ophiuchi2,3. The hard X-ray emission from RS Ophiuchi early in the eruption emanates from behind a blast wave, or outward-moving shock wave, that expanded freely for less than 2 days and then decelerated owing to interaction with the nebula. The X-rays faded rapidly, suggesting that the blast wave deviates from the standard spherical shell structure4,5,6. The early onset of deceleration indicates that the ejected shell had a low mass, the white dwarf has a high mass7, and that RS Ophiuchi is therefore a progenitor of the type of supernova (type Ia) integral to studies of the expansion of the Universe.
Editor's Summary
20 July 2006
A star is reborn
In February this year the recurrent nova RS Ophiuchi (RS Oph) burst into life. Every 20 years or so the white dwarf component of this binary accumulates sufficient material from its red giant companion to power a thermonuclear explosion that we see as an increase in magnitude from a very dim 12.5 to magnitude 5. Two groups report observations of the recent outburst. Satellite X-ray observations by Sokoloski et al. reveal an initial phase in which the blast wave expanded freely. Within two days the outbound wave started to slow, suggesting that there was much less debris than had been expected from such an event. O'Brien et al. trained the largest terrestrial radio telescope arrays on RS Oph and were able to directly image a shock wave in a nova explosion for the first time, 14 days after its initial discovery. The structures revealed show an evolution to a remnant similar to that of a type II supernova — but evolving over months rather than millennia.
Letter
Nature 442, 279-281(20 July 2006) | doi:10.1038/nature04949; Received 6 April 2006; Accepted 31 May 2006
An asymmetric shock wave in the 2006 outburst of the recurrent nova RS Ophiuchi
T. J. O'Brien1 (http://www.nature.com/nature/journal/v442/n7100/abs/nature04949.html#a1), M. F. Bode2 (http://www.nature.com/nature/journal/v442/n7100/abs/nature04949.html#a2), R. W. Porcas3 (http://www.nature.com/nature/journal/v442/n7100/abs/nature04949.html#a3), T. W. B. Muxlow1 (http://www.nature.com/nature/journal/v442/n7100/abs/nature04949.html#a1), S. P. S. Eyres4 (http://www.nature.com/nature/journal/v442/n7100/abs/nature04949.html#a4), R. J. Beswick1 (http://www.nature.com/nature/journal/v442/n7100/abs/nature04949.html#a1), S. T. Garrington1 (http://www.nature.com/nature/journal/v442/n7100/abs/nature04949.html#a1), R. J. Davis1 (http://www.nature.com/nature/journal/v442/n7100/abs/nature04949.html#a1) and A. Evans5 (http://www.nature.com/nature/journal/v442/n7100/abs/nature04949.html#a5)
Top of page (http://www.nature.com/nature/journal/v442/n7100/abs/nature04949.html#top) Nova outbursts1 take place in binary star systems comprising a white dwarf and either a low-mass Sun-like star or, as in the case of the recurrent nova RS Ophiuchi2, a red giant. Although the cause of these outbursts is known to be thermonuclear explosion of matter transferred from the companion onto the surface of the white dwarf3, models of the previous (1985) outburst of RS Ophiuchi failed to adequately fit the X-ray evolution4 and there was controversy over a single-epoch high-resolution radio image, which suggested that the remnant was bipolar5,6 rather than spherical as modelled. Here we report the detection of spatially resolved structure in RS Ophiuchi from two weeks after its 12 February 2006 outburst. We track an expanding shock wave as it sweeps through the red giant wind, producing a remnant similar to that of a type II supernova but evolving over months rather than millennia7. As in supernova remnants, the radio emission is non-thermal (synchrotron emission), but asymmetries and multiple emission components clearly demonstrate that contrary to the assumptions of spherical symmetry in models of the 1985 explosion, the ejection is jet-like, collimated by the central binary whose orientation on the sky can be determined from these observations.
Enjoy,
Al.
Letter
Nature 442, 276-278(20 July 2006) | doi:10.1038/nature04893; Received 21 March 2006; Accepted 11 May 2006
An X-ray-emitting blast wave from the recurrent nova RS Ophiuchi
J. L. Sokoloski1 (http://www.nature.com/nature/journal/v442/n7100/abs/nature04893.html#a1), G. J. M. Luna1 (http://www.nature.com/nature/journal/v442/n7100/abs/nature04893.html#a1),2 (http://www.nature.com/nature/journal/v442/n7100/abs/nature04893.html#a2), K. Mukai3 (http://www.nature.com/nature/journal/v442/n7100/abs/nature04893.html#a3) and Scott J. Kenyon1 (http://www.nature.com/nature/journal/v442/n7100/abs/nature04893.html#a1)
Top of page (http://www.nature.com/nature/journal/v442/n7100/abs/nature04893.html#top) Stellar explosions such as novae and supernovae produce most of the heavy elements in the Universe. The onset of a nova is well understood1 as driven by runaway thermonuclear fusion reactions on the surface of a white dwarf in a binary star system; but the structure, dynamics and mass of the ejecta are not well known. In rare cases, the white dwarf is embedded in the wind nebula of a red-giant companion, and the explosion products plough through the nebula and produce X-ray emission. Here we report X-ray observations of such an event, from the eruption of the recurrent nova RS Ophiuchi2,3. The hard X-ray emission from RS Ophiuchi early in the eruption emanates from behind a blast wave, or outward-moving shock wave, that expanded freely for less than 2 days and then decelerated owing to interaction with the nebula. The X-rays faded rapidly, suggesting that the blast wave deviates from the standard spherical shell structure4,5,6. The early onset of deceleration indicates that the ejected shell had a low mass, the white dwarf has a high mass7, and that RS Ophiuchi is therefore a progenitor of the type of supernova (type Ia) integral to studies of the expansion of the Universe.
Editor's Summary
20 July 2006
A star is reborn
In February this year the recurrent nova RS Ophiuchi (RS Oph) burst into life. Every 20 years or so the white dwarf component of this binary accumulates sufficient material from its red giant companion to power a thermonuclear explosion that we see as an increase in magnitude from a very dim 12.5 to magnitude 5. Two groups report observations of the recent outburst. Satellite X-ray observations by Sokoloski et al. reveal an initial phase in which the blast wave expanded freely. Within two days the outbound wave started to slow, suggesting that there was much less debris than had been expected from such an event. O'Brien et al. trained the largest terrestrial radio telescope arrays on RS Oph and were able to directly image a shock wave in a nova explosion for the first time, 14 days after its initial discovery. The structures revealed show an evolution to a remnant similar to that of a type II supernova — but evolving over months rather than millennia.
Letter
Nature 442, 279-281(20 July 2006) | doi:10.1038/nature04949; Received 6 April 2006; Accepted 31 May 2006
An asymmetric shock wave in the 2006 outburst of the recurrent nova RS Ophiuchi
T. J. O'Brien1 (http://www.nature.com/nature/journal/v442/n7100/abs/nature04949.html#a1), M. F. Bode2 (http://www.nature.com/nature/journal/v442/n7100/abs/nature04949.html#a2), R. W. Porcas3 (http://www.nature.com/nature/journal/v442/n7100/abs/nature04949.html#a3), T. W. B. Muxlow1 (http://www.nature.com/nature/journal/v442/n7100/abs/nature04949.html#a1), S. P. S. Eyres4 (http://www.nature.com/nature/journal/v442/n7100/abs/nature04949.html#a4), R. J. Beswick1 (http://www.nature.com/nature/journal/v442/n7100/abs/nature04949.html#a1), S. T. Garrington1 (http://www.nature.com/nature/journal/v442/n7100/abs/nature04949.html#a1), R. J. Davis1 (http://www.nature.com/nature/journal/v442/n7100/abs/nature04949.html#a1) and A. Evans5 (http://www.nature.com/nature/journal/v442/n7100/abs/nature04949.html#a5)
Top of page (http://www.nature.com/nature/journal/v442/n7100/abs/nature04949.html#top) Nova outbursts1 take place in binary star systems comprising a white dwarf and either a low-mass Sun-like star or, as in the case of the recurrent nova RS Ophiuchi2, a red giant. Although the cause of these outbursts is known to be thermonuclear explosion of matter transferred from the companion onto the surface of the white dwarf3, models of the previous (1985) outburst of RS Ophiuchi failed to adequately fit the X-ray evolution4 and there was controversy over a single-epoch high-resolution radio image, which suggested that the remnant was bipolar5,6 rather than spherical as modelled. Here we report the detection of spatially resolved structure in RS Ophiuchi from two weeks after its 12 February 2006 outburst. We track an expanding shock wave as it sweeps through the red giant wind, producing a remnant similar to that of a type II supernova but evolving over months rather than millennia7. As in supernova remnants, the radio emission is non-thermal (synchrotron emission), but asymmetries and multiple emission components clearly demonstrate that contrary to the assumptions of spherical symmetry in models of the 1985 explosion, the ejection is jet-like, collimated by the central binary whose orientation on the sky can be determined from these observations.