Affiliation
Astronomical Society of South Australia (ASSAU)
Wed, 08/28/2013 - 00:38
A friend pointed me to this Astronomy Picture of the Day of Nova Del 2013's spectrum at maximum showing bands of emission. Very nice.
David
Not just emission bands. Each one of those bright bands has a dark (absorption) band on the blueward side! Very cool.
Neil
Have a look at this lovely animation of Nova Del spectrum evolving over the first six days, obtained by amateur Paolo Beradi - resolution of ~2.5A using a LHIRES Littrow spectograph
http://quasar.teoth.it/html/spectra/novadel_15_21.gif
Robin Leadbeater originally posted this link on the BAA forum.
Gary [PYG]
[quote=SNE]
Not just emission bands. Each one of those bright bands has a dark (absorption) band on the blueward side! Very cool.
[/quote]
Hi Neil,
This combination of emission and absorption is known as a P Cygni profile (after the archetype showing this sort of spectrum feature) and signifies an outward flow of cooler material from a hot object (From the Nova explosion in this case or from stellar winds in the case of P Cygni) The hot central region excites the expanding region of cooler gas causing it to emit in all directions eg here most obviously at the Hydrogen Balmer line wavelengths. The emission component of the line mainly comes from the material which is thrown out sideways and therefore has no relative velocity in our direction. We see a net absorption however in the material comming directly towards us which is illuminated from behind by the hot central region. This is blue shifted due to its velocity in our direction and produces the absorption component on the blue edge of the line. The velocity of the material can be estimated from the blue shift.
Cheers
Robin
I forgot to mention the absorption lines in the APOD spectrum.
That animation is fantastic!
It'd be great to see some analysis of both of these spectra. Is it perhaps worth pointing to this topic from the Spectroscopy forum in the Nova Del topic?
David
Hi David,
There is an ongoing detailed commentary by amateur Francois Teyssier and professional Steve Shore published here
http://www.astrosurf.com/aras/novae/Nova2013Del.html
They are working with amateur spectroscopists around the globe covering this object. Spectra of this event currently total 388 at a wide range of resolutions and wavelengths, coordinated by the ARAS group
http://www.astrosurf.com/aras/Aras_DataBase/Novae/Nova-Del-2013.htm
Presentation and discussions of new spectra as they come in are ongoing in the ARAS forum
http://www.spectro-aras.com/forum/viewtopic.php?f=5&t=682
Cheers
Robin
Thanks for the excellent pointers Robin!
David