spectro-aras.com

Hi there

My second attempt with this nova was a little more successfully. I had hard time finding a direction that will produce as little contamination as possible, and when I found clouds came.

Here's the result, I'm really not sure what to make out of this. I know Beta Aur is not the best choice for a calibration star, but I need something bright before the clouds closed the skies.

(PS. I've been through all the data again, maybe there's a slight focus shift between the nova and the B Aur recording?)

Hi again

Been working hard on processing and validating the data from the two days. It seems that my calibration and data reduction is
okay, so the major error is coming from guiding, clouds, seeing, atmosphere and missing flats.

I think I see hydrogen emission in the spectrum from 5. April compared to 4. April. If I combine my ref. star and the two nova spectre it's
looking fairly well although with quite some noise and contamination from stars in the FOV.

It also looks like there some broad heavy adsorption around 4700Å and between the hydrogen lines. For the moment I haven't a clue about
what it is, could it be from the white dwarf, the ring like disk or some else?

There's very little information on this type of dwarf nova WZ Sag.

Well here's my data:

The probable progenitor star - if so, it's a huge increase in luminosity, more than 9-10 mag.


To days of observing. On 5 April the CCD/Grating is rotated approx. 90dg.


The ref. star. B Aur:

Hello Laars,
It may be the spectrum of a cataclysmic in outburst. With a intense blue coontinuum (in outburst, the accretion disk becomems very hot : 15 to 20 000 K
Unfortunatly, cataclysmics in outburst are difficult targets for a staranalyser : the lines (Balmer, HeI, HeII) in emission/absorption are weak.
See an example of such an outburst with a LISA at R = 1000 : http://astronomie-amateur.fr/feuilles/S ... Stars.html.

A good exercice is to follow an outburst of the brightest CV, SS Cygni (Mag 12 aat quiescence, near 8 in outburst) , about 40 days (20 to 80) between outbursts.


Outburst of SS Cyg with a SA and LhiresIII, 150 l/mm :
http://astronomie-amateur.fr/feuilles/CV/SS%20Cyg.html

Alpy600 will be a very good spectro for such surveys of faint cataclymic stars.

All the best

François

Hi Francois

Thanks for the information.

Done some reading, this is where I am right now.

It seems it's a good candidate for a WZ Sge-type dwarf nova, only 4 or 5 is known. SWIFT was looking at it some days ago.

Although I'm little confused, I hope my assumptions is correct.

It should be a very small companion (maybe 0.1 solar mass) very close to the star that starts this, and the collapsed gas falls onto the star and creates bremsstrahlung and synchrotron radiation from the gravitational potential energy?
The energy is released in the UV region and therefore I see a intense blue continuum. This energy heats up the disk(s), (I assume this more complicated because the companion is so close the star) and we see emission.
For this type of dwarf nova I'm not sure we can say it's an accretion disk in the usual shape and size. Some places it's described as ring like and small, whatever that means exactly.

The results I'm getting with the SA is strange from around 6700 Å -the flux seems to rise into the red, could that be the extreme UV radiation from the second order I see so far down into the red? Or just contamination from other stars in the field?

The best source so far I've found for spectre of such very rare superoutburst on WZ Sge dwarf nova's is the this powerpoint. I can't tell how the emission line shows up on SA spectre, but it looks like it should be detectable.

http://www.noao.edu/meetings/wildstars2 ... Nogami.ppt


Well I hope it's clear again tonight, can't wait to get a new fresh look at it.

And yep, I'm saving up for a ALPY

Cheers
Lars
(sorry for the novice questions)

Hi Lars,

Cataclysmic stars are close binaries with a white dwarf of about 0.5 solar mass and a companion, a main sequence star of late type (generally M) . The companion fills its Roche Lobe and loose material throw Lagrangian point.This material forms a disk around the white dwarf. As The companion and the white dwarf are not luminous stars, much of the light comes from the accretion disk. The density of the disk increases with time, also its viscosity. When viscosity becomes high, the temperature of the disk increases suddently, from about 5/7000 to 15/20000 K. This is the outburst : the cataclymic becomes much more luminous.

Amoung the non magnetic CV, there's 3 types :
SS Cygni CV : only normal outbursts
SU UMa : normal outburts and somtimes a superoutburst, brighter and longer than normal outburts
WZ Sge : secial type of SU UMa with ONLY superoutbursts

Thank you for the link. I see that V455 Abd shows intense emssion lines in outburst ; but generally, lines of CV in outburst are weak.

François