Call for observation: SU Aur

[Hans Moritz Guenther]

H alpha is by far the most important, because it traces the mass infall and the mass outflow in the wind. Also, its wavelength is conveniently located where CCDs are typically most effective.

Other line of interest would be:

• Ca H & K at 3934 and 3969 Ang (traces cromospheric activity)
  The Ca infra-red triplet at 8498, 8542, 8662 Ang (traces accretion spots)

Ca H & K are likely broad absorption lines with narrow, but high emission peaks in the center. The Ca IRT is most likely in emission do to the strong mass accretion on SU Aur.

Moritz

[Christian Buil]

Add of a new observation from François Teyssier. Low spectral resolution (LISA) but good potential spectrophotometric quality:
http://www.astrosurf.com/aras/surveys/suaur/index.html

Just a view arcminutes from SU Aur, the star AB Aur :



But, priority is SU Aur !

Very bad weather prevision for me from Toulouse (south of France) for the moment...

Christian

[Thierry Garrel]

Strong wind and sparse could cover prevent me to observe for the moment.
The observatory is open and ready to go at the time of the wind will stop.

[Francois Teyssier]

Rainy weather in Normandy.
Sorry.
François Teyssier

meteo.PNG (14.3 KiB) Viewed 9062 times

[Christian Buil]

Cloud in Haute-Garonne
Pour la France, seul le contour de la Méditeranée semble l'un des seul endroit OK, en en particulier la région de Nice (avec peu de vent à cet endroit - j'y étais hier pour le job, ciel parfait !).

Christian B

[Hans Moritz Guenther]

That's a pity, but nothing can be done about bad weather.
As far as I know, XMM-Newton did the observations. If all went well I'll receive the data in 2-3 weeks. I'll post an image here when I get it so you can see why we do all this.

All of you: Thanks for your help, even it the clouds stopped us this time. I hope I can ask you again, when I do a similar project in the future.

Hans Moritz

[Christian Buil]

Hello Hans,

Consult the ARAS page:

http://www.astrosurf.com/aras/surveys/suaur/index.html

Conditions in Spain are more favorable and note the formidable Joan Guarro continuous survey for the period!

So, we have finaly some data for the satellite period observation, but for this first tentative, the time
coverage is not excellent (bad weather, low number of well equiped and experimented observers).

Note also a tentative (experimental !) of SU Aur observation with a very small telescope (a 85 mm
diameter refractor only - C. Buil). With modern equipement (high efficiency spectrograph, optimal slit
wide and low noise CCD camera), the star spectrum is "lisible" and show Halpha
features - but time resolution is poor of course (one hour exposure).

You can download all fits calibrated spectrum of the survey from the ARAS page.

Christian Buil

[Hans Moritz Guenther]

Hallo,

about two weeks ago I received the X-ray data (it takes 3-4 weeks until that is fully processed at the ESA data center). I have started with the analysis and I will post a few pictures below, so you get an idea what the X-rays look like. So far, I did not compare that to the optical spectra, but I will do that.
Also, I am still waiting for some of the optical photometry that people from the AAVSO might have taken. Most likely I'll do the full scientific analysis and and publication some time in autumn.

First, I want to show you some bits of SU Aur.
Here is the lightcurve:



In the first panel I show the X-ray lightcurve. As you can see, SU Aur is mostly constant except for a flare in the end. In previous observations it did flare more often, but we never know that in advance. There is a high chance of flaring, but that does not mean that it actually happens. In the middle of the observations there is a short time period (which I marked in red) when the background (mostly from solar energetic protons) is so high, that the detector saturated.

The second panel shows the hardness ratio. A higher number here means a hotter plasma. There is some low scale variability until the temperature rises in the very end in the flare. As last panel I show optical photometry from the AASVO (that is easier to show on a plot than your spectra), but unfortunately the flare is not covered (but there might still be people submitting observations later).

Not to bore you with lightcurves too much, here is a spectrum:


This shows the X-ray spectrum of AB Aur (SU Aur is hotter, but does not look too different). On the x-axis I plot the photon energy (higher energy = lower wavelength, 1keV = 1.24 nm), on the y-axis the count rate. This is a low-resolution spectrum. Really, the spectrum consists of mostly lines with very little continuum, but the resolution is so low (R = ca. 10) that all lines blend together and make it look like a continuum. Fortunately, we know the energy of the lines we expect, so we can still compare the strength of e.g. oxygen and neon lines, but I have not done that yet.

Errorbars show the noise on every single data point. That is due to the low number of photons (each point contains only 15 photons!). You may notice, that the y-axis is in units of "counts". In X-ray astronomy we generally do not show spectra in units of flux (as you do in the optical), but in a way that allows us to basically read off the number of photons directly form the plot.

The next steps for me are to reduce the X-ray high-resolution (R=500) spectrum, fut that with an accretion model and determine the mass accretion rate form the optical spectra you took.

Thanks so much for your help again.
I'll keep you updated on my progress.

Moritz

[Francois Teyssier]

Dear Hans,

Thank very much for the explanations.
Waiting for the next campaign ... (with clear skies !)

Al the best

François Teyssier