CoRoT lightcurves from Guide 8

lightcurves@Safe-mail.net Nov 23, 2009

Wanna play with CoRoT stuff? Well, it used to be a bit tedious, needing the download of fits files from esoteric data servers, files best viewed in the java app topcat or such, but now you can more or less play directly.

This came out recently

http://cdsarc.u-strasbg.fr/viz-bin/Cat?J/A%2bA/506/519

the data for a recent paper. It's the N3 data release. They've classified all the exoplanet fields' variable stars, and they've even decided they're all variable and invented new variability types at times. ie as far as corot is concerned, all the exoplanet field stars turned out to be variable at the millimag or less capabilities corot has.

I dunno. Sounds a bit iffy to me, but there are certainly real variables in there.

Anyway, there's also a log file at vizier

http://cdsarc.u-strasbg.fr/viz-bin/Cat?B/corot

which is a bit out of date, as there are now data for around 39000 objects, but a lot of the stuff is there (30,000 as of the mid 2009 corot update release, it's the October short run data that's missing I think, which can be found at the laeff and nasa servers for the truly keen).

That's the N2 data delivery, is the b/corot vizier logfile stuff.

I glued them all together a few weeks back to make a usable whole. Because N2 is lagging at vizier compared to the direct data servers the file has stars with no coords that won't be plotted, but otherwise it's there, and they can be glued in when b/corot is updated.

To make access even easier, why not use Guide 8, I bethought.

The combined data and tdf can be found here

http://wikisend.com/download/571642/corot.tdf

you'll need cookies enabled, download the nigh on four megabytes of it and copy to the Guide directory and (re)run Guide.

I didn't take all the N3 data columns, just the first guesses re variability type and probability thereof, not the third or second. The automated identification system's first guess is wrong a lot of the time anyway, so no need worrying about the more wrong guesses. It's a look and see thing more than anything. I mean, when they class a star as M0 V and the first and most probable classification picked is that of a BE variable star, you know one of those data are going to be wrong.

Now, purple circles ring the corot stars involved for fields of one degree or less, adjustable via right click and display.

Basic info is stuff like spectral type, main probable variability type (you'll need to find the N3 paper, via the above N3 vizier readme to find a table of all those, although most are standard acronyms seen before, or guessable acronyms like "ecl" for eclipser, there's an astroph version linked via ADSABS) and the probability of that variability type being valid. There's the first (of three in the full catalogue) probable period, amplitude thereof, and "fit" for said, on a scale of 0 to 1, with 1 bestest, the 'fit' being an estimate of how the model lightcurve based on the variability type assumption and the probable period actually fits the true data.

The above tdf has coords within it so you can goto RA one of those to start off, the field will be obvious once you get there (only small bits of sky involved with CoRoT).

But goto tdf -> corot -> then entering a corot ID number works too.

In more info the red CoRoT link takes you to the above b/corot default short entry for the object, and at the far right of that is the PLOT link for getting to look at the lightcurve via a VizieR interface, which is adjustable, but a little buggy at the moment (always defaults to red mag, even when it's the monochromatic whiteflux being looked at and not the chromatic red, green and blue fluxes).

If you click on the TS link you can download the fits file and examine corot HJD versus flux in FV or Topcat or probably VOPlot or such, google for said if that keen.

Fits files aren't small, and the chromatic ones can be quite big.

As an example let us play with CoRoT 102708916 which is one of the objects typed as an eclipser with 100% certainty.

More Info has a link that launches this page in your web browser if clicked

http://vizier.u-strasbg.fr/viz-bin/VizieR?-source=B/corot/exo&CoRoT=102708916

Click the green background plot link at the endmost column to get this

http://cdsarc.u-strasbg.fr/viz-bin/vizExec/Vgraph?B/corot/102708916;ftp://ftp.ias.u-psud.fr/corotpub/N2-1.0/2007/02/03/EN2_STAR_CHR_0102708916_20070203T130553_20070402T070126.fits&

(url has wordwrapped, be careful with it)

and use inputs in X cuts and Y cuts and the axes values to zoom in and out, for example :-

http://cdsarc.u-strasbg.fr/viz-bin/vizExec/Vgraph?cat=B%2Fcorot%2F.%2F102708916%3Bftp%3A%2F%2Fftp.ias.u-psud.fr%2Fcorotpub%2FN2-1.0%2F2007%2F02%2F03%2FEN2_STAR_CHR_0102708916_20070203T130553_20070402T070126.fits&LIST_Band=Red%3BGreen%3BBlue&Band=Red&P=0&-x0=2598&-x1=2606&--bitmap=600x600&-y0=100000&-y1=140000

wordwrapped again

Now, counts isn't very informative, so to get an uncalibrated rough instrumental differential magnitude we'll reckon maximum for this object in the last zoom link is 134000 counts, and we'll use that as the "normaliser", just for messing around.

Then differential mag from that point is -2.5 x log10(counts/134000)

Deepest minimum reads off the axis something like 107000 so that's about 0.24 mags fainter. And this is a relatively high amplitude CoRoT object, you'll find plenty of stuff at around the millimag level. But look at the detail on the curve for that amplitude, and the tightness of it. Bottom right is "data as a table" link, so you can click on that look at the data, save it, shove it in a spreadsheet, convert to differential mags or just leave it in fluxes, and make up your own graphs.

Notice this randomly chosen object is not only an eclipsing binary, it's an eccentric eclipsing binary, as evidenced by the secondary minimum not being halfway between the two primary minima.

And if you're thinking you've seen just as nice a plot before, well, this isn't a _phaseplot_, this is the continuous sequential raw observation time series!

Plot it up in a spreadsheet and you could do a good estimate of the period just by reading off the minima here.

Lots of stars to play with and look at and see how CoRoT data really is. Whether the exoplanet stuff is included in there I know not, I dunno if any transit have been found in the exo fields, or how many.

Cheers

John