Sunday, March 7, 2010

GW Lib data to support Hubble COS mission

One of the delights of being an amateur astronomer is being able to assist real scientists with (hopefully) useful data on various targets that they need to keep an eye on prior to observation runs with toys that I can't afford eg the HST.

An alert (Notice#417) went out this week from the AAVSO requesting data on two cataclysmic variable stars to support Dr Paula Szkody's upcoming spectrograph observations on the Cosmic Origins spectrograph on the HST.

GW Lib is a CV that needs to be fainter than Mag 14 when the mission takes place, and it has been known to infrequently outburst.

AAVSO members regularly fly cover and give early warnings on any unexpected events that may affect the mission integrity.

GW Lib is at DEC -25.00.25 so that immediately eliminates a good number of the world's telescopes. Australia has had large monsoonal lows pushing into the interior of Australia and the weather has been pretty ordinary this week as a result.


My choice of a couple of 300 sec images was a little short in duration as the SNR was a bit low with the moon still being at 55%. I was able to confirm that the target was about Mag 15.39 (given the low SNR maybe a little closer to 16) in the Johnson V filter (untransformed).

I'll try again tonight with a little longer exposure.

Peter

UPDATE: 10/03/2010
JD Airmass GW_Lib 147 143 Err SNR
2455265.209 1.11373 15.501 14.422 14.000 0.025 42
2455265.214 1.100 15.421 14.432 13.988 0.031 34
2455265.219 1.08756 15.514 14.422 14.003 0.041 26

Ave 15.479 14.425 13.997 0.032 34

Peter

UPDATE: 11/03/2010
Today I tidied up my Sequence a little, deleting 128 and I added 157 to the comp star list as visually it looked to be the identical magnitude to GW Lib. I also stacked the three images with a median combine to give a much much stronger SNR. With the SNR of a number of the comp stars now being over 100 (preferred) the Magnitude of 147 was almost identical to the chart magnitude listed in AAVSO chart 2084CCS. Comfortable with the improvement in accuracy GW Lib magnitude was measured at 15.629 (Johnson V untransformed).

Note the stronger SNR of the target now at 60 with the comp star's SNR >100.


Seven AAVSO members contributed observations and Dr Paula was pleased to hand the observations to the Hubble space controllers this morning who then gave the go-ahead for tonights UV run on the Cosmic Origins spectrograph.

Congrats to Dr Paula, hope everything goes well tonight! It all starts again on the 14th as the next COS run is on V842 Cen.

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