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.

When you wish upon a star

Welcome. This week has been characterised by some fairly average weather. Those of you tuning into Australia's premier football event around the world this afternoon will see plenty of our famous Melbourne weather on show.

Weather can have an impact on an observing campaign, so there have been some challenges in obtaining some of the data I have been chasing this week. I am getting great positive feedback on the blog - largely because I am blogging on my observations.

So this week, given the weather, I thought it would be good to talk about observation campaigns. This week I have barely jagged a couple of short sessions on
V4743 SGR and some of the surrounding variables in the same field. V4743 Sgr is also referred to as Nova Sgr 2002c making it an object of some interest, given its nova outburst in 2002. Over 200 observers have contributed to the AAVSOs lightcurve.



So what is it that makes an object "interesting"? Clearly a Nova outburst is something that is interesting, as professional astronomers are quick to follow up with highly accurate spectroscopy. The advantage of having amateurs "on their toes" and participating in regular campaigns is that professional astronomers can't afford to have billion dollar telescopes pointed at stars, waiting for years, for something to happen. (The hubble deep field shot is a noteable exception...but a deliberate experiment to look at nothing to see if something WAS there)

A good example of leveraging the skills of amateur astronomers is my data here on QU Sgr. This is a Mira variable star of little or no interest to anyone.....but who knows one day it may be significant or do something. If that ever happened, what would we have to compare it with? So whilst gathering some data on V4743 with my set up which has a fairly large field of view, it is important to grab a couple of readings on any other Variables in the field, as other observers are unlikely to ever go specifically to QU Sgr to collect data.



There are a plethora of variable stars requiring regular observations and a limited number of observers. Today we have the fantastic use of social networking, blogs, forums and membership of organisations such as AAVSO. In this environment connected communities of dedicated amateurs have organised campaigns based on a prioritised list of "interesting objects".

Rod Stubbing who discovered this months outburst of VX For was working through a carefully targeted list of variables that were "in season" ie at an optimal position in the sky for observing. Rod indicated to me it was his first observing session on VX For for the year. So you never know what you will find, and how many other people who are observing.



So I leave you this week with the completely insignificant Mira Variable QU Sgr that noone else has reported on for over 4000 days.

Vx For Dwarf Nova outburst

Great work last night Rod. I jumped on it as soon as it came over the side of the shed and have it in the first image at an average of 12.951 M across the first three images I have downloaded (airmass of 1.5)

I should be able to tighten that up a bit when I process the rest of the run.

Data from my first image....

VX For 12.951 SNR 103

126 12.555 SNR 137
137 13.652 SNR 59

More later....

Firrst three images down:

#TYPE=EXTENDED
#OBSCODE=LPB
#SOFTWARE=Photometrica 3.0
#DELIM=,
#DATE=JD
#NAME,DATE,MAG,MERR,FILT,TRANS,MTYPE,CNAME,CMAG,KNAME,KMAG,AMASS,GROUP,CHART,NOTES
VX For,2455090.09733,12.936,0.011,V,NO,ABS,ENSEMBLE,na,137,13.660,1.55703,na,090915,na
VX For,2455090.09994,12.959,0.010,V,NO,ABS,ENSEMBLE,na,137,13.665,1.53358,na,090915,na
VX For,2455090.10256,12.991,0.011,V,NO,ABS,ENSEMBLE,na,137,13.662,1.51102,na,090915,na

Looks like Rod has bagged a beauty!!!!


Peter