CCD Views #326: Special Edition on IL Aqr/GJ 867 Campaign

                 25 Birch Street, Cambridge, MA 02138 USA
                 Tel. 617-354-0484       Fax 617-354-0665

                             C C D   V I E W S   #326
                                 October 7, 2004


Table of Contents
 1. Exoplanet Transit Campaign for IL Aqr/GJ 867


 The AAVSO has teamed up with to coordinate an observing
campaign for IL Aqr, a.k.a GJ 867 in the transit search community. Dr.
Greg Laughlin, University of California at Santa Cruz, is looking for
observations during an upcoming transit opportunity.
 IL Aqr is located at R.A.: 22:53:17  Decl.: -14:15:48 
 The GJ 876 system contains two planets orbiting a nearby M-dwarf star.  
The planets are in an orbital resonance which leads to significant
precession of their orbits. The causes the transits to be somewhat
unpredictable and by observing the transits we can learn more about the
orbital dynamics of the system.

 The purpose of the campaign is to detect transits of planet "b" if they
are occuring, or to convincingly rule them out. Below are the 
transit windows:

=== Observations

Transit Prediction:
         October 21 23:22 UT - October 22 03:27 UT 
w/3 sigma uncertainty:
         October 20 11:22 UT - October 23 15:27 UT

 ** Observations are needed during the entire 3 sigma window!! **

 In addition, IL Aqr is a variable star that has not been well monitored.
It has a tiny GCVS range of V=10.15-10.19, however that is just 
enough to interfere with transit detection. We need observations of IL Aqr 
to begin now so we can set a baseline of activity. Please begin observing 
IL Aqr at least once per night in B and V with as high precision as possible. 
Use the 119 comp star on the chart (below) and set your exposure for a good
SNR. If possible, get a few time series runs in of at least four hours. 
Submit your data as soon as you can so we can evaluate IL Aqr's typical 
activity (so as not to confuse it with any transit activity). 

 An e-scale chart has been created with 3 comparison stars from ASAS-3.
It can be downloaded at:
[obsolete link; create charts using VSP at ]

 The predicted transit depth *could* be relatively large, up to 0.1  
magnitude. However detection of a transit is not assured, much less 
its amplitude! 

 However, there is a catch. IL Aqr is a very red star so you need 
to use a filter, preferably a V filter. Also, be sure to use the 
star labelled 119 on the chart as your comp star and use the others 
as check stars. The 119 star is also red, but not as much, so it 
will provide more accurate photometry for untransformed observations.

 Observers should begin practicing on the object right now to make sure
you can achieve the required level of precision. Try to get 0.01 mag
precision to look for structure in the transit light curve. Time 
resolution is not as important as photometric precision.

=== Sign Up!

 Please observe as much as possible during the 3 days. We are creating 
a list on our web site of observers who can participate and during what 
windows they can observe. Please sign up by e-mailing 

 Name, observer code, location, time zone and when you can observe. 

 This will help us coordinate observations between observers. 
Weather has been a real challenge with prior observations of this 
object so we need multiple people observing from multiple locations 
around the globe. 

=== Coordination

 A web page will be setup and maintained during the campaign:

[ obsolete link; page is at ]

 The campaign will be coordinated via the web page and the AAVSO-
Photometry Discussion Group. Visit the web page for links to the
discussion group archives, updated light curves, progress reports, links
to charts and more information. If you plan to participate in the
campaign send us a note and we'll put you on the web page.

 During the campaign itself we may setup a chat server for observers to 
participate in.

 This transit would be of GJ 876b, the first (outer) planet discovered in
the system. Details on the system and other transit results can be found

 The results of this transit will be combined with other transit results
and research and submitted for publication. All observers who contribute
significant photometry to this effort are welcome to be listed as
co-authors of the manuscript.

 Note: IL Aqr was also the subject of Alert Notice 281 issued on May 11, 
2001 and CCD Views Vol. 2 No. 1 for June, 2001. It can be read at this URL: [obsolete link; read at ]
 If you have any unsubmitted data from those publications please submit 
them as soon as possible. They may be very valuable!


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 Good observing!

 Aaron Price, AAVSO Technical Assistant (PAH)
 Gary Walker, Chairman of the AAVSO CCD Committee (WGR)

Copyright 2004, American Association of Variable Star Observers
                25 Birch Street, Cambridge, MA 02138 USA
                Tel. 617-354-0484       Fax 617-354-0665