Alert Notice 478: Transformed photometry of young stars in Cha requested

January 16, 2013: Dr. Péter Ábrahám (Konkoly Observatory, Budapest, Hungary) has requested the assistance of AAVSO observers in monitoring eight young stars in Chamaeleon in support of photometry he and his colleagues will be obtaining with the VLT/ISAAC (infrared) and Herschel Space Observatory (far-infrared) during January-February 2013.

Calibrated, transformed VRI photometry is requested to precisely monitor changes in the optical brightness and colors of these objects. Calibration and transformation of the photometry is crucial - if all of the data are not on the same system and particularly if the colors are not transformed, it will be extremely difficult to correlate the data usefully.

Previous observations indicate that the stars are highly variable. Brightness changes can be expected from a few tenths of a magnitude to up to 1-2 magnitudes on a timescale of a few days to a few weeks.

Names, coordinates, and average V magnitudes of the targets:

NAME RA_2000 DEC_2000 V mag
CR Cha 10:59:06.972 -77:01:40.307 11.1
CT Cha 11:04:09.090 -76:27:19.380 12.5
HP Cha (Glass I) 11:08:14.938 -77:33:52.190 12.7
VW Cha 11:08:01.486 -77:42:28.850 12.8
VZ Cha 11:09:23.790 -76:23:20.760 13.3
WW CHa 11:10:00.10 -76:34:57.890 13.1
WX Cha 11:09:58.738 -77:37:08.880 14.0
XX Cha 11:11:39.656 -76:20:15.250 15.3

Observers are asked to try to obtain one to two sets of VRI images per night. It is recommended to take one set of VRI images on as short a timescale as possible (15-30 minutes for a full set of image pairs in all three filters), and then a second set later in the night if the object is at a favorable airmass (1 < z < 2).  Intensive time-series are not needed.

Charts for these objects may be created using the AAVSO Variable Star Plotter ( Please use the photometry table provided for each of these objects.

Please submit observations to the AAVSO International Database using the names provided in the table, including HP Cha (not Glass I).

This campaign is being followed from the AAVSO Observing Campaigns page (

This AAVSO Alert Notice was compiled by Elizabeth O. Waagen.


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