White Dwarf G29-38 (WD 2326+049) Photometric Monitoring Observations by Amateurs
B. L. Gary, Last updated 2015.11.30

This web page is devoted to a photometric monitoring of white dwarf G 29-38 (WD 2326+049) for the purpose of identifying transit features produced by an asteroid dust cloud (an idea given a bost of inspiration by Vanderburg et al (2105) and Croll et al (2015) Kepler K2 observations of WD 1145+017). The goal for these observations is to detect a transit feature or to constrain how deep such a feature could be. The observations are by advanced amateurs using telescope apertures of 14" or smaller.

G 29-38 (hereafter G29-38) is classified as a DAZd white dwarf, meaning that it has a mostly hydrogen atmosphere with metal absorption lines, indicating the presence of a continuous flow of dust onto the WD surface (and rapidly sinking). The IR flux spectrum exhibits emission lines that can be used to produce a mineralogy model (Reach et al, 2009). Brightness variability is well-established (McGraw et al, 1975), with timescales typically 10 to 17 minutes and range of variation ~ 0.23 magnitude. These variations are too slow for the radial pulsation mechanism, so it has been suggested that the pulsations are non-radial (e.g., movement parallel to the surface). 

Summary of Results

No transit events have been observed during 4 observing sessions (totaling 21.7 hrs).
The non-radial pulsations are prominent, with 4 main LS components (6 to 14 min periods), which vary slightly from night to night.
No transit features have been found.

Lomb-Scargle periodogram is similar for 3 observing sessions, with 13.8-minute period dominant.

Observing Sessions

2015 Nov 29

2015 Nov 08

This 4.8-hr observing session was windy, so seeing was variable.

2015 Nov 06

This 4-hr observing session was windy, so seeing was variable.

Synthetic LC compared with observed one, using just 3 components.

2015 Nov 05

This 5-hr observing session was windy, so seeing was variable.

Lomb-Scargle periodogram, showing a power peak at P = 14 min.

Upper panel shows a observed LC compared with a 3-component synthetic LC (P, amp, phase all free parameters). Lower panel is the difference, which can be used to search for a transit feature.

2015 Nov 01

This 8-hr observing session demonstrates the feasibility of monitoring G29-38 with a 14" telescope.

Light curve with fit using slope and air mass curvature.

Same data but with a stretched timescale to better show the variation structure.

Finder Image

Finder image, 27 x 18 'arc, north-east at upper-left. Target is at 23:28:47.2 +05:14:50 (J2000).

    McGraw, John T. and Edward L. Robinson (1975), "G29-38 and G39-29: Two New Large-Amplitude Variable White Dwarfs," ApJ, 200, L89-93.
    Reach, William T., Carey Lisse, Ted von Hippel and Fergel Mullally (2009), "The Dust Cloud Around the White Dwarf G 29-38. II. Spectrum from 5 to 40 um and Mid-Infrared Photometric variability," ApJ, 693, 697-712, 2009 Mar 1, arXiv

Return to Croll  observing list main page.


WebMaster: B. GaryNothing on this web page is copyrighted. This site opened:  Nov 01, 2015