Abstract: Dr. Timothy Cunningham (CfA | Harvard & Smithsonian) writes: ZZ Psc (G 29-38) is a pulsating white dwarf accreting planetary debris—the prototype for studying rocky debris disks in evolved planetary systems. In November 2025, JWST will obtain high-cadence time-series spectroscopy to study the composition and structure of its debris disk. Simultaneous optical light curves are vital for linking disk behavior to the white dwarf’s pulsations (~5% amplitude, 100–1000s periods). The white dwarf is relatively bright (G=13.1 mag). We would like to obtain optical light curves with ≤40 sec cadence 04–25 November 2025, focusing on 12–16 November to coincide with JWST. The JWST window is the top priority, but the long baseline observations will be essential to probe the weakest pulsation modes. This system is also the subject of ongoing multi-cycle HST and Chandra programs, which aim to measure the accretion rate of planetary debris from the disk. See below for instructions.
Justification: AAVSO observers who can achieve 40-second cadence with <1% precision (<10mmag) for this relatively bright white dwarf (G = 13.1 mag) will provide crucial long-term coverage of its pulsations during the JWST campaign. As many as 50 pulsation modes may be active, and both their amplitudes and frequencies can vary over time, making comprehensive monitoring essential. Full characterization of all active modes during the JWST epoch is necessary for robust interpretation of the time-resolved JWST spectroscopy. Observations at longer cadences are also valuable, as they will help characterize the longer-period pulsations, contributing important information for our asteroseismic analysis.
The cadence of 40 seconds and 10 mmag precision precludes filter changes for the most part. What band would be most useful? Is 10 mmags a one sigma number, implying that the p-p noise should be .066 mags or less? Does the result require Transforming to be most useful? To be most useful, all observers should use the same comp star and mag value–do you have a suggested one?
Nice Ken. Looks pretty much like the LC I was just looking at in Wikipedia.
If I take 30 sec exposures with my CDK12.5, Using that, I was estimating about 4 data points on the first spike whereas your plot shows 6. Do you mind mentioning your camera, exposure, binning and gain? I’m planning to do some test images tonight to see what snr I can get with 30 sec exposures at gain 0 and gain 100 - probably with both a Clear and V filter.
Not sure, but given the short peak-peak times, it strikes me as unlikely that, with a 12" scope, I could get any benefit from going with shorter exposures and some stacking. Might be interesting to try 20 sec and see where the snr ends up.
The cadence of 40 seconds and 10 mmag precision precludes filter changes for the most part. What band would be most useful?
A single band, with no changes is the preferred strategy. The most useful band would be Johnson V or sloan g, but really any filter is useful. The target is brightest in the blue, so for signal, the bluer/broader the better.
Is 10 mmags a one sigma number, implying that the p-p noise should be .066 mags or less?
10mmags is an approximate required precision, the pulsation have amplitude of ~5-20% in flux, so lower precision is still valuable in order to resolve the largest flux variations.
To be most useful, all observers should use the same comp star and mag value–do you have a suggested one?
The closest comparison star is TYC 584-1035-1. This is just 5 arcmin from the target, so should be with the FOV for most setups. Within 10 arcmin there are 5–10 suitable comparison stars which could be used in addition if the FOV allows.
I have started again to observe ZZ Psc in V band solely for a couple of hours. Last data are submitted to the AAVSO database. Attached is a screen shot from Peranso including period analysis like Ken did. I took 10 sec images with a C14 at f/7 and QHY600M CMOS camera.
Last nights observations in Perasnso and a phase plot below left. There was a drop in the comp star around JD…88.10. High cirrs clouds during the night, but nearly similar period like yesterdays night.
Hi All:
Within 5’, a single star, 124, is identified on the AAVSO charts. Is this the noted, and preferred Comparison star (TYC 584-1035-1)? Is there another designation for this star?
Another star labelled 130 is shown a bit further from the target on the same chart. Eleven total Comparison stars are identified on the 60’ chart. Star 135 shown on the 30’ chart appears to be closest in B-V to the Target. For those observers who have access to 30’ FOV, would it be appropriate to use 135 as the check star?
I had been torn between using 132 and 135 for the check star. Star 132 has a nice low error while 135 is closer to the b-v color index of the target. Probably for a time series analysis, these don’t matter so much. Cheers…
Three sets of data submitted to the AID - JD2460986, 987 and 988 - under ID IGE. Cadence was 30 sec, V-filter, 0.432m CDK, unguided. Analysis package was AstroImage J, v5.5.1.00. X-axis is HJD; BJD_TDB is also available.
AAVSO sequence was X41171BWN. Check and ensemble comp stars from that sequence are 124, 127, 125, 132, 119, 135, 130, and 127, respectively. No data were transformed, but I can do transform for my system if requested. Other filters are available: B, R, and I.
Images were calibrated with dark with bias and flat. Dark current for my Moravian C5-100 at -25C is very low, so flats (0.7 - 1.2 sec) were only corrected for bias. I have all the science and calibrated images as well as calibration master images and will provide when upload instructions received.
Will collect more sequences as skies permit over the next week or so.
I’ve just uploaded a data set from last night’s observation, covering approximately 1.8 hours. I must say, this star is a fascinating object. Photometry in the V band with 30-second exposures (minimum SNR of 50) shows clear variability with an amplitude of about 0.06 mag.
A Generalized Lomb-Scargle (GLS) periodogram highlights two strong periodic signals:
~ 0.0098 days (~14 minutes)
~ 0.0072 days (~10 minutes)
I can continue monitoring the target, weather here looks favorable for the coming nights. While I cannot do very long sessions, I’d be happy to keep observing if such data are considered useful.
Thank you all, some nice looking light curves here. The JWST observations will be occurring on Nov 13th, approximately halfway through these long baseline observations that will be invaluable for interpreting the JWST data.
I’ve just uploaded a new data set from tonight’s (2025-11-12) observation, covering about 2h57m.
This time-series was taken in V filter with 30-second exposures (average SNR ~85).
The Generalized Lomb-Scargle (GLS) periodogram shows a strong peak at:
P ≈ 0.0100 days** (~14.4 minutes)
I am able to continue observing the object on November 13 and 14, during the same time interval, if additional data would be helpful.
Let me know if this cadence and analysis are useful to the campaign.
