RA/DE = 03:28:33.7 -12:19:45, g'-mag = 16.7, r'-mag = 16.6, white dwarf type = DZ, T_eff = 7630 ± 140 K (Vanderbosch et al., 2021), R_star = 1.167 ± 0.022 × R_earth =  0.0107 ± 0.0005 × R_sun = 7.443e+3 km, M_star = 0.731 ± 0.023 × M_sun, A-system orbit radius = 0.0098 a.u. = 1.466e+6 km (for P = 9.952 hrs), A-system orbital speed = 257 km/s, star diameter crossing time for A-system = 3.59 min. Radius of star as seen from A orbit is 0.29 deg. Temperature of rotating particles in A orbit = 388 K. Observing season is centered on Nov 18 (and extends from about Aug 01 to Mar 05).

Waterfall Plots

Dip #5 has been present since mid-November (4.5 months).

Most dips belong to the A-system. Some dips persist for >4 weeks; other dips are shorter-lived.


Dips have the same depth at R-band as at g'-band. This implies that dust particles are large (e.g., radii >0.2 micron).


Another way of presenting the same data with a more accurate treatment of SE (as explained at link).



J0328 is therefore just like WD 1145+017 in having dips with the same depth at all wavelengths. This suggests that small particles (radii < 0.2 micron) aren't produced by whatever process is responsible for dust production (such as collisions). Light pressure is negligible for both J0328 and WD1145, so radiation pressure can't be blamed for the lack of small particles.

Observing Session Dates

Observing Session Light Curves

Since J0328 is a blue star it is important to use only blue stars for reference. Any use of red stars would produce an unwanted amount of "airmass curvature" in the light curve.

Interpretation of the Nov 11 and 12 Events

On 2023 Nov 11 and 12 both observatories (HAO and RVO) observed the same short-duration dip events, and the excellent agreement of structure provides confirmation of each other. This means we have an opportunity to observe the temporal evolution of a few dips over a one day interval (actually, 2 A-system orbits, or 20 hours). Below are 3-hour segments for the two dates using a 2-orbit shift.

J0328 resembles WD1145 in the following ways: 1) dips are present some of the time, 2) dips exist for weeks to months, 3) the inner-most orbit is the most active in producing dips, and 4) dust clouds are in orbits that can (or must) be close to the WD's tidal radius. J0328 differs from WD1145 in the following respects: 1) during seasons #1 and #2 J0328 dips were present essentially all the time, whereas for WD1145 there are almost always plenty of OOT time per orbit, 2 ) the J0328 dust clouds are in a larger orbit , with P > twice the WD1145 P's. 

Since the WD1145 dust cloud sources (fragments of a planetesimal source) are certainly related in some way to being on the verge of tidal disruption I suggest that the J0628 dust clouds are produced by the same mechanism. I propose that the fragments for both WD1145 and J0328 are being bombarded by a background of rock collisions that become exhausted at the fragment location after a few weeks to months. This replenishment of dust that is continually lost from Keplerian shear and radiation pressure amounts to a steady-state of production and loss, thus accounting for long timescale preservation of dust cloud shape (depth and width) that would not occur in the absence of continual collision bombardment.

When a fragment begins to be bombarded by a swarm of rocky debris it will start with a shape that is narrow and will deepen quickly, while eventually reaching a steady-state level of collisional bombardment. While the rate of rocky bombardment is constant the dip will have a quasi-constant shape (depth and width). As the background level of rocky debris diminishes the dip should broaden and become reduced in depth. These three life-cycle phases can be thought of as "early, "middle" and "late." Accordingly, this observing season's A dip is in a late phase whereas the B dip is in an early phase.

My Collaboration Policy

Please don't ask me to co-author a paper! At my age of 84 I'm entitled to have fun and avoid work. Observing and figuring things out is fun; writing papers is work. My observations are "in the public domain" and are available for use by anyone. If my data is essential to any publication just mention this in the Acknowledgement section.

References

Vanderbosch, Zachary P., Saul Rappaport, Joseph A. Guidry, Bruce L. Gary and 13 others, "Recurring Planetary Debris Transits and Circumstellar Gas around White Dwarf ZTF J0328-1219," MNRAS arXiv

Xu, Siyi, Samuel Lai and Erik Dennihy, 2020, "Infrared Excesses around Bright White Dwarfs from Gaia and unWISE I," arXiv 

Guidry, Joseph A., Zachary P. Vanderbosch, J. J. Hermes, Brad N. Barlow, Isaac D. Lopez, Thomas M. Boudreaux, Kyle A. Corcoran, Bart H. Dunlap, Keaton J. Bell, M. H. Montgomery, Tyler M. Heintz, D. E. Winget, Karen I. Winget, J. W. Kuehne, 2020, "I Spy Transits and Pulsations: Empirical Variability in White Dwarfs Using Gaia and the Zwicky Transient Facility," submitted to ApJ, arXiv

Rappaport, Saul, Roberto Sanchis-Ojeda, Leslie A. Rogers, Alan Levine & Joshua Winn, 2013, "The Roche Limit for Close-Orbiting Planets: Minimum Density, Composition Constraints and Applications to the 4.2-Hour Planet KOI 1843.03," ApJ L, arXiv 


External Links of Possible Relevance

Gary, Bruce L. and Thomas G. Kaye, 2024, "Absence of Small Dust Cloud Particles Transiting the White Dwarf J0328-1219," arXiv.
J0328 Photometry observations by Bruce Gary during observing season #1 (2020/2021)
WD1145 summary of 4 observing seasons
WD1145 for 2020/21 observing season
Resume of webmaster

This site opened August 28, 2023. Nothing on this web page is copyrighted.