This web page is meant to be an archive of light curve observations for "observing season #5" (2024 December to 2025 March) of white dwarf J0328-1219 using Tom Kaye's 44" home-built telescope (link). My web pages can sometimes serve to help with collaborations if I join with others to study the same star. This web page may serve this purpose since I'm aware of a group of astronomers (headed by Zachary Vanderbosch) that was engaged in the first and second observing seasons of observations following publication about the variable nature of J0328. My Web Site #4 is located at http://www.brucegary.net/J0328-4/; it includes Tom Kaye's and my observations during the 4th observing season (2023.08.28 to 2024.03.04).
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).
Observing
Session Light Curves
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 January 04, 2025. Nothing on this
web page is copyrighted.