J0328-1219 Photometry Observations, Season #4
by amateur Bruce L. Gary, using a 0.4-m (16") telescope at the Hereford Arizona Observatory (HAO)
with additional data by Tom Kaye, using a 1.1-m (44") telescope at his Roemer VIsta Observatory (RVO)


Last updated: 2024.03.04, 23 UT

This web page is meant to be an archive of light curve observations for "observing season #4" (2023 August to 2023 February) of white dwarf J0328 using: 1) my HAO backyard observatory 16" Ritchey-Chretien AstroTech telescope with a SBIG XME-10 CCD (link) and 2) Tom Kaye's 44" home-built telescope (link). Most of my web pages are meant for documenting observations and analysis results for myself (it's easier than using a filing cabinet). 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 these dual purposes 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 #3 is located at http://www.brucegary.net/J0328-3/; it includes my observations during the 3rd observing season (2022.08.29 to 2023.02.10).

Current Status

A-period is still dominant (over B-period). Very little OOT time is present (~ 30 %). Both behaviors resemble the past 3 years. Recently (2024 Jan 15) a deep triplet dip structure appeared with a B-system periodicity. For dips in both the A- and B-systems depths for two wavelengths (g'- and R-band) are the same. This means that small dust cloud particles (radii < 0.1 micron) are absent (see model at link). This is also true for WD1145 (which J0328 resembles in other respects).   

General Information About J0328

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).

List of Internal Links
    Waterfall Plots  
    List of Observing Dates  
    Observing Date Graphs  
    Finder image  
    Interpretation of the Nov 11 and 12 events 
    Physical model suggestion  
    References  
    Related external links  


Waterfall Plots


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








This waterfall plot (for only the past month) is for an A-system period that produces vertical drift lines for the main group of dips (at phases 0.60 to 0.85).
Dips with solid bars inside are optically thin (lower depth at R band than g' band). Open circles indicate inexplicable relationship between g' and R levels (R being deeper than g').


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

2024.03.04  
2024.02.12  
2024.02.05  
2024.02.04  
2024.01.27  
2024.01.19  
2024.01.18  
2024.01.17  
2024.01.16  
2024.01.15  
2024.01.11  
2024.01.10  
2024.01.09  
2024.01.07  
2024.01.06  
2024.01.05  
2024.01.03  
2023.12.17  
2023.12.16  
2023.12.15  
2023.12.14  
2023.12.13  
2023.12.11  
2023.12.10  
2023.12.09  
2023.12.08  
2023.12.07  
2023.12.04  
2023.12.03  
2023.11.23  
2023.11.22  
2023.11.13  
2023.11.12  
2023.11.11  
2023.11.10  
2023.11.07  
2023.11.06  
2023.11.05  
2023.11.04  
2023.11.03  
2023.11.01  
2023.10.26  
2023.10.23  
2023.10.20  
2023.10.19  
2023.10.16  
2023.10.15  
2023.10.11  
2023.10.09  
2023.10.05  
2023.10.04  
2023.10.03  
2023.09.26  
2023.09.25  
2023.09.24  
2023.09.03  
2023.08.31  
2023.08.28  

Observing Session Light Curves


2024.03.04  

This will probably be this season's last observing session for J0328. The dip at 2.5 UT has been present for at least 4.5 months (since mid-November).







2024.02.12  

Good observing weather for both unfiltered observatories. All dips have the same depth for both observatories (so systematic errors in LC shape must not exist).











2024.02.05  





2024.02.04  





2024.01.27  

A full moon and cirrus ruined the first 1.5 hours.







2024.01.19  

Only HAO unfiltered LC today. Dip#9 belongs to the B-system, and all other dips belong to the A-system. The new and deep B-system dip pair are supposed to have occurred just after observations ended.







2024.01.18  

Clouds ruined most of this night's LC data.







2024.01.17  

Dip #1 qualified for inclusion in the Depth Ratios list.



The waterfall plot can now be understood as showing B-system dips that were present as deep dips in the LCs for Jan15 and 16. There might be other shallower dips in recent days that also belong to the B-system.













2024.01.16  

No RVO R-band data for this date.

The deep dips in HAO data (at UT ~ 02 UT) may belong to the B-system! They match the triple dip structure for the previous date (at UT ~ 3.5 UT) using P = 11.17 hours.







2024.01.15  

A new dip structure appeared since our last observation, 4 days ago. It's a triple-dip-structure, and it has the same depths at g'- and R-bands.











2024.01.11  

As often happens, RVO & HAO differ near the end of our LCs. Only the dip #2 &  #4 (combined) were usable for adding to the depth ratios plot.











2024.01.10  

It's disconcerting when some structures are present in both LCs and other structures aren't.











2024.01.09  

Four dips qualified for inclusion in the dip ratio graph.













2024.01.07  

We were able to add two dips to the dips ratio graph. Wind spoiled some HAO data.













2024.01.06  

None of the dips met our criterion for ratio analysis acceptance.













2024.01.05  





2024.01.03  

Dip#5 has become a deep (21 %) and broad dip. It might be thee superposition of two dips produced by dust clouds in slightly different orbits tha have drifted in orbit azimuth to cross our line of sight at the same time. More waterfall data will be needed to determine if this is true..











2023.12.17  

HAO observed unfiltered (to confirm previous night's overall LC dip pattern), and RVO observed with polarizer (in attempt to detect polarization due to dust during dips).









2023.12.16  

Again, the ratio of depths is the same for g' and R bands.













2023.12.15  

Data quality was good for both observatories. Dip depths were small (11.0, 5.5, 5.0,7.0 %) so dip depth ratios were expected to be uncertain. However, they appear to be well-established in the following graph, and they are compatible with all dust clouds being optically thick (or composed of only large particles, > 0.5 micron).  













2023.12.14  

Depth ratios are uncertain (since all depths were shallow?).















2023.12.13  

Both HAO and RVO observed unfiltered (disregard g' and R info in the graphs for this observing session)/.











2023.12.11  

There seems to be a problem with RVO data variability.











2023.12.10  

This observing session allowed for the measurement of 2 dip depths vs wavelength (# 1 & 2).













2023.12.09  

The RVO image rotater wasn't working properly, so a non-standard image processing was employed for that data.














2023.12.08  

Dip #2 is slightly "optically thin." Dip #3 is inexplicably the opposite (may be noise).













2023.12.07  

RVO LC is suspicious so we won't assign optical properties to dips..















2023.12.04  

Among the 9 dips identified for this observing session only two appear to be optically thin (shallower at R band than g' band). These two dips are at UT = 5.6 and 7.7. The following waterfall plot shows which dips are optically thin by the placement of a dot inside the dip pattern:



We should expect that a dip that is really optically thin on one date should be optically thin on all dates It is disappointing that there is a lack of consistency for the last two dates (the only ones where an assignment is possible, due to the presence of g' and R observations).






Re-processeed version.













2023.12.03  

This observing session was devoted to an attempt to determine whether J0328 dips are due to dust clouds that are optically thick or thin. The approach was for Tom Kaye to observe using his 1.1-m telescope with a R band filter while I observed using my 0.4-m telescope with a g' band filter. If the dips were optically thick they would have the same depth at both bands, whereas if the dust clouds were optically thin the depth at R band would be less than the depth at g' band. We succeeded in demonstrating that a 3-dip structure exhibits a smaller depth at longer wavelength, so the answer is: optically THIN due to dominance of small particle sizes (<0.2 micron radius)!

The next set of 6 graphs are in the same order as presented for other observing sessions. They are best viewed from the last one (link), upward, to the one just below here. After doing that I suggest that you resume reading this observing session's story by going to the 2nd set of graphs (e.g., location #2, link).










..



Dec03 story. location #1: Start here, and view upward. After reaching the top return to here (e.g., Location #2) and continue reading downward.

Location #2: Here's a version of the g' band LC, zoomed-in to show the UT range 6.6 too 8.8 UT:



This graph shows an AHS fit consisting of 3 dips, shown by dotted traces. The product of these 3 dotted traces is the thick black trace (that fits the green trace data).



The graph above is for the same UT interval, and shows the g' and R band LCs. Throughout the UT region of the dIp 1, 2 and 3 structure the R band level is less deep than the g' band level. We conclude that all three dips are optically thin due to the particle size distribution (PSD) favoring smallness (radii < 0.2 micron).

The next graph is a waterfall plot for the past month.



The top=most dip strength set of traces corresponds to this observing session. Above this set of traces are numbers 1, 2 and 3 - corresponding to the 3 dips in the previous figure. Dips 1 and 2 are at phase 0.66.and 0.64, respectively. This waterfall plot allows us to associate all previous observations of a dip at these phases to also be optically thin.

It should be remarked that there are two ways for a dust cloud to be optically thin: 1) an insufficient column density of large particles, and 2) the presence of particles smaller than ~ 1/3 the wavelength (and also an insufficient column density for them). The first situation will produce dips with the same depth at all wavelengths (that are < 1/3 particle radius). The second situation will produce dip depths that are greater for shorter wavelengths. For this second situation, when the wavelength ratio =1.30 the ratio of depths is ~ 0.6.

The ratio of wavelengths R / g' = 1.31. We should therefore expect depths at R band to be ~ 60 % of the depths at g' band. Referring to the penultimate figure, the depths at R band are indeed ~ 60 % of the depths at g' band. We conclude that these 3 dust clouds are optically thin due to the dust PSD being dominated by small particles (and their column number density ratio <1). It is therefore reasonable to adopt the default assumption that all J0328 dips are due to dust clouds that are optically thin (due to PSD favoring smallness).

WD 1145+017 (hereafter WD1145) is the only other WD star with well-studied dips due to dust clouds. For WD1145, dip depths are the same for all wavelengths (that have been observed). This lack of depth vs. wavelength is due to a lack of small particles. The lack of small particles is due to a combination of proximity to the WD and emissivity at the particle blackbody emission wavelengths being small compared with the low albedo at WD irradiation wavelengths. In other words, WD1145 dust particles are good at absorbing light from the WD but poor at radiating it away. This raises the temperature of the particles over what it would be if albedo was constant at all wavelengths.

The most famous star with dust cloud dips having depths that increase at shorter wavelengths is KIC 8462852 (hereafter KIC846), also known as Tabby's Star and Boyagian's Star. In essentially all dips that have been observed at two or more wavelengths, the ratio of depth = 0.6 when wavelength ratio WL_longer / WL_shorter = 1.3. The wavelength ratio for r' / g' is 1.29, and for i' / r' it is 1.21. The dip depth ratios for KIC846 are indeed ~ 60 %, which means that the KIC846 dust clouds are optically thin due to the presence of small particles (with column density ratios < 1).

With data from this observing session we have shown that J0328 is the only WD known to have dips that vary with wavelength in a way that can be accounted for by the dust clouds having a PSD that is dominated by small particles (radii < 0.2 micron). It therefore is a nice complement to WD1145, which is the only known WD to have dust clouds orbiting in front of it with no wavelength dependence of dip depth; it is not known whether these dust clouds are optically thick because the PSD is devoid of small particles.

2023.11.23  

Let's compare a portion of this date's LC with the corresponding portion of the previous day's LC (same phase range, 3 orbits apart) :





The dip labeled "2" in the Nov 23 LC appears to have changed shape )and possibly phase). Their depths are about the same (13 % & 12 %).

Below are graphs belonging to my normal sequence of presentation.













2023.11.22  

This observing session was a little noisier than usual due to a nearby 1st crescent moon. Nevertheless, there was excellent agreement between RVO and HAO LCs. The first 5 dips align perfectly in a waterfall plot with the same dips from the previous two observing sessions (a week earlier). This will allow constraints to be placed on models for their evolution (in terms of depth and width).















2023.11.13  


Notice the "new" dips (designated by "?" symbols).















2023.11.12  

With two observatories showing the same dip structure it is possible to believe in that structure, and therefore fit it with AHS functions. This leads to a fitted AHS model with better temporal resolution. The shortest dust clouds must have sizes comparable to the WD star.















2023.11.11  

Many dips aaaaare present in both the HAO and RVO LCs, and some of them are narrow (as short as ~ 5 min).















2023.11.10  





2023.11.07  

First combined HAO & RVO observing session.











2023.11.06  







2023.11.05  





2023.11.04  





2023.11.03  





2023.11.01  

Gibbous moon nearby and windy - so noisy data.





2023.10.26  





2023.10.23  





2023.10.20  







2023.10.19  





2023.10.16  







2023.10.15  







2023.10.11  







2023.10.09  


The AFS model is meant to fit oct 05 data (allowing changes in 4 days to be seen).





2023.10.05  







2023.10.04  

Finally, the moon is out of the way and data is less noisy.







2023.10.03  

A gibbous moon was nearby so data is noisy.







2023.09.26  







2023.09.25  







2023.09.24  







2023.09.03  

This observing session, and the one before, were noisy due to a nearby full moon.








2023.08.31  








2023.08.28  





Finder Image


Finder image. FOV = 15 x 10 'arc. North up, east left. The best stars to use for reference are the clue-circled ones; I avoid use of the 3 red stars.

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.




Figures N1 and N2. 3-hour LC segments speparated by two System-A orbits (20 hours), showing nearly identicccal dip structure.

The lower of these two LC segments occurs 2 orbits after the upper panel (2 x 9.9422 hours = 19.9 hours). The AHS model for dip 6 is shown in both panels.

My first remark is that all 8 dips belong to the A-system. There is no statistically significant shift in phase for any of the dips, so they all have the same period.

We can investigate each dips change during this 20-hour interval by plotting the AHS model's depth and width for each dip. This is shown in the next two graphs.


Figure N3. Depth and width for the dips in the previous figures, showing changes during the 20-hour interval between the observations.

Depth increased for 3 dips, stayed the same for 4, and decreased for 1 dip (using 2 % for a change criterion). Width increased for 1 dip, stayed the same for 4, and decreased for 3 dips (using 2 minutes for a change criterion). All of these category assignments are uncertain because we don't know the measurement uncertainties for both depth and width. A third night of observations would have enabled an approximate solution for trends and SE for each parameter, but clouds didn't permit this. The average dip depth is 5..7 % and the average dip width is 9.3 minutes (using units of AHS width parameter).

It will be convenient to convert from "AHS width units" to "equivalent width units." This is illustrated by the following figure:


Figure N4. Showing the relationship between AHS width parameter, FWHM and equivalent width.

If the average AHS parameter width = 9.34 minutes, then the average FWHM width = 12.3 minutes, and the equivalent width = 13.4 minutes.

Let's try to model how dust cloud size and the way widths should broaden with time due to Keplerian shear

We assume WD mass = 0.731 M_sun, and P = 9.942 hrs. A circular orbit then has radius = 1.466e+6 km and orbital velocity = 257 km/s. A point source would cross the WD diameter in 3.59 minutes. Dust clouds are clearly longer (along the orbit) than a point source. Dips 2 and 8 were observed to have an AHS function with widths of 5.5 min, so how long would their dust clouds be to match that observation? To answer this I'll assume the dust cloud is opaque and the vertical size is whatever produces the observed depth. The average depth for all dips is 5.7 %, which can be produced by a band (intersecting disk center) that has a total width = 4.6 % of the WD's diameter. For this high opacity assumption we can treat the dust cloud as having an elliptical shape that is longer along the orbit than the WD's diameter and much narrower in the orthogonal direction. Mathematically, we need to convolve a rectangular function with an ellipse function, and then match a set of these with AHS functions..

Gere are a couple model calculations for opaque dust cloud shapes and the resultant dip shapes.




Figures N5 & N6. Model based dip structure for two optically thick elliptical dust clouds. The x-axis can be converted to time by multiplying hour marks by 3.59 minutes per WD radius.

Here's how to interpret Fig. N6: An optically thick dust cloud that has a length of 2.7 x WD radius, and width of 0.045 WD radius, will produce a dip depth of 6 % that has a FWHM = 3.4 WD radii, which corresponds to 12.3 minutes. This dust cloud model corresponds closely to the average dip in Fig's N1 and N2.
 
What about a model whose dust cloud is optically thin? The next figure shows one that satisfies the LC measurements of Fig's N1 and N2:


Figure N7. An optically thin dust cloud that is also compatible with measurements.

At the present time we don't know if the dust clouds are optically thin or thick (Vanderbosch et al., 2021) because LC measurements have not yet been made at different filter bands at them same time. Therefore, the size of the dust clouds could be anything like those depicted in the last two graphs (Fig.'s N6 and N7).

Let's investigate the effect on dust cloud size due to "Keplerian shear." - the spreading along the orbit of dust particles due to them having different periods. If a dust cloud is produced by a collision, or many small collisions that repeat every orbit (more about that later), we have a starting point for deriving dust cloud size.

Let's assume that a collision between a small object and a more massive planetesimal (such as an asteroid) yields dust going in all directions (isotropic) with speeds that have a well-defined maximum value, Vd. If the velocity vector is pointed up or down the dust will be in an orbit inclined to the asteroid's orbit. It will orbit with the same period as the asteroid, and will therefore not contribute to a spreading out along the orbit. However, these up/down particles will be displaced above and below the asteroid's orbit plane by maximum amounts at the 1/4 and 3/4 locations in their orbital motion, using as reference the collision site. Consider, for example, Vd = 78 m/s. It will rise above the asteroid's orbit plane with this velocity and at the 1/4 orbit location reach a maximum height of 446 km {Vd x P/(2 pi)}. This height corresponds to 6 % of the WD's radius (446/7443). This Vd value is what could account for a 6% dip depth if the cloud is optically thick.

If the collision ejects dust isotropically then what about the dust ejected in the forward and backward directions (i.e., parallel to the orbit)? If the more massice object, which I'm calling an asteroid, has an orbit speed of 257 km/s, then what's the period of particles that have a new orbit speed of 257.078 km/s? Using knowledge that the raius vector "sweeps through equal areas per unit time" throughout the orbit, it is possible to derive that small changes in speed lead to periods that are 1/3 of the fractional change in speed. Since 257.078 / 257 = 1.000303, the ratio of periods will be 1.000101. The forward ejected particle will therefore have P = 9.942 * 1.000101 hours. Another way to express this is to say after one orbit the particle will arrive at the collision site 3.62 seconds late (0.000101*9.942*3600). Since there are 2.41 orbits per day, the forward particle will arrive 8.74 seconds late per day. The backward ejected particles will arrive 8.74 seconds early. The asteroid crosses a WD diameter in 3.59 minutes, or it crosses a WD diameter in 3.59 minutes = 215.4 seconds. Therefore, the dust cloud length, front to back (produced by forward and backward ejected particles), spreads at a rate of 0.081 WD diameters per day (2 x 8.74 / 215.4). A spreading rte of 8.1 % of a WD size per day leads to a full WD size in 12.3 days. A size of 2.7 times the WD is achieved in 33 days. The dust cloud in Fig. N6 would require 33 days. This, to repeat, assumes that the dust cloud is opaque.

Another assumption, not explicitly stated yet, is that we are observing dust clouds produced by collisions that occurred at a location corresponding to 1/4 or 3/4 of an orbit before the dust cloud crosses our line-of-sight to the WD. If, for example, the collision occurred at the location in front of the WD, the vertical size of the cloud would forever be close to zero and due to orbit shear it would broaden along the orbit but still remain with a projected area ("solid angle") of close to zero for all time.

Finally, a third assumption for this modeling is hat the asteroid's orbit, and any dust clouds that are produced from it, are inclined at 90 degrees (i.e., are viewed edge-on).

When the above calculation is repeated for other dip depths, ranging from 3 % to 30 %, for example, we obtain time for Keplerian shear spreading to 2.7 times the WD size along the orbit) shown in the next graph:


Figure N8. Relationship between Keplerian spread time (how long it takes for dip to reach the value associated with a line) and dip depth and dip length (FWHM). This graph is for only J0328-1219 and it's A-system dips.

Here's how to read the above graph: For a dip with depth = 10 % and FWHM = 2.7 times the WD diameter (e.g., 9.7 minutes) takes 15 days from the time of a collision.Another way to use the graph is to ask, for example "How long will it take from the time of a collision for a 10 % dip to spread to a FWHM width of 10 minutes?" Moving up aaat the 10 % x-axis value the blue trace (which is close to 10 minutes) is found at a y-axis value of 15 minutes.







Physical Model Suggestion

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.

Whereas WD1145's planetesimal source for fragments is a planetary core (with density ~ 7 g/cc), the J0328 planetesimal source for fragments is an asteroid (with density ~ 2 g/cc).

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

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