10. White Dwarf WD 1145+017 Photometric Monitoring Observations
by Amateur Observers Bruce Gary (HAO 0.4-m), Tom Kaye (RVO 1.1-m) and Ed Mullen (SCO 0.5-m)

B. L. Gary, this is the 10th web page devoted to observations of WD1145. Last updated 2023.03.30, 21 UT
Why WD 1145+017 is Important


White dwarf stars provide us with time-travel views of our solar system's future. Almost all stars become white dwarfs after their supply of hydrogen fuel in the core is exhausted. For decades astronomers have wondered if a star's solar system survives the transition from a normal star through an expansion phase to a red giant, followed by a shrinking phase to an earth-sized white dwarf. The answer came slowly, and the first hint of it was from spectroscope measurements of white dwarf atmospheres; it was found that 1/3 of white dwarfs were "polluted" with minerals that had to come from planets or asteroids generating dust that continually fell upon the white dwarf atmosphere. So "Yes, some stars retain part of their solar system after becoming white dwarfs."


But the ultimate proof came when WD1145 was discovered: it had dust clouds in orbit around it that would block the white dwarf's starlight every orbit. This discovery hinged on the good fortune that the WD1145 system was oriented favorably, presenting an edge-on view to Earth. The dust cloud orbit periods ranged from 4.5 to 4.9 hours, which required that the orbiting objects have densities of at least 6 g/cc. This density can only be found in planetary cores, so this was evidence that a planet had survived the transition to a white dwarf. This was evidence that "For most stars their asteroids and planets will survive and accompany them on their eternal journeys as white dwarfs - for billions, if not trillions, of years."


Our sun and solar system are 4.5 billion years old. In another 4 or 5 billion years our sun will undergo the transition to a white dwarf. Afterward, our sun will remain a white dwarf forever for 100 billion years, or however long the universe lasts. Our sun, like most stars, will therefore spend most of it total lifetime as a white dwarf accompanied by most of our present solar system of planets and asteroids. This is an amazing discovery!

 
  1 of 10 - 2015.11.01 to 2016.01.21:  LC Observations  -  1st  set of LCs, for 2015/16 observing season   
  2 of 10 - 2016.01.17 to 2016.07.13:  LC Observations  -  2nd set of LCs, for 2015/16 observing season    
  3 of 10 - 2015.11.01 to 2016.07.13:  LC Observations  -  3rd set of LCs, for 2015/16 observing season  (N = 158) + Overview, Results & Model Speculations 
  4 of 10 - 2016.10.25 to 2017.06.18:  LC Observations  -  4th set of LCs, for 2016/17 observing season 
  5 of 10 - 2017.10.23 to 2018.06.19:  LC Observations  -  5th set of LCs, for 2017/18 observing season 
 
6 of 10 - 2018.11.06 to 2019.07.09   LC Observations  -  6th set of LCs, for 2018/19 observing season 
  Previous observing seasons summary of results:    Observational findings that need to be explained by models
 
7 of 10 - 2019.12.02 to 2020.07.09   LC Observations  -  7th set of LCs, for 2019/20 observng season
 
8 of 10 - 2020.11.19 to 2021.06.07   LC Observations  -  8th set of LCs, for 2020/21 observing season 
 
9 of 10 - 2021.12.12 to 2022.07.16   LC Observations  -  8th set of LCs, for 2021/22 observing season
10 of 10 - 2022.11.21 to present         LC Observations  - 10th set of LCs, for 2022/23 observing season   (YOU ARE HERE)

Links on this web page:

  Status & summary of results for recent observations  
  Waterfall plots  
  Activity plots  
  Phase-folded LCs for date groups  
  Kepler K2 observations analysis  
  Waterfall plots for date groups  
  List of observing session dates 
  Observing session LCs 
  Finder image & basic info  
  Data exchange files (for all years: 2015/16, 2016/17, etc)
  My collaboration policy 
  Physical layout of debris ring system  
  References & related external links 
  Summary of  3.7 years of ground-based LC measurements 
  Collisions (tutorial: Collisions for Dummies, other web site)   
  Cloud crossing event (on another web page)

Status & Summary of Results for this Observing Season: 

The level of dip activity during this observing season is the lowest for all ground-based observations during the past 8 years, and similar to what was observed by Kepler in 2014. However, since late 2023 February activity has begun to increase. In late February a two-dip structure appeared and lasted for the week that observations were possible. The deeper dip was fixed in phase using the A-system period of 4.4955 hours while the smaller dip shifted in phase corresponding to it being in a larger orbit. When observations resumed in late March (after a long stretch of cloudy weather) a single dip was observed. It was present for a total of 5 days and varied in depth with a "time scale" of 3 days.


Waterfall Plots







One interpretation of the following two waterfall plots is to say that a collsion occurred at JD-2450000 = 10002.3 (Feb 26), which produced two dust clouds in different orbits. The longer period (i.e., larger) orbit dust cloud. labeled "2" in the next figure, was produced by a large ("mothership") planetesimal that is the source for all fragment sin the A-system. The shorter period dust clod (labeled "1" in the next figure) is from a fragment that vame off the star-facing hot pole of the planetesimal. That dust clod is has a deeper depth (25 %) and retains a narrow width for the 6 days covered by the post-collision observing dates. The other dust cloud loses depth and has almost disappeared by the last observing date.




Activity Plots

The next 4 graphs show the level of "dust production dip activity" vs. date:


Activity for a 6-month interval for this season's observations using a  linear scale for activity.


Activity for the last nine years, using a linear scale for activity.



Activity for the last nine years, using a log scale for activity.



Activity for the last nine years, showing a smooth "eyeball fit."


A possible "model" for activity based on collisions as triggers for increased activity. Only two actual measurement of dip activity has been achieved this season (the other symbols are estimattes, based on 1/2 of max). Kepler K2 data is represented by two symbols,the lower one is for the A-system periodicity and the upper one is the sum of EW for each of the A through F periodicities. The A-system EW is more appropriate for comparison with the other data since they are exclusively for the A-system (which dominated activity after the 2015 outburst). If duration of phase "A" is twice the duration of the combined phase "B" and "C" then it could be said that WD1145 is "active" 1/3 of the time. Does "1/3" call to mind anything (hint: fraction of WDs that are "polluted.")? 

Data exchange file for activity values: link


Phase-folded Light Curves for Date Groups  

Since our SNR isn't sufficient for ruling out the presence of dips (at the 1 % depth level, for example) the following phase-folded LCs for observing session groups (of only "a few" days) will be our best product for assessing the presence or absence of dip activity.

Mar 25 - 27



Mar 03




The 2nd dip is really not detected.

Mar 03





Group Feb 27,28






Group Jan 25-27 










Group Jan 20-22


Adopted dip model fit for a LC for 3-day observing interval showing candidate dips and their statistical significance (sigma) and contribution to dip activity (EW).


Phase-fold LC for a 3-day observing interval showing two possible dips .
   

Group Dec 20 - 31


Phase-fold LC after combining all data for 4 days (5 observing session data sets) of the current group of observing sessions (using the A-system ephemeris).


Phase-fold LC after combining all data for the first 10 days of the first group of observing sessions (using the A-system ephemeris).


This LC shows no dips (> 1 %) when data are combined on the assumption that any dips that are present belong to the A-system (4.49126 hrs) and that they persist for the duration of the 10-day observing interval.


Waterfall Plots for Date Groups

There are no credible waterfall plots yet because none of the LC show dips and we only have two credible phase-folded LCs (due to the low activity level).


List of observing sessions   


2023.03.29  
2023.03.28  
2023.03.27  
2023.03.26  
2023.03.25  
2023.03.24  

2023.03.19  

2023.03.13 

2023.03.04  
2023.03.03  

2023.02.28  
2023.02.27  

2023.02.16  

2023.01.27  
2023.01.26  
2023.01.25  

2023.01.22  
2023.01.21  
2023.01.20  

2023.01.05  
2022.12.31  
2022.12.25  
2022.12.22  
2022.12.21  
2022.12.20  

2022.12.01   Data exchange file (BJD-2450000, NF, SE): link
2022.11.30  
2022.11.29  
2022.11.27  
2022.11.26  
2022.11.25  
2022.11.24  
2022.11.21  

__________________________________________________________________________________________________________________________________________________


2023.03.30  






2023.03.29  


The dip at phase 0.59 has an interesting depth variation during the past 5 days.











Moonlight and open tube led to noisy data.





2023.03.28  













2023.03.27  














2023.03.26  














The "dome synchonizing with telescope" feature was "off" until 8.5 UT, so data before then is very noisy.


2023.03.25  



















2023.03.24  

This date has only one observer's data, and it is shorter than an orbit. It appears to be flawed by systematics at the beginning at 1 hhour later (due to clouds). It is presented here for "completeness" but is omitted from trend plots.





2023.03.19  





2023.03.13 


Tjis dip is statistically significant, but I don't believe it. I consider it an upper limit.







2023.03.04  













2023.03.03  






2023.02.28  















2023.02.27  

The Gary/Kaye/Mullen triad of observers obtained full observing sessions on this date. Each of us saw the same double-dip structure two times (twice per observing session), for a total of 6 observations of the double-fip that repeated during the observing sessions. The activity level has taken a jump, and we think it occurred during the previous 11-day data gap.




Note: a double-sip structure would fit the data better.
















2023.02.16  

Only two observers and one observing night are available for this data group. The data for observer EM didn't corroborate dip features in data for BG, so we decided to discount the BG features. No dip features are deemed present in the combined data.

















2023.01.27  

Only two observers on this date.











2023.01.26  














2023.01.25  

Only Ed Mullen had usable data for this date.







The B.Gary data is too noisy for use.





2023.01.22  

Three observers contribute to this date's LC data: B. Gary, T. Kaye and E.. Mullen.





   







2023.01.21  







2023.01.20  







2023.01.05  





2022.12.31  


I'm unconvinced that a dip is present at 11.2 UT. All we can say is that on this date there were no appearances of a new, large dip.




The weather was bad, mostly due to cirrus clouds.

2022.12.25  





2022.12.22  




2022.12.21  


I am unconvinced that any dips are present.




I aborted early due to computer problems.

2022.12.20  


The two candidate dips are unconvincing.





2022.12.01  







2022.11.30  





2022.11.29  





2022.11.27  





2022.11.26  





2022.11.25







2022.11.24  







2022.11.21  - 1st observation of the season






Finder Image  


Finder image. FOV = 15.6 x 10.5 'arc. North up, east left. (Image taken with 16" AstroTech.)

RA/DE = 11:48:33.6 +01:28:29, B-V = +0.26, r'-mag = 17.2, Teff = 15,020 K (young cooling age ~ 224 My), Spectral Type DBZA, He atmosphere, photospheric absorption lines for 11 "metals," star mass = 0.63 M_sun, R = 1.29 R_earth, distance = 142 parsec.

Data Exchange Files   

    2015.11.21 to 2016.07.15  
    2016.10.25 to 2017.06.18  
    2017.11.10 to 2018.06.18 
    2018.11.09 to 2019.06.09 
    2019.12.02 to 2020.07.09  
    2020.12.xx to 2021.03.22  (more to come)

Data exchange files are available in two formats: light curve details (one line per image) and dip fits (asymmetric hypersecant (AHS) model fits for each dip). The first of these is available for download using the above links (though I recommend that anyone using these data check with me for updates since I sometimes find errors and post the corrected files here). Data exchange files of the second format (AHS dip fits) may be requested from B.Gary. These may also be available here in due time.

My Collaboration Policy

Please don't ask me to co-author a paper! At my age of 83 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." If my data is essential to any publication feel free to use them; just mention their source in the Acknowledgement section.


Physical Layout of Debris Ring System - one possibility

Kepler spacecraft data was used to detect the presence of six periodicities for WD1145 (Vanderburg et al., 2015). Ground-based follow-up observations have detected three of these periodicities (shown in the next figure). The inability for ground-based measurements to detect the other three periodicities is most likely due to the handicap of having to observe through an atmosphere.


Figure P1. Periods for WD1145 brightness variations determined from Kepler data (6 vertical bars) and ground-based follow-up observations (+ symbols). The white dwarf star is located to the left (at the x = zero location). 

The following graph shows period determinations for the A- ans D-systems using ground-based data analyzed with waterfall plots. It is apparent that the A-system is the most active system, so let's consider a possible physical mechanism for that system.


Figure P2. Zoom-in of previous figure, showing only the A and D systems.

The following graph is for the A-system. Presumably, something similar is occurring for the other five systems.

A possible physical mechanism to account for this system will be presented next.
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Figure P3. Zoom-in of previous figure, showing only the A-system. The parent body, either an asteroid or remnants of a planet, is shown by a "football-shaped" object orbiting with a period of 4.50 hours (the Kepler A-system periodicity). The left end of the object, which faces the WD star, is a "hot pole."  Fragments that break off the hot pole orbit inside of the parent body. Collisions between fragments produce dust of all sizes. The small dust particles (radius < 2 micron) are blown away by WD radiation pressure, while larger dust particles remain in the fragment region. Gas produced by sublimation (and collisions) migrate inward, and end up falling on the WD atmosphere, accounting for it's "polluted" spectrum.

The object is shaped like a football due to tidal distortions of the gravitational field in this region (i.e., the object is so close to the WD that the object's Hill sphere has shrunk in size to match the size of an object with asteroid or planetary material). The "hot pole" is a source for essentially all fragments. At the object's surface there is a balance of gravity between the object and the WD, so any loose debris resting on the object's surfce can easily "drift away" from the object with a minimal push, or encounter. Fragments and large dust migrate inward for some reason (possibly the Poynting-Robertson effect for large dust and the Yarkovsky effect for the fragments).

Fragments are continually orbiting within the region of large dust particles. When a fragment collides with another fragment, fresh surfaces are exposed, and it is the continual bombardment of a fresh surface by large dust particles that releases a continuous stream of small dust away from the fragment. But small dust is blown away by radiation pressure, so there soon evolves a steady-state equality of dust generation and dust loss. This is why a new dip feature evolves from a small but deep dip structure to a broader dip of lower depth and stays in this lower state until the dust production process is exhausted (no more fresh surface exposure). The steady-state phase typically lasts a week, sometimes a month and in one case a year.

It will be useful to consider dust as belonging to three categories, based on size:
    1) small dust, radius < 1 micron,
    2) intermediate size dust, radius between 1 and 10 micron,
    3) large dust, radius > 10 micron (which I'll refer to as "sand")

Small dust is removed from the site of its production by two processes: radiation pressure and over-heating to the point of sublimation. Over-heating is due to the fact that the effectiveness of radiating away of heat by blackbody radiation is reduced when size is small compared to the blackbody wavelengths (i.e, emissivity is small at wavelengths < 1 micron) whereas all of the WD's radiation is absorbed by these particles (i.e., albedo is small at wavelengths as small as 0.1 micron). These two processes cause small dust to start moving away from the WD, and during this journey the smallest particles are sublimated to gas (and move inward, eventually forming a gas disk, 10 to 50 WD radii, and ending up falling into the WD's atmosphere and "polluting" it)..

Intermediate size dust is pushed in both directions, away from and toward the WD (by radiation pressure and Poyntin-Robertson drag, respectively). It therefore has a longer residence time near the orbit of its origin. It's residence time may be of the order 1 day; this is based on constraints provided by Keplerian azimuth spreading and maximum dip width arguments. It is this "intermediate size dust that produces dips!

The large dust can be thought of as a background level of "sand" that is continually impacting fragment surfaces, and maintaining the production of smaller size dust. The A-system parent object is orbiting with a speed of 310 km/s. Fragments are likely orbiting at the same speed (in orbits that may be slightly inclined). Ejection speed of collision material is on the order of 1.5 km/s (for intermediate size particles). The ejection speeds of large particles will be less (I don't have a good model for this relationship). A history of previous collisions, at a variety of orbit locations, guarantees that at any point along a fragment's orbit there will be a bombardment of "sand" from all directions with velocity differences as large as 1.5 km/s. I suggest that this is the source of the steady-state production of smaller size dust (intermediate size and small) that is required to exist in order to account for the long lives of dips with a constant depth and width.

The key question for understanding WD1145 dip behavior is all about the mechanism that creates the component of intermediate size dust. The description given above calls for a continual erosion of fragment surfaces by large dust particles, and this is analogous to what happens on the moon - referred to as "micro-meteoroid bombardment." Whereas this is my favorite mechanism for dust creation, another mechanism under consideration for removing material from a fresh surface is sublimation and re-condensation (Vanderburg et al., 2015). Temperatures at the distance of the A-system can be 1300 to 1800 K, depending on surface geometry (crater-shaped bottoms will be hottest, and deeper pits will be the hottest). At these temperatures minerals will sublime (from solid to vapor). It is assumed that the tiny sublimation molecules then re-condense before escaping too far from the sublimating surface.

Here's an example of a typical dip feature evolving into existence (during a 1 or 2 week interval), and enduring for at least 4 months (until the end of the 2018/19 observing season). It's ending occurred sometime during the 5 months between the end of the 2018/19 observing season and the start of the next one.


Figure P4. Dust cloud width and depth vs. date for a 4-month interval in 2019.

The following figure is a waterfall plot for the second half of the 2018/19 observing season, showing the phase wandering of this dip (close to phase = 0.20).


Figure P5. Dust cloud dip feature starting in March, 2019 at phase 0.20 and lasting until July (the end of this observing season). I claim that the phase wandering, starting in late May, is real. The red drift lines correspond to the A-system planetesimal (asteroid or planet core). Drift lines can be seen diverging from early May, indicating when a collision occurred, yielding fragments with fresh surfaces. The 5 fragments produced by the collision were actively producing dust clouds for months. 

To quote a famous line from an old TV crime show, this is "my story" for the creation and behavior of dust clouds orbiting WD1145, and "I'm sticking to it!" 


 

References


    Budaj, Jan, Andrii Maliuk and Ivan Hubeny, 2022, "WD 1145+017: Alternative Models of the Atmospherre, Dust CLouds and Gas Rings, arXiv
    Farihi, J., J. J. Hermes, T. R. Marsh & 11 others, 2021, "Relentless and Complex Transits from a Planetesimal Debris Disk," submitted to MNRAS, arXiv 
    Guidry, Joseph A., Zachary P. Vanderbosch, J. J. Hermes & 13 others, 2020, "I Spy Transits and Pulsations: Empirical Variability in White Dwarfs Using Gaia and the Zwicky Transient Facility," ApJ, arXiv
    Duvvuri,Girish M., Seth Redfield and Dimitri Veras, 2021, "Necroplanetology: Simulating the Tidal Disruption of Differentiated Planetary Material Orbiting WD 1145+017," accepted by ApJ, arXiv 
    Steckloff, Jordan K., John Debes, Amy Steele, Brandon Johnson, Elizabeth R. Adams, Seth A. Jacobson, Alessondra Springman, "How Sublimation Delays the Obset of Dusty Debris Disk Formation Around White Dward Stars," 2021, arXiv
    Duvvuri, Girish M., Seth Redfield and Dimitri Veras, 2020, "Necroplanetology: Simulating the Tidal Disruption of Differentiated Planetary Material Orbiting WD 1145+017," submitted to ApJ, arXiv
    Fortin-Archambault, M., P. Dufour, S. Xu, 2019, "Modeling of the Variable Circumstellar Absorption Features of WD 1145+017," arXiv
    Xu, Siyi, Na'ama Hallokoun, Bruce Gary, Paul Dalba, John Debes and 14 others, 2019, "Shallow Ultraviolet Transits of WD 1145+017," arXiv 
    Gansicke, Boris T., Matthias R. Schreiber, Odette Toloza, Nicola P. Gentile Fusillo, Detlev Koester and Christopher L. Manser, 2019, "Accretion of a Giant Planet onto a White Dwarf," arXiv
    Gansicke, Boris + 26 others, 2019, "Evolved Planetary Systems around White Dwarfs," Astro 2020 Science White paper, arXiv
    Manser, Christopher + 31 others, 2019, "A Planetesimal Orbiting the Debris Disk around a White Dwarf Star," arXiv
    Veras, Dimitri + 8 others, 2019, "Orbital Relaxation and Excitation of Planets Tdally Interacting with White Dwarfs," arXiv  
    Vanderburg, Andrew and Saul A. Rappaport, 2018, "Transiting Disintegrating Debris around WD 1145+017," arXiv 
    Rappaport, S. B. L. Gary, A. Vanderburg, S. Xu, D. Pooley & K. Mukai, "WD 1145+017: Optical Activity During 2016-2017 and Limits on the X-Ray Flux," MNRAS, arXiv 
    Xu, S., S. Rappaport, R. van Lieshout & 35 others, "A dearth of small particles in the transiting material around the white dwarf WD 1145+017," MNRAS link, preprint arXiv: 1711.06960     
    Redfield, Seth, Jay Farihi, P. Wilson Cauley, Steven G. Parsons, Boris T. Gansicke and Girish Duvvuri, 2016, "Spectroscopic Evolution of Disintegrating Planetesimals: Minutes to Months Variability in the Circumstellar Gas Associated with WD 1145+017,"  ApJ, 839, 42, arXiv 
    Alonso, R., S. Rappaport, H. J. Deeg and E. Palle, 2016, "Gray Transits of WD 1145+017 Over the Visible Band," Astron. & Astrophys., arXiv:1603.08823
    Petit, J.-M and M. Henon, 1986, Icarus, 66, 536-555 (link)
    Veras, Dimitri, Philip J. Carter, Zoe M. Leinhardt and Boris T. Gansicke, 2016, arXiv 
    Hallakoun, N., S. Xu, D. Maoz, T.R. Marsh, V. D. Ivanov, V. S. Dhillon, M. C. P. Bours, S. G. Parsons, P. Kerry, S. Sharma, K. Su, S. Rengaswamy, P. Pravec, P. Kusnirak, H. Kucakova, J. D. Armstrong, C. Arnold, N. Gerard, L. Vanzi, 2017, Earth and Planetary Astrophysics, arXiv 1702.05486
    Farihi, J., L. Fossati, P. J. Wheatley, B. D. Metzger, J. Mauerhan, S. Bachman, B. T. Gansicke, S. Redfield, P. W. Cauley, O. Kochukhov, N. Achilleos & N. Stone, "Magnetism, X-ras, and Accretion Rates in WD 1145+017 and other Polluted White Dwarf Systems, MNRAS, arXiv
    Tom Kaye presentation at 2016 Society for Astronomical Science meeting: link   
    Gary, B. L., S. Rappaport, T. G. Kaye, R. Alonso and F.-J. Hamsch, "WD 1145+017 Photometric Observations During Eight Months of High Activity," 2017, MNRAS, 465, 3267-3280. PDF  or arXiv  
    Rappaport, S., B. L. Gary, T. Kaye, A. Vanderburg, B. Croll, P. Benni & J. Foote, 2016, "Drifting Asteroid Fragments Around WD 1145+017," MNRAS, arXiv:1602.00740
    Gaensicke et al, 2015, "High-Speed Photometry of the Disintegrating Planetesimal at WD 1145+017: Evidence for Rapid Dynamical Evolution," arXiv :1512.09150
    Croll et al, 2105, "Multiwavelength Transit Observations of the Candidate Disintegrating Planetesimal Orbiting WD 1145+017," ApJ, arXiv:1510.06434 
    Vanderburg et al, 2015, "A Disintegrating Minor Planet Transiting a White Dwarf," Nature, 2015 Oct 22, arXiv:1510.063387

Related Links  
    Mukremin Kilic's pro/am search of dusty WDs for dips:  https://www.nhn.ou.edu/%7Ekilic/Docs/dusty.html
    Some observing "good practices" for amateurs (book): Exoplanet Observing for Amateurs
    Hereford Arizona Observatory (HAO):  http://www.brucegary.net/HAO/
    Tutorial for faint object observing techniques using amateur hardware: http://brucegary.net/asteroids/  
    Master list of my web pages & Resume

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WebMaster:   Nothing on this web page is copyrighted. This site opened:  2022 November 22