Inverse Transits

I was talking to last week’s seminar speaker, and we were talking about Planet Hunters and some of the things that might be lurking in the Kepler data.  One cool thought is there might be inverse transits so instead of dimming events, instead the star actually appears brighter.

There are lots of eclipsing binaries that you’ve probably seen as you’ve been classified, but another interesting type of eclipsing binary might be a transiting white dwarf orbiting a main sequence star. White dwarfs are about the same size or a little bit bigger than the Earth about half as massive as the Sun. Depending on where the white dwarf orbits, there could be magnification causing a brightening as the white dwarf crosses in front it’s companion star. This magnification is caused by gravitational microlensing, where a massive object bends  light of a background source resulting in images of the source that are magnified and distorted. Transiting exoplanets are not massive enough to bend and distort the light of their companion stars significantly. For eclipsing binaries it looks white dwarfs are in the sweet spot, if they are orbiting extremely close to their partner main sequence star. Papers in 2003  by Sahu and Gilliland (2003) and Farmer and Agol predicted that Kepler might be able to detect such events. In these cases during the transiting event, the ligthcurve gets brighter rather than fainter. These events last as long as the transit does so only a few hours (if the white dwarf is orbiting at 1 AU the event is ~10 hours in duration).

Here’s some examples from a paper by Sahu and Gilliland (2003) .

A transiting 0.6 solar mass white dwarf orbiting at 1 AU


0.6 solar mass white dwarf at different orbital radii from a solar-type star

There are some estimates of how many might be there ranging from a few to a about a hundred or so events in the Kepler monitored stars, but we really don’t know.  No one has detected them, and there could be 1 or none but with so many eyeballs staring at the data, we might uncover them if they’re there. Anyone seen anything like this in the light curves you’ve classified? It would be very exciting if we found one, it would be the first such discovery – if you see an inverse transit like the examples above, please share on Talk and let us know about your discovery!




21 responses to “Inverse Transits”

  1. Paul Drye says :

    As a matter of fact, I do:

    First quarter. It rises and drops *extremely* quickly, to the point that I rather suspect it’s wonky data, but otherwise it fits your description.

    • Meg says :

      yeah that definitely looks like it – though ti would be nice to see and ingress and egress which makes my suspicious about it – the key would be saying the repeat – each transit will have the magnification – I’d definitely watch this star over the coming data releases but I also think the timescale might be wrong these events only last a few hours like transits

  2. betto_rayados says :

    at the very beginning I remeber I saw something like this and I commented the star, but I don’t know how to recover this comment and therefore the star….

  3. MICHEL (cosmicphil) says :

    Is SPH10064892 a candidate for White dwarf transit ? But SPH10125745 is also fascinanting

  4. MICHEL (cosmicphil) says :

    And also SPH10072124 ?

  5. MICHEL (cosmicphil) says :

    SPH10067659 looks like another inverse transits

  6. MICHEL (cosmicphil) says :

    SPH10058273 is extremely wonderfull

  7. Greg_78 says :

    Hi, is it something like that :


  8. Andres Eloy (andsul) says :

    Something like this? OBJECT APH22088182

  9. Meg says :

    Thanks for searching for light curves for these things.

    Most of these look like flares to me – nice examples of flares – so these would be symmetric and if you zoom in should have a very U symmetric shape – the flares rise really sharply – also really you would need to see repeats so same event repeated –
    Also I think alot of flares have much higher amplitudes – check out the plots you see that the amplitude is only .02 to .002 above the median value for the light curve – flares jump really high

    a few others have the shape but last for several days implying something else maybe a cataclysmic variable. these events only last several hours like transits, so if you see something that lasts days that’s not the events I’m talking about

    APH22088182 is just stellar variability

    APH10058273 – looks like it’s contaminated by another star


  10. cosmicphil says :

    What do you think about this one Meg ?

  11. cosmicphil says :

    Other inverse transits at :

  12. Dipayan says :

    Would be interesting to watch a white dwarf transiting another white dwarf (I wonder if that would be possible).

  13. echo-lily-mai says :

    In case it gets missed here is the link for the “Inverse transit” candidates discussion on PH Talk #inverse

  14. Kris says :

    How about this one?

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