Searching for Exoplanets Around X-Ray Binaries with Accreting White Dwarfs, Neutron Stars, and Black Holes

We recommend that the search for exoplanets around binary stars be extended to include X-ray binaries in which the accretor is a white dwarf, neutron star, or black hole. We present a novel idea for detecting planets bound to such mass transfer binaries: we propose that the X-ray light curves of these binaries be inspected for signatures of transiting planets. X-ray transits may be the only way to detect planets around some systems, while providing a complementary approach to optical and/or radio observations in others. Any planets associated with X-ray binaries must be in stable orbits. We consider the range of allowable separations and find that orbital periods can be hours or longer, while transit durations extend upward from about a minute for Earth-radius planets in very close orbits, to hours for Jupiter-radius planets in wider orbits. The search for planets around mass transfer binaries could begin at once with existing X-ray observations of these systems. If and when a planet is detected around an X-ray binary, the size and mass of the planet may be readily measured, and it may also be possible to study the transmission and absorption of X-rays through its atmosphere. Finally, a noteworthy application of our proposal is that the same technique could be used to search for signals from extraterrestrial intelligence. If an advanced exocivilization placed a Dyson sphere or similar structure in orbit around the accretor of an X-ray binary in order to capture energy, such an artificial structure might cause detectable transits in the X-ray light curve.

Comments: Submitted to ApJ

Similar Publications

Linear polarization can be used as a probe of the existence of atmospheric condensates in ultracool dwarfs. Models predict that the observed linear polarization increases withthe degree of oblateness, which is inversely proportional to the surface gravity. We aimed to test the existence of optical linear polarization in a sample of bright young brown dwarfs, with spectral types between M6 and L2, observable from the Calar Alto Observatory, and cataloged previously as low gravity objects using spectroscopy. Read More

We present here in full detail the evolution of the angular momentum deficit (AMD) during collisions as it was described in (Laskar, PRL,2000). Since then, the AMD has been revealed to be a key parameter for the understanding of the outcome of planetary formation models. We define here the AMD-stability criterion that can be easily verified on a newly discovered planetary system. Read More

In recent laboratory studies the robustness of a bouncing barrier in planetesimal formation was studied with an ensemble of preformed compact mm-sized aggregates. Here we show that a bouncing barrier indeed evolves self-consistently by hit-and-stick from an ensemble of smaller dust aggregates. In addition, we feed small aggregates to an ensemble of larger bouncing aggregates. Read More

Dormant or near-dormant short-period comets can unexpectedly regain ability to eject dust. In many known cases, the resurrection is short-lived and lasts less than one orbit. However, it is possible that some resurrected comets can remain active in latter perihelion passages. Read More

High resolution Hubble Space Telescope (HST) image analysis of the MOA-2008-BLG-310 microlens system indicates that the excess flux at the location of the source found in the discovery paper cannot primarily be due to the lens star because it does not match the lens-source relative proper motion, $\mu_{\rm rel}$, predicted by the microlens models. This excess flux is most likely to be due to an unrelated star that happens to be located in close proximity to the source star. Two epochs of HST observations indicate proper motion for this blend star that is typical of a random bulge star, but is not consistent with a companion to the source or lens stars if the flux is dominated by only one star, aside from the lens. Read More

The gas giant planets in the Solar System have a retinue of icy moons, and we expect giant exoplanets to have similar satellite systems. If a Jupiter-like planet were to migrate toward its parent star the icy moons orbiting it would evaporate, creating atmospheres and possible habitable surface oceans. Here, we examine how long the surface ice and possible oceans would last before being hydrodynamically lost to space. Read More

TRAPPIST-1 is a nearby 0.08 Msun M-star, which has recently been found to harbor a planetary system of at least 7 Earth-mass planets, all within 0.1 au. Read More

We present a new "completed event" microlensing event-finder algorithm and apply it to the 2015 Korea Microlensing Telescope Network (KMTNet) data. The algorithm works by making linear fits to a (t0,teff,u0) grid of point-lens microlensing models. This approach is rendered computationally efficient by restricting u0 to just two values (0 and 1), which we show is quite adequate. Read More