First Detection of Candidate Exoplanets and Brown Dwarfs Orbiting X-Ray Binaries via Direct Imaging

Myriam Prasow-Émond1, 2, Julie Hlavacek-Larrondo1, Kevin Fogarty3, 4, Julien Rameau5, Louis-Simon Guité1, Dimitri Mawet3, 6 et al.
1Université de Montréal, 2 iREx, 3 California Institute of Technology, 4 NASA Ames Research Center, 5 Institut de Planétologie et d’Astrophysique de Grenoble, 6 Jet Propulsion Laboratory


X-ray binaries are thus unique laboratories for studying astronomical objects and phenomena under extreme conditions.


RX J1744.7-2713

Sub-Stellar Companion Candidates

Fig. 5 - L'-band high-contrast image of RX J1744.7-2713. Source: Prasow-Émond et al. (to be submitted).
Fig. 6 - Ks-band high-contrast image of RX J1744.7-2713. Source: Prasow-Émond et al. (to be submitted).



A detected source is not always necesserally bound to the system: it could be, for example, a bright background star. Some of the most common techniques to determine the nature of the sources are listed below.

  1. Astrometry (follow-up observations). It is The most rigorous way to confirm that candidates are sub-stellar companions to the host system. By taking additional data several days/months/years, we can study the proper motion of the objects and therefore conclude if they are bound or not. In the case of RX J1744.7-2713, this kind of analysis will be available in a least 10 years.
  2. Color-magnitude diagram. If observations in two different bands are available, we can construct a color-magnitude diagram to determine if their color and magnitude are more coherent with stars or exoplanets. For RX J1744.7-2713, see Fig. 7 and audio for more detail.
  3. Background probability. Using 3D models of the sky, we can estimate the expected number of sources in a certain area. Depending on the number of sources, we can calculate the probability of finding a source with the same magnitude of a detected candidate.
  4. More observations. In order to study an object more in depth, we can ask for additional observations, e.g. spectoscopic analysis, other band, etc.
Fig. 7 - Absolute magnitude in L'-band versus Ks-L' color for 16 detected sources (circles) in RX J1744.7-2713. More detail in the audio. Source: Prasow-Émond et al. (to be submitted).
There are between 4 and 8 sub-stellar companion candidates in RX J1744.7-2713.