ZTF J1539+5027

ZTF J1539+5027 is an binary star consisting of two white dwarfs. Its orbital period is just under 7 minutes and is measurably decreasing (orbital decay), most of the decrease attributed to gravitational waves, and analysis suggests LISA would detect them. It is an eclipsing binary and a double-line spectroscopic binary. The hotter of the two has a temperature on the order of 50,000 K. The light curve shows not only the reductions due to the eclipses, but a brightening of the less bright star when illuminated by its companion, something like that of a transiting planet. Characteristics:

• Boötes - constellation.
• 15h39m32.1588s - right ascension.
• +50deg27m38.783s - declination.
• 8000 ly - distance.
• 415 seconds - orbital period.
• 0.610 and 0.210 - solar masses.
• 0.01562 and 0.03140 - solar radii (the more massive star has the smaller radius, a characteristic of white dwarfs).