The ultracool helium-atmosphere white dwarf companion of PSR J0740+6620?

Abstract

We report the detection of the likely companion of the binary millisecond pulsar J0740+6620 with the Gran Telescopio Canarias in the $r^{\prime }$ and $i^{\prime }$ bands. The position of the detected starlike source coincides with the pulsar coordinates within the 1$\sigma$ uncertainty of $\approx$ 0.2 arcsec. Its magnitudes are $r^{\prime }=26.51\pm 0.17$ and $i^{\prime }=25.49\pm 0.15$. Comparing the data with the white dwarf cooling tracks suggests that it can be an ultracool helium-atmosphere white dwarf with the temperature $\lesssim$ 3500 K and cooling age $\gtrsim$ 5 Gyr. The age is consistent with the pulsar characteristic age corrected for kinematic effects. This is the reddest source among known white dwarf companions of millisecond pulsars. Detection of the source in other bands would be useful to clarify its properties and nature.

Accepted for publication in MNRAS

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Cited by in corpus (4)

• NICER X-ray Observations of Seven Nearby Rotation-Powered Millisecond Pulsars
• Searching for optical companions to four binary millisecond pulsars with the Gran Telescopio Canarias
• Diagnosing pulsar winds in black-widow, redback, and other binary millisecond pulsar systems
• Binary evolution leading to the formation of the very massive neutron star in the J0740+6620 binary system