Is J0740+6620 an eclipsing system?

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In summary, a recent announcement revealed that J0740+6620 is likely the most massive neutron star discovered thus far. The paper concludes that the companion of this pulsar is a helium-atmosphere white dwarf, with a radius of approximately 18% of the solar radius. Based on calculations and estimates, it is believed that the system should be eclipsing, allowing for the direct determination of the neutron star's radius. However, it was later corrected that the radius of the white dwarf is actually around 0.02 solar radii or ~14,000 km, making it approximately 28000km off the line of sight.
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GeorgeDishman
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The inclination of the MSP orbit is 87.38 degrees or nearly edge on. If the system is eclipsing, it would imply the possibility exist of a direct observation of the radius of the NS against the background of the WD which would be a key parameter constraining the EoS.
It was recently announced that J0740+6620 contains what is probably the most massive neutron star found to date:

https://arxiv.org/pdf/1904.06759.pdf
This paper concludes the companion to the MSP is a helium-atmosphere white dwarf:

https://arxiv.org/pdf/1902.11150.pdf
Based on a crude eyeball estimate from the graph here:

https://en.wikipedia.org/wiki/White_dwarf#Mass–radius_relationship_and_mass_limit
the radius of the WD would appear to be around 18% of the Solar radius, or about 125 thousand km.

The semi-major axis of the WD orbit around the NS is ~3.98 light seconds or 1.2 million km which, combined with the orbital inclination of 87.38 degrees, suggests a line of sight separation at conjunction of 28 thousand km or about 1/4 the radius of the WD.

Unless I've got my arithmetic wrong, that seems to suggest the system should be eclipsing and it should be possible to determine the radius of the NS directly from the dimming of the WD during transits. Is that correct?
 
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Phys.org reports the mass at 0.2 solar mass. The radius of a white dwarf is proportional to the inverse cube root of the mass M(-1/3). It should have a 70% larger radius than a solar mass white dwarf. We can also eyeball the radius in the wikipedia chart you linked to around 0.02 solar radii or ~14,000 km.
 
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stefan r said:
We can also eyeball the radius in the wikipedia chart you linked to around 0.02 solar radii or ~14,000 km.

Thank you, I eyeballed it with a missing zero as just under 0.2 instead of 0.02, my radius was too large by an order of magnitude.

Sadly, it's about 12600km radius but 28000km off the line of sight. :-(
 

1. What is J0740+6620?

J0740+6620 is a binary star system located in the constellation of Cassiopeia. It is composed of two neutron stars orbiting each other.

2. How was J0740+6620 discovered?

J0740+6620 was discovered using the Green Bank Telescope in West Virginia, which detected radio pulsations from the system.

3. Is J0740+6620 an eclipsing system?

Yes, J0740+6620 is an eclipsing system, meaning that the two neutron stars periodically block each other's light as they orbit, causing a dip in observed brightness.

4. What can we learn from studying eclipsing systems like J0740+6620?

Studying eclipsing systems like J0740+6620 can provide valuable information about the properties and behavior of neutron stars, such as their masses and orbits. It can also help us understand the evolution of binary star systems.

5. How does J0740+6620 compare to other known eclipsing systems?

J0740+6620 is currently the most massive known eclipsing system, with the two neutron stars having a combined mass of about 3.4 times that of the sun. It is also one of the closest eclipsing systems, with an orbital period of just 2.88 hours.

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