I Is J0740+6620 an eclipsing system?

418
29
Summary
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:


This paper concludes the companion to the MSP is a helium-atmosphere white dwarf:


Based on a crude eyeball estimate from the graph here:


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?
 

stefan r

Science Advisor
Gold Member
764
208
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.
 
418
29
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. :-(
 

Want to reply to this thread?

"Is J0740+6620 an eclipsing system?" You must log in or register to reply here.

Related Threads for: Is J0740+6620 an eclipsing system?

  • Posted
Replies
2
Views
2K
  • Posted
Replies
5
Views
3K
  • Posted
Replies
2
Views
2K
  • Posted
Replies
11
Views
3K
Replies
7
Views
3K
Replies
8
Views
1K
Replies
1
Views
3K
Replies
5
Views
6K

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving
Top