RLOF in same timestep as SN

[reinhold-willcox]

Describe the bug When RLOF occurs in the same timestep as a SN, some of the parameters and physics become confusing and/or wrong.

Linked below is a very unequal mass system which undergoes CE, followed by an episode of RLOF, leading into an USSN. The RLOF and SN occur in the same timestep, although the RLOF should have resulted in a merger and no SN. Because the system is very close immediately before the SN, the SN remnant ends up as an ultra-fast runaway pulsar. Also, some of the post RLOF parameters more correctly apply to the post SN system, including the type and mass of the SN star, and a negative separation.

I believe the issue is that the merger flag is not correctly set in the middle of the timestep before the SN is initiated, so that the SN goes ahead and results in the output it thinks is appropriate. Then the post-RLOF printing occurs at the end of the full timestep, so that these parameters reflect the effect of the SN.

There may be a way to tweak the order of functions called, flags raised, and output printed, but I think the cleanest approach is to split the events completely, and enforce that only 1 major event (MT, CE, SN) occurs in a given timestep.

Label the issue urgency_moderate - This is a moderately urgent issue severity_moderate - This is a moderately severe bug

To Reproduce I've attached an args file and a grid file. Download them into a convenient directory and run COMPAS $(< comp_args.txt)

Expected behavior Should end in a merger, with no SN.

Versioning (please complete the following information):

• COMPAS v02.18.09

[reinhold-willcox]

grid.txt comp_args.txt

[reinhold-willcox]

@jeffriley The grid and arguments above should reproduce the case BB issue.

[reinhold-willcox]

Closing this issue as it falls under the umbrella issue #805