Last night I was measuring the secondary eclipse of the binary NV Cnc. VSX marks it as a EA/SD binary.
I was surprised to see a well defined bump during the middle of the secondary eclipse.
To see if this was real, I downloaded the data for the star from ASAS-3. Here is the phase plot that was generated.
So it appears this shows the same bump during the secondary minimum.
Does anyone know what could be causing this? Is it a known phenomenon?
VSX says EA/RS type and mean magnitude variation.
This AAVSO J. article has a multi-spot model. https://apps.aavso.org/media/jaavso/3512_SBasPVN.pdf (Corrected the duplicated link 2026-Mar-10 (DEY)
Jim (DEY)
Looks like Sebastian just changed the type today. From the revision history:
| Otero, Sebastian Alberto | 2026-03-09 17:38 UTC | Type, period, epoch and range from ASAS-3 and ASAS-SN data. | |||
|---|---|---|---|---|---|
Your link is corrupted (two links run together). Here is the correct one:
Yes, they are talking about NV Cnc. They say:
NSVS 7322420 is a semi-detached system with the primary component filling its critical lobe. The system contains a G3 primary and an M secondary, and the model indicates that the stars are of significantly dissimilar mass. The light curve of the system displays a pronounced O’Connell effect and an unusual “kink” as the system enters and exits secondary eclipse.
I don’t see the kink but I do see a hump. I will write to the authors to see if they have seen this.
Bill
Since the rest of the LC seems to have cycle-to-cycle variations it might be the spot position, size, etc. variability contribution. Could be an interesting star that might allow for generating a spot model variation time-series!
I fixed the duplicated link… I blame Microsoft, and/or the spell/context checker AI. 
Jim (DEY)
