Hello everyone,
while comparing the spectra of V0488 Sge available in AVSpec, I noticed a possible rapid blueward shift of the absorption minimum on the blue side of Hα.
The following sequence is visible:
-
2026-08-26 16:31:57 UTC: approximately 6531.4 Å
Corresponding radial velocity: approximately −1435 km/s
AVSpec Record -
2026-08-26 21:57:19 UTC: approximately 6526 Å
Corresponding radial velocity: approximately −1680 km/s
AVSpec Record -
2026-08-27 05:21:52 UTC: approximately 6514.7 Å
Corresponding radial velocity: approximately −2200 km/s
AVSpec Record
The velocities were estimated using the Hα rest wavelength of 6562.8 Å and the non-relativistic Doppler formula.
Over a period of approximately 12 hours and 50 minutes, the measured absorption minimum therefore moved about 16.7 Å toward shorter wavelengths. If all three measurements trace the same absorption component, the corresponding apparent outflow velocity increased by approximately 760 km/s.
The middle observation is my low-resolution SA100 spectrum. Its absorption minimum is broad and blended with the strong Hα emission, so the value of 6526 Å should be treated as an approximate estimate. Nevertheless, it lies between the other two measurements both chronologically and in wavelength.
I would be very interested to know whether others can reproduce these wavelength measurements from the spectra or have additional observations covering this interval.
All the best,
Philipp