Upcoming eclipse of V0795 Cas

American Association of Variable Star Observers (AAVSO)
Wed, 07/27/2022 - 00:20

V0795 Cas is a bright (V= 8.9) eclipsing binary system discovered by the Hipparcos satellite.

Its period had remained unknown until today's revision by Paul York combining TESS and Hipparcos data.
TESS caught a primary and a secondary eclipse.

Now we know that the system is an EA/GS with a period of 82.595 d. and -as usual- the amplitude of each of the eclipses varies strongly with wavelenght due to the different temperatures of the components.
TESS amplitude (Ic-like) of the primary eclipse is much shallower than in the visual bands, while the opposite happens with the secondary, which has an amplitude of 0.03 mag. for TESS but might be almost undetectable in V.

There is a small chance that the period is not correct so obtaining more observations (especially of the secondary eclipse, if you are able to reach 0.01 mag. precision or better) is important.

The ephemeris for the next primary eclipse (0.2 mag. deep in V) indicates that it will start around
September 11, 2022 00:15 UT, with mideclipse at September 12, 06:00 UT, and ending around September 13, 11:44 UT.

But the interesting news is that Min II should happen next Monday!
The eclipse lasts 2 and a half days, so it will start on Sunday and will end on Tuesday:
first contact on July 31, 2022 17:08 UT, with mideclipse at August 1, 22:52 UT, and ending around August 3, 04:35 UT.

So if you are an observer able to observe a 9th magnitude star in Cassiopeia the upcoming days, we encourage you to do so.

As mentioned above, the amplitude will be larger in longer wavelengths, so if you have Ic or Rc filters, we encourage you to use them, along with V.
Unfiltered observations might also show an amplitude larger than in V.

Eclipses are total and the size of the stars is very different so the ascending and descending branches of the eclipses are very fast.
Securing observations before and after the eclipse is important, to know the zero point of your observations and to see if there are intrinsic variations present. These systems may show some long-term variability.

Information about the target can be found on its VSX entry.

Coordinates are:  02 53 34.73 +73 46 16.3 (J2000.0)

Good observing!