[vsnet-alert 26170] ASASSN-21qa likely eclipse period

[Denis Denisenko d.v.denisenko@gmail.com via vsnet-alert]

Following [vsnet-alert 26168] by Taichi Kato, I have analyzed ZTF DR6 data
for ASASSN-21qa. The star is definitely eclipsing, with the most likely
orbital period of 0.193898 d (4.65 hr or 279.2 minutes) and epoch of
minimum JD=2458643.963.

Phased light curve from ZTF DR6 in r filter:
http://scan.sai.msu.ru/~denis/ASASSN-21qa-ZTF-phased_LC.gif

Preliminary eclipse ephemeris for the next two days supposing the period
above is correct:

------------------------  ASASSN-21qa   ------------------------
Epoch          Primary min                  Secondary min
number     JD      YYYY MM DD HH.H       JD      YYYY MM DD HH.H
----------------------------------------------------------------
4129  2459444.5678 2021  8 18  1.6  2459444.6648 2021  8 18  4.0
4130  2459444.7617 2021  8 18  6.3  2459444.8587 2021  8 18  8.6
4131  2459444.9556 2021  8 18 10.9  2459445.0526 2021  8 18 13.3
4132  2459445.1495 2021  8 18 15.6  2459445.2465 2021  8 18 17.9
4133  2459445.3434 2021  8 18 20.2  2459445.4404 2021  8 18 22.6
4134  2459445.5373 2021  8 19  0.9  2459445.6343 2021  8 19  3.2
4135  2459445.7312 2021  8 19  5.5  2459445.8282 2021  8 19  7.9
4136  2459445.9251 2021  8 19 10.2  2459446.0221 2021  8 19 12.5
4137  2459446.1190 2021  8 19 14.9  2459446.2160 2021  8 19 17.2
4138  2459446.3129 2021  8 19 19.5  2459446.4099 2021  8 19 21.8
4139  2459446.5068 2021  8 20  0.2  2459446.6038 2021  8 20  2.5
4140  2459446.7007 2021  8 20  4.8  2459446.7977 2021  8 20  7.1
----------------------------------------------------------------

Keeping in mind that for some "EW-type" dwarf novae the primary quiescent
eclipse becomes the secondary in outburst (remember 2016 June outburst of
CSS_J162117.3+441254 with P=4.988 hr), we might expect similar variations
(and even reversal) of eclipse depths in the case of ASASSN-21qa.
Observations are definitely encouraged.

ASASSN-21qa position: 18 14 39.37 +02 19 08.3

Denis Denisenko