Neglected Southern CVs

This post is mostly for the Southern hemisphere observers (and, of course, for remote users of telescopes in Australia, South Africa, Chile and Argentina). I have noted recently that some rather bright cataclysmic variables discovered over the last 15 years by Calan-Tololo and Edinburgh-Cape surveys were not included in AAVSO VSX or had wrong coordinates in the database. In the last three days I have updated the positions of CTCV J0333-4451 and CTCV J2056-3014, plus made initial submissions for CTCV J1940-4724 and EC 21147-6437. Though they are not formally the part of any campaign (yet), I will try to persuade the observers (CCD or visual ones) to keep your eyes on them. One by one, constellation by constellation.

CTCV J1940-4724: https://www.aavso.org/vsx/index.php?view=detail.top&oid=477956 - dwarf nova in Telescopium. Range 13.2-17.5m from Siding Spring Survey, orbital period 0.0809 d from single-night spectroscopic observations covering 0.11 d (less than 1.5 period)! The star is quite active, it has shown at least 14 outbursts in nine years of SSS observations. Some outbursts are to ~14m and the others to ~13m. Thus, it can be a SU UMa-type dwarf nova. Position (J2000.0): 19 40 37.6 -47 24 50

CTCV J2056-3014: https://www.aavso.org/vsx/index.php?view=detail.top&oid=133436 - dwarf nova in Microscopium with an even brighter range 12.6-17.1m in SSS data. This one has an orbital period 0.0732 d and white dwarf spin period of 0.0107 d (15.4 min). That's why the type is UG/DQ, even though He II 4686 line is very weak in spectra. J2056-3014 was in outburst on two DSS plates out of six, and also several times in ASAS-3 data. Well worth following, too! Coordinates: 20 56 52.15 -30 14 39.1

EC 21147-6437: https://www.aavso.org/vsx/index.php?view=detail.top&oid=477966 - eclisping CV in Pavo (Peacock) with an X-ray counterpart 1RXS J211859.0-642522. Note the Edinburgh-Cape (EC) name is in archaic B1950.0 coordinate system, so the J2000.0 position has different figures: 21 18 49.93 -64 25 13.3. This is the only eclipsing Novalike variable (NL+E) in the period gap. P is 0.111682 d (2.68 hr), the maximum magnitude varies from 14.2 to 14.6, and the minimum is 15.8m. Note the eclipses are asymmetric, so the minimum and mid-eclipse times are different. Also, if this star ever goes into an outburst, it may become brighter than VW Hya (8.4m) and SS Cyg (7.8m). Why? Because the UGSU-type variable TU Men with the closest period ( 0.1172 d) has an amplitude of 7 magnitudes (11.6-18.5 V). If EC 21147-6437 ever decides to become a dwarf nova, it will be the brightest DN on the whole sky. But who knows, it may turn into VY Scl-type anti-nova instead and go to a low state. Only observations will tell!

Good observing, and clear skies to the rest of the world while Siding Spring is clouded out until June 12th!

Denis (DDE)