New CVs by MASTER

During the last 10 days MASTER robotic telescopes have discovered six new cataclysmic variables brighter than 17m, two of which are brighter than 14m. Three of six new CVs are truly remarkable. Two of them are being covered pretty well by the observers, but I would like to draw your attention to the stars which are in the need of more observations right now.

First I will summarize the newly discovered CVs in chronological order omitting the 'MASTER OT' prefix before their J2000.0 coordinates.

J000820.50+773119.1  Sep. 27.888  16.6-21.0  Cep  ATel #4441
J042609.34+354144.8  Sep. 30.663  12.6-16.7  Per  ATel #4441
J054317.95+093114.8  Sep. 30.785  13.4-21.0  Ori  ATel #4446
J194741.84-020348.9  Oct. 04.667  16.8-21.5  Aql  ATel #4458
J192739.31+020014.3  Oct. 04.680  15.2-19.5  Aql  ATel #4458
J071856.78+601833.3  Oct. 08.088  15.5-<21:  Cam  ATel #4465

J042609.34+354144.8 in Perseus is the first dwarf nova discovered in the common proper motion pair with another red dwarf 16.6" away. This is a hierarchical triple system with the orbital period about 1.6 hr for the close pair and more than 60,000 yr for the third component. The proper motion (16, -42 mas/yr) is as fast as that of U Gem and only 2.5 times slower than SS Cyg - the brightest (and likely the nearest) Northern dwarf nova. This new CV is related to the bright ROSAT X-ray source 1RXS J042608.9+354151 and also has an UV counterpart GALEX J042609.3+354145 (FUV=17.70, NUV=17.52). Following the detection by MASTER, I have found another outburst on Feb. 1993 plates of Moscow collection and yet another 'prehistoric' one on the 1912 (!!!) plate from the digitized Heidelberg observatory plates. Superhumps with an amplitude more than 0.2m and the period evolving from 0.0676d to 0.06715d were found in this system, confirming it to be a UGSU-type variable.

J054317.95+093114.8 is the other object of special interest which is currently entering the most important phase of its light curve. Thanks to Josch Hambsch, we have a uniform coverage of this star in 7 nights from the same telescope and with the same reference stars. Amazingly, the averaged light curve is nearly copying that of MASTER OT J211258.65+242145.4 - UGWZ-type dwarf nova in Vulpecula discovered on June 25 which has collected more than 11,000 observations in AAVSO database. During first 4 nights J0543+0931 was fading at nearly the constant rate of 0.2 mag/day, after which it has entered a plato at around 15.4m (even the magnitude is the same as for J2112+2421)! Meanwhile the amplitude of variability has grown from 0.1m to more than 0.3m. The similarity of two stars is as striking as the difference in their orbital periods. J2112+2421 had superumps period evolving from 0.0598 to 0.0606d. Despite the outburst amplitude (~8m) typical for the WZ Sge type dwarf novae, J0543+0931 is showing the period closer to 0.10d. But if the analogy with J2112+2421 persists, it should fade to ~18m in 3-4 nights from now, after which it can show multiple rebrightenings to ~16m in the next month. This is why the continued observations of this star in Orion are required.

And the third star from the list that can be very interesting is J071856.78+601833.3 in Camelopardalis. The amplitude of variability is at least 6 magnitudes since nothing is visible on the combination of DSS plates to limiting magnitude fainter than 21.5. No time-resolved photometry has been reported so far. The only thing I can tell for sure is that it's blue, since we have obtained confirmation images from MASTER-Tunka in two tubes with two filters simultaneously, and it is definitely brighter in V than in I. So, this one may be a dwarf nova of UGWZ type, or yet another UGSU. In any case, observations are needed!

Best regards,

Denis in Moscow