Observations of Var Her 04, a newly discovered CV

After the discovery announcement of Var Her 04 by Nakamura (Japan), I had a first opportunity to observe this new cataclysmic variable on June 24th, 2004. Its position is RA = 18h39m26s, Decl = +2604'10" (J2000.0). 

2004, June 24/25

Skies were clear on Jun 24/25 for most of the night, but strong winds reduced the overall quality of the run, which lasted for 0.11 d. I used a 0.35-m f/6.3 telescope and unfiltered ST-7XME CCD camera. The resulting light curve is depicted below. It clearly shows (super?)humps, with an average amplitude of 0.10 mag. It also shows the presence of an eclipse-like dip (around JD +3181.463) with an amplitude of 0.07 mag.

Using Peranso, I deduced a preliminary hump period value of 0.057 +/- 0.009 d (PDM method). The high uncertainty is due to the short observing window. The value is in good agreement with results obtained by other CV colleagues.
 


Var Her 04 lightcurve on Jun 24/25, 2004. Unfiltered CCD observations at CBA Belgium Observatory, 
using a 0.35-m f/6.3 SCT telescope and ST-7XME CCD.

 

2004, June 25/26

June 25/26, 2004 again was a clear nigth, with less winds, and therefore yielding a better accuracy in the overall light curve (see below). I observed Var Her 04 for 3.9 hours (unfiltered CCD), and captured 3 humps. Again, there's a dip superimposed on the hump, but this time less pronounced than during the Jun 24/25 observations. However, the hump profile itself has a clearer signature, closer to a typical superhump profile.

Using a total of 416 observations (2 nights), I looked for periodic signals in Var Her 04's lightcurve, using 4 different methods (in Peranso) : ANOVA, PDM, Dworetsky and Lomb-Scargle. ANOVA, PDM and Dworestky are statistical methods for period determination, whilest Lomb-Scargle is a Fourier method. Yet, all four methods yield a consistent (super?)hump period value of 0.0579 +/- 0.0002 d, so we may assume that this period is already fairly accurate.


Var Her 04 lightcurve on Jun 2
5/26, 2004. Unfiltered CCD observations at CBA Belgium Observatory, 
using a 0.35-m f/6.3 SCT telescope and ST-7XME CCD.

 

I have included the ANOVA period window below, as well as the Var Her 04 light curve folded on the reported period. The phase diagram shows an average hump amplitude of 0.14 mag.

Var Her 04 period analysis window, using the ANOVA method. Significant period at 0.0579 d.

Var Her 04 phase window, showing the light curve folded over a period of 0.0579 d.

 

2004, June 27/28

Another clear night on June 27/28, 2004 over CBA Belgium Observatory, and again completely used to monitor Var Her 04. The resulting light curve (below) shows a number of intruiging, but hard to explain modulations, that arise over various parts of the superhump profile. In some cases, Var Her 04 drops by almost 0.15 mag in a couple of minutes. This might again be eclipses, reappearing in the light curve. Michael Richmond's observations, obtained on the same night, confirm the irregular modulations.

2004, June 28/29

Apart from some initial clouds, the night of June 28/29, 2004 again was clear over CBA Belgium Observatory. Var Her 04's light curve is depicted below, and is once more very different from previous night. In addition to superhumps, the curve clearly shows a fading trend, which is the onset of a rapid dimming of Var Her 04 (observed in detail on June 30th, at which moment it was cloudy over Belgium).

2004, July 01/02

Poor summer weather over Belgium equals poor nights. So, we missed the decline of Var Her 04, and had to wait till Jul 01/02 to again observe the variable at CBA Belgium Observatory. At mag 15.2, and with strong moonlight, this was not an easy target, and the noise in the light curve (see below) clearly has increased. Yet, a hump like profile is still visible, with an amazing amplitude of about 0.3 mag. 

2004, Jul 03/04

During the night of Jul 03/04, Var Her 04 was fluctuating around mag 15.2 (unfiltered), showing a modulation of about 0.2 mag. No dimming or rebrightening trend was visible. 

 

2004, Jul 05/06

This night, Var Her 04 initially was around mag 15.4 (unfiltered), but then showed a sudden fading by 0.15 mag over a very short period. The variable then remained 'steady' around mag 15.6 - 15.7. I tried a period analysis on the this dataset, and the one above, but no conclusive results were obtained.

 

2004, Jul 06/07

This night, Var Her 04 initially was around mag 15.6 (unfiltered), i.e. still slowly fading. At the same time, the variable continues to show irregular hump like modulations of about 0.2 mag.

 

 

 

 
 

 

 

Copyright © 2004 - Tonny Vanmunster.