[vsnet-alert 21190] Re: CTCV J1940-4724 outburst and a bonus

[Rod Stubbings]

Hi Denis,

I have also been keeping tabs on this star after your request and 
noticed a brightening. Expecting the star to brighten further I checked 
the field 7 hours later and it had faded.

Regards,
Rod.

CTCV J1940-4724           170630.574   170  Stu.RASNZ 

CTCV J1940-4724           170701.392   154  Stu.RASNZ 

CTCV J1940-4724           170701.689  <165  Stu.RASNZ 


Rod Stubbings
Tetoora Road Observatory
Victoria, Australia
Telescope: "Infinity" 22" f/3.8
stubbo at sympac.com.au
http://rodstubbingsobservatory.wordpress.com/


On 2/07/2017 5:33 AM, Denis Denisenko wrote:
> The neglected dwarf nova in Telescopium CTCV J1940-4724 is going into
> outburst on the images from iTelescope.Net T32 in Siding Spring.
> 
> CTCV J1940-4724
>    20170630.6832  17.065CV  T32
>    20170630.6857  17.184CV  T32
>    20170701.6072  14.801CV  T32  Outburst!
>    20170701.6097  14.774CV  T32  Outburst!
> 
> VSX entry: https://www.aavso.org/vsx/index.php?view=detail.top&oid=477956
> Range from Siding Spring Survey data: 13.2-17.5 CV
> Approximate orbital period: 0.0809 d from spectroscopic observations
> covering 0.11 d (less than 1.5 period!)
> 
> With a period like that CTCV J1940-4724 must be nothing but a UGSU
> dwarf nova. Time-resolved photometry is requested. Recommended
> Comparison and Check stars are 135 (V=13.479) and 152 from AAVSO
> sequence marked on the color-combined DSS finder chart
> http://scan.sai.msu.ru/~denis/J1940-4724-comp_stars.jpg (10'x10' FOV).
> 
> Bonus: there's another hot star 15' from CTCV J1940-4724 named
> SSS_J194140.2-473502. SSS catalog (Drake et al., 2017, MNRAS) lists it
> as a Delta Scuti variable with P=0.142769 d and range 17.7-18.0 CV.
> However, it is impossibly hot in the ultraviolet to be the HADS star.
> FUV=16.378, NUV=16.714 in GALEX DR5. (FUV-NUV)=-0.34 is too hot even
> for CVs, rather typical of sdB stars. Hot subdwarf varying by 0.3m at
> P=0.14277 d is even more interesting than the dwarf nova in outburst.
> 
> Chart showing the position of both stars:
> http://scan.sai.msu.ru/~denis/J1941-4730.jpg
> 
> Please take the opportunity to investigate two poorly studied hot
> variables in one field!
> 
> Denis Denisenko
> Sternberg Astronomical Institute of Moscow State University
> 
>