[vsnet-alert 21207] Re: CTCV J1940-4724 outburst and a bonus

[Josch Hambsch]

Last nights the star was back at the mag 16 level. Dropping from mag. 16 to 16.5 at the end of the session.
Data are with the AAVSO and VSNET

Josch

-----Original Message-----
From: vsnet-alert [mailto:vsnet-alert-bounces at ooruri.kusastro.kyoto-u.ac.jp] On Behalf Of Josch Hambsch
Sent: Montag, 3. Juli 2017 22:00
To: 'Denis Denisenko'; vsnet-alert at ooruri.kusastro.kyoto-u.ac.jp
Subject: [vsnet-alert 21204] Re: CTCV J1940-4724 outburst and a bonus

Hi Denis,

I do have a time series of this CV and it shows some variation, but on a longer time scale. Via Peranso I got a preliminary period of about 0.24d. I have observed about the same time, so could be a coincidence. Needs definitely more data. The magnitude variation is about 0.32 mag. It varied from about mag 14.62 to mag 14.95.
Data are sent to the AAVSO and VSNET.

Regards,

Josch

-----Original Message-----
From: vsnet-alert [mailto:vsnet-alert-bounces at ooruri.kusastro.kyoto-u.ac.jp] On Behalf Of Denis Denisenko
Sent: Samstag, 1. Juli 2017 21:34
To: vsnet-alert at ooruri.kusastro.kyoto-u.ac.jp
Subject: [vsnet-alert 21188] CTCV J1940-4724 outburst and a bonus

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


---
Diese E-Mail wurde von Avast Antivirus-Software auf Viren geprüft.
https://www.avast.com/antivirus