[vsnet-outburst 24919] Re: [vsnet-alert 24139] Re: (cba:chat) ASASSN-15kd: new SU UMa-type dwarf novae

Sat Apr 4 04:48:49 JST 2020

Hi John,

Thanks for mentioning. The 17th mag G star and ASASSN-15kd must be two
different objects. Here's my astrometry of ASASSN-15kd (J2000.0, residuals
0.2"):

RA = 18h 21m 34.64s

Dec = +02° 03’ 07.0”

ASASSN-15kd is showing a remarkable decline rate of ~0.26 mag/day, which is
high for a SU UMa-type dwarf nova. I therefore waited to report below
findings, till I had a second night of superhumps confirmation. I combined
both nights of observations to the below phase diagram,  folded on the
reported period. I believe it's the obvious signature of superhumps.

Best regards

Tonny 

-----Original Message-----
From: vsnet-alert [mailto:vsnet-alert-bounces at ooruri.kusastro.kyoto-u.ac.jp]
On Behalf Of John.R.Thorstensen at Dartmouth.edu
Sent: vrijdag 3 april 2020 17:58
To: cba-chat at cbastro.org
Cc: 'ALERT, VSNET'; 'vsnet-outburst'; vsnet-outburst at yahoogroups.com;
vsnet-newvar at yahoogroups.com; 'Taichi Kato';
vsnet-campaign-dn at ooruri.kusastro.kyoto-u.ac.jp
Subject: [vsnet-alert 24139] Re: (cba:chat) ASASSN-15kd: new SU UMa-type
dwarf novae

I took a spectrum of a roughly 17th mag star on this position in 2017 March,
and found it to be an ordinary G star.

This is very likely a chance superposition; the CV evidently gets much
fainter than this star, so its range of variability is larger than it might
appear.

John Thorstensen

On Fri, 3 Apr 2020, Tonny Vanmunster wrote:

> 

> Dear colleagues,

> 

>  

> 

> I have collected 4 nights of unfiltered CCD observations of 

> ASASSN-15kd (2020, Mar 25/26, 29/30, Mar 31/Apr 01 and Apr 02/03), using
my CBA Belgium Observatory and CBA Extremadura Observatory telescopes.

> 

>  

> 

> During the first two nights, there was hardly any periodic modulation 

> in the observations. However, the data from Mar 31/Apr 01 and Apr 02/03
show well developed superhumps with an amplitude of 0.18 mag, hence
establishing ASASSN-15kd as new SU UMa-type dwarf nova.

>  Using 4 different period analysis methods [Lomb-Scargle, Generalized 

> Lomb-Scargle, PDM, ANOVA] (Peranso 3.0), the combined superhump period is
0.0843 +/- 0.0045d. ASASSN-15kd was at mag 16.8 (CV ) on Apr 03rd.

> 

>  

> 

> Observations will be sent to AAVSO, CBA and VSNET for further analysis.

> 

> Follow-up observations are highly recommended to refine the superhump
period and to study its further evolution.

> 

>  

> 

> Best regards

> 

> Tonny

> 

> 

> --

> 

> Tonny Vanmunster

> CBA Belgium Observatory

> CBA Extremadura Observatory

>  <http://www.cbabelgium.com> www.cbabelgium.com

>  <http://www.peranso.com> www.peranso.com

> 

>  

> 

> 

> 

--------------------------------------------------------

John R. Thorstensen

Department of Physics and Astronomy

Dartmouth College

6127 Wilder Laboratory

Hanover, NH 03755

Office: 239 Wilder Hall

Phone:  603 646 2869     Fax: 1446   Hinman Box 6127

--------------------------------------------------------

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