Skip to main content


16 posts / 0 new
Last post
SPK's picture

PNV J20422233+2712111 (updated: UGWZ:)

2017 04 13.736 UT
RA 20 42 22.33 DEC +27 12 11.1
11.1 mag (CCD, unfiltered)

"2017 04 13.736
Discovered by H. Nishimura, Kakegawa, Shizuoka-ken, Japan, using Canon EOS 5D digital camera + 200-mm f/3.2 lens. Independent discoveries by T, Kojima (April. 13.743 UT, mag.= 10.5), Gunma-ken, Japan and by S. Kaneko (April 13.754 UT, mag.= 11.1), Kakegawa, Shizuoka-ken, Japan. Nishimura writes discovered from three frames, nothing is visible two recent frames taken on 2017 April 3.749 and 11.740 UT (limiting mag.= 13). Kojima writes discovered from three frames, nothing is visible a recent frame taken on 2017 April 4.779 UT limiting mag.= 13.5). Kaneko writes discovered from four frames, nothing is visible a recent frame taken on 2017 April 11.7 UT (limiting mag.= 14.8)."

"2017 04 13.736
Discovery images by Nishimura and Kojima are put at

The UV source GALEX J204222.4+271210/J204222.5+271211 (NUV= 20 mag) is within 2" of the reported position of the transient.
This UV source is probably identical with the blue object SDSS J204222.39+271210.9 (SDSS DR7: g= 20.01, r= 20.12, u= 20.21, i= 20.19 mag; Gaia DR1: G= 20.09 mag).
Several other optical sources are within few arcseconds of the reported position of the transient.

(Spectroscopy and precise astrometry are urgently required.)
UPDATED: Time-resolved photometry is urgently required!

Clear skies,

SPK's picture
Independent discovery by Yukio Sakurai

"2017 04 13.773
Mag.= 11.1, Independent discovery by Y. Sakurai, Ibaraki-ken, Japan, using Nikon D700 + 180-mm lens."

perdiguero's picture


yes, definitively there is a new object on this position and it doesn't appear on DSS images, at least with this magnitude. I tried to take a low resolution spectrum (R=888) but I only see a confuse continuum with a maximun intensity near 4000 A.

Traitement with a gaussian filter shows only weak Balmer absortion bands at 4343 A (H-gamma) and 4101 (H-delta). This spectrum remembers me a dwarf nova (UGSS or similar) near the maximun.

All the best,


wkl's picture
PNV J20422233+2712111


here is a first CCD image from this morning (bright moon).

6inch Newton f3 in my observatory in Wenigumstadt Germany

Best Regards


SPK's picture
Shizuo Kaneko's report

"2017 04 13.786
Kaneko reports his photometric magnitudes after discovery, 2017 April 13.754, 11.2; 13.755, 11.1; 13.785, 11.2; 13.785, 11.1; 13.754, 11.1; 13.755, 11.4; 13.786, 11.3; 13.786, 11.3."

SPK's picture
WZ Sge-type dwarf nova? Time-resolved photometry is required.

PNV J20422233+2712111 seems to be a dwarf nova in outburst rather than a classical nova. The outburst amplitude is apparently very large (9 magnitudes) --> probably UGWZ subtype.

***** Time-resolved photometry is urgently required. *****

SPK's picture
Akira Takao's negative observation on 12 April 2017

"2017 04 12.828

No object brighter than about 12.5 mag was detected one day before at the reported position. My image taken with 100 mm lens is here:

Akira TAKAO (Kitakyushu, Japan)"

SPK's picture
Seiichiro Kiyota's follow-up report

2017 04 14.4709 UT

Photometry results were B=11.72, V=11.91, Rc=12.00 and Ic=12.18 with 0.43-m f/4.5 CDK Astrograph + FLI-PL6303E CCD (T21, iTelescope.NET) at Mayhill, NM, USA. It has rather blue color. So it might be dwarf nova. My image is available at

Seiichiro Kiyota (Kamagaya, Japan)

SPK's picture
Koichi Itagaki's report

2017 04 13.712 UT

Itagaki, Yamagata, reports his observation mag= 11.8 on 2017 Apr. 13.712 UT, position 20h 42m 22s.34, +27 12' 12.9.

HBB's picture
PNV J20422233+2712111

CCD images at 2017 04 17.396

V=12.369, err=0.003

B=12.268, err=0.001


Deconinck Michel
Deconinck Michel's picture
Thank ou for all info, I

Thank ou for all info, I appreciate!

My visual estimation this morning 2017/04/17 2:37 UTC : +12.2 


SPK's picture
Katsumi Yoshimoto's follow-up report

2017 04 14.462 UT

K. Yoshimoto, Yamaguchi, reports his observation using 0.25-m f/3.4 Mayhill telescope remotely, mag. B=11.91, V=11.96, I=12.07, position 20h 42m 22s.42, +27 12' 11".2. Image at

SPK's picture
T. Noguchi's follow-up report

2017 04 14.716 UT

Mag.= 12.3 observed by T. Noguchi, Chiba-ken, Japan, using 0.23-m f/6.3 Schmidt Cassegrain + unfiltered CCD. Image at

WBY's picture
PNV J20422233+2712111 Sequence available on VSP

A sequence for PNV J20422233+2712111 was uploaded to VSP this morning. Be aware that the target is only about 3 arcsec separation SE of the centroid of  a 17th magnitude star.  

Brad Walter, WBY

SPK's picture
Superhumps detected!

This star was observed with the 14" robotic unit part of the Virtual Telescope Project in Italy.
After two hours of observations, we see this transient is clearly showing 0.1-mag large superhumps with period of around 90 minutes. More details will follow.

Gianluca Masi and Patrick Schmeer

SPK's picture
OT J204222.3+271211: superhump period

(PNV J20422233+2712111 --> OT J204222.3+271211, our policy is not to use PNV for an apparent non-nova)

Tamas Tordai has reported observations and detected one superhump. ... We have received observations during the early superhump phase but we have not yet detected confident early superhumps.

Colin Littlefield and Stephen Brincat have reported observations. The superhump period is 0.05481(2) d. We need more observations, since each run has not been long enough to exclude an alias. Littlefield's data on Apr. 18 already showed superhumps (likely stage A rather than early superhumps). We will examine them after more data become available.

Taichi Kato (vsnet-alert messages 20959 and 20960, 26 April 2017)

Log in to post comments
AAVSO 49 Bay State Rd. Cambridge, MA 02138 617-354-0484