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New Dwarf Nova in Gemini

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garypoyner's picture
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New Dwarf Nova in Gemini

VSNET-alert 26492 issued on December 28 reports the discovery of a large outburst amplitude (7.7 magnitudes) transient in Gemini, discovered by "Tadashi Kojima, Tsumagoi,Gunma-ken, Japan, on three frames(5_s exp) under limiting mag.= 14.2 taken by Canon EOS 6D + 200mm f/3.2 lens. Nothing is visible at this location taken on 2021 Dec14.741 UT under limiting mag.= 14.0. Mag=13.5 on 2021 Dec28.610UT with same instrument."

Position 07 09 49.36 +14 12 28.0

The object 'may' be a new UGWZ type Dwarf Nova.

A SLOOH image taken on Dec 29.037 revealed a magnitude of 12.15CV.

Please use the desigation TCP J07094936+1412280 when reporting to either the BAAVSS or AAVSO.   An AAVSO chart and sequence is available from the AAVSO VSP.

Gary

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Is this correct?

I believe it's this one and AstroImageJ gives me a V mag of 12.3.

Taken this evening 29-12-2021 21:55 UT

3x180s subs stacked
250mm f4.8 Newtonian
QHY168C - green channel only

Mark Phillips
Edinburgh

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Potential dwarf nova

Conditions weren't great - certainly not photometric quality - but I imaged the field and the image gives a ballpark indication of brightness (certainly consistent with Forth's obs). Midpoint 2021-12-29T21:44. PA 297deg; 80' x 60'.

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Forthimage's picture
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Colour image and comparison chart

Just for reference, I believe this is correct. My image:

From Aladin

Denis Buczynski's picture
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TCP J07094936+1412280

Image of this object taken 20211230 0153 at Tarbatness. Image is south up and west left

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Brightness estimate | eve of 29 Dec

I estimated the brightness at about 12.595 CV, with a delta for the check* star (*corrected) of 0.021.

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Fading now 31 Dec

Very poor conditions tonight with drifting cloud and only enough gaps for 30s exposure, but clearly fainter. 
AstroImageJ gives 13.1 V now.

At 2021-12-31 23:31UT

garypoyner's picture
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Slowly fading

Eleven days into the outburst, this dwarf nova of the relatively rare type UGWZ is still fairly bright in the evening sky after fading by just over two magnitudes since discovery, and remains worthy of continued observation - visual, single image or time series.

My own light curve consiting of visual observations from Birmingham and CCD images from COAST and SLOOH is shown below.

Gary