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Possible overlooked CV in DSS2 (1984)

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Trygve Prestgard
Trygve Prestgard's picture
Possible overlooked CV in DSS2 (1984)

Hi everyone,

While hunting for unknown Planetary Nebulae in DSS2 images online, I stumbled upon a relatively bright star that only appears in the DSS2_Red plate from 1984. It doesn't appear in any other image taken of the area (that I know of).

It doesn't look anything like the typical artefacts one often sees in these DSS images, as this object appears very stellar and includes obvious "diffraction spikes". Furthermore, the object isn't elongated, suggesting that it's not a minor planet. I do lack however to create a Point Spread Function of this object.

The object also doesn't appear in the in any other image taken at a different wavelenght (including the near infrared images of DSS2_IR and 2MASS). So it's definitely not something like a Charbon star.

Using and comparing neighbouring stars, I estimate the magnitude of the object to have been around +10 in DSS2_Red. In it's "normal" state, the object must be below +21st magnitude, knowing that it's not at all detectable in DSS. This very large difference in brighteness is what lead me to think that it might be a CV of some sort.

I have also contacted scientists, Estelle Moraux and Guillaume Dubus, at the IPAG (Institut de Planetologie et Astrophysique de Grenoble) and amateurs on the Deep Sky Hunting forum, and everyone seemed convinced that the object could indeed be real. Guillaume Dubus agreed especially that it could be an overlooked Nova.

The problem however with this object is that it only appears in one image, over 30 years ago. Furthermore the object is now likely very faint and hard to follow up on. So I don't know if there's any way of confirming this object or reporting it to the CBAT or AAVSO. 

I don't know if the CBAT or AAVSO includes "Possible unconfirmed CVs"? Or if there's anyway to get this object listed somewhere.


Here are the coordinates (J2000.0) of this object: 20 24 52.6 -16 13 35.9

The attachment shows the object in DSS2_Red in comparison to different images.


Apologies for a long message,

Thanks for your help and best regards,

Trygve Prestgard

Checking Sonneberg plate collection

I have quick-checked the Sonneberg plate collection for possible parallel exposures. The coordinates of this object are covered by two fields of the sky patrol: centered 20h -20° and 21h -20° (26° FOV, limit 14 mag). Unfortunately, these fields end 1980 and 1982 due to growing light pollution.
There are about 300 to 400 plates of these fields spanning 1950ies to 1980/82 which could be checked for former outbursts. However, there is currently nobody who could do this, may be later this year.
Peter Kroll / Sonneberg Observatory / Germany

lmk's picture

These would be a great research tool for everyone, if the whole Sonneberg plate sets were digitized and available online! Maybe could find a student intern project to do it :)



HSW's picture
Re: Possible overlooked CV in DSS2 (1984)

It might be the asteroid (10) Hygiea at magnitude 10.4.  I downloaded the red POSS2 FITS and plugged the date and the position into MPChecker and that is what it came up with.  It was barely moving at the time.


Trygve Prestgard
Trygve Prestgard's picture
Replies/False alert

Hi all,

Thanks for your replies!

Stan: Yep, I agree with you, it's more likely to be asteroid Hygiea than a Nova, beginners fault! :) Sorry for the false alert. I also replied to your post on the DSH forum.

Best regards,


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