Affiliation
Royal Astronomical Society of New Zealand, Variable Star Section (RASNZ-VSS)
Wed, 08/03/2016 - 02:52
In VSX there is a comment by Kato that it could be a slow nova. It erupted in 1926.
However, it has positive observations between about 1990-2000 in the 14.7-15.5 range from two experienced observers, Tom Cragg and Andrew Pearce.
So my question is, could this star be a recurrent nova? If not, how is this increase in brightness explained.
Kind regards
Stephen
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Stephen Hovell [HSP]
Pukemaru Observatory
341 Snelgar Road, RD 2
Kaitaia, New Zealand 0482
Hi Stephen
The pre and post discovery observations, mostly negatives, appeared in Harvard College Observatory Bulletin Nos. 847 and 851. Apparently the star had faded by about 1.1 mag ptg based on an observation made almost two months after the discovery epoch and max mag given in VSX. According to HB no. 851, there were then five negative observations, all <15.0p, made between May 6 and June 8 the following year (1927). I don't see any other data on it again until the earliest observation currently in the AAVSO Database, of fainter than 12.8vis on February 2, 1990 by JA. I did a quick look back from the present to 1997 and found 3 apparent positives, 16.08V on Oct 21, 2009, 14.9vis on Feb 14, 2001, and 15.2vis on Dec 11, 1999. Of course, these could be real but then again, perhaps they are mis-IDs or cases of simply forgetting to include a '< ' before the magnitude value.
At the currently published position of RY Dor, there is no stellar object on DSS2 Red (1996), DSS2 IR (1981), nor 2MASS J (1998), so presumably mag <19-20 or so. As far as I know, no post nova counterpart has been identified. The Downes online (2006) chart and error circle is quite a clear one and is at the same coordinates as our VSX, and Simbad positions. There appear to be a couple of very faint detections there, mag 20 ?? which may or may not have anything to do with the spectacle of 1926.
Kind regards,
Steve
OCN
Hi Stephen,
I agree with Steve.
And I have to add that the star identification is actually uncertain so the published coordinates of this object vary depending on the source that you use.
There is an entry in VizieR for ESO observations with a position 60" away.
So it could be a missing "<" symbol or it could be a misidentification.
While checking the observations I see that the observers that consistently observed this star never detected it while the positive observations are made by the same observer (= misidentification) or by an observer who used a different chart that time and whose previous and following observations of the object are years apart (= observer not used to the star's field).
The most likely explanation is that the positive observations are thus spurious.
Cheers,
Sebastian