Researchers have used both "YY Dra" and "DO
Dra" to refer to the same object. I have long prefered the former,
but with this version of the IP catalog, I'm switching to the latter as
the primary designation. The two main reasons are: (1) The GCVS team
still considers DO Dra to be the correct name; and (2) a larger fraction
of the papers use the designation DO Dra. Since the primary function of the
name of an astronomical object is to tell the readers what object you are
describing, the most important consideration is for the community to agree
to use a single designation.
Here is the history and current status of the two designations, for the record.
This low luminosity IP was identified
as the optical counterpart of an X-ray source, and initially announced, by
et al. (1982), who considered the optical counterpart to be known variable
star, YY Dra, supposedly of Algol type. However, the GCVS team disagreed and
assigned a new variable star designation, DO Dra, to this CV. This happened
before the first comprehensive refereed publication
(Patterson et al. 1992)
was published, noting that this was an intermediate polar. The disagreements
regarding the designation are summarized in a pair of IBVS articles.
- Patterson & Eisenman (1987)
argued that the CV is the previoulsy cataloged variable star, YY Dra.
- The cataloged position of YY Dra is coincident with that of CV,
to within the errors of variable stars discovered in old photographic
- Mis-classification of variable star type is common, when based on
- At the high Galactic latitude of YY Dra, the very presence of an
Algol type star and its positional coincidence with the X-ray
source is statistically unlikely.
- Kholopov & Samus (1988)
argued that the YY Dra was not a CV, and hence a new designation is
warranted for the CV.
- Tsesevich could not have misclassified a dwarf nova as an
Algol type star.
- Both the position and the brightness of the variable star,
on the other hand, could be in error.
- Patterson's arguments are primarily statistical in nature,
and cannot definitively prove that the CV is YY Dra.
The main substantive point of Kholopov & Samus can be quickly dismissed.
This object is not a (normal) dwarf nova; it is a
Low Luminosity IP with occasional
(dwarf nova-like) outbursts. If this was a normal dwarf nova, their statment
might be true. However, the long-term variability of IPs is an
active research field that has yieled many suprises in recent years.
Thus, it would be presumptious for any of us to think that we would know
IPs from their >1 day variability alone.
Is there a lost Algol star somewhere near the LLIP?
Motivated by Hill et al. (2022),
Kato & Pavlenko (2022)
revisited Tsessevich's original report as well as related materials and
considered it likely that the original classification was based on relatively
few points. They suggest that the star Tsessevich observed was the LLIP,
DO Dra, in a long-lasting bright, with occasional non-detections.
- I have performed a quick search for such an object for this page,
as follows. Virnina (2011) reported
on "Tsessevich Project: an Attempt to Find the System YY Dra,"
which provides additional details about the original discovery: it was
made on 10 x 10 deg plates centered on Z Dra. There are 177 entries
listed in the ASAS-SN variable
star database, none of which matches the supposed 4.2 day period of
"YY Dra." If a 4-day period Algol really did exist in this area
of the sky, it almost certainly would have been discovered by ASAS-SN (see
latest paper on the ASAS-SN variable star catalog).
- Hill et al. (2022) performed
a far more comprehensive and systematic search using the Catalina Surveys
Periodic Varible Star Catalog and the ASAS-SN Catalog of Variable Stars.
They point out that a periodic variable star of the characteristics
of "YY Dra" should have been recovered, quite easily, by these
surveys. However, no matches were found, discounting a star of similar
characteristics in the far southern (declination -53) sky, unobservable
from Russia. Hill et al. (2022)
therefore argue that YY Dra and DO Dra is one and the same.
Please send your comments, suggestions etc. to