Nova Sgr 1990


(from vsnet-chat 144)

NN Sgr: I didn't know a star with such a name existed. The object in question has no official name (and ?? Sgr was already used for another one)! NN stands for 'nomen nescio' = latin for 'I don't know the name'. The refered object is categorised as UG: (1990) at (2000) position 17 59 18 -29 10, taken also from the D&S cv- atlas. Maybe you got some more on this suspected DN.

Yes, obscure targets they are! Someone must keep an eye on them or what.

Regards,

Berto Monard

(from vsnet-chat 146)

> NN Sgr: I didn't know a star with such a name existed. The object
> in question has no official name (and ?? Sgr was already used for
> another one)! NN stands for 'nomen nescio' = latin for 'I don't
> know the name'. The refered object is categorised as UG: (1990) at 
> (2000) position 17 59 18 -29 10,  taken also from the D&S cv- atlas.
> Maybe you got some more on this suspected DN.

I now understand. In Japanese we say "na-na-shi" for "no name" -- another interpretation for "NN", though Baba-san rather uses Hoge-Hoge in the same meaning (^_^;). NN Ser is another well-known variable star among CV enthusiasts.

Anyway, your "NN" Sgr at 17 59 18 -29 10 is called Nova Sgr 1990 (as called in IAUCs), which was first discovered as a possible nova, later turned out to be by spectroscopy a possblie WZ Sge-type object. If only the star erupted three months later, I might have tried CCD photometry. Happy to hear this star has been monitored!

Regards,
Taichi Kato

(vsnet-chat 147)

Thanks for enlightening on na-na-shi Sgr! As to the identity of V3941 Sgr, there are existing charts from the VSS of RASNZ. I am sure they are only too pleased to send you copies plus some additional info. AC Sco also a non-cv? It's a close neighbour to AF Sco. Is it not strange that often similar peculiar stars or stars with similar records are close neighbours (in the sky), and that novae seem to occur in certain regions during brief periods and occur in other regions during later periods. I don't have examples of it here, but I remember this impression re-occuring several times. In how far is this coincidence? Or is this a matter of mistaken impressions?

Regards,

Berto Monard

(vsnet-chat 148)

Re: Taichi's reply to Berto on Nova Sgr 1990

> Anyway, your "NN" Sgr at 17 59 18 -29 10 is called Nova Sgr 1990 (as
> called in IAUCs), which was first discovered as a possible nova, later
> turned out to be by spectroscopy a possblie WZ Sge-type object.  If only
> the star erupted three months later, I might have tried CCD photometry.

This star definetely warrants monitoring. It was discovered by Bill Liller, Vina del Mar, on Feb 23 1990. His photographic magnitude estimates were as follows:

	    Feb 20.4 1990 <11
                23.4   "    8.0
                24.3   "    8.9
            Mar  2.4   "    9.8

Rob McNaught reported additional fading of about 0.3-0.4 mag between March 8.7 and March 9.8 on films taken with the Uppsala Southern Schmidt.

The variable appears to be in quiescence on POSS-I O and E plates as a blue object at about magnitude 18.3B. The following positions are available:

         RA (2000)     Dec (2000)
	17 59 18.20   -29 09 52.9   McNaught 1990, precessed from B1950
	17 59 17.535  -29 09 52.81  USNO A1.0 (POSS-I (O), Apr 1958)
	17 59 17.54   -29 09 53.8   DSS (UK SRC-J, Apr 1987)			

McNaught's position is the outburst position, while the USNO and DSS positions are of the proposed candidate at minimum. McNaught's position, some 10 arcsec east of the candidate, is empty to about magnitude 20B in the DSS and empty to about mag 21B in USNO A1.0. The colour index (blue-red) of the candidate in A1.0 is -0.4, and even allowing for the very poor photometic calibration of A1.0 (see vsnet 983 from Brian Skiff), it seems probable that this is the variable at minimum. Thus with a range of about 10 magnitudes, a classification of WZ Sge is quite possible. Lets keep it under observation.

Bruce Sumner
Melbourne, Australia


Chart and CCD image

V and I-band image taken at Ouda Station

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