[vsnet-chat 3043] (fwd) ?Cataclysmic Star in CMa in 1917? (Greaves)

[Taichi Kato <tkato>]

(fwd) ?Cataclysmic Star in CMa in 1917? (Greaves)

Date: Sat, 10 Jun 2000 16:41:47 +0000
From: JG <jgts@jgws.totalserve.co.uk>
Subject: ?Cataclysmic Star in CMa in 1917?

The ROSAT All Sky Survey Faint Source Catalogue (rass_fsc, Voges+ 2000)
has just been made available at the CDS, Strasbourg
[http://cdsweb.u-strasbg.fr] under subdirectory .../IX/29

During checks against some of this data I have only _one_ strong
coincidental position between this catalogue and objects classed as
being single images in the AC2000 (Urban et al), thus :-

1RXS J064359.1-205234  with AC2000 2654611 at  06h 43m 58.9s -20d
52'.33"

[though note that the rass_fsc position has an uncertainty of 31
arcsecs, including an internal systematic error of 6 arcsecs].  All
coordinates are to J2000.0

The AC2000 object is BT magnitude 11.44 and is listed as not being found
in either GSC 1.2 _or_ the overlapping AC plate.  The plate epoch is
1917.126.

Investigations reveal no USNO A2.0 object, nor catalogued QSO, BLLAC,
AGN or known or suspected CV at this position.  The nearest USNO A2.0
star is about 30" distant. Negative results also occur when testing
against many suspected variables catalogues.

Examination using the CDS's Aladin server reveals no object at this
position according to SIMBAD or NED data.

No object is visible to plate limit within ten arseconds of this
position on DSS1 J or DSS2 R plates, as checked via the same server.

I have no access to original astrographic plates, so am not able to
check the original image, which will have been part of the Hyderabad
South Astrographic Charts.

Most asteroids of that magnitude would mostly likely be trailed on AC
plates, nevertheless a test at that approximate date using MPCorb data
from the Minor Planet Centre, Harvard, revealed no likely asteroids for
that position.

Therefore, there is a strong suggestion that an object which is a faint
xray source was 9+ blue magnitudes brighter than usual at 1917.126.
This is akin to the range expected from a classical nova, although a
"normal" CV or recurrent nova cannot be ruled out.

[The field is on the edge of the Milky Way, and very adjacent to the
open cluster Messier 41, but the star density is not too great, as the
field probably also lies on the outer edge of more northerly CMa R1].


Cheers

John

John Greaves
UK

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