THE ASTRONOMER Electronic Circular No 670 1992 Sept 24 21.36UT
Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise, Basingstoke,
Hants, RG22 4PP,England. Telephone/FAX(0256)471074 Int:+44256471074
TELEX: 9312111261 Answerback: TA G TELECOM GOLD: 10074:MIK2885
GMH at UK.AC.RUTHERFORD.STARLINK.ASTROPHYSICS STARLINK: RLSAC::GMH
GMH at UK.AC.CAM.ASTRONOMY.STARLINK STARLINK: CAVAD::GMH
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V418 CAS
Hans Bengtsson, Sweden, e-mails:
"We have some observational evidence that rapid variations may take
place in V418 Cas, which is classified as a Mira-type star. The
following observations support the idea:
1992 Aug 7.99 UT 11.6 v M. Westlund Maksutov-Cass 0.09-m
Aug 8.95 UT <11.3 v M. Westlund Maksutov-Cass 0.09-m
Aug 10.93 UT 13.3 v M. Westlund Schmidt-Cass 0.20-m
Aug 21.90 UT 13.4 v M. Westlund Schmidt-Cass 0.20-m
Aug 24.90 UT 13.3 v M. Westlund Schmidt-Cass 0.20-m
Aug 26.89 UT 13.4 v M. Westlund Schmidt-Cass 0.20-m
Aug 30.86 UT 13.3 v M. Westlund Schmidt-Cass 0.20-m
V418 Cas was faintly but clearly seen in a 0.09-m telescope on
Aug 7.99, estimated at 11.6, while it was estimated mag 13.3
only three days later.
To find out whether something similar has been reported for the
star in the past, Margareta contacted the Sonneberg Observatory,
and received the following information from S. Roessiger:
Variability was discovered by Hoffmeister in 1965. On the basis of
survey plates from 1963, it was classified as "Nl?", with the range
15 - <17.5 p. Some observations from 1963: Aug 26: 17.5 p;
Sep 11: 15.5 p; Sep 15: 15 p. Then followed a slow decline to the
limiting magnitude, which was reached in December 1963. An earlier
max was also found in September 1942.
On plates taken in 1968, the star was studied by Meinunger. He
classified it as a Mira star with P = 480 days, and range 14.6 -
[17.5 p.
In October 1990, the star was found by D. Kaiser on a plate taken
1989 November 24. It was estimated at mag 10! On plates taken
1958-1990, the star was then found in 14 maxima. The period was
slightly adjusted to 479.5 days, and maxima were on the average
at mag 14 p. An exception from this was 1989 November 29,
when it was estimated mag 13.0 p.
Provided that the plate from 1989 Nov 24 (mag 10) has about the
same colour sensitivity as the plate of 1989 Nov 29 (mag 13.0),
this case of extremely rapid variation is strikingly similar to
the event reported by Margareta. Anyhow, the star deserves to
be carefully studied in the future. Rapid variations in Mira stars
have been reported on several occasions, but they have never been
fully proved. Another possibility could be that the star is not a
'pure' Mira star, but perhaps some kind of symbiotic LPV (for
instance, flare-like fluctuations are known in the CH Cyg system)."
Editor: The 1989 event was also detected by Mike Collins as
reported on E-Circular 366.
Guy M Hurst