[vsnet-chat 3841] NSV4721 Vel - A Large Amplitude Semi Regular Variable

["Peter F Williams" <pfwilliams@onaustralia.com.au>]

NSV4721 Velorum - A Large Amplitude Semi Regular Variable.

I have been observing NSV4721 Vel (= BV1410 = CSS652 = IRAS
10015-4634 = Hen 4-78 = GSC 8182-00076) since early 1993 when
attention was directed to it by Paul Camilleri in IBVS3923.  During
the 8 year interval 1993 February through 2000 July these visual
observations indicate this star is a semi regular variable of class
SRB with a magnitude range of 10.3 to 13.0 but with variable
amplitude and period.

The light curve shows 12 cycles and there appears to be a long term
trend and correlation between the observed amplitude and period
length, wherein a large amplitude corresponds to a long period and
small amplitude to a shorter period.  For example,  cycle 2 has an
amplitude of 2.6 magnitudes and 417 day period which are reduced
to 0.7 magnitude and 91 days by cycle 7.  At end of the interval 
covered by the observations NSV4721 is again showing large
amplitude long period variations.

The data also suggests a long period cyclic trend may be present but
which is of longer period (~3000 days?) than the 2706 days covered by
the observations thus far.  Further close monitoring is planned to help
confirm if any correlation and long term trends do in fact exist.

Because of the significant variation shown in the observed period,
no epoch for maximum or minimum is given as this would seem of
little practical value.  A paper giving details of these results is
under preparation for the Pubications of the VSS RASNZ and will be
submitted shortly.

A summary of the observed cycles in NSV4721 follows :

No.	MAX	MAG	INT.	DELTA-M	MIN	MAG	INT.
	JD24		DAYS			JD24		DAYS

1	48970	10.5	401	2.5		49167	13.0	409
2	49371	10.3	417	2.6		49576	12.9	356
3	49788	10.4	280	2.1		49932	(12.5)	257
4	50068	10.7	152	1.0		50189	11.7	114
5	50220	10.8	113	1.4		50303	12.2	182
6	50333	11.1	235	1.0		50485	12.1	91
7	50568	11.4	91	0.7		5076	12.1	197
8	50659	10.8	152	1.2		50773	(12.0)	220
9	50811	10.7	257	1.3		50993	12.0	235
10	51068	(10.7)	174	2.1		51228	12.8	287
11	51242	11.0	485	2.3		51515	(13.3)	-
12	51727	10.9	-	-		-	-	-

Please post this detail to other mailing lists as necessary.

Regards

Peter Williams
Heathcote NSW

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