[vsnet-campaign-be 188] Correct amplitude for FW CMa

["Sebastian Otero" <varsao@fullzero.com.ar>]

FW CMa is a bright GCAS variable.
Its variability range in the GCVS is V= 5.00 - 5.50.

This probably comes from two works from Feinstein but there is a mistake in
one of them.
The first work (Feinstein, A., 1970, pub. ASP. 82, 132) gives V and B-V
measures as follows:

Oct. 1967   5.29 ; -0.04
Feb. 1968   5.30 ; -0.06
Dec. 1968   5.00 ; -0.02

The second work (Feinstein, A., 1975, pub. ASP. 87, 603) includes new data
and revised values for those observations of 1968 published in 1970. Here we
can find:

Oct./Nov. 1967   5.28 ; -0.04
Feb. 1968           5.29 ; -0.06
Dec. 1968           5.50 ; -0.02
Feb. 1972           5.34 ; -0.06
Mar. 1972           5.34 ; -0.04

We can see from this comparison that the value 5.50 is a typo. It should be
5.00, consistent with a redder color of the star in outburst as can be
expected.
A search through Mermilliod's GCPD confirms this. These are all the V
measurements included:

UBV values =

5.19 ; -0.04
5.33 ; -0.05
5.37 ; -0.07
5.38 ; -0.06

uvby values =

5.33
5.335

Geneva mean values (converted to Johnson's V) =

5.35


Finally, Hipparcos' data is very useful for settling the question down. This
star was intensively observed and we can find the following extreme values
converted to V (using my own table at my website
http://ar.geocities.com/varsao/conversion_entre_hp.htm) based on B-V -0.02
at maximum ann -0.07 at minimum:

Range = 5.06 - 5.38 V

As a conclussion, the variability range of FW CMa is V= 5.00 - 5.38.
The quiescent state of the star is around 5.35 (5.28 - 5.38).


Regards,
Sebastian Otero



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