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[vsnet-sequence 55] U Monocerotis sequence
Norwegian Astronomical Society - Variable Star Section
***** Sequence for the RV Tauri type variable U Monocerotis *****
0726-09 U MON [R.A. = 07h30m47s.5, Decl. = -09o46'37" (2000.0)]
U Monocerotis is - after R Scuti - the brightest variable star of the
RV Tauri type. The Variable Star Section of British Astronomical
Association (http://www.telf-ast.demon.co.uk/) has studied it for many
years and found an extreme visual magnitude range from 5.4 to 8.5.
I have compiled a sequence for U Mon. It is given in table 1 and should
cover the full light variation of this star. The sequence is mainly
intended for visual observers and only contains stars that are bluer
than B-V = +0.6.
Data for some other stars is given in table 2. These stars are less
suitable as comparison stars due to strong colour, multiplisity etc.
These tables contain positions, Johnson V magnitudes and B-V colours
from The Hipparcos catalogue (HIP, ESA 1997), except for the faintest
star that are taken from The Tycho-1 Catalogue (TYC1, ESA 1997). The V
and B-V should generally be accurate to within 0.01-0.02 mag., although
larger systematic errors may be present in some cases. R.A. and Decl.
are for equinox and epoch 2000.0. Identifications are due to BAA.VSS
(letters D-L) and undersigned (A, R-Z). Star names are Bayer and
Flamsteed designations for bright stars, otherwise they are HR and
Hipparcos numbers from Bright Star Catalogue (HR, Hoffleit et al. 1991)
and HIP, respectively. Angular distances between U Mon and the reference
stars are in degrees. AAVSO magnitudes in units of 0.1 mag. are given in
last colomn. These magnitudes are photoelectric V (denoted V) or visual
and are taken from the AAVSO chart, last revised in 1986.
Table 1: Sequence stars
------------------------------------------------------------------------
Id R.A. (2000.0) Decl. Star Name V-mag B-V Ref Dist AAVSO
h m s o ' " o
------------------------------------------------------------------------
R 07 37 16.7 -04 06 40 25 Mon 5.14 +0.44 HIP 5.89 52
S 07 47 56.8 -12 11 34 5 Pup 5.48 +0.48 HIP 4.85 55
T 07 32 05.8 -08 52 51 HR 2883 5.90 +0.54 HIP 0.95 59V
W 07 22 02.0 -08 58 46 HR 2806 6.42 -0.19 HIP 2.30 64V
F 07 28 34.4 -10 02 38 HIP 36320 6.63 -0.10 HIP 0.61 66V
X 07 26 25.3 -10 05 22 HIP 36120 6.97 +0.18 HIP 1.12
H 07 32 41.8 -09 40 10 HIP 36673 7.56 -0.07 HIP 0.48 75
K 07 30 43.0 -09 18 36 HIP 36516 7.76 +0.05 HIP 0.47
L 07 29 35.5 -09 15 33 HIP 36419 7.97 +0.44 HIP 0.60
Z 07 26 55.4 -09 33 47 TYC 5400-3758 8.51 +0.19 TYC1 0.75
------------------------------------------------------------------------
Notes:
* Star R = 5 Pup is a binary, Worley et al. (1997) give components at
mag. 5.6 and 7.7, sep. 1".7 and PA 356 deg. for epoch 1988.
* Star T = HR 2883 is a double with stars of mag. 5.9 and 8.8 at sep.
23".4. (Worley et al. 1997).
* Star K = HIP 36516. It should be noted that there is a discrepancy
between the magnitudes in HIP and Hipparcos Input Catalogue (HIC,
Turon et al. 1993). HIC has V = 7.660 (+/- 0.031), i.e. 0.10 mag.
brighter than the HIP value.
* Star Z = TYC 5400-3758 is double, Worley et al. (1997) have mag. 9.1
and 13.5, sep. 5".2, epoch 1969.
Table 2: Field stars
------------------------------------------------------------------------
Id R.A. (2000.0) Decl. Star Name V-mag B-V Ref Dist AAVSO
h m s o ' " o
------------------------------------------------------------------------
A 07 41 14.9 -09 33 04 Alpha Mon 3.94 +1.02 HIP 2.59 39V
E 07 29 22.1 -10 19 36 HR 2867 5.75 +1.62 HIP 0.65 60
D 07 27 51.7 -11 33 25 HR 2859 5.79v +0.58 HIP 0.58 58
G 07 30 58.7 -10 06 27 HIP 36539 6.60 +1.62 HIP 0.33 70
Y 07 32 44.8 -09 24 40 HIP 36677 7.41 +1.42 HIP 0.61
------------------------------------------------------------------------
Notes:
* Star D = HR 2859 is a multiple system. According to Worley et al.
(1997) the primary (star A) is mag. 6.0, while the components are of
mag. 8.0 at sep. 0".8 (B), 8.5 at 20", 9.5 at 23", and 12.2 at 32".
Data in table refers to stars A and B (HIP 36251), this system is
also a variable with a Hipparcos amplitude of 0.11 mag.
Acknowledgement:
For this study I have made extensive use of the VizieR service of CDS
and I wish to thank CDS for this service.
References:
ESA, 1997: "The Hipparcos Catalogue", ESA SP-1200. [HIP]
ESA, 1997: "The Tycho Catalogue", ESA SP-1200. [TYC1]
Hoffleit D. and Warren Jr. W. H., 1991: "Bright Star Catalogue, 5th
Revised Edition", Astronomical Data Center, NSSDC/ADC.
Turon, C. et al., 1993: "Hipparcos Input Catalogue, Version 2", Bull.
Inf. CDS 43, 5.
Worley C. E. and Douglass G. G., 1997: "The Washington Visual Double
Star Catalog, 1996.0.", Astron. Astrophys. Suppl. Ser. 125, 523.
Yours sincerely,
Bjorn H. Granslo
(NAS.VSS)
vsnet-adm@kusastro.kyoto-u.ac.jp
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