Zeta (z) Puppis

	z Puppis		Bayer designation (1603)
	HR 3165		Harvard Revised Photometry designation (1879+)
	HD 66811		Henry Draper Catalogue (1918+)
	SAO 198752		Smithsonian Astrophysical Observatory (1966+)
	39429		Hipparcos catalogue (1997)

Synopsis

Single star; early Of-type supergiant (O4I(n)f); located in Puppis; R.A. 08:03:35.052, dec. -40:00:11.64; culmination early March; magnitude 2.25; distance 429 pc (approx 1400 light years).

Description

Zeta Puppis is one of the best studied O-type stars; several important parameters have been determined with good accuracy, including the distance 352 (429) 549 pc (~ 1400 light years); diameter 20 R_¤; effective temperature 42,000 ą 1500 K; and period of rotation ~4.8 – 5.2 days (Howarth et al. 1995, Schaerer et al. 1997).

The spectral type is certainly early O: Ochsenbien et al. 1988 published a value of O5Iaf; the earlier value of O4I(n)f derived by Walborn 1972 is preferred by Howarth et al. 1995 (table 1) and also by Schaerer et al. 1997.

[Howarth et al. 1995, table 1, quotes T_eff = 42,000 ą 1500K from other sources, although their value for B-V, -0.27, suggests a somewhat lower temperature: around 32,500 K is typical for supergiants with this value of B-V. Böhm-Vitense 1989a, p. 59, gives a value of 30,700 ą 2500K for z Puppis. Schaerer et al. 1997 adopts the 42,000K value.]

Property	Value	Notes/References
R.A.	8:03:35.000
Declination	-40:00:11.64
Precession in RA	21.100
Precession in dec.	-103.000
Proper Motion RA	-0.031	Includes cos(dec) term.
Proper Motion dec	0.011
Radial Velocity	-24.0 km/s
Parallax	2.33ą0.51 mas	Schaerer et al. 1997
Distance	429 pc	Schaerer et al. 1997
m_v	2.25
M_v	-6.06	calculated with d=460 pc
M_*/M¤	59	Lamers & Cassinelli 1999
L_*/L¤	740,000 790,000	log L/L¤ = 5.74 (5.87) 6.02, Schaerer et al. 1997 Lamers & Cassinelli 1999
B-V	-0.27
U-B	-1.09
V-R	-0.11
R-I	-0.22
b-y	-0.146
m1	0.115
c1	-0.198
H_b	2.534
Spectral Type	O4I(n)f O5Iaf	Howarth et al. 1995 Ochsenbien 1988
R/R¤	20 14 (16.3) 21.7 17	Howarth et al. 1995 Schaerer et al. 1997 Lamers & Cassinelli 1999
T_eff	30,700K 42,000K 42,400K	Böhm-Vitense 1989a Howarth et al. 1995 Lamers & Cassinelli 1999
Rotational Velocity	211.000 km/s	Howarth et al. 1995
Period	4.8-5.2 days	Howarth et al. 1995
Table 1: Known Parameters for Zeta Puppis. (After Ochsenbein & Halbwachs 1987 except where otherwise noted.)

Discussion

Mass Loss

Mass loss is typical for hot luminous stars. For Zeta Puppis a mass loss rate was determined from radio data by Lamers and Leitherer and rescaled by Schaerer et al. (1997) to reflect their revised distance estimate, yielding log M-dot = -5.57 ą 0.15.

Zeta Puppis possibly belongs to the young Vela R2 association of stars (Sahu 1992, Schaerer et al. 1997).

Observation

Easily seen with the naked eye.

References

Böhm-Vitense, Erika (1989a): Introduction to Stellar Astrophysics. Volume 1 – Basic Stellar Observations and Data. Cambridge.

Howarth, Ian D.; Prinja, Raman K.; Massa, Derck (1995): The IUE MEGA Campaign: The Rotationally Modulated Wind of z Puppis. The Astrophysical Journal, 452:L65-L68, 10 October 1995.

Lamers, Henny J.G.L.M.; Cassinelli, Joseph P. (1999): Introduction to Stellar Wind. Volume 3. Cambridge.

Ochsenbein F.; Halbwachs J.L. 1987: Le Catalogue des Etoiles les Plus Brillantes (Catalogue of the Brightest Stars). Bull. Inform. CDS 32, 83. NASA Astronomical Data Centre, catalogue 5053A.

Sahu, M. (1992): Unpublished PhD thesis, cited in Schaerer et al. (1997).

Schaerer, Daniel; Schmutz, Werner; Grenon, Michel 1997: Fundamental Stellar Parameters of z Pup and g² Vel from HIPPARCOS Data. ApJ Letters 484: L153-156.

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