*Astron. Astrophys. 355, 69-78 (2000)*
## Appendix A: Notes on individual PNe
Here, we provide detailed information on the physical properties of
the PNe of our sample. Unless otherwise noted, *B* and *V*
magnitudes are from the Acker et al. (1992) catalogue. Fluxes,
extinction constants, and diameters are from Cahn et al. (1992,
hereafter CKS).
**NGC 7027** : The Zanstra analysis yields
and
. We have used the expansion distance
from the radio image of Masson (1989). The derived mass of the
central star is
.
**NGC 2346** : The distance,
kpc, is derived from the
average extinction distance (Pottasch 1996). We obtain
and
. The mass of the central star
results
.
**NGC 7293** : Many distance measurements are available for
this nebula. Pottasch (1996) quotes a very uncertain (error up to
100%) parallax distance of kpc.
A more reliable value of kpc
comes from averaging several individual distances
(Pottasch 1996). We obtain and
or
, using the parallax and average
distances, respectively. The corresponding central star masses are
and
0.60 . The progenitor masses are
2.6 and 2.0 . Given the large
error on the parallax, we prefer the latter value for the initial mass
of NGC 7293.
**NGC 6781** : We obtain .
By using the statistical (CKS) and the average of individual (Acker et
al. 1992) distances, we obtain respectively
and
. In both cases, the mass of the
central star coincides with the evolutionary track for
.
**M 1-16** : By using
kpc (CKS method with a newly
measured diameter), we find and
. The inferred mass of the central
star is
.
**M 1-17** : With a distance of
kpc (from CKS method), we
obtain and
. The location on the HR diagram is
just below the 0.55 .
**M 2-9** : We calculate the distance with the method of
CKS, but we evaluate the effective diameter from the
image
( arcsec). The new distance to
this nebula is kpc. No
HeII flux has been detected. Thus, the Zanstra analysis
gives lower limits to the temperature and luminosity. We obtain
and
from the hydrogen recombination
lines. To date, nothing has been published on this nebula to set
better constraints on the mass of the central star.
**M 2-51** : The Zanstra analysis gives
and
. The luminosity is estimated using a
distance kpc, derived with the
CKS method and a new estimate of the diameter. The resulting final
mass is
.
**M 4-9** : The distance evaluated with the newly measured
angular size based on the H image by
Schwarz et al. (1992) is
kpc. For the central star, only
a photographic magnitude exists. Thus, the resulting Zanstra analysis
is quite uncertain. The flux is from
Acker et al. . The HeII flux has never been
measured. We obtain and
. A value of the mass of the central
star cannot be derived.
**CRL 2688** : Catalogued as a "possible planetary nebula",
the famous Egg nebula is actually a proto-PN. The standard analysis
via Zanstra method is not feasible, as the nebula is still very thick
to optical radiation. There are two mass estimates in the literature,
or
2.7 respectively, which depend
on the assumed mass loss rate (Sahai et al. 1998).
**CRL 618** : The HeII flux is not
available. Therefore, we cannot derive a Zanstra temperature. Hydrogen
recombination lines give and a
luminosity of , if
kpc is used. This distance has
been derived with the CKS method and diameter measured by Manchado et
al. (1996). No mass determination is possible.
**OH 09+1.3** : Another proto-PN, with no published mass to
date.
**IC 5117** : The distance is the average of the extinction
distances quoted in Acker et al. (1992). We calculate
and
. The derived mass of the central
star is
.
**M 1-59** : Since no stellar magnitudes are available for
this object, we calculate the effective temperature with the
"crossover" method (Kaler 1983). We use the statistical distance
kpc from CKS, based on a new
diameter measured by Manchado et al. (1996) and obtain
and
. The mass of the central star mass
is
.
**NGC 6853** : The parallax distance quoted in
Pottasch (1996) is of the best quality, so we can confidently use
this value to evaluate the luminosity. From the Zanstra analysis we
derive and
, and a central mass
**BD+30**^{o}3639 : The HeII flux is not
detected. Thus, we obtain lower limits to the luminosity and
temperature: and
, using the hydrogen recombination
lines and the average of extinction distances from Acker et
al. (1992). No mass determination is possible.
**NGC 7008** : We calculate
and
. The distance used is the average
of the extinction distances quoted in Acker et al. (1992). The
derived central mass is
.
**M 1-7** : The Zanstra analysis gives
and
when using
kpc, as derived from the
diameter of Manchado et al. (1996) and the method of CKS. The
mass of the central star is
.
**M 1-13** : Since no stellar magnitudes are available for
this object, we calculate the effective temperature with the
"crossover" method (Kaler 1983). We use the statistical distance
kpc from CKS to obtain
and
. The central star mass is
.
© European Southern Observatory (ESO) 2000
Online publication: March 17, 2000
helpdesk.link@springer.de |