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Astronomy & Astrophysics manuscript no.
(will be inserted by hand later)
A new Wolf-Rayet star in Cygnus ?
Anna Pasquali 1 , Fernando Comeron 2 , Roland Gredel 3 , Jordi Torra 4 , and Francesca Figueras 4
1 ESO/ST-ECF, Karl-Schwarzschild-Strasse 2, 85748 Garching bei Muenchen, Germany
e-mail: apasqual@eso.org
2 ESO, Karl-Schwarzschild-Strasse 2, 85748 Garching bei Muenchen, Germany
e-mail: fcomeron@eso.org
3 CAHA, Centro Astronomico Hispano Aleman, C/Jesus Durban Remon 2-2, 04004 Almera, Spain
e-mail: gredel@caha.es
4 Departament d'Astronomia i Meteorologia, Universitat de Barcelona, Av. Diagonal 647, 08028 Barcelona, Spain
e-mail: jordi@am.ub.es, cesca@am.ub.es
Received; submitted
Abstract. We report the discovery of a new Wolf-Rayet star in the direction of Cygnus. The star is strongly
reddened but quite bright in the infrared, with J = 9:22, H = 8:08 and KS = 7:09 (2MASS). On the basis of its
H + K spectrum, we have classied WR 142a a WC8 star. We have estimated its properties using as a reference
those of other WC8 stars in the solar neighbourhood as well as those of WR 135, whose near-infrared spectrum is
remarkably similar. We thus obtain a foreground reddening of AV ' 8:1 mag, MJ ' 4:3, log(L=L ) 5:0 5:2,
R = 0:8 R , T ' 125; 000 K, M = 7:9 9:7 M , _
M = (1:4 2:3) 10 5 M yr 1 . The derived distance
modulus, DM = 11:2 0:7 mag, places it in a region occupied by several OB associations in the Cygnus arm, and
particularly in the outskirts of both Cygnus OB2 and Cygnus OB9. The position in the sky alone does not allow
us to unambiguously assign the star to either association, but based on the much richer massive star content of
Cygnus OB2 membership in this latter association appears to be more likely.
Key words. Stars: emission line { Stars: fundamental parameters { Stars:individual:Wolf-Rayet { Galaxy: open
cluster and association
1. Introduction
Wolf-Rayet (WR) stars, rst discovered by Wolf and Rayet
in 1867, are characterised by an emission-line spectrum
dominated by strong He, N and C features. Their ob-
served properties are believed to be the result of stellar
evolution at high initial masses, during which strong mass
loss in winds of a few 10 5 M yr 1 at terminal velocities
between 400 and 5000 km s 1 (cf. van der Hucht 2001)
\peels" the star until it comes to expose at its surface the
heavy elements synthesized in its core. WR stars represent
the last evolutionary stage of massive stars before the -
nal supernova explosion (Maeder & Conti 1994, Langer
& Woosley 1996, Langer & Hegel 1999). The ux ratios
among the He, N, and C lines allows the classication
of WR stars into subclasses, WN (where He and N lines
dominate), WC and WO (when He, C and O features be-
Send oprint requests to: apasqual@eso.org
? Based on observations collected at the German-Spanish
Astronomical Centre, Calar Alto, operated by the Max-Planck-
Institut fur Astronomie, Heidelberg, jointly with the Spanish
National Commission for Astronomy.
come stronger), and subtypes (WN3-9 and WC4-9 as the
ionization degree increases).
WR stars signicantly contribute to the energy budget
and chemical enrichment of their parent galaxy. Through
their stellar winds, they enrich the hosting environment
with heavy elements and release over time a kinetic en-
ergy comparable to that from supernovae (Leitherer 1998).
Given their high luminosities (few 10 5 L ) individual WR
stars are easily identied in all the galaxies of the Local
Group (Massey & Johnson 1998), while the short lifetimes
of such massive stars (several Myr) make them appear
generally near their birthplaces, tracing star formation in
spiral and starburst galaxies. Indeed, their unmistakable
features, detected in the integrated spectra of galaxies un-
dergoing intense bursts of star formation (cf. Conti 2000),
make them useful to study starburst phenomena and star
formation processes on cosmological scales.
The latest census of WR stars detected in the Milky
Way lists 227 such objects (van der Hucht 2001), or about
10% of the estimated Galactic WR population (' 1500
- 2500; Shara et al. 1999). The majority of Galactic WR
stars has escaped detection using traditional techniques

2 Anna Pasquali et al.: A new Wolf-Rayet star in Cygnus
(such as visible spectroscopy or narrow-band photometry
with lters centered on the characteristic WR signature
at ' 4670 A and its adjacent continuum, cf. Massey &
Conti 1983) which are naturally limited by their unability
to penetrate the large column densities of absorbing dust
along the lines of sight towards distant regions of the galac-
tic disk. Such limitation can be overcome by observing at
near-infrared wavelengths, where WR stars also display
easily identiable spectral signatures and the extinction
by dust is only a fraction of that at shorter wavelengths.
In this paper we report the discovery of a new nearby
WR star, supporting the prediction by van der Hucht
(2001) that many such stars in the solar neighbourhood
still await discovery at near-infrared wavelengths. Indeed,
the object reported here is bright at near-infrared wave-
lengths but has escaped recognition so far in the visible
despite its proximity, due to the high extinction in its di-
rection. The discovery of yet another nearby WR star de-
serves attention in several respects, as each WR star has
its own special features and represents a unique contribu-
tion to our understanding of the late stages of massive stel-
lar evolution. Moreover, its location and relation to other
young stars in the region yields information on the star
formation history in the complex where it formed. The
near-infrared observations of the star, to which we will
refer as WR 142a following the nomenclature in van der
Hucht's (2001) catalogue, are described in Section 2. The
results concerning its spectral classication and intrinsic
properties can be found in Section 3. Finally, Section 4 dis-
cusses some implications of the WR population in Cygnus.
2. Observations
The selection of WR 142a as a target for spectroscopic
observations was based on its 2MASS photometry, from
which it was apparent that this star is a bright, red ob-
ject with colours signicantly deviating from those of nor-
mal stars reddened by foreground dust. Infrared mag-
nitudes listed by 2MASS are J = 9:22, H = 8:08,
KS = 7:09. Its location at (2000) = 20 h 24 m 06:2 s ,
ф(2000) = +41 ф 25 0 33 00 places it in the general direction of
Cygnus, in a region where several OB associations over-
lap (see Section 3.4). The USNO catalog lists a star of
B = 18:1, R = 14:7 at the position of this object. The
only previous reference to it in the literature seems to
be Melikian & Shevchenko (1990), who recognized it as a
strong emission-line star in their search for such objects
in the proximities of the cluster NGC 6910. However, its
actual WR nature has not been recognized until now.
We observed WR142a on June 24 and 25 2002, us-
ing the near-infrared imager and spectrograph MAGIC
mounted on the 1.23m telescope of the German-Spanish
Astronomical Center in Calar Alto (Spain). This instru-
ment uses a NICMOS3 256 256 pixel 2 detector yield-
ing a scale of 1 00 :15 per pixel in imaging mode. JHKM
imaging and H and K band spectroscopy were obtained
and reduced using the same instrumental setups and tech-
niques described in Comeron et al. (2002); the reader is
Fig. 1. The observed H-to-K spectrum of WR 142a. The spec-
tral resolution is R ' 240. The drop between 1.8 and 1.9 m
is due to the Earth atmosphere transmission.
thus referred to that paper for details. Two spectra ob-
tained on the night of 24 June 2002 at airmasses of 2.05
and 1.67 were individually reduced to conrm the real-
ity of individual features, especially in regions of rapidly
varying telluric absorption. The exposure time of the com-
bined spectrum is 12 min. As for the imaging, the expo-
sure times are 7.5 min in each of the J , H and KM lters.
The images were obtained under conditions suspected to
be non-photometric, and ux calibration using a separate
image of a standard star was thus not attempted.
3. Results
3.1. IR spectroscopy and classication
The low-resolution infrared spectrum of WR 142a (R '
240) is plotted in Figure 1. Emission lines have been
identied by cross-correlation with the The Atomic Line
List v2.04 (http://www.pa.uky.edu/peter/atomic) and
the K-band spectral atlas of Figer et al. (1997). The most
prominent features are due to HeI and HeII, CIII and CIV.
Their equivalent widths are listed in Table 1.
We have cross-checked the spectrum of WR 142a with
the K-band spectral atlas of Galactic WR stars by Figer et
al. (1997) in order to assign WR 142a a WR subtype. The
line complex between 2 and 2.2 m has been particularly
useful in the spectral classication, since it is a specic
signature (in line wavelength and ux ratio) of WC8 stars
(cf. Figure 10 in Figer et al. 1997). Although the dispersion
of Figer et al.'s (1997) data is a factor of two higher (R
' 525 against 240 of this work), the comparison indicates
that the spectrum of WR 142a is almost identical to that
of WR 135, a WC8 star in the Galactic OB association

Anna Pasquali et al.: A new Wolf-Rayet star in Cygnus 3
Table 1. Line equivalent widths in the IR spectrum of
WR 142a
Line (m) EqW ( A)
CIII + HeII 1.474 50
HeII 1.488 30
HeI 1.70 60
HeI + CIV 1.736 200
CIV 2.07 + HeII 2.076 + CIV 2.08 780
HeI 2.11 + CIII 2.108 160
HeI + HeII 2.16 40
HeII 2.18 70
CIV 2.278 30
HeII 2.31 + CIII 2.32 30
HeII 2.347 30
CIV 2.42 200
Cygnus OB3. And similarly to WR 135, a weak absorption
can be detected blueward of the CIV + HeII emission line
at = 2.075 m suggesting a P Cygni prole for this line
blend (or for the HeII 2.06 m feature buried in this line
blend). Therefore, we classify WR 142a as a WC8 star.
3.2. Colors, distance, reddening and variability
As a rst step towards the estimate of the physical proper-
ties of WR 142a, we have compared its near-infrared pho-
tometry to that of six other nearby WC8 stars (WR 53,
WR 60, WR 77, WR 101, WR 117, and WR 135) se-
lected from Williams et al. (1987). Stars with detected
companions were excluded. WR 101 and WR 135 have
JHK photometry also from 2MASS, and WR 113 from
Pitault et al. (1983); in all these cases, all published mag-
nitudes agree to better than 0.1 mag. Extinctions in the
visible, A V , are given for the six reference objects by van
der Hucht (2001) based on their visible photometry. A
seventh WC8 star, WR 102e, also has available 2MASS
photometry. However, the fact that this star is located in
the galactic center raises some concerns about its valid-
ity as a reference for comparison to the WR population in
the solar neighbourhood. Besides the published JHK pho-
tometry we have also used the extinction given in van der
Hucht catalogue, from which we derive intrinsic colours
(J H) 0 , (H K) 0 using the extinction law of Rieke &
Lebofsky (1985).
Assuming that the intrinsic colours of WR 142a are
the same as the average of those of the reference stars, we
obtain (J H) 0 = 0:28 0:25. The uncertainty includes
both the intrinsic scatter in colours among WC8 stars and
possible errors in determining the extinction, which is gen-
erally done using BV colours. The derived extinction for
WR 142a is thus A V = 8:1 2:3, or A J = 2:3 0:6. Using
the K band to estimate the extinction introduces larger
uncertainties due to the larger scatter in derived intrinsic
(H K) 0 colours among the reference objects, and we have
preferred to exclude it for this purpose. A more accurate
estimate is possible by using the measured B = 18:1 in
the USNO catalogue, keeping in mind that a possible error
may be introduced by variability in the non-simultaneous
B and JHK observations. In that case, we have calcu-
lated (B V ) 0 = 0:14 using the observed (B V ) of the
reference stars and dereddening them with the A V listed
by van der Hucht (2001), using A V =(AB A V ) = 3:1, thus
obtaining (B J) 0 = 0:42. The observed (B J) = 8:9
thus implies A V = 8:1, practically identical to the value
derived from J H but based on a much longer wave-
length baseline. The uncertainty, mostly due to the scat-
ter in (B J) 0 , is accordingly smaller and estimated to be
0.4 mag. We thus adopt A V = 8:10:4, or A J = 2:30:1,
as the extinction towards WR 142a.
A similar procedure applied to the (V J) photom-
etry of the reference stars yields an estimate of (V
J) 0 ' 0:56 0:24 for WR 142a, again with the caveat
of the non-simultaneity of the visual and infrared obser-
vations although the relatively small scatter that we nd
in (V J) 0 suggests that this may not be an important
factor. Proceeding with the (V J) 0 given above and as-
suming for the visual absolute magnitude of WR 142a the
mean value derived by van der Hucht (2001) for WC8
stars, M V = 3:74, we obtain M J = 4:30. In this case,
to the already noted uncertainty in (V J) 0 we must add
the scatter in M V found for these stars, which van der
Hucht evaluates at 0.5 mag. Using the estimates of the
extinction and the absolute magnitude we obtain a dis-
tance modulus of DM = 11:2 0:7, corresponding to a
distance of 1:8 +0:6
0:5 kpc.
An alternative possibility consists of using the close
similarity between the spectra of WR 142a and WR 135
to assume that the intrinsic properties of both are identi-
cal, including intrinsic colours and absolute magnitudes.
WR 135 is the bluest star in the reference sample both in
(J H) 0 and (V J) 0 . The brighter M V listed by van
der Hucht (2001) is balanced by the bluer colours to give
M J = 4:33, practically identical to the value used in
the above estimate. However, tting the colours requires
a higher extinction (A V = 11:0 or A J = 3:1) and the dis-
tance modulus thus reduces to 10.2 mag, corresponding to
a distance of 1.2 kpc, in the lower end of the range given
above.
Despite of the fact that our observations were probably
performed under non-photometric conditions as noted in
Section 2, it is still possible to check for possible variabil-
ity by comparing WR 142a to other 2MASS stars in the
eld. Such comparison suggests that WR 142a was slightly
fainter when we observed it than when it was observed by
2MASS, with J = 0:08, H = 0:07, K = 0:25. Only
the signicance of the K variability is more than marginal,
lying within the amplitude range of the long-term variabil-
ity of Wolf-Rayet stars reported by Hackwell et al. (1979)
and well below the rather extreme case described by Danks
et al. (1983).

4 Anna Pasquali et al.: A new Wolf-Rayet star in Cygnus
3.3. Properties and environment
The physical properties of WR 142a (mass M , radius R,
temperature T ) may be estimated with simple relations
derived by Schaerer & Maeder (1992) from their mod-
els of WNE/WC stars, with the caveat that these mod-
els are quite sensitive to the assumed morphology of the
stellar wind, i.e. clumpiness, which may change the bolo-
metric luminosity of WRs. The luminosity can be esti-
mated by adopting for WR 142a M V = 3:74 as de-
termined by van der Hucht (2001) for WC8 stars, and
the average bolometric correction BC V = 4:12 found
by Nugis & Lamers (2000) for the WC8 subgroup (tak-
ing into account their equation (6) to transform from
narrow- to broad-band V magnitude). Since log(L=L ) =
0:4(M V +BC V M BOL
), the total luminosity of WC8
stars turns out to be log(L=L ) = 5:04. If the individual
luminosity of WR 135 is adopted instead as more appro-
priate for WR 142a, we obtain log(L=L ) = 5:24.
Using Schaerer and Maeder's mass-luminosity relation,
log(L=L ) = 3:032+2:695 log(M=M ) 0:461(log(M=M )) 2
we obtain a mass between 7.9 and 9.7 M (assuming re-
spectively log L=L = 5:04 and 5.24 as described above).
Likewise, the stellar radius R and temperature T are given
approximated by
log(R=R ) = 1:845 + 0:338 log(L=L )
and
log(T ) = 4:684 + 0:0809 log(L=L )
from where we obtain R ' 0:8 R , T ' 125000 K, with
little dependence on the choice between 5.04 or 5.24 for
log L=L . Finally, adopting Nugis & Lamers' equation
(24), which gives the stellar mass loss as a function of
the stellar present mass, we derive for WR142a a mass-loss
rate of 1:410 5 M yr 1 or 2:310 5 M yr 1 , depend-
ing on which one of the masses given above is adopted. It
must be stressed that the values above are a simple esti-
mate of the stellar properties of WR142a based on average
properties of WC8 stars, and an accurate model atmo-
sphere tting of its IR spectrum is indeed needed.
Although the winds of late-type WC stars are generally
a source of warm dust (Smith & Houck 2001, Chiar et al.
2001), no IRAS mid-infrared point source is detected near
the position of WR 142a. This is somewhat unexpected, as
the sensitivity of IRAS should enable detection of a typi-
cal late WC star within 7 kpc from the Sun (Cohen 1995).
Mid-infrared observations provide no evidence either for
any extended structure at larger scales around WR 142a,
as is sometimes found the neighbourhood of other WR
stars (e.g. Miller & Chu 1993, Saken et al. 1995, Pineault
& Terebey 1997, Gervais & St-Louis 1999, and references
therein). This does not completely rule out the possible
existence of an extended nebula, as the wide range of ring
Fig. 2. A view of the eld around WR 142a (the bright star
at the center of the image) showing no evidence for extended
emission. The printed version of this paper shows the K-band
image, while a JHK colour composite is presented in the elec-
tronic version.
nebula sizes around WR stars (Miller & Chu 1993) and
the intricate structure of thermal infrared emission in the
general direction of Cygnus would naturally make the de-
tection of such a nebula elusive. Near-infrared images of
the immediate surroundings of WR 142a (Figure 2) also
show it to be rather inconspicuous, with no obvious neb-
ulosity associated to it within the 5 0 eld of view of our
images.
3.4. Membership
At the estimated distance of ' 1:8 kpc, WR 142a lies in
the extended complex of massive star forming regions com-
posed by several OB associations and part of the molecular
complex Cygnus X (e.g. Odenwald & Schwartz 1989). Its
location with respect to the three most nearby associa-
tions and the other WR stars identied within 5 ф of it are
shown in Figure 3.
The overlap among the associations and the diф-
culty in precisely establishing their boundaries (or even
in establishing them as dierent entities) makes it diф-
cult to unambiguously assign WR 142a to one of them.
Adopting the distribution of members given by Garmany
& Stencel (1992), WR 142a lies near the boundaries of
both Cygnus OB2 and Cygnus OB9. Association to the
latter may be suggested in view of its proximity (less than
1 ф ) to the open cluster NGC 6910. The average extinc-
tion towards Cygnus OB9, where members obscured by
A V > 6 are listed by Garmany & Stencel (1992), does
not con ict with this assignment. It may be interesting

Anna Pasquali et al.: A new Wolf-Rayet star in Cygnus 5
galactic
latitude
galactic longitude
WR 144
WR 145
WR 146
WR 140
WR 147
WR 139
WR 143
WR 136
WR 141
WR 142
Cyg OB2
WR 138
Cyg OB1
Cyg OB9
WR 142a
* NGC6910
Fig. 3. Location of WR 142a with respect to the three OB
associations in its neighbourhood. Also shown are the positions
of other WR stars, with full circles representing WC stars and
empty circles WN stars. The boundaries of the associations are
a rough approximation to the distribution of their members as
plotted in Garmany & Stencel (1992).
to note that WR 142a appears in the sky about 10 0 West
of the compact HII region DWB87 (Dickel et al. 1969)
and may be obscured by the molecular cloud surround-
ing it. No detailed studies of this nebula seem to exist in
the literature, preventing us from ascertaining whether a
physical connection between WR 142a and DWB87 may
exist. On the other hand, it is also possible that WR 142a
is actually a member of Cygnus OB2. Cygnus OB2 is a
compact OB association (see Knodlseder 2000, Comeron
et al. 2002, and references therein) rich in very massive
members which are on the average more reddened than
those of Cygnus OB9. Cygnus OB2 has four other WR
stars, two of which also belong to the WC class, indicating
progenitors with initial masses above 60 M (Crowther
et al. 1995a), and in this respect the higher content of
very massive stars of Cygnus OB2 favors the hypothesis
that WR 142a is a member of this association lying in
its outskirts. Given the considerable uncertainties aect-
ing the denition of the membership, the boundaries, and
the distances of each of these associations (see Comeron
et al. 1998 for an additional discussion), the assignment
of WR 142a to either Cygnus OB2 or Cygnus OB9 must
remain as only tentative for the time being.
4. Discussion and conclusions
Our near-infrared observations of a source in Cygnus with
infrared colours deviating from those of normal, reddened
stars has brought up the serendipitous discovery of an-
other WR star in this complex of rich OB associations.
Table 2 summarizes the parameters of this star, WR 142a.
The detection of WR 142a adds one more example
of a late evolved star to the massive star content of this
region. It is a remarkable fact that Cygnus OB2 contains
Table 2. Summary of properties of WR 142a
(2000) 20 h 24 m 06:2 s
ф(2000) +41 ф 25 0 33 00
J (2MASS) 9.22
H (2MASS) 8.08
K (2MASS) 7.09
J (June 2002) 9.31
H (June 2002) 8.15
K (June 2002) 7.34
spectral type WC8
r (kpc) 1:8 +0:6
0:5
AV (mag) 8:1 0:4
log(L=L ) 5.04 1
M (M) 7.9 1
R (R) 0.8 1
T (K) 125,000 1
1 : Quantities derived from average properties of WC8 stars
examples of all the stages in the evolutionary path of the
most massive stars, O main sequence ! Of/WN ! LBV
! WN ! WC for initial masses about 60 M (Langer
et al. 1994). The addition of one more member of the
rare class of stars with such high initial masses is thus a
valuable one to a region that can be considered as the best
avaliable laboratory for the observational study of stellar
evolution at the upper end of the main sequence.
The abundant massive stars content of the complex
Cygnus OB2/OB9, where over 100 O-type stars and de-
scendants have been identied (Garmany & Stencel 1992,
Massey et al. 1995, Knodlseder 2000, Comeron et al. 2002),
leads to the expectation that this complex may be at
present or in the near future the scenario of intense su-
pernova activity. Taking 7.1 Myr as the expected lifetime
of a late O-type star (Meynet et al. 1994, Schaerer &
de Koter 1997), the content of Cygnus OB2/OB9 would
lead to the expectation of a rate of about 1 SN every less
than 70,000 yr. The observability of the radio-continuum
signature of individual supernova remnants is limited in
time and highly dependent on selection eects that are
diфcult to model (Green 1991), but the inferred inter-
val between supernovae in Cygnus is rather short as com-
pared to the estimated age of many supernova remnants
(Matthews et al. 1998). Thus, the fact that none has been
observed within 2 degrees from the centre of Cygnus OB2
(cf. Green 2001) suggests that no evolved massive star has
gone through the supernova phase yet. This poses some
constraints on the age of Cygnus OB2. According to the
evolutionary track for an initial mass of 60 M computed
by Langer et al. (1994), a star enters the WC phase when
its mass has decreased to 15.3 M . Only when its present
mass is as small as 3.92 M , the star can be considered a
probable candidate for a supernova explosion. This hap-
pens after 4.065 10 6 yrs from the main-sequence phase.
Moreover, according to Langer et al. (1994), WC stars
pop up around 3 million years. Hence, we may argue that

6 Anna Pasquali et al.: A new Wolf-Rayet star in Cygnus
Cygnus OB2 is as young as 3 - 4 million years, basically
in agreement with Massey et al. (2001) who derived, from
photometry of OB main-sequence stars, a mean age of 2.6
10 6 yrs.
An inspection of van der Hucht's (2001) catalogue re-
veals that Cygnus OB2 is the richest association in number
of WC stars compared to WN stars, and the discovery of
the new WC star reported here underlines this dierence
with respect to other associations. This could be inter-
preted as the result of a shallower IMF combined with the
young age of the association. Indeed, an IMF slope of -0.9
has been measured for Cygnus OB2 by Massey (1998) and
the cluster turn-o mass has been determined of about 120
M by Massey et al. (2001).
The discovery of a new Wolf-Rayet at a distance less
than 2 kpc from the Sun reported here dramatically illus-
trates the incompleteness that aects the census of even
the most massive stars in our galactic neighbourhood,
while stressing the need for dedicated infrared surveys to
improve the sample. Such eorts will be certainly worth-
while, given the critical dependence that our understand-
ing of the star formation history and stellar mass function
in OB associations has on working on complete samples,
especially when the most massive and rarest members are
concerned.
Acknowledgements. We would like to thank an anonymous ref-
eree whose comments improved this manuscript. Also, it is
a pleasure to thank the sta of the Calar Alto observatory,
especially Mr. Santos Pedraz, for their assistance during the
observing run in which the observations presented here were
obtained. We also appreciate the help of Ms. Uta Grothkopf
in making available to us the original article of Melikian and
Shevchenko, and of Ms. Petia Andreeva in translating it from
Russian. This paper made use of data obtained as part of the
Two Micron All Sky Survey (2MASS), a joint project of the
University of Massachusetts and the Infrared Processing and
Analysis Center/California Institute of Technology, funded by
the National Aeronautics and Space Administration and the
National Science Foundation; and of the SIMBAD database,
operated at CDS, Strasbourg, France.
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