SELECTED SOUTHERN DOUBLES and VARIABLES
R.A. 09 Hours
HJ 4171 (09000-6444)
(Vol) lies due 1.0°W of Miaplacidus
and is yet another faint pair. Quoted magnitudes
are 10.1 and 11.1 as first measured by Innes in
1918. Contained in a starry field, the pair is
separation is 14.6 arcsec at PA of 237°.
and is visible in 7.5cm. Although separation of
the pair is easy for small apertures, the
magnitude of the stars may require 10.5cm. to
see it clearly in less than perfect skies.
GP Vel / Vel X-1 / HD
77581 (09021-4033) is one truly remarkable
astronomical object which lies 3.0°NW
of NGC 2792. At first glance it appears just to
be another eclipsing binary with small
fluctuations in brightness, but it has proved to
be much more complicate object, as one of the
components is an example of an Alpha Cygni
(ACYG) variable, also being the X-ray source
Vel X-1. (This should not to be confused with
the radio source Vel X nor the Vela Pulsar
associated with the Vela Supernova Remnant or
VSR.) It is also an spectroscopic binary
associated with HD 77581. Vela X-1’s
optical component is also being known as EQ Vel.
GP Vel itself varies between 6.79 and 6.99 in
the period of 8.9647 days, based on the rough
epoch 2444275.20. The primary is extremely
luminous being of spectral class B0.5 Ia+ and
shows extremely violet-shifted Hα
absorption lines with a velocity of some
400kms-1. The companion star is much
smaller in mass whose influence is significant
enough to cause gas to stream between the two
stars. We know this because the spectra of the
primary star has several superimposed bright
emission lines characteristic of a gas stream.
What is unusual about this system is the longer
than expected period compared to other sources,
but if the orbit eccentricity is significant,
this may only be contrived effect - the
conclusion that Hutchings (1974) and Bessell
(1975) first suggested. Based on the observed
radial velocity of the components (~+300
kms-1 and ~+20kms-1) the
mass of the companion is between 1.5M⊚ and
2.0M⊚, suggesting a neutron star. Its
size is exactly in between what would be
expected for either a white dwarf or black
hole.
GP Vel is one of the closest of the eclipsing
X-ray sources known whose distance maybe
anywhere between 1.0kpc and 1.6kpc.
References for Vel X-1 /
GP Velorum
1. Bessell, M.S., Astroph. J.,
195, L113 (1975)
2. Heintz, W.D., “Double
Stars” p.162. (1978) Pub. D.Reidel
Pub.
3. Hutchings, J.B., Astroph. J,
180, 151 (1974)
E Carinae/ V345 Car /
SAO 256583 (09057-7032) is a Gamma
Cassiopeia (GCAS) type variable. This blue-white
4.67 mag star lies 24.6'SW (0.97°) of
Miaplacidus, and is one of the brightest of its
class. Most of these types of stars often vary
by up to 1.5 magnitudes that normally appear
without any known periodicity. They are peculiar
to the spectral class of sub-giants B-type (B0
III-B3 V), and are exhibited in about 0.4% of
all known variable stars. Known as shell stars,
they are subject to temporary fades of one to
three magnitudes. The variation of this one is
only 0.11 magnitudes that vary between 4.67 and
4.78. V348 Carinae has the spectral class of B2Vne.
λ Vel / Lambda
Velorum / SEE 109 / HIP 44816 / PPM313999 / SAO
220878 / HD 78647 (09080-4326) is commonly
named Al Suhail or just Suhail,
and can be usefully employed to find NGC 2792,
and appears in the north-western part of Vela.
As the 55th brightest star in the sky, this
orange star is 2.14v magnitude and is an example
of the rare Lc-type irregular variable stars
-one of only forty-five known. Sharing kinship
with Taurus’ first magitude star
Aldebaran, it holds the honour of being the
second brightest example of its class.
Brightness fluctuations have been observed to
diverge by some 0.08 magnitudes. The Lc
variables are significant because they sometimes
show complete absence of periodicity in their
light-curves where as other show at least some.
A few examples show the brightness changes that
are slow and continuous, but several have
changed quite abruptly. Most display spectral
types between K and S and are exactly the same
of the more common Lb-type irregular variables
except for being supergiants. Vel is classed as
K4 Ib-II, upgraded from the K5 data. Lambda
Velorum shares kinship with the first magnitude
Alpha Tauri, Aldebaran, which is an Lb-type that
varies roughly by only about 0.2 magnitudes.
However, although Aldebaran is of similar
spectral type, K5, it is just a giant star of
luminosity class III. Other bright Lc variables
include Beta (β) Gruis, Omicron 1
(ο1) Canis Majoris, Psi (ψ)
Aurigae and Eta (η) Aurigae.
The orangery-redness of the star is shown with
the B-V is 1.665±0.013 (HIP) and
1.685±0.006 (Tycho) Hipparcos found the
parallax of 5.69±0.53 giving the distance
of 177±16.5pc. Proper motions are in RA
-23.31±0.50 and 14.28±0.41, and
this is similar to the PPM and Tycho data.
Suhail is also the double star SEE 109, however,
it is a very difficult object to resolve as the
magnitude difference is 12.6. Since discovered
in 1897, no change has been observed in the
position angle or separation, which is given as
18.2 arcsec along PA 137°.
TX Vel (09130-5449)
is an irregular variable star that varies
between 10.0 and 13.0. Placed a mere 10.4'W from
the planetary He2-22 (PA 287°), I saw
the magnitude as 10.5, based on two or three
nearby field stars of known magnitude. Little is
known about this star, except that it is a
yellow G5 supergiant, though I did not see any
colour in 30cm.
Two pairs are found in the southern part of the
same field, but both could be clearly separated
using a high magnification.
β Car / Beta
Carinae / Miaplacidus (09132-6943) is
one of the brighter stars of the southern skies,
and can be found about halfway between the
Southern Cross and Canopus. From Sydney it is a
circumpolar star, and although it is today
placed in the modern day constellation of
Carina, it was once, prior to the mid-17th
Century, lay within the super-constellation of
Argo Navis. Later, Argo gained a new
sub-constellation called Robur Carolinum.
Created by Edmond Halley and officially
published in 1679, Robur was made to commemorate
the place known as the Royal Oak. This location
protected the defeated Charles II, after his
army was routed by Oliver Cromwell at the Battle
of Worcester in September 1651. La Caille
complained bitterly about Halley’s
addition because it destroyed most of the
prominent stars in the Ship. (Halley, however,
didn’t complain. It ensured that he
received his Masters Degrees by royal
proclamation!) From about 1720, popularity for
the constellation of ‘The Oak’ was
slowly reclaimed back into Argo Navis. Its
common usage probably ended in 1800 with Johann
Elert Bode’s star atlas
‘Uranographica’. From then,
like many others, Robur simply fell into
antiquity as an obscure constellation. American
astronomer Benjamin Apthorp Gould in 1879
subdivided this part of Argo Navis into smaller
constellations, and Miaplacidus became part of
Carina. This change was permanently adopted by
the IAU in 1930.
Once known as Alpha Roburis, Miaplacidus was
supposed to have been derived from the Arabic
Mi’ak or ‘waters’,
while the Latin 'placidus' was added much later.
I assume that from Arabia, the Chaldeans would
have seen this bright star in Summer glimmering
close to the southern horizon of the Indian
Ocean. Today, however, Miaplacidus is fully
translated to mean ‘placid waters’ -
appropriate because the star lies in the bilge
of the ship!
This white star culminates annually at 9 pm on
the 26th March. In order of brightness, at
1.674v magnitude, makes 28th among the naked-eye
stars. Distance is given as 26.1pc. or 85 ly.,
although the latest information by Hipparcos
gives the much further distance of 34.09pc. or
111.2 ly. The spectrum of this giant star was
for many years given as A0 III, though it has
recently been downgraded to an A2 IV, indicating
a surface temperature of 8 700K. Measurements
suggest an absolute magnitude of -0.4, so the
true luminosity is about sixty times brighter
than the Sun. Miaplacidus has been shown from
the radial velocity that it is approaching us at
a pedestrian 5kms-1. This is similar
to the first measure in 1927, from the famous
southern station of Harvard University in Chile.
By 1970, careful inspection of the broadening of
the spectral lines showed that the rotational
(V.sin i.) velocity is
c.145kms-1. Using general stellar
evolution theory, the rotation of the star would
have a period possibly as long as c.2.5 days or
60 hours for its nine million kilometre girth.
Proper motion measures is 36.7 arcsec per 100
yr.-1 towards the constellation of
Volans, which it will crawl into about the year
9 800 AD. Also in the future it will become the
southern pole star in 6 200 AD, approaching by
some 5° 42'. It is interesting to note that
about the same time, Alpha and Beta Centauri
will also be making their closest approach of
23'. Today, it stands as a lonely sentinel on
the edges of the magnificent southern Milky Way.
HJ 4164 (09135-6455)
is in the same field as NGC 2808, some 9.5' ESE,
is this John Herschel pair first measured by
Russell in 1879. The stars are 10.0 and 10.6
mag, separated by 16.4 arc sec along position angle
64°.
HU 1457 (09144-5500)
is the first, which was discovered by Hussey in
1913. Both these white stars are of near equal
magnitude, which is stated as 10.3 and 10.8,
respectively. Separated by 1.3 arcsec at PA
260°. Since the last measure in 1957,
the position angle has reduced by 10°
since discovery. The proper motions suggest that
the two are likely physically associated.
I 11 (09152-4533) is a
wonderful close and near equal brightness pair
some 10.7'WSW (PA 244°) from the
planetary known as Pb5 or He2-24, and hence, is
useful for finding this PNe. I saw this pretty
bluish-white / white pair being resolved with
some difficulty using the 20cm (C8) at 234X.
(AOST2 describes I 11 as having “...no
perceivable colour difference.”) My
own estimates for the Δm was 0.6, and this
is quite comparable with the WDS 2001 that gives
0.8 from the 6.7 and 7.5 listed magnitudes.
AOST2 claims it can be split in 15cm, though at
present time, it would have to be the best
observing conditions to do so, as the pair's
distance is slowly diminishing. I would consider
20cm is closer to the mark but using telescopes
greater than 30cm will become much easier. I 11
was first discovered by Innes in 1895 and was
first measured by R.P. Sellors in early 1896.
Since this time the PA has increased (direct
motion) from 271° to 292°
- nearly 30° while the separation has
decreased by about 0.15 arcsec. (2002) The
spectral class of the duo is B8V. This system is
without doubt a binary system of a moderately
long period and will be worth watching in the
coming decades. A nice pair.
LW Car (09157-6921)
is some 7'E is the faint galactic RR Lyrae
variable. I only mention it, as photographers
can easily detect it it. LW Car’s
magnitude varies between 14.5 and 15.5 and has a
poorly estimated period.
R 107 (09165-5824) was
discovered by H.C. Russell, sometime in 1881, as
he unfortunately gives no specific date for this
object's first observation. He estimated
separation as 8 arcsec, and said the magnitudes were
9th and 10th. Of the three observations between
1882 and 1917, separation has remained at 9.5 arcsec
at PA 285°. Observers can find it
near a bluish 6.1 mag star in Carina (SAO 236772;
Spectra B5), some 10'S and 39' due west
of NGC 2867. Stated magnitudes are 9.5 and 11.2,
making an attractive contrast, and the pair is
in a rather pretty field of moderately bright
stars. It is easily visible in 7.5cm, though I
could not distinguish any colour. This was the
same in both the 20cm (C-8) and 10.5cm
refractor.
FIN 133 (09166-5506)
is the second and lies 19'SE. Using the triple
star mentioned in the text with He2-22,
continuing along the same direction until the
solitary 10th magnitude is found. This is the
pair. Discovered by Finsen in 1930, this pair is
almost identical to HU 1457. Magnitudes are
given as 10.3 and 10.4, and are separated by
1.7 arcsec. at PA
273o. Again the proper
motions suggest that the stars are associated.
In all, both stars can be separated in 15cm,
with care, and easily in 20cm.
RMK 10 (09179-6948)
is a white and yellowish pair of magnitude 7.8
and 8.1 magnitude, first discovered by
Rümker at Parramatta. The pair lies 24'E of
2nd magnitude Beta Carinae. Of the nine
measures, last in 1958, the positions remain
10.5 arcsec and PA 18°. No significant
change has been observed with this pair. It is
possible that it is a true binary, though its
period is probably very long. In the same field
as RMK 10, is the pair R110.
R110 (09182-6941),
that H.C. Russell first found using the
29cm.(11.5-inch) at Sydney Observatory on 21st May
1881. Russell’s measures revealed a PA of
26.6° and a separation of 11.1 arcsec. The
magnitude of the two stars is 10 and 11. Little
has changed with the pair, and is likely to be
just an optical system.
R111 (09208-5716) is
found in a starry field some 55'SWW of IC2488
(See last month) or exactly 1.0° of
NGC 2867. Within a small horseshoe-shaped
asterism, R 111 lies next to another field 9.8
mag star to the east. Discovered by Russell at
Sydney Observatory on the 5th March, 1873, with
the first measure occurring on the 7th May 1880.
His observations records 11th and 12th
magnitude, separated by 8.52 arcsec at PA
209.1°. Later observations have
determined the respective as 10.0v and 11.0v
magnitudes, with only three measures since this
time, with the latest being in 1948. This last
observation shows an increase separation to 9.2 arcsec
at position angle 213°. My estimate
in 1992 suggests the separation has increased to
about 11 arcsec. We know few details about this pair,
and glancing at the proper motions of the
components, it is likely that this is a chance
alignment of an optical system.
V Velorum (09223-5558)
is a Cepheid variable that fluctuates between
7.19v and 7.95v magnitude over 4.370991 days,
whose period is set from 30th May 1970
(JD2440736.25) at 18h UT. The rise in magnitude
in the outward pulse takes about 1.3 days to
reach maximum brightness. Spectrally, this
sub-giant varies between F6 at maxima and F9 at
minima.
Jacob 5 / JC 5 / ADS
7379 (09267-2847) was discovery in 1858 to
lie 40'E of λ Pyxis and halfway towards
the variable S Antliae but still within the
constellation of Pyxis. Jacob 5 is the close
0.6 arcsec bluish-white coloured pair of 6.5 and
7.2 magnitude. (Burnham's Celestial Handbook,
incorrectly states that the stars are 8 and 8.5
magnitude.) A 30cm telescope can probably
resolve the two, using high magnifications and
under good seeing. Since, the separation between
the two stars has remained fixed but has PA has
decreased by 40° since this time. It
seems likely that this is a true binary system
with several hundred years as the period. The
spectrum reveals a B8 star, with the individual
component spectral classes still unknown.
BRT 2548
(09281-5652) is some 6'NE from the planeary
nebulae IC 2488's centre, and is placed near the
cluster’s edge. (Top left in Figure 4)
Discovered by S.J.Barton in 1924, this faint
pair is 11.0 and 12.0 magnitude, whose solitary
micrometric measurement gives the separation as
3.6 arcsec at PA 174°.
RST 408 / NSV
4516 (09304-5822) appears as a naked-eye
brightish red star some 35'SW of R123 (PA
235°) position. This pair is very
difficult as the magnitudes are 5.9 and 13.5
(Δm=7.6) and the two are separated by
2.3 arcsec along position angle 98°.
Since discovered and measured by R.A. Rossiter
in 1930 there has been no further measures.
Whether the companion is still in this position
some seventy-five years later is anyone’s
guess.
I could not see the companion in 20cm the two
times I looked at RST 408 even when I tried
using an occultation bar to eliminate some of
the primary’s overwhelming light. I
suspect either 30cm to 40cm could see the stars
elongated and under very good seeing split the
duo.
Both the GVSC4 and the WDS03 Notes lists the
primary as the suspected irregular variable NSV
4516 / HR 3793 (09304-5821) that changes
between 5.86V and 5.94V is an uncertain period.
It nature is yet to be determined.
Catalogued as HIP 46620 / PPM 338035/ SAO
237056/ HD 82536 this average 5.88 mag. star
shows a B-V of +1.676 and the spectral class of
M2 III. Hipparcos gives the parallax as
3.08±0.55giving the distance as
325±56pc. or 1060±195ly. It is
unknown from the available information if the
stars are associated.
N Vel / SAO 237067
(09312-5702) is an orange K5 III star (B-V of
+1.538) that is listed in the GCSV4 as possible
variable star. It is suggested that changes
between 3.12V and 3.15V magnitude in a unknown
period, but little change has been seen in
recent decades. However the designation of
“CST:” means this star actually
shows constant light. The N Velorum designated
name is also misleading, as all variables may
only be in the range between R and Z in any
particular constellation. N Velorum is the Roman
letter given to the star by Bayer’s
original Uranometria when Carina and Vela were
in the grander constellation of Argo Navis. This
star locates the double star SYO 1 which is only
13.2' away. Hipparcos gives the parallax as
13.72±0.51 that calculates the true
distance as 72.9±2.7pc. or
238±8ly. It is possible this might be a
secular variable.
R119 (09316-5602) is
another fainter pair 3'W of R120. Discovered on the same night
as R122 and R120, the magnitudes of this duo are
10.6 and 11.5. Separation is a wide 17.0 arcsec at
position angle 200°. These last
measures were taken 1934. Little has changed
since then. Faint but visible in 7.5cm.
R120 / SAO 237073
(09319-5602) is some 3'W of R122, and was
discovered on the same night as R122.
Russell’s original measures show a
separation of 9.59 arcsec at PA 34.5° Later
observations of R120 show that Russell PA was
out by 180°, a common problem
sometimes facing double star observers. The
current PA is 215°. Both are written
as 10th magnitude, though later observations
suggest the respective 9.2 and 10.2 mag. I saw
both colours as slighly bluish. In all, R122 (and R119
and R120) are contained in a
starry background and easily found some 42'ENE
of the planetary NGC 2899 or 20'NNE from the
planetary, Sa3-10. A 7.5cm will ind these pairs
faint but certainly it would be better placed in
10cm or above.
R122 / SAO 237078 / HD
82789 (09322-5601) was discovered by H.C.
Russell at Sydney Observatory using the 17.5cm.
(7.3-inch) on the 18th March 1873. The magnitudes of
this yellow and white pair are 8.4 and 10.2.
Separation is 2.5 arcsec at PA 110° , and
these values have slowly been decreasing since
discovery. Right now it is uncertain if this is
a physical system or an optical pair, but if it
is a true binary, the period must be more than
three hundred years. This pair will be
interesting to watch over the ensuing decades.
In all, these three pairs above are contained in
a starry background, and can be easily found
some 42'ENE of NGC 2899 or 20'NNE of
planetary nebula SA3-10. A 10cm is
required to see R119, R120, R122 clearly.
Jacob 5 / S Ant/ S Antliae (09323-2838)
is the brightest example of this class even
though it is ignored in the literature. S Ant
lies close to Antlia's border with Pyxis, being
2°E of yellow 4.7 magnitude Lambda
(λ) Pyxis. Also, exactly halfway to S
Antliae is the 6th magnitude close pair Jacob 5.
Magnitudes vary between 6.4 and 6.92, changing
equally in both the primary and secondary minima
by the 0.5 magnitudes every 15.92 hours. (0.6484
days) The period between successive magnitude
drops have been measured as 07 hrs 46 min 50
sec. S Antlia lies within a starry field and
20'W is two faint 7th magnitude stars that are
suitable comparison. The variable has a
magnitude greater at maximum and lesser at
minimum than these stars.
In real terms, both S Ant's stars are separated
by only 2.2 million kilometres, with each star
having an average diameter of 2.4 million and
1.3 million kilometres, respectively. Due to
this close separation, both stars are highly
distorted, with mass transfer as presently
observed being a real possibility. Total mass is
the same as the Sun, with the individual masses
dividing as 0.68 M⊚ and 0.32 M⊚.
Surface temperatures are 8 300K and 7 350K. In
solar terms, the luminosity output of the
components is 12 times for the primary and 2.3
times for the secondary. Present distance for S
Ant is estimated to be 91pc or 300 ly.
SYO 1 (09328-5706) is
a charming blue-white and white pair lies 1.8'S
of the southern Vela border with Carina being
suitably placed 13.2' ESE (PA 107°)
from 3.1 mag. variable star, N Velorum. The pair
can be seen in 7.5cm but would be better in
anything over 15cm. An obvious 8½th
magnitude yellow field star also lies 3.8'SE of
the SYO 1.
Discovered probably by R.T.A. Innes before he
moved to South Africa, as the first pair in the
Sydney Observatory double star catalogue of
1895, it is listed in the WDS Reference file
“from additional DD list.” This
should not be confused with the H.C.
Russell’s Second “New Double
Stars” list presented to the Royal Society
of N.S.W. on the 5th September 1883 that Russell
later published himself. (See WebPage) SYO 1 is
also the first of the pairs discovered away from
the influence H.C. Russell’s earlier
double star work - properly named for the
Observatory ad not the individual Government
Astronomer. (In 1893 Russell had long stopped
his work of double stars almost twelve years
earlier.)
SYO 1 itself is a 7.1 and 11.0 (7.12V and
11.06V) magnitude star that is separated by
10.7 arcsec along position angle 20°.
Little has changed in the relative positions of
the two stars since discovery. It is likely
these two are a true pair as the motions are
similar but the orbital period of this must be
very long. Spectral type in the WDS03 as
B6/7II/III.
R 123 (09333-5758)
has a combined magnitude of 6.1 making it a
naked-eye star in Carina. It lies
1.0° SSE of N Velorum or some
2°E from the planetary NGC 2867. This
wonderful near equally bright blue / bluish pair
can be seen in 7.5cm but is fairly attractive in
15cm or 20cm. Magnitudes were visually estimated
as 7.8 and 7.9, but the latest Tycho data
suggests it is brighter than this giving 6.82V
and 6.96V.
Russell discovered this pair on the night of the
5th March 1873, describing it as “8 and
8” appearance in the field saying
“This is the following star of a small
triangle.” In the telescope I could
not identify these stars.
Up till the last measures in 1977, the pair
seems to be fixed, but there is evidence that
now shows direct motion that has increase
+4° to position angle 34°.
However, the separation is clearly closing. In
1880 this was 2.5 arcsec and this has reduced to
1.9 arcsec. If the trends continue, the stars
will become difficult in about 2200AD with
closest approach being in 2340AD. Spectral Class
of both is B8V. An attractive and enticing duo
in a field of scattered stars.
Nearby Planetary
He2-32 / Sa3-9 / ESO
166-19 / Wray 16-49 / PK 278-4.1 / PNG
278.5-4.5 (09309-5737) is a faint PNe that
is listed as 16.1p and subtends some 56&215;31 arcsec.
Double star R123 lies within the same field some
28'SE (PA 137°). It is likely
invisible to most amateur telescopes except
perhaps the larger Dobsonians.
RST 413 (09335-5823)
lies 25'S of R 123’s position and is a
very difficult pair that would be a true
challenge for any southern amateur to either see
elongated or clearly separated. If the Hipparcos
separation of 0.396±0.002 arcsec,
however, is true then it is unlikely to be
split. I have never divided this pair R.A.
Rossiter found this pair in 1929 and it has been
measured five times in the ensuing years. The
star at low magnification looks like a 7.2
magnitude blue star. When divided, the stars
appear visually as 7.9 and 8.0 mag, however more
recent photoelectric estimates give 8.10 and
10.04. Since found the separation remains
unchanged at 0.4 arcsec, but the position angle
seems to be prograde and now orientated at
237°. A pair to watch in the future
to see if the two are attached.
GW Car (09364-5959)
is an EB/KE* eclipsing binary that lies in the
same field as the planetary IC2501, some 1.9'
along PA 287°. Visual magnitude
variations change between 9.55 and 10.1 in the
period of 1d 03h 05.6m (1.128911 days.), based
on the starting date on the 23rd October 1941(JD
2430291.0395). The blue B1 III star show
nebulose characteristic in the spectra,
suggesting that the stars are, or have been, in
the process of mass transfer.
* KE classification is a contact binary
whose components have early spectral types in
the range of O-types and A4 spectral
types.
R133 (09432-8120) has
magnitudes 9.5 and 9.5 was first discovered by
H.C. Russell from Sydney Observatory on the 26th
May 1880. His observation is given as 3.5 arcsec
and the PA of 44°. In 1983, the
separation was measured at 3.65 arcsec while the
PA was given as 46°, indicating
little change. This is a delightful even pair,
with yellowish components. As both have similar
common proper motions, it is likely that these
stars maybe associated. If it is a true binary
then the period is probably very long.
HJ 4240 (09433-6002)
is an 8th and 10th magnitude pair 34'E of the
small planetary IC2501. Although
discovered by Sir John Herschel, Lawrence
Hargrave made the first measures at Sydney
Observatory on the 12th May 1882. Separated by
12.4 arcsec at PA 57°, little has
changed in the positions in the last 116 years.
I saw the colours as bluish and white, which is
easily visible in 7.5cm According to the WDS96,
the magnitudes are 7.5 and 10.0, with the
primary's spectra being B5V.
W UMa / W Ursa
Majoris (09438+5557) is one of the most
famous and interesting of the EW eclipsing
binary systems that is not visible from Sydney's
-33° latitude. W Ursa Majoris varies
from 7.9v to 8.63v over 0.3333639 days - or
nearly exactly 8 hours. Both appear as dwarf F8V
spectral class stars, both containing
peculiarities in their spectrum. W UMa has the
true separation of 3.6 million kilometres, each
with diameters of 2.6 and 1.1 million
kilometres, respectively. Luminosities are
comparable with the Sun, being 1.3 L⊚ and
0.8 L⊚, while both the temperatures are
5 920K and 6 140K and masses are 1.3 M⊚ and
0.76 M⊚. Both stars appear grossly
distorted, surrounding the whole system with a
bright glowing gas, torn either by mass transfer
between the stars or material is stripped from
their surfaces. Some of these energies appear
strongly in X-ray. Distance to W UMa is 55pc. or
180ly. from us.
υ Car / Upsilon
Carinae / RMK 11 (09471-6504) is one
of the brightest double stars in the southern
skies and rates among the very best pairs for
small apertures. Discovered by Charles
Rümker and later measured by John Herschel
in 1836 this magnificent double star is listed
as 3.0 and 6.0 visual magnitude on a continuing
virtual fixed position of 5.0 arcsec along the
128° position angle. Both stars are
pale bluish-white to white and yellowish -
though some say the companion’s colour is
yellow being likely a slight contrast effect but
does agree with the spectral class of A8Ib or A9.
E.J. Hartung says of this pair;
“...there has been no real change in
this very fine pair, and the proper motions are
sufficiently similar to indicate a long period
binary. It is an admirable object for small
apertures.”
Canberra observer Ross Gould in "Seeing Double"
(Southern Astronomy, Mar/ Apr 1994 pg.52-53)
“The 18cm refractor showed it as an
easy and beautiful pair at x180.”
This is a wonderful pair especially as it shares
the field with the faint and just as easy HJ
4252. The main star of υ Car is
catalogued as HIP 48002 / T8950:2272:1/ PPM
357553/ SAO 250695/ HD 85123 whose exact
position is RA: 09h 47m 06.14s and Dec:
-65° 04' 19.3″ and the given visual
magnitude is 2.92 with a B-V of +0.273. Tycho
gives the primary as 3.01V magnitude and the B-V
of +0.267.
Proper motions here are quite similar and it is
highly likely that the two are physically
attached. Hipparcos parallax is
2.01±0.04mas giving the distance of
498±10pc. (1620±32ly.) calculating
the current true separation as 6 500AU.
Estimates of the orbital period maybe as long as
200 000 years. Absolute magnitudes (Mv) are -5.4
and -2.5, respectively, with the sum mass
(ΣM⊚) of 17.8M⊚. Using
the Mass-Luminosity Relationship (MLR) for
supergiant stars, the masses divide into roughly
as 12.0M⊚ and 5.8M⊚ suns.
This is a wonderful pair - especially as it
shares the field with the faint and easy HJ
4252. A really "must see" pair!
HJ 4252 (09478-3507)
lies only 5.4'SE (PA 123°) from
Upsilon (υ) Carinae / RMK 11. This
bluish-white stars are 9.3v and 9.5 magnitude
(or 8.74V and 9.13V) and are presently separated
by 12.2"arcsec along PA 303°. Both
stars continue to slowly reduce in distance,
going from the Herschel measure of 13.0" (1836)
to 12.2" (1991). As the proper motions are
similar, it is likely these two stars are
attached. Assuming the parallax is
12.10±0.84mas is correct, being the
distance of 83.3±5.9pc
(279±19ly.), then the true separation is
now around 1 100 AU with the a period being
around of 20 000 years.
Hartung (AOST1) states under his description of
Upsilon Car;
“...a small pair h.4242 (9.3 9.5 12"
303°) almost 5'Sf. is also
easy.”
Ross Gould in "Seeing Double" (Southern
Astronomy, Mar/Apr 1994 pg.52-53) states;
“...5' South-east is HJ4252, a wide
faintish fixed pair...[and] showed well with
18cm at 180x.”
This is interesting pair that shares the same
field as υ Car that
best is seen using medium to moderately high
magnification. A true southern splendour.
Δ81 / DUN 81
(09543-4517) also known as Bode star 524 Argus,
is one of the most magnificent jewels of the
southern sky and not to be left out of in any
southern observer’s object lists. Hartung
describes it as “ornaments, a lovely
field, a real treat to see.”
I saw the colours as pale yellow and bluish,
seemingly being two’s colour little more
prominent than when Dunlop saw the pair in 1827.
Dunlop measured the pair first, but for some
reason the first recognised measures were
achieved by John Herschel in 1836 (as stated in
AOST2). Dunlop actually did measure this star
first, giving the PA as 30° 34'sp.
equally the PA of 270° -
30.57° = 239.4° and
4 arcsec. Little change has occurred in these star since
Dunlop found the duo in 1836. Presently the PA is 240°
with the separation of 5.4 arcsec, and the stated
magnitudes are 5.8v and 7.9v. As there is little movement
in positions it is uncertain if these two are connected,
but there is evidence of similar common proper motion. If
they are really attached the period will be very long.
“Southern Astronomical Delights”
© (2009) |
LAST UPDATED
10 Mar 2009 |
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