Southern Doubles, Stars and Variables
SOUTHERN ASTRONOMICAL DELIGHTS : Presented by Andrew James
|PAGE DS 008
10 Mar 2009
|RA : 08h
Dec : -30° to -90°
Constellations :Pup, Pyx, Vel, Car, Vol, Cha, Oct.
Best Observed : Dec - May (Text Ordered by RA)
|RA : 08h
Dec : -30° to -90°
SELECTED SOUTHERN DOUBLES and VARIABLES
|HJ 4084 System|
If these proper motions are to continue then the A-BC will close. (See Figure xx) Based on the values within the Table, by 2330AD all four star will form a roughly straight line along PA 94° with all separations being a little less than half of today’s distances. The AC stars will approach each other but will be no closer than c.20 arcsec (2270AD), while the “AD” closest approach will be 13.7 arcsec along PA 40° in 2490AD. (Arrow near 2500AD mark for both ‘A’ and ‘D’.
Overall, this is an attractive group of stars worth looking for if you are near the False Cross.
Coloured Pair (08182-6019) This lies only some 1°SW from Epsilon Carinae. These two bright stars I found while sweeping the general area with 7x50 binoculars. Not list as any WDS pair, this blue-bluish and orange pair is remarkable for its colour contrast. At 7.3 and 7.8 magnitude (7.29 and 7.75V), with the two stars separated by 2.2' at the near eastern PA of 85°.
This one is almost a worthy of a Dunlop-like pair.
I 194 (08190-6012) is a yellow duo in the same field as the “Coloured Pair” mentioned above by about 10'NE. Another 9.4 magnitude star lies 1.9'N of the I 194, making certain identification a little easier. Magnitudes are 8.8 and 9.8, respectively, while the PA is 129° and separated by 1.5 arcsec. Interestingly, the WDS gives fainter magnitudes of 9.18 and 10.16. Clearly divided in 20cm at 333x, this dainty pair is worth seeking out. Since Innes discovered this pair in 1897, the stars have been slowly closing, while the prograde motion has reduced by some 5°. Looking at the proper motions, these two are probably connected.
Epsilon (ε) Carinae / NSV4058 / HIP 41037 / PPM 336856 / SAO 235932 / HD 71129 (08225-5931) is a suspected eclipsing binary system whose variations are thought to change between 1.64V and 1.82V in an unknownperiod. The combined spectral class of the two unresolvable stars is K3-III+B2V, merged to give the light yellow colour of the star to the naked-eye. Hipparcos and Tycho both gives the B-V as 1.195±0.003, while the Hiparcos parallax is 5.16±0.49 giving the distance as 194±18.5pc or 632±60.6 ly.
HJ 4096 (08234-6100) & HJ 4097 (08234-6059) are two pairs in close proximity within the constellation of Carina. Normally I would not mention these two pairs because they are quite though easy to resolve. The position of this and the galaxy ESO 124-15 can be quickly found by moving directly 1.5° due south from Epsilon Carinae / Avior, or alternatively, moving 3.1° due east of NGC 2516. HJ 4096 stars are 10.0 and 12.5 magnitude separated by a wide 15.2 arcsec along PA 88°. HJ 4097 stars are 10.0 and 11.4 and a separated by a smaller 11.0 arcsec along PA 8°. Since discovery HJ4096 has only rapidly increased in separation (c.5.2 arcsec), while HJ 4097 has decreased by 1.2 arcsec and has shown some direct PA motion. For a fleeting moment I thought I was looking at an obviously fainter but mini-version of the famous northern double-double Epsilon Lyrae near the first-magnitude star Vega. These are not the most enchanting pair I have looked at, but seeing two pairs together like this is a bit more unusual.
ESO 124-15 / PGC 23550 (08237-6053) is 7.6'N from HJ4096/ HJ4097’s position a the 14.3p magnitude galaxy in the same field. This should be visible in telescopes in dark skies above 20cm or 25cm. Data on this object gives the size as 1.7'x0.8', but expect to see only between half to one-third this size in the telescope. ESO 124-15 is also deemed a SB(s)bc barred spiral galaxy.
R 84 (08246-5909) is a near equal yellow duo is presently separated by 8.9 arcsec along PA 33° (1991) It can be very easily found without much trouble 27'NE of Epsilon Carinae. The pair is readily identifiable, as another yellowish star lays 1.5°NNE. H.C. Russel discovered this pair and provided the first measures at around 10pm on the 9th May 1881 - being 7.71 arcsec at PA 213.8°. Magnitudes by Russell were stated as both 10th, and subsequent observers adopted 11th. The latest WDS02 gives the magnitudes as 10.46 and 10.53. In the last hundred-odd years the two stars have slowly widened while the PA has remained much the same. It is still uncertain if the stars are associated, as the proper motion in RA disagree and the proper motion is declination are opposite. Yet the Tycho parallaxes agree quite well, being ‘A’ 121.60±31.50mas and ‘B’ 135.80±29.40mas.If these are true, then the distance of ‘A’ is 8.22±2.28pc (26.8ly) and ‘B’ 7.36±1.67pc (24.0ly.) If they are joined then the true separation is presently about 70AU.
Another 40 arcsec ESE (PA 118°) is a fainter 12th magnitude star. In all this field is very attractive under high magnification. Glorious, in a faint star-filled field.
A pm RA 077.72 +32.50 Dec -72.20 +37.70
B pm RA 125.30 +28.70 Dec +48.30 +31.70
I 801 (08264-5926) is a more difficult pair than R 84 (above) but lies in the same eyepiece field. Some 22'SE of R 84, the field contains eight 9th to 10th magnitude stars roughly organised in an arrow-like shape. I 805 is the brightest of all these stars, being 8.6 magnitude, and when split, 8.82 and 10.33 magnitude. The companion appears as a fainter star the SW. Little has changed in the relative positions since R.T.A. Innes discovered the pair in 1910, though Innes measure oddly found the separation as 0.8 arcsec. It was just seen in 20cm at 333x, and I estimate that 15cm is about the minimum aperture to clearly split the duo. The colours I saw as yellowish and white. Common proper motion suggest the stars are connected.
FIN 392 (08265-5912) lies 13.6'N of I 801. I looked at this pair in 20cm, because it is near I 801, but I could not split these two faint stars in the early 1990's. The WDS November 02 gives the present separation as 0.8 arcsec along PA 171°, and the fainter magnitudes of 11.24 and 11.11 - suggesting the discoverer’s estimating that the primary was bright was wrong. The positions really have changed little since it was discovered by Finsen in 1937. Data on this pair is still poor. If the present widening is true the pair could be seen in 20cm with care.
V Car (08287-6007) is a Cepheid variable varying between 7.08V and 7.82V over a period of 6.69668 days. Like most Cepheid it appears just like a yellow star, and this reflects the mean changes seen in the spectral type, which the GVSC5 gives as between F6 and G2 Ib-II. he rise from the minimum to maximum takes about 30% of the period, equal to almost exactly two (2) days (2.009 days, in fact). This augers well for observations at the same time each night over one whole week, and would be an interesting project for a new comer to see a real Cepheid in action. (JDE 2437454.023) A 7.8v magnitude comparison star appear 6.7' WNW which fortunately has a similar spectral class.
V343 Car (08290-5948) is a red Mira type variable that varies between 13.3p and 17.5 in an unknown period. Positioned 24'N of V Carinae, the general field chart shows its overall position in case you see it. The location can be further identified by another 11.8 magnitude star only 44 arcsec to the northwest. I could find little in the literature about this star.
X Car (08313-5913) is an EB/KE eclipsing binary showing a smallish magnitude range. It can be located 1.1° E of Epsilon Carinae and lies on the westward line passing through I 801 (above) Magnitude change between 7.90V and 8.65V in a period of 1.0826310 days or 01d 01h 59m59.3 s from the epoch of 18th November 1937 (JDE 2428857.146.) Both stars are classed as A0V P=1.0926310 in ACTA (1980).
ESO 124-19 (08317-5947) lies 33'S of X Car and I only mention these for completion. These faint two are both 14.8p magnitude separated east-west by 31 arcsec. At least 30cm is required to see them, and they look like to small wisps of cloudy nebulosity, being about 30×25 arcsec and 16 arcsec across, respectively. Looking at the STScI image, ESO 124-18 is a barred spiral with some ring structure, while ESO 124-49 looks as it is probably a companion spiral galaxy of some sort. The RV’s are almost the same, with the mean of +6 374kms-1, so they must be associated.
d Velorum / HJ 4133 (08444-4239) is a wide yellow pair with a substantial difference in brightness. Given magnitudes, since discovery in 1835, the separation has slowly decreased from 47.2 to 44.8 arcsec while the PA has increased from 61° to 63°. Spectral class of the primary is G5III. Judging from the proper motions, this is certainly an optical pair.
I 815 (08447-4117) is a multiple whose four components are listed as;
|I 815 AB : 7.3 and 11.5, 4.4″ 002°
I 815 AC : 7.2 and 13.3, 8.3″ 130°
I 815 AD : 7.2 and 11.0, 35″ 225°
This particular multiple appears in Uranometria 2000.0 Map 397 drawn with the "box" of nebulosity of superimposed on the object Gum 15. Both I 815 AB and I 815 AD were discovered by Innes in 1911, with I 815 AD is the widest and the most easiest to see.
The AB system can be seen with 10.5cm with care and is easier in 20cm - the problem being the magnitude difference. I 815 AC is slightly more difficult, but should be visible in 20cm under good seeing and moderately high magnification. Again, the five-odd magnitude difference made it hard to resolve when combined with its faint 13.3 magnitude. I only glimpsed "C" once in 30cm in moderately good seeing and made a rough sketch. This later pair was discovered by Innes in 1933.
All stars in this system are bluish-white, likely matching the spectral class of B3/5 II of the primary. Little has changed in the positions since discovery, and it is uncertain if these stars are dynamically behaving like multiples or as open clusters, but they certainly must be associated. I 815 certainly adds to the Cr 197’s appearance.
H Vel / R 87 (08563-5243) is an interesting bright blue and white pair in Vela some 2.8°NE of Delta Velorum or alternatively 2.4°E of the naked-eye open cluster IC 2391. Given as 4.67 and 7.92 magnitude, these stars are just visible in 7.5cm and easy in 15cm. (2002) Since discovery on 4th April 1881 (1881.256) both the PA and separation have decreased by 6° to 335° in PA and by 0.9 arcsec to 2.5 arcsec. No doubt the stars are associated and it is extraordinary that both J. Dunlop and J. Herschel had missed this obvious pair. It is possible the orbital motion of the two stars were unresolvable at the time.
Russell saw these two stars as “yellow and bluish”, while oddly AOST sees pale yellow and yellow, which to me is the reverse in how it appears in the sky. However, there are far more severe problems with Russell’s data. For example, he gives the PA as 249.5° and the distance of 3.17 arcsec. Furthermore the magnitudes of the two components are 6th and 9th, and are significantly different than WDS01’s magnitudes. None of these values seem to match this pair, though the 1880 positions of 08h 53m -52° 16' are correct for this star. I searched for other pair that might match R87 in case there is two possibilities that exist.
The component “R87 A” is a known spectroscopic binary with a period of almost exactly twenty-two hours or 0.917 days.
AOST2 says that the main stars is still indeterminate regarding the binary nature of these stars because of the small proper motions of the stars, which is true, however the twenty-six measures to date shows a curve that suggests association. In the years to come this system will be interesting to watch, and perhaps some of its mysteries warrant some future investigation.
Δ74 / b2 Car (08570-5914) was discovered by Dunlop in 1836 and appears in the same field in a medium magnification eyepiece as I 318 mentioned below. I saw the colours as blue and bluish-white. This bright and wide pair, with magnitudes of 4.87 and 6.58, the pair has a separation of 40 arcsec whose orientation is along PA 76°. These last measures being taken from the 1991 Tycho Star Catalogue and little has changed in the positions since discovery with the PA reducing by 1° and the Sep by 0.7°.
J Graham Little says of Δ74;
(Southern Astronomy, “Ten O'clock
High” Mar/ Apr 1994 pg.54)
“This is a very wide double that, with a steady hand, can be seen through binoculars. The primary star is a bluish-white... The companion star is... roughly the same colour (B8), but is obviously fainter... [and] looks best with low magnification, when the stars are kept close together.”
Primary star Δ74 A / HIP 43937 / SAO236436 is of B2IV-V spectral type and is the Beta Cepheid variable star V376 Car. Originally this star was NSV04328 identifying the star HR3582 as the variable, giving the magnitude variance as about 0.10. Observations of the variations find a 0.05 magnitude difference over a period of 0.208 days (4hr 59.5m)
In the Δm catalogue of the WDS the difference was observed by Pickering in 1912 as 1.67 magnitudes and later, by A. Wallenquist in 1948 using a wedge photometer and finding a delta-m of 1.34. The latest photometric observations give the difference of 1.71 magnitudes. If the HIP parallax of 5.25±0.46mas is correct, then the distance of the system is about 190±15pc or 620±50ly. If the stars are truly connected, the period must be very long.
I 318 / b1 Car (08594-5905) is another wide pair with a considerable difference in magnitude lying some 21'ENE (PA65°) of Δ74.Both stars are separated by The WDS01 shows the PA had increased by 7° and reduced in separation by 2.7 arcsec between 1900 and 1914. I saw the colours as yellow and white. It is unknown if these two are associated as no proper motion information has been collected. This field is has numerous stars in it, and has two 8th magnitude stars - the yellowish 8.3 mag HIP 44158 (3.1'NNE) and the white 7.8 magnitude HIP 44055 (14'SW). This last star being roughly midway between b 1 and b 2 Carinae. This is also a nice field.
|“Southern Astronomical Delights”
10 Mar 2009