SELECTED SOUTHERN DOUBLES and VARIABLES
R.A. 03 Hours

T Hor (03008-5038) this moderately bright richly coloured red star is a Mira variable that lies 54'NW (PA 319°) from Δ10. Magnitude range averages between 7.2 and 13.7 magnitude that varies over some 217.6 days (JDE 2441957). Its rise and fall in brightness is almost sinusoidal, with the change in brightness roughly 48% of the period. An entire cycle can be seen in dark skies with 20cm. Spectral class is M5III.e. A precise position is RA : 03h 00m 51.9s Dec. : -50° 38′ 30″.

Δ10 / DUN 10 (03046-5119) is a yellow and orange pair that lives in Horologium. This moderately wide pair has a one magnitude difference for the 7.6 and 8.6 magnitude pair. Dunlop discovered it in 1828 and the separation has continued to increased from 30.0 to 38.3 arcsec while the PA has decreased from 75° to 70°. From the available proper motions, this is likely a real pair that is presently widening, If so, the period must be very long. This is a quite nice pair for apertures as low as 5cm.

Δ11 / DUN 11 (03075-5823) is described by Dunlop as “A triangle of stars. The following a double star.” Precessed position is 03h 07m 30s -58° 23' (2000), but nothing from the clues appears here, and observations confirm no such pair exists in this place. It is obvious that Dunlop has likely given an incorrect position. Possibilities for this pair are still uncertain.

Δ12 / DUN 12 (03152-6427) is a multiple star placed in Reticulum some 7.5'E of the border constellation of Horologium. Δ12 forms the apex of an isosceles triangle of stars with ζ^1,2 Ret / Zeta ^1,2 Recticuli (ζ^1,2 ) and β Hor / Beta Horologium ( ) - being easily found 1.8°E of 5.0 magnitude β Hor. This pretty pair hallmarks a really poor region of sky that is almost totaly devoid of any bright stars.
DUN 12 A-BC is the moderately wide pair that is separated by 19.1 arcsec along PA 104°.
Precessed values of Dunlop locate Δ12’s position in 2000 co-ordinates, as 03h 13m 27s -64o 32', which are out by 12.4'ENE along PA65° from the observed placement.

The B star is again double, being the pair as RST 67 / Δ12 BC.Its two components are invisible in most telescope because of their general proximity. Discovered by Rossiter in 1928, this 9.5 and 9.8 magnitude duo is separated by 0.7 arcsec along PA 25°, which was last measured in 1978. In 1928, the separation was only 0.3 arcsec and its PA was 48°. In 1983 and 1992 I attempted to split this pair in 20cm but was quite unsuccessful - not even seeing any elongation. If any widening is real, then the projected pair should have been visible. In 2000, 2005 and the 2010, the respective components distance should roughly be; 0.88 arcsec 14.9°; 0.91 arcsec, 12.6° and 0.96 arcsec, 10.3°. This “prediction” assumes there is a linear expansion still continues with the few measures available.

DUN 12 A-BC 03 15 12.0 -64 27 00 6.9 8.9 19.1 --- 103 104 1836 1959 F5
RST 67 BC 03 15 12.0 -64 27 00 9.5 9.8 0.3 0.7 48 25 1928 1978

Date         1st  2nd  Delta mas.yr-1

Date         1928 1978  50     1     

Sep.(arcsec) 0.3  0.7   0.4   0.008  

P.A. (deg)   048  025  -23   -0.46   

WDS Nov 02
DUN 12 A-BC RST 67 BC 1826 1993 18 098 104 14.0 19.2 6.68/8.95 F5 -030 -058 -64 235 NpD0315110-642638-027-057

RST 67 BC
1928 1978 4 48 25 0.3 0.7 9.5/9.8 -027 -057 D0315139-642643-027-057

It is likely that all three star are associated as they show similar common proper motions.

Surrounding Pairs
Desig Cmpnts RA Dec PMag SMag Sep1 Sep2 PA1 PA2 Yr1 Yr2 Sp
FIN 361 Aa 03 10 06.0 -63 55 00 7.4 7.4 0.2 0.1 65 286 1961 1990 A3III/IV
HJ 3559 Aa-B 03 10 06.0 -63 55 00 6.7 10.7 43.1 --- 40 -- 1879 1919

WDS Nov 02
03101-6355 FIN 361 Aa 1961 1991 18 74 288 0.2 0.1 6.65 6.89 A3III/IV +040 +013 -64 229 pD0310033-635449
03101-6355 HJ 3559 Aa-B 1837 1991 8 38 41 40.0 43.2 6.67 10.14 +039 +011 N 0310033-635449
RST 2298 03 11 00.0 -63 47 00 10.8 10.9 0.3 --- 222 231 1934 1983 G0
WDS02
03110-6347 RST2298 1934 1991 4 222 213 0.3 0.5 11.00 10.97 G0 +006 -021 -64 232 pD0311009-634710+006-021

HJ 3562 03 12 06.0 -64 20 00 9.0 9.3 34.3 --- 330 -- 1836 1913 F2/3V
wds02
03121-6420 HJ 3562 1836 1991 12 329 331 48.4 34.4 9.25 10.14 F2/3V -022 -005 -64 234 N 0312058-641957-022-005

Some 2.3°S of the pair Δ12 are four main NGC galaxies. These are NGC 1244 and NGC 1246, with the fainter galaxy ESO 82-10 some 9'NE of NGC 1244. The two others are NGC 1313 and NGC 1313a, along with one of about five or six very faint galaxies. 063.

NGC 1244 (03065-6647), NGC 1246 (03070-6656) and ESO 182-10 (03407-6640) are a collection of galaxies that can be squeezed into a field as small as 18 arcmin. NGC 1244 is the larger one, but is orientated nearly edgewise having the size of 1.9#8242;×0.3′. In 20cm, it looks less than this, perhaps being 1.3′×0.2′ or 72×x12 arcsec, looking like a thin slit of nebulous light. Its companion NGC 1246 appears more oval at 1.3′×0.7′.

Both NGC 1244 and NGC 1246 are of similar 13.9p magnitude and likely associated, as the radial velocities are nearly equal I.e. +5,385kms^-1 and +5,310kms^-1, respectively.

NGC 1244 ESO 82-8 IRAS 3058-6657 PGC 11659 03 06 30.2 -66 46 31 GLXY 13.9p 1.9'x0.3' 2 +5385 .SAR2P* RC3
NGC 1246 ESO 82-9 Fair 229 PGC 11680 03 07 01.1 -66 56 14 GLXY 13.9p 1.3'x0.7' 40 +5310 .E.5.*. RC3
ESO 82-10 Fair 230 PGC 11712 03 07 40.3 -66 40 10 GLXY 14.2p 1.2'x1.0' 90 +5748 .SXR5.. RC3

NGC 1313 / ESO 82-11 / VV436 (03183-6630) is the best of these, being a brightish peculiar barred spiral ‘SBc' galaxy covering 9.1'x6.9'. In photographs it looks like a real pig’s breakfast, and although it is listed as 9.9B magnitude and having a surface brightness of 12.9 magnitude, this extended object is just visible between 25cm or 30cm. NGC 1313 is relatively nearby, and from the radial velocity of only +446kms^-1, the distance is about 4.3Mpc.

A 14.7p companion galaxy, NGC 1313A / ESO 83-1 (03201-6642) is 17'SE (PA 139°) from NGC 1313’s centre. This is not mentioned in AOST2, and it is likely because it is 18′NE from the 6.0 magnitude white star HIP 15353 / PPM 353439 / SAO 248776 (03180-6656). Visible with care in 25cm, but better in 25cm or greater, this companion looks like a thin wisp of tenuous gossamer, roughly 60×10 arcsec in size and oriented at about PA 30°. It is best to centre a little northeast of NGC 1313, then look towards the bottom of the eyepiece field for the object as to place it away from HIP 15353.
1313A 03 20 05.5 -66 42 09 MLTG 14.7p 1.2'x0.2' 30 --- .S..3*. RC3

RZ For / SAO168619 (03325-2530) in Fornax is a deep red SRa regular variable in the same field as the plantary NGC 1360. Directions to find this variable are likely obvious – but it does lie 18′NE. SRa's are fairly stable in their light curves with regular amplitudes. Another SRA example of the class is Antares. RZ For has the spectrum as late M5, while the magnitude variations are about 0.8 magnitude. This changes between 8.5 and 9.4 magnitude (9.2p to 10.0p), over the period of 64.6 days (Julian Date for the period is stated in the 4th General Variable Star Catalogue and Sky Catalogue 2000.0 as JD 2428075, as long ago as the 30 August 1935!)

Δ13 / DUN 13 (03377-4005) is listed by Dunlop as the Bode star 172 Eridani. Seeing Δ13 as triple, he describes the appearence as; “A triangle of stars. Large star fine yellow.” No one has listed it in any of the more modern double star catalogues. The stellar position in 1827 Epoch is 03h 31m 34s -40° 41', however, Dunlop gives no positions or angles for the components except the magnitudes being 5th, 8th and 9th - making identification today a bit difficult.
Dunlop’s precessed coordinates are 03h 37m 47s -40° 06' (2000) and no actual star marks these coordinates, however, the star he is certainly referring to is 4.57 magnitude y Eridani / HIP 16870 / PPM 307805 / SAO 216405 (03371-4017) some 13.4'SW (PA 219°) away. This star has the spectral type of K0III and has the B-V of 1.017. Distance is 67pc or 220ly. If this is the correct star, then the only one that would match it is orange 9.4 magnitude PPM 307794 some 8.6'E and the white 10.0 magnitude PPM 307813 some 9.0'NNE of HIP 16870. These seem a little too wide for atypical Dunlop pairs, especially as few Dunlop pairs exceeded 1' or 2' separation. Yet there is no other 5th magnitude star within 5°.
Another suspect grouping for these stars is about 2.5°N from yellowish e Eridani, and is placed some 1°E of the galaxy NGC 1291, however, these are also too wide apart. Nothing else exists within several degrees that matches this grouping of stars. Another Dunlop mystery. Nearby is Δ15 merely 33'W (PA 99°).

Note: Do not confuse the ‘y Eridani’ with γ Eridani

Δ14 / DUN 14 (03382-5947) is a wide yellow pair in Reticulum with the separation of 58.2 arcsec along PA 270°. Magnitudes are given as 7.1 and 8.9 and both appear in an average starry field, which Dunlop originally listed as 7.8 and 8. He also gave the separation as 45 arcsec angled at 10°np or equal to the PA of 280°, the value presently listed in the WDS 01. It seems the separation has increased almost by 25% since this time, while the position angle has reduced nearly 10°. Common proper motion (c.p.m.) suggests the stars are associated, and the period is perhaps several hundreds of years. Both are main sequence class F3V and F5V. Δ14 is easy in even 5.0cm.

Δ15 / DUN 15 (03398-4022) is a moderately faint pair in the same wide field 0.5°E of y Eridani (which is possibly Δ13) and 3.4°SW of f Eridani / Δ16 as mentioned below. The magnitudes of the white pair are 6.55v and 7.45v, respectively, with the north-south PA of 327° and the separation of about 7.9 arcsec. The pair has continued to increase in separation (by 2.9 arcsec) and decreased in PA (by 8°) since 1826. The spectral class of the primary is a white main sequence A3V and the secondary is likely mid-"A V". Looking at the Tycho data – the only catalogue to show data on the two stars finds attachment of the two seems unlikely. To add to the thirty-six measures to date shows linearity instead of typical orbital curvature. Distance is about 130pc, and if attached, this suggests a rough separation of 1000AU and the rough estimated orbital period of 15 000 years. Enjoyable pair in apertures of 7.5cm or above.

Note: Tycho gives this 6.91 mag star the parallax as 6.30±4.60mas and the cpm as RA 15.50±6.4 Dec 4.60±5.00. The secondary is presented as 7.79 magnitude with the parallax of 9.30±5.70. Cpm is RA 27.20±7.60 and Dec 20.60±6.30

HJ 3589 (03441-4040) lies a further 0.8°E of Δ15. 5.2 arcsec separates this duo along PA 349°. Little has changed in the stars since discovery by John Herschel in 1837. I saw both stars as rich orange in colour, with the secondary even showing a hint of red. The component magnitudes are 6.6 and 9.2, and should be visible in 7.5cm. This pair was good in 20cm. Little is known of the pair.

Δ16 / f Eri (03486-3737) is a moderately close pair in mid-southern Eridanus and is placed in a faintish triangle of stars with h and g Eri. The prominence of the double is that it is 3°SE of the centre of the well-known Fornax cluster of galaxies, and that southern deep-sky observers have used both the triangle and f Eridani to find this rich galaxy cluster. At 4.30 and 4.90 magnitude, this marvellous pair sees both stars as blue and white that is visible even in smallest of telescopes. Visible easily in 7.5cm, both components have slowly widened since discovery while the PA has increased by nearly +15° in the last 180 years to 217° (2002). Proper motions suggest this is likely a binary with a long period. One component is suspected to be a Beta Lyrae eclipsing binary because the overall light-curve suggests periodic behaviour – but this needs much more observation to confirm this is the case. Spectral classes are given as B9V and A1V approximating the colour of the stars seen in the telescope. This is a great pair.

γ Eri / 34 Eri / HJ 3608 / Gamma Eridani (03580-1330) is a long irregular period giant of spectral type M0 III whose spectrum also shows lines of both Calcium and Chromium. Varying in brightness over 64 days, the magnitude difference is merely 0.08 mag between 2.88-2.96V. Gamma Eri is also a double star whose primary is 3.2 magnitude, while the companion is 12.7. First measured in 1877, the separation is a wide 52.8 asrcsec, while the PA is 242°. Even 7.5cm should have little trouble separating this red and yellow pair.