Southern Doubles, Stars and Variables
SOUTHERN ASTRONOMICAL DELIGHTS : Presented by Andrew James
PAGE DS 017
LAST UPDATED
10 Mar 2009
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RA : 17h
Dec : -30° to -90°
Constellations : Oph, Sco, Ara, Pav, TrA, Aps, Oct.
Best Observed : May - Sep (Text Ordered by RA)
RA : 17h
Dec : -30° to -90°
DS 00h 01h 02h 03h 04h 05h 06h 07h 08h 09h 10h 11h
NEW 12h 13h 14h 15h 16h 17h 18h 19h 20h 21h 22h 23h
PAGE INDEX

SOUTHERN DOUBLES
Δ213 Ara
Δ214 Ara
SOUTHERN VARIABLES
DW Aps / HIP 85095 Aps
BRIGHT STARS
None Given
OTHER DOUBLES
and VARIABLES

ZZ Her / u Herculis / OΣ328
DEEP SKY
None Given

NOTES 1
Positions given as;
I.e. (13583-6018), are;
RIGHT ASCENSION
13h 58.3m
DECLINATION
-60° 15'
EPOCH
2000.0
This follows the current
WDS Conventions.

NOTES 2
S E P A R A T I O N
" or "arcsec
In arc seconds or
' or 'arcmin
In arc minutes or
mas - milli arc seconds

POSITION ANGLE
( ° ) Angle in degrees.
Measured from
North through East

M A G N I T U D E S
v - visual (naked-eye)
p - photographic
V - Photometric Visual
B - Photometric Blue
MV - Absolute @ 10pc.

ABBREVIATIONS
pc. - parsecs
ly. - light-years
AU - Astronomical Unit

NOTES 3
O R B I T A L
E L E M E N T S

T: Periastron (yr.)
P: Period (yr.)
a: Semi-Major Axis (arc sec.)
e: Eccentricity
i: Inclination
Ω: Orbital Node (°)
ω: Angle True Orbit (°)

See BASIC
DOUBLE STAR
INFORMATION

SELECTED SOUTHERN DOUBLES and VARIABLES
R.A. 17 Hours


Δ213 (17103-4644) is a lovely blue pair in Ara that has a slightly unequal magnitudes of 6.7v and 8.3v (6.73V & 8.12V). Δ213 lies some 4.7°NNW (PA 339°) of 2.8 mag. α Ara / Alpha Arae or 3.5°S of 3.8 mag. η Sco / Eta Scorpii and is close to the northern Ara border with Scorpius. In a moderately starry field, the duo is separated by 8.2 arcsec along the seemingly fixed position angle 168°. Since discovery this wonderful pair has slowly been increasing in separation. Spectral classes for both stars is B1I and B1.5V, but how the 1.6 magnitude difference translates into such diverse luminosity classes is still quite puzzlingly. Considering the very small parallax, Δ213 B seems classed in a much lower luminosity class than it really is. Both the proper motion and parallax are small and it still remains uncertain about the physical nature of the system. A really joyful pair for small apertures.

Early Observational Discrepancies With Δ213

Herschels observation in 1834 found the separation of 5 arcsec which is in conflict with James Dunlops estimate of 8” and 63° sf” (being position angle 153° (1826). The WDS96 gives only the John Herschel measure of 1834, but the WDS01 given Herschel 1836 measure which is 8.1 arcsec along PA 167°. Bizarrely, the WDS03 has reverted to the older value of the observations by Herschel in 1824! In looking at he old references here, it seems that the first two values made in 1826 and 1934 have some problems I.e. Dunlop's PA is out by 10° while Herschel's separation is 3° too low.


Δ214 (17133-6712) (U455) is placed in far southern Ara some 28' from the mutual borders of Apus and Triangulum Australe and Ara. It a moderately starry field that is just beyond the boundary of the Milky Way. 214 is best found some 2.9° (PA 54°) from the 1.9 magnitude orange-yellow α TrA / Alpha TrA / Atria (16487-6902). Visually it is best to draw an imaginary line in the sky between Atria and 3.6 magnitude Eta Pavonis (17457-6443) with 214 being roughly one-third the linear distance from Atria.

Δ214 is a medium wide pair itself is 5.9 and 9.2 (5.99V and 8.78V) magnitude that is separated presently given as 36.5arcsec along the northerly PA of 12° (1991) in the ever changing WDS03. Easily seen split in as small as 5cm aperture this orange primary and fainter white (perhaps greenish?) companion is quite elegantly pretty.

Dunlop didnt make any measures in 1826 and gives and the odd estimation of 50° np” that translates into PA 270° + 50° =320° and the separation of 22.0 arcsec. This is different to what is produced in the WDS 1996 to WDS 2001, which gives the 1835 PA of Herschel instead of Dunlop 1826 one. There pair have been fifteen (15) measures between 1835 and 1991, with the following positions of;

YEAR P.A. Sep.
1835 328 22.0
1918 356 30.1
1968 008 34.1
1991 012 36.5

These four (4) sets of data alone show linear motion suggesting that the components are not attached.

The linear prediction calculator gives the following results;

YEAR P.A. Sep.
2000 15 37.3
2003 15 37.6
2005 16 37.8
2010 17 38.4
2015 19 38.7
2020 20 39.2
2050 29 42.0
2100 43 46.6

NOTE: These predictions will likely be fairly accurate if the pair is unattached.

Available and Calculated Data

Δ214 A is listed as the star HIP 84248/ SAO 253827 / PPM 362557 with a B-V of+1.070 and the spectral class of K0III-IV. Δ214 B is T9064:3629:1, being listed as 8.75 magnitude, with a B-V of +0.228. I notice here that the white/ greenish? colours seen in the telescope do not match were well with the given B-V value. I can only assume that some colour contrast effect is prevalent here.

Looking at the parallaxes of A: 9.98±0.66 (Hipparcos and B: -11.90±8.60 (Tycho) it could be assumed that both stars appearing at similar distances might infer they are attached. Distances, incidentally, are A: 100±7pc. (327±22 ly.) and B: 84pc.

Yet looking at the available positional data, the proper motion of the primary are given in the Hipparcos Catalogue as pmRA; -156.26±0.49mas.yr-1 and Dec -90.10±0.55mas.yr-1. However, Δ214 B appears only in the Tycho but is not listed in the Hipparcos one. The Tycho data gives quite poor quality data here (pmRA; -34.90±11.90 : pmDec; -2.70±6.80.) In comparison with the data, there is significantly large difference between the two but it seems unlikely that these two stars are genuinely attached.


ZZ Her / u Herculis / 68 Her / OΣ328 (17173+3306) is the second brightest northern eclipsing binary - second only to the eclipsing binary Beta Persei or Algol. ZZ Her is easily located by the naked eye some 5.5°S of the bright orange 3.16 magnitude star Pi (π) Herculis (67 Her) and varies between 4.6p and 5.3p magnitude over 2.0510 days. Burnhams Celestial Handbook Vol.2 pg.956 listed the star as 68 Her, but gives the magnitude range as slightly brighter 4.7v to 5.4v. Spectral classes have been found to be B1.5 Vp and B5 III, respectively.

Both stars are separated by 10.2 million kilometres, each having the individual diameters of 3.2 and 3.1 million kilometres. By luminosity, the primary is 1 159 times the solar output, while the secondary is 295 times. Both are B-spectral type stars, with respective temperatures of 15 780 and 11 450K. Masses of the stars are 7.2 M⊚ and 2.9 M⊚.

There is some indication that the secondary has exceeded its Roche Lobe in the past, and has already bestowed most of its mass to the primary. This is a clear example of the so-called Algol paradox, with the primary being the smaller in mass although it is the most evolved component in the system. The shape of the secondary is still likely a teardrop, with the primary is only slightly distorted by the gravitational field. Distance is 220pc.or 720 ly.

u Herculis is also the double star OΣ328 / STT 328, whose 10th magnitude blue-white to greenish companion is separated by 4.4 arcsec along PA 59°. Little has changed in the positions since Otto Struves discovery in 1843. It is likely that the stars are physically associated with the close eclipsing binary.


DW APS

DW Aps / HIP 85095 / SAO 253891 / PPM 362664 (17235-6756) lies 1.2° (PA 217°) from Δ224 or alternatively 13' (PA 130°) from the 4.8 magnitude yellow-orange star Zeta Apodis. The field of this light bluish star is marked by many faint stars visible in 20cm but very few through 15cm or less. DW Aps is an Algol-type (β Lyr) eclipsing binary of the semi-detached [SD] type that displays moderately sized variations compared to some other eclipsing binaries. Changes are between 7.9p and 9.1p in the period of 2.312950 days. DW Aps is the only established eclipsing binary with well known parameters in the constellation Apus. The fall of 1.2 magnitudes during the primary eclipse occurs over 7% (3h 53m 09s or 0.1619065 days) of the period while the entire primary eclipse is twice this (14%) (0.323813 days) of the entire cycle. The current given epoch is 2439209.502 [25th March 1966 (02h 53m U.T.)] Spectral class is B6III.

A SD or semi-detached systems are those which have the surface of the less massive component being close to its inner Roche lobe.

Based on the collected data, the separation of the two stars is 12.58 R⊚ (8.766 million km) whose component sizes is A 2.26 R⊚ (1.57 million km.) and B 3.78 R⊚ (2.63 million km), respectively, being based on the solar radius of 696 850 km. Luminosities are 38.81L⊚ and 13.37L⊚ times that of the Sun. Physically, both stars have not at present filled there potential Roche lobes, even though it is highly likely this has occurred in the past. Calculation suggests this is A 44% and B 86%.

Temperatures are given as 9 620K and 5 750K, while the component masses are A 2.93M⊚ and B 2.17M⊚. (ΣM⊚ of 5.00) Spectral type is B9III and A0+. (See Graphical Representation.)

Unfortunately the derived parallaxes of 3.20 mas is small, making these parameters with some uncertainty.

REFERENCES

1. A Catalogue of Parameters for Eclipsing Binaries”. Brancewiez, H.K. and Dworak, T.Z.; ACTA Astronomica, 30, 4, p.508 (1980)


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Southern Astronomical Delights”
© (2009)
LAST UPDATED
10 Mar 2009