SSP- 4 Observing Projects
Delta Orionis (Mintaka)

Program Star
(variable)
34 delta Orionis

Spectral Type:
B01H+09V

SAO132220
HR1852
HD36486

RA (2000)
05h 32m 0.3s
Dec(2000)
-00d 17' 57"

J~ 2.22
H~ 2.22
V~ 2.23
(R-I)~ 0.22
B~ 2.01
(B-V)~ -0.22
U~ 0.96
(U-B)~ -1.05

Period~ 5.73261
± 0.00001 d


Comparison Star
24 gamma Orionis

Spectral Type:
B2III

SAO112740
HR1790
HD35468

RA(2000)
06h 25m 7.85s

Dec (2000)
+06d 50' 59"

J= 2.17
H= 2.23

V= 1.64
(R-I)= 0.22
B= 1.42
(B-V)= -0.22
U= 0.55
(U-B)= -0.87


Check Star
1 Pie 3 Orionis

Spectral Type:
F6V
SAO112106
HR1790
HD35468

RA(2000)
04h 49m 50.413s

Dec (2000)
+06d 57' 40.66"

J= 2.35
H= 2.15
V= 3.19
(R-I) = +0.26
B= 3.64
(B-V)= +0.45
U= 3.63
(U-B)= -0.01

Principal Investigator: Dirk Terrell e-mail: terrell@boulder.swri.edu

Objective: To determine sub-periods of the star system.

According to an email 22 December 2006 from Dirk Terrell "The reason for wanting to extend the observations to the infrared was to be able to get a handle on the third light in the system when we do the analysis. The geometry of the system will be better determined by the UBV data (deeper eclipses) and the third light contribution will be greater at JH. Since there is known intrinsic variability, the extended spectral coverage might enable us to pin down which of the three stars is the source of that variability. This won't be an easy one but it's bright and we have good radial velocity data". The photometry is in poor shape.

Season: Best observing will begin in January when the system is rising in the early evening and providing night long observing sessions.

Notes: delta Orionis is a double star with the fainter star (V= 6.85). Using a 12" F10 system with 1 mm SSP-4 detector the fainter companion star is easily left out of the measurement area.

Delta Orionis is one of the three stars of the belt of the constellation Orion. It also has the traditional name Mintaka (from ???? manaqah which means "belt" in Arabic). Mintaka is actually a multiple star with a magnitude 7 star about 52" away from the main component and an even fainter star in between. The main component itself is also double, consisting of a class B giant and a smaller but hotter class O. The stars orbit each other every 5.73 days. These two stars are both about 70,000 times as luminous as the Sun with a mass of some 20 solar masses.

AAS 197, January 2001 Session 46. Variable Stars
[46.19] The Components of the Delta Orionis Triple Star System
J. A. Harvin, D. R. Gies (Georgia State University), L. R. Penny (College of Charleston)

Delta Orionis is a massive triple star system consisting of a close spectroscopic binary and a distant tertiary star. Using cross-correlation methods with 59 IUE spectra, we have for the first time measured the secondary star's reflex motion. The mass ratio is q=m2/m1=0.54 ±0.03. We present revised orbital elements that generally agree with those presented by Harvey et al. (1987, The Observatory, 107, 205) based on 44 IUE spectra. Our period is 5.73261 ± 0.00001 days. Harvey et al. also give a series of previous orbital element determinations for delta Orionis, starting in 1902 and continuing through 1982, which they conclude are consistent with apsidal periods between 216 and 227 years and our results agree. In spite of the caution expressed in Harvey et al., we believe that the variation in gamma velocity seen over the past century is the reflex motion of the central binary in its orbit about the center of mass of the binary-tertiary system. In support of our opinion, we find a gamma velocity that is significantly higher than the previous determinations.

Data Summary

2004
JD
J
#
Err
H
#
Err
X
Obs
Notes
FEB 27.0799
2,453,062.5799
2.68
1
0.05
2.80
1
0.05
?
WJD
4,5,7
MAR 12.0708
2,453,076.5708
2.70
1
0.05
2.76
1
0.05
?
WJD
4,5,7
MAR 16.0764
2,453,080.5764
2.72
1
0.05
2.84
1
0.05
?
WJD
4,5,7
MAR 18.0819
2,453,082.5819
2.74
1
0.05
2.80
1
0.05
?
WJD
4,5,7
APR 02.0743
2,453,097.5743
2.71
1
0.05
2.85
1
0.05
?
WJD
4,5,7
SEP 08.4340
2,453,256.9340
2.86
3
0.08
2.90
3
0.05
?
WJD
1,2,4
2005
NOV 02.5208
2,453,677.0208
2.73
3
0.01
2.94
3
0.10
?
WJD
1,2,4
2006
JAN 16.1167
2,453,751.6167
2.73
3
0.06
2.86
?
0.05
?
WJD
1,2,4
JAN 22.2236
2,453,757.7236
2.77
3
0.02
2.84
?
0.03
?
MTU
1,2,4
JAN 23.1188
2,453,758.6188
2.76
3
0.03
2.81
?
0.03
?
WJD
1,2,4
SEP 05.4264
2,453,983.9264
2.77
2
0.05
2.86
2
0.05
?
WJD
2,3,4
SEP 13.4243
2,453,991.9243
2.77
2
0.02
2.81
2
0.02
?
WJD
2,3,4
SEP 14.4312
2,453,992.9312
2.82
2
0.02
2.83
2
0.05
?
WJD
2,3,4
SEP 19.4292
2,453,997.9292
2.78
2
0.07
2.84
2
0.01
?
WJD
2,3,4
SEP 25.4264
2,454,003.9264
2.79
2
0.03
2.89
2
0.07
?
WJD
2,3,4
SEP 26.4271
2,454,004.9271
2.81
2
0.01
2.73
2
0.03
?
WJD
2,3,4
SEP 28.4264
2,454,006.9264
2.77
2
0.01
2.83
2
0.01
?
WJD
2,3,4
OCT 02.4264
2,454,010.9264
2.86
2
0.07
2.79
2
0.04
?
WJD
2,3,4
OCT 04.4456
2,454,012.9456
2.798
3
0.020
2.902
3
0.077
1.258
HPO
2,8,9
OCT 08.3859
2,454,016.8859
2.786
3
0.006
2.888
3
0.034
1.466
HPO
2,8,9
OCT 10.3783
2,454,018.8783
2.819
3
0.004
2.908
3
0.017
1.480
HPO
2,8,9
OCT 12.3554
2,454,020.8755
2.765
3
0.012
2.861
3
0.024
1.471
HPO
2,8,9
OCT 13.4278
2,454,021.9278
2.85
2
0.01
2.87
2
0.00
?
WJD
2,3,4
OCT 14.4653
2,454,022.9653
2.75
2
0.08
2.82
2
0.04
?
WJD
2,3,4
OCT 17.3936
2,454,025.8936
2.7428
3
0.0023
2.8149
3
0.0053
1.311
HPO
2,8,9
OCT 20.4271
2,454,028.9271
2.74
2
0.07
2.80
2
0.01
?
WJD
2,3,4
OCT 22.4583 2,454,030.9583
2.82
 2
0.00
2.84
 2
0.01
?
 WJD
2,3,4
OCT 23.4583 2,454,033.9389
2.68
 2
0.03
2.83
 2
0.05
?
 WJD
2,3,4
                     


Comparison Star: SAO 112740 (J=2.17, H=2.23)

Check Star: SAO112106 (J=2.35, H=2.15)

Observers:
TDI: Dirk Terrell
HWD: Doug Hodgson
MTU = Troy Miller, 11" SCT, Las Vegas, NV
HPO = Jeff Hopkins, Phoenix , Arizona, 12" LX200GPS SCT

Notes:
1. Observation procedure CVCVCVK.
2. Err is the standard deviation.
3. Observation procedure: CVCVK
4. Not corrected for color or airmass differences
5. Observation procedure: CVK
6. Observations have been corrected for color and airmass differences between the stars.
7. Err is an estimate based on an average of other observations.
8. Observation procedure: CVCVCVCK.
9. Observations corrected for color and airmass differences.

Phase Plot
04 January 2007
by Doug West

Period= 5.73230124,
Epoch= 2,444,207.86

 

Created 20 October 2006
Modified 08 January 2007

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