DI Herculis

Last updated
DI Herculis
DIHerLightCurve.png
A visual band light curve for DI Herculis, adapted from Marshall et al. (1995) [1]
Observation data
Epoch J2000       Equinox J2000
Constellation Hercules
Right ascension 18h 53m 26.23992s [2]
Declination +24° 16′ 40.7926″ [2]
Apparent magnitude  (V)8.47 [3]
Characteristics
Spectral type B5 / B4 [4]
Variable type Algol
Astrometry
Radial velocity (Rv)−2.1 ± 2 [5]  km/s
Proper motion (μ)RA: −1.350(17) [2]   mas/yr
Dec.: −3.995(22) [2]   mas/yr
Parallax (π)1.5813 ± 0.0221  mas [2]
Distance 2,060 ± 30  ly
(632 ± 9  pc)
Orbit [6]
PrimaryDI Her A
CompanionDI Her B
Period (P)10.550164 days
Eccentricity (e)0.489
Inclination (i)89.3°
Argument of periastron (ω)
(secondary)		330.2°
Semi-amplitude (K1)
(primary)		110.7 km/s
Semi-amplitude (K2)
(secondary)		126.6 km/s
Details [7]
DI Her A
Mass 5.15  M☉
Radius 2.68  R☉
Temperature 17300  K
DI Her B
Mass 4.52  M☉
Radius 2.48  R☉
Temperature 15400  K
Other designations
DI Her, BD+24 3568, HD  175227, HIP  92708, SAO  86544, WDS J19079+4652AB, TYC  2109-775-1, 2MASS J18532623+2416408 [3]
Database references
SIMBAD data

DI Herculis is an Algol-type eclipsing binary star in the constellation of Hercules. The system has an apparent magnitude of about +8.5 and consists of two young blue stars of spectral type B5 and B4. [4] It is about two thousand light years from Earth. [2]

Contents

The orbit of the stars around their mutual centre of gravity is very elliptical, with an eccentricity of 0.489 and a semi-major axis of 0.201 astronomical units, resulting in an extremely close approach of the two stars at periastron.

Stellar masses of 5.15 and 4.52 solar masses lead to a theoretical precession of 4.27 degrees per century, at odds with the observed precession. However, detailed observations reveal an unexpectedly extreme obliquity of the spin axes of the two stars. [6] One of the two stars is tipped over by at least 70 degrees from the vertical, and the other is tipped the opposite way by more than 80 degrees. Incorporating the effect of oblateness of the stars due to the unusually tilted axes, the predicted precession is consistent with general relativity. [8]

Precession of periastron

The precession of the periastron of the orbit of the stars serves as a test of the predictions of Einstein's general theory of relativity. The known factors of the orbital distance of the stars, eccentricity, and stellar masses allows a theoretical prediction of precession of 4.27 degrees per century (1.93 degrees from classical effects and 2.34 degrees from general relativistic effects). However, the observed precession can be measured from eclipse timing, leading to an original measure of 1.04 degrees per century, and a more precise recent measurement of 1.39 degrees per century.

This discrepancy between theory and experiment has led to extensive studies of the bright binary system in the last thirty years; solutions discussed included

After observations of the Rossiter–McLaughlin effect in 2009, it emerged that the rotation axes of the two stars lay roughly in the orbital plane of the system. When this is taken account in calculating the rate of precession, the difference between expected and observed precession disappears; so DI Hercules is no longer a test case for a possible falsification of general relativity. However, a more recent research article [11] shows that the 2009 study leaves many questions unanswered regarding the solution for the axes. For example, orbital effects caused by the tilting of the axes have not been observed; also, the stars' rotation axes themselves may also be precessing.

Journal references

Related Research Articles

<span class="mw-page-title-main">Epsilon Volantis</span> Multiple star in the constellation Volans

Epsilon Volantis, Latinized from ε Volantis, is a quadruple star system in the southern constellation Volans. This star is at the center of the constellation of Volans and connects the "wings" of the constellation. Based upon parallax measurements, is roughly 640 light years from Earth.

<span class="mw-page-title-main">VV Cephei</span> Binary star in the constellation Cepheus

VV Cephei, also known as HD 208816, is an eclipsing binary star system located in the constellation Cepheus, approximately 5,000 light years from Earth. It is both a B[e] star and shell star.

3 Centauri is a triple star system in the southern constellation of Centaurus, located approximately 300 light years from the Sun. It is visible to the naked eye as a faint, blue-white hued star with a combined apparent visual magnitude of 4.32. As of 2017, the two visible components had an angular separation of 7.851″ along a position angle of 106°. The system has the Bayer designation k Centauri; 3 Centauri is the Flamsteed designation. It is a suspected eclipsing binary with a variable star designation V983 Centauri.

<span class="mw-page-title-main">23 Vulpeculae</span> Star in the constellation Vulpecula

23 Vulpeculae is a triple star system in the northern constellation of Vulpecula. It is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of 4.52 and it is located approximately 327 light years away from the Sun based on parallax. The system is moving further from the Earth with a heliocentric radial velocity of +1.47 km/s.

<span class="mw-page-title-main">EZ Canis Majoris</span> Binary star system in the constellation Canis Major

EZ Canis Majoris is binary system in the constellation of Canis Major. The primary is a Wolf-Rayet star and it is one of the ten brightest Wolf-Rayet stars, brighter than apparent magnitude 7.

HD 225218 is a quadruple star system in the northern constellation of Andromeda. The primary component, HD 225218 A, is a giant star with a stellar classification of B9III, an apparent magnitude of 6.16, and is a candidate Lambda Boötis star. It has a fainter, magnitude 9.65 companion, HD 225218 B, at an angular separation of 5.2″ along a position angle of 171°. The primary itself has been identified as a binary star system through interferometry, with the two components separated by 0.165″. The pair, HD 225218 Aa and Ab, orbit each other with a period of about 70 years and an eccentricity of 0.515. Component B is likewise a spectroscopic binary.

<span class="mw-page-title-main">S Monocerotis</span> Star in the constellation Monoceros

S Monocerotis, also known as 15 Monocerotis, is a massive multiple and variable star system located in the constellation Monoceros. It is the brightest star in the Christmas Tree open cluster in the area catalogued as NGC 2264.

<span class="mw-page-title-main">DP Leonis</span> Star system in the constellation Leo

DP Leonis is binary star system in the equatorial constellation of Leo. It is a variable star that ranges in apparent visual magnitude from 17.5 down to 19. The system is located at a distance of approximately 990 light-years from the Sun based on parallax. It is a cataclysmic variable star of the AM Herculis-type also known as polars. The system comprises an eclipsing white dwarf and red dwarf in tight orbit and an extrasolar planet. This eclipsing variable was discovered by P. Biermann and associates in 1982 as the optical counterpart to the EINSTEIN X-ray source E1114+182.

<span class="mw-page-title-main">Epsilon Herculis</span> Multiple star systen in the constellation Hercules

Epsilon Herculis, Latinized from ε Herculis, is a fourth-magnitude multiple star system in the northern constellation of Hercules. The combined apparent visual magnitude of 3.9111 is bright enough to make this system visible to the naked eye. Based upon an annual parallax shift of 21.04 mas as seen from Earth, it is located 155 light years from the Sun. The system is moving closer to the Sun with a radial velocity of −25 km/s.

Chi Herculis, Latinized from χ Herculis, is a Sun-like star in the northern constellation of Hercules. Based upon an annual parallax shift of 63.16 mas as seen from Earth, it is located 51.6 light years from the Sun. The star is faintly visible to the naked eye with an apparent visual magnitude of 4.59. It has a relatively high proper motion, showing a transverse movement of 0.769 arc seconds per year and is drifting closer to the Sun with a radial velocity of −56 km/s.

<span class="mw-page-title-main">68 Herculis</span> Triple star system in the constellation Hercules

68 Herculis is a triple star system located around 950 light-years away from the Sun in the northern constellation of Hercules. In the astronomical community it is often referred to by its Bayer designation of u Herculis, while 68 Herculis is the Flamsteed designation. The system is visible to the naked eye as a faint, blue-white-hued point of light with a peak apparent visual magnitude of 4.80. It is approaching the Earth with a heliocentric radial velocity of −17 km/s.

g Herculis Star in the constellation Hercules

g Herculis is a binary star system in the northern constellation of Hercules. It has the Flamsteed designation 30 Herculis, while g Herculis is the Bayer designation. This system is visible to the naked eye as a faint, red-hued point of light. Based upon a measured parallax of 9.2 mas, it is located around 354 light years away from the Sun. The system is moving further from the Earth with a heliocentric radial velocity of 1.5 km/s.

Tau1 Hydrae is a triple star system in the equatorial constellation of Hydra. Based upon the annual parallax shift of the two visible components as seen from Earth, they are located about 18 parsecs (59 ly) from the Sun. The system has a combined apparent visual magnitude of +4.59, which is bright enough to be visible to the naked eye at night.

<span class="mw-page-title-main">FL Lyrae</span>

FL Lyrae is the variable star designation for an eclipsing binary star system in the northern constellation of Lyra. The combined apparent magnitude of the pair is 9.36, which means they are too faint to be seen with the naked eye. Parallax measurements put the system at a distance of around 437 light years from the Sun. This star system was in the view field of the Kepler space telescope during 2009−2014, which allowed monitoring during that spacecraft's mission.

<span class="mw-page-title-main">AD Andromedae</span> Eclipsing binary star in the constellation Andromeda

AD Andromedae is an eclipsing binary in the constellation Andromeda. Its maximum apparent visual magnitude is 11.2, but it shows a decrease of 0.62 magnitudes during the main eclipse and 0.58 during the secondary one. It is classified as a Beta Lyrae variable star with a period of almost one day.

<span class="mw-page-title-main">DH Cephei</span> Binary star system in the constellation Cepheus

DH Cephei is a variable binary star system in the northern circumpolar constellation of Cepheus, positioned about two degrees to the east of the star system Delta Cephei. With an apparent visual magnitude of 8.61, it is too faint to be visible without a telescope. Based on parallax measurements, this system is located at a distance of approximately 9.6 kilolight-years from the Sun. At present it is moving closer to the Earth with a radial velocity of −33 km/s.

<span class="mw-page-title-main">GK Tauri</span> Binary star system in the constellation of Taurus

GK Tauri is a young T Tauri-type pre-main sequence star in the constellation of Taurus about 421 light years away, belonging to the Taurus Molecular Cloud.

<span class="mw-page-title-main">HD 165590</span> Triple star system in constellation Hercules

HD 165590 is a quintuple system dominated by the binary Algol variable star known as V772 Herculis. The system lies in the constellation of Hercules about 123 light years from the Sun, and is suspected to be a part of the Pleiades moving group.

<span class="mw-page-title-main">HS Hydrae</span> Triple star in the constellation of Hydra

HS Hydrae is a triple star system in the equatorial constellation of Hydra. The inner pair were an eclipsing binary during the period 1920 until 2019, with HS Hya being the variable star designation. With a base apparent visual magnitude of 8.08, HS Hya is too dim to be viewed with the naked eye. During the primary eclipse, the magnitude dropped to 8.61; the secondary eclipse lowered the magnitude to 8.55. Based on parallax measurements, the system is located at a distance of approximately 335 light years from the Sun. It is drifting closer with a mean radial velocity of −7 km/s.

<span class="mw-page-title-main">HU Tauri</span> Binary star in the constellation Taurus

HU Tauri is a tight binary star system in the equatorial constellation of Taurus. It is an eclipsing binary, which means that the member stars periodically eclipse each other every 2.056 days. They have a combined apparent visual magnitude of 5.85, which is bright enough to be dimly visible to the naked eye. During the primary eclipse, the magnitude drops to 6.68, while the secondary eclipse decreases the magnitude to 5.91. The distance to this system, based on parallax measurements, is approximately 414 light years.

References

  1. ↑ Marshall, James J.; Guinan, Edward F.; McCook, George P. (February 1995). "Possible Low Amplitude Light Variations of DI Her". Information Bulletin on Variable Stars. 4161: 1. Bibcode:1995IBVS.4161....1M . Retrieved 9 January 2022.
  2. 1 2 3 4 5 6 Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics . 649: A1. arXiv: 2012.01533 . Bibcode:2021A&A...649A...1G. doi: 10.1051/0004-6361/202039657 . S2CID   227254300. (Erratum:  doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  3. 1 2 "HD 175227". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2022-01-10.
  4. 1 2 UBVR photometry of DI Herculis [ permanent dead link ]
  5. ↑ Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Carnegie Institute Washington D.C. Publication. Bibcode:1953GCRV..C......0W.
  6. 1 2 S. Albrecht; S. Reffert; I. Snellen (2009). "Misaligned spin and orbital axes cause the anomalous precession of DI Herculis". Nature. 461 (7262): 373–376. arXiv: 0909.2861v1 . Bibcode:2009Natur.461..373A. doi:10.1038/nature08408. PMID   19759615. S2CID   4401340.
  7. ↑ Philippov, A. A. (2013). "Analysis of Spin-Orbit Misalignment in Eclipsing Binary DI Herculis". The Astrophysical Journal. 768 (2): 112. arXiv: 1303.6980 . Bibcode:2013ApJ...768..112P. doi:10.1088/0004-637X/768/2/112. S2CID   119179139.
  8. ↑ Naeye, Robert, "Stellar Mystery Solved, Einstein Safe", Sky and Telescope, September 16, 2009. See also MIT Press Release, September 17, 2009. Accessed 8 June 2017.
  9. ↑ Hsuan, Keith; Mardling, Rosemary A (2006). "A Three Body Solution for the DI Her System". Astrophysics and Space Science. 304 (1–4): 243–246. Bibcode:2006Ap&SS.304..243H. doi:10.1007/s10509-006-9121-0. S2CID   122215657.
  10. ↑ Khodykon, S A (2007). "Evidence for a Third Body in the Eclipsing Binary DI Herculis". Information Bulletin on Variable Stars. 5788 (5788): 1. Bibcode:2007IBVS.5788....1K.[ permanent dead link ]
  11. ↑ Zimmerman N. (2010). "The Eclipsing Binary Di Herculis: One Mystery Solved, But Another Takes Its Place". American Astronomical Society. 215: 419.34. Bibcode:2010AAS...21541934Z.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.