HP Draconis

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HP Draconis
HPDra TESS data.png
Light curve for HP Draconis, plotted from TESS data. [1]
Observation data
Epoch J2000       Equinox J2000
Constellation Draco [2]
Right ascension 18h 54m 53.4810s [3]
Declination +51° 18′ 29.792″ [3]
Apparent magnitude  (V)7.974 [4]
(8.234 (primary eclipse), 8.204 (secondary eclipse)) [4]
Characteristics
Evolutionary stage Main sequence + main sequence [4]
Spectral type F9V + F9V [2]
Variable type Eclipsing binary [5]
Astrometry
Radial velocity (Rv)−16.07±0.63 [6] km/s
Proper motion (μ)RA: +23.234 mas/yr [3]
Dec.: +83.306 mas/yr [3]
Parallax (π)12.6153±0.0516  mas [3]
Distance 259 ± 1  ly
(79.3 ± 0.3  pc)
Absolute magnitude  (MV)3.46±0.08 [4]
Orbit [5]
Period (P)10.76154±0.00009 [6] days
Semi-major axis (a)26.814±0.017  R☉
Eccentricity (e)0.03647±0.00011
Inclination (i)87.5554±0.0060°
Argument of periastron (ω)
(primary)		41.38±0.19°
Semi-amplitude (K1)
(primary)		61.971±0.056 km/s
Semi-amplitude (K2)
(secondary)		64.067±0.060 km/s
Details [5]
HP Draconis A
Mass 1.1354±0.0023  M☉
Radius 1.2474±0.0046  R☉
Luminosity 1.82+0.19
−0.17  L☉
Surface gravity (log g)4.3012±0.0032  cgs
Temperature 6,000±150  K
Rotational velocity (v sin i)5.864±0.021 km/s
Age 3.5  Gyr
HP Draconis B
Mass 1.0984±0.0022  M☉
Radius 1.1498±0.0049  R☉
Luminosity1.48+0.12
−0.11  L☉
Surface gravity (log g)4.3376±0.0037  cgs
Temperature 5,935±150  K
Rotational velocity (v sin i)5.406±0.023 km/s
Age 3.5  Gyr
Other designations
BD+51°2459, HD 175900, HIP 92835, TYC 3552-394-1 [7]
Database references
SIMBAD data

HP Draconis is a binary star system in the constellation of Draco. At an apparent magnitude of +7.974, it is not visible to the naked eye. Parallax measurements give a distance of 259 light-years (79 parsecs ).

Characteristics

This is an eclipsing binary system whose components are detached. [5] Each 10.76 days (the orbital period of the system), [8] the apparent magnitude of the system drops to 0.26 in the primary (deeper) eclipse and to 0.23 in the secondary eclipse. [4] The variability of this system was discovered in 1997 by the Hipparcos satellite, and it was given its variable-star designation HP Draconis in 1999. [5]

The components of this binary system are separated by 26.814 solar radii (18,654,000 km; 0.12470 au) with an eccentricity of 0.036. [5] Both are F-type main-sequence stars with identical stellar classifications of F9V. [2] Star A has 1.135 times the mass, 1.247 times the radius, and 1.8 times the luminosity of the Sun, while star B has 1.098 times the mass, 1.15 times the radius, and 1.48 times the Sun's luminosity. The effective temperatures are 6,000 and 5,935  K , [5] giving them the yellow-white hue typical of late-type F-type stars. [9] The estimated age of the system is 3.5 billion years. There is evidence of a third component in the system from eclipse timing variations. [5]

HP Draconis makes a wide triple system with a white dwarf that has a projected separation of 1,140  astronomical units, giving an estimated orbital period of 23,000 years. This companion has 0.45 times the Sun's mass, a temperature of 7,087±205 K and has been a white dwarf for an estimated 1.15 billion years. [10]

References

  1. ↑ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 1 August 2025.
  2. 1 2 3 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters . 38 (5): 331. arXiv: 1108.4971 . Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. XHIP record for this object at VizieR.
  3. 1 2 3 4 5 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv: 2208.00211 . Bibcode:2023A&A...674A...1G. doi: 10.1051/0004-6361/202243940 . S2CID   244398875. Gaia DR3 record for this source at VizieR.
  4. 1 2 3 4 5 Milone, E. F.; Kurpińska-Winiarska, M.; Oblak, E. (2010). "Observations and Analyses of the Eccentric Orbit Eclipsing Binary HP Draconis". The Astronomical Journal. 140 (1): 129. Bibcode:2010AJ....140..129M. doi:10.1088/0004-6256/140/1/129.
  5. 1 2 3 4 5 6 7 8 Southworth, John (2025-08-06). "Rediscussion of eclipsing binaries. Paper XXVI. The F-type long-period system HP Draconis". The Observatory. arXiv: 2508.04218 .
  6. 1 2 Milone, E. F.; Munari, U.; Marrese, P. M.; Williams, M. D.; Zwitter, T.; Kallrath, J.; Tomov, T. (2005-10-01). "Evaluating Gaia performances on eclipsing binaries - IV. Orbits and stellar parameters for SV Cam, BS Dra and HP Dra". Astronomy & Astrophysics. 441 (2): 605–613. arXiv: astro-ph/0506106 . Bibcode:2005A&A...441..605M. doi:10.1051/0004-6361:20052734. ISSN   0004-6361.
  7. ↑ "HP Dra". SIMBAD . Centre de données astronomiques de Strasbourg.
  8. ↑ "VSX : Detail for HP Dra". vsx.aavso.org. Retrieved 2025-08-08.
  9. ↑ "The Colour of Stars". Australia Telescope, Outreach and Education. Commonwealth Scientific and Industrial Research Organisation. December 21, 2004. Archived from the original on 2013-12-03. Retrieved 2012-01-16.
  10. ↑ Jalowiczor, Peter A.; Casewell, Sarah; Schneider, Adam C.; Faherty, Jacqueline K.; Kuchner, Marc J. (2021-07-22). "Identification of a White Dwarf Companion in the V* HP Dra System". Research Notes of the AAS. 5 (7): 170. Bibcode:2021RNAAS...5..170J. doi: 10.3847/2515-5172/ac151f . ISSN   2515-5172.
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