HP Draconis
| 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 |
| 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☉ |
| Luminosity | 1.48+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
[edit]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
[edit]- ^ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 1 August 2025.
- ^ a b c 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.
- ^ a b c d 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.
- ^ a b c d 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.
- ^ a b c d e f g h Southworth, John (2025-08-06). "Rediscussion of eclipsing binaries. Paper XXVI. The F-type long-period system HP Draconis". The Observatory. arXiv:2508.04218.
- ^ a b 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.
- ^ "HP Dra". SIMBAD. Centre de données astronomiques de Strasbourg.
- ^ "VSX : Detail for HP Dra". vsx.aavso.org. Retrieved 2025-08-08.
- ^ "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.
- ^ 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.
