HD 139319

Short description: Triple star system in constellation Draco

Coordinates:  15h 33m 51.0571s, +63° 54′ 25.6950″

HD 139319

A light curve for TW Draconis, plotted from TESS data[1]

Observation data
Equinox J2000.0]] (ICRS)
Constellation | Draco
Right ascension |  15h 33m 51.0571s
Declination | +63° 54′ 25.6950″
Apparent magnitude (V) | 7.46[2]
Characteristics
HD 139319A
Spectral type | A8V+K0III [3]
Apparent magnitude (g) | 7.39[4]
HD 139319B
Spectral type | F7V
Apparent magnitude (g) | 9.65[5]
Astrometry
HD 139319A
Proper motion (μ)|  RA: 11.44±0.03[4] mas/yr
Dec.: 22.39±0.02[4] mas/yr
Parallax (π)| 6.0571 ± 0.0179[4] mas
Distance| 538 ± 2 ly
(165.1 ± 0.5 pc)
HD 139319B
Radial velocity (Rv)| 1.6±0.7[5] km/s
Proper motion (μ)|  RA: 12.09±0.02 mas/yr
Dec.: 21.278±0.018 mas/yr
Parallax (π)| 6.0345 ± 0.0160[5] mas
Distance| 540 ± 1 ly
(165.7 ± 0.4 pc)
Orbit[6]
Primary| TW Draconis A
Companion| TW Draconis B
Period (P)| 2.8068491 d
Semi-major axis (a)| 0.057 AU
Inclination (i)| 86.8°
Semi-amplitude (K1)
(primary)| 64.05 km/s
Semi-amplitude (K2)
(secondary)| 150 km/s
Details[7]
TW Draconis A
Mass| 2.16±0.11 M☉
Radius| 2.64±0.04 R☉
Surface gravity (log g)| 3.928±0.026 cgs
Temperature| 7815±92 K
TW Draconis B
Mass| 0.93±0.05 M☉
Radius| 3.66±0.06 R☉
Surface gravity (log g)| 3.314±0.026 cgs
Temperature| 4442±32 K
Other designations

BD+64 1077, HIP 76196, 2MASS J15335104+6354257, GSC 04184-00061

HD 139319A: TW Draconis, TYC 4184-61-1, Gaia DR2 1640708022815757568
HD 139319B: TYC 4184-61-2, Gaia DR2 1640708022815757824
Database references
SIMBAD| data

HD 139319 is a ternary system composed of the binary Algol variable star known as TW Draconis, and a main-sequence companion star at a separation of 3 arcseconds.[6] The system lies in the constellation of Draco about 540 light years away.

## System

The primary star is an eclipsing, semi-detached binary, the brighter component of which is a pulsating star of Delta Scuti type. Its pulsation frequency is 17.99 cycles per day.[3] Mass transfer between stars is ongoing in the system[8] with a transfer rate of 6.8×10−7M☉/year. The 2.8 day period of the Algol binary is cyclically variable with a period 116.04 years, possibly due to gravitational influence of the distant companion HD 139319B. Another three stars in the system are suspected.[6]

## References

1. ↑ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html.
2. ↑ "TW Dra". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=TW+Dra.
3. ↑ 3.0 3.1 Kim, S.-L.; Lee, J. W.; Kwon, S.-G.; Youn, J.-H.; Mkrtichian, D. E.; Kim, C. (2003), "Search for A–F Spectral type pulsating components in Algol-type eclipsing binary systems", Astronomy & Astrophysics 405: 231–236, doi:10.1051/0004-6361:20030630, Bibcode: 2003A&A...405..231K
4. ↑ 4.0 4.1 4.2 Brown, A. G. A. (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics 649: A1. doi:10.1051/0004-6361/202039657. Bibcode: 2021A&A...649A...1G. Gaia EDR3 record for this source at VizieR.
5. ↑ 5.0 5.1 5.2 Brown, A. G. A. (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics 649: A1. doi:10.1051/0004-6361/202039657. Bibcode: 2021A&A...649A...1G. Gaia EDR3 record for this source at VizieR.
6. ↑ 6.0 6.1 6.2 Liao, Wen-Ping; Qian, Sheng-Bang; Zejda, Miloslav; Zhu, Li-Ying; Li, Lin-Jia (2016), "Lunar-based Ultraviolet Telescope study of the well-known Algol-type binary TW Dra", Research in Astronomy and Astrophysics 16 (6): 009, doi:10.1088/1674-4527/16/6/094, Bibcode: 2016RAA....16...94L
7. ↑ Bozic, H.; Nemravova, J.; Harmanec, P. (2013), "Standard UBV photometry and improved physical properties of TW Dra", Information Bulletin on Variable Stars 6086: 1, Bibcode: 2013IBVS.6086....1B
8. ↑ Norton, A. J.; Lohr, M. E.; Smalley, B.; Wheatley, P. J.; West, R. G. (2016), "SuperWASP discovery and SALT confirmation of a semi-detached eclipsing binary that contains aδScuti star", Astronomy & Astrophysics 587: A54, doi:10.1051/0004-6361/201526881, Bibcode: 2016A&A...587A..54N

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*[RA:]: Right Ascension
*[Dec.:]: Declination