Astronomy:DS Tucanae

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Short description: Binary star system in the constellation of Tucana
DS Tucanae
DS Tuc A(right)B(left) H+OPEN.png
DS Tucanae imaged with the NTT. DS Tucanae A is on the right and DS Tucanae B is on the left.
Observation data
{{#ifeq:J2000.0|J2000.0 (ICRS)|Epoch J2000.0      Equinox J2000.0 (ICRS)| [[History:Epoch|Epoch J2000.0]]      [[Astronomy:Equinox (celestial coordinates)|Equinox J2000.0}}
Constellation Tucana
DS Tucanae A
Right ascension  23h 39m 39.48081s[1]
Declination −69° 11′ 44.7077″[1]
Apparent magnitude (V) 8.47[2]
DS Tucanae B
Right ascension  23h 39m 39.26965s[3]
Declination −69° 11′ 39.4936″[3]
Apparent magnitude (V) 9.84[4]
Characteristics
Spectral type G6V+K3V[4]
Variable type RS CVn[5]
Astrometry
A
Radial velocity (Rv)7.20[6] km/s
Proper motion (μ) RA: 79.529[1] mas/yr
Dec.: −67.551[1] mas/yr
Parallax (π)22.6367 ± 0.0150[1] mas
Distance144.08 ± 0.10 ly
(44.18 ± 0.03 pc)
B
Radial velocity (Rv)5.32[7] km/s
Proper motion (μ) RA: 78.133[3] mas/yr
Dec.: −65.845[3] mas/yr
Parallax (π)22.6524 ± 0.0125[3] mas
Distance143.98 ± 0.08 ly
(44.15 ± 0.02 pc)
Details
DS Tucanae A
Mass1.01±0.06[8] M☉
Radius0.964±0.029[8] R☉
Luminosity0.725±0.013[8] L☉
Temperature5,428±80[8] K
Rotational velocity (v sin i)27.75+1.73−1.54[9] km/s
Age45±4[8] Myr
DS Tucanae B
Mass0.84±0.06[8] M☉
Radius0.864±0.036[8] R☉
Luminosity0.327±0.010[8] L☉
Temperature4,700±90[8] K
Age45±4[8] Myr
Other designations
DS Tuc, HD 222259, CCDM J23397-6912AB, CD−69°2106, HIP 116748, WDS J23397-6912AB, TIC 410214986, TOI 200
Database references
SIMBADAB
A
B
Ab

DS Tucanae (HD 222259) is a binary star system 144 light years away in the constellation of Tucana. It has an apparent visual magnitude of 8.5,[8] and is a RS Canum Venaticorum variable.[5] The system is notable for being young as a member of the 45 Myr old Tucana-Horologium moving group[10] and for the primary star hosting the confirmed exoplanet DS Tucanae Ab, discovered by THYME, using TESS.[11][8][12][13]

Stellar system

A light curve for DS Tucanae, plotted from TESS data[14]

DS Tucanae is a visual binary.[4] The binary consists of a G6V primary and a K3V secondary separated by 5″.[15] Based on radial velocity measurements it was suggested that the secondary itself is a binary, but later studies could not find evidence for this claim.[8]

Physical properties

High levels of magnetic activity, a strong 6708Å lithium line, and the position on the color-magnitude diagram, slightly above the main sequence, strongly support a young age of the system.[12] The primary star is emitting a frequent and powerful (up to 5-8×1034 ergs) X-ray flares.[16]

Both components of the binary are main sequence stars. The primary has a mass very similar to the Sun, but slightly cooler and smaller, meaning it is only 72% as luminous as the Sun. The secondary is only 84% as massive as the Sun and only 33% as luminous.

Planetary system

The DS Tuc A planetary system[8][12]
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius
b <14.4[9] M⊕ 0.18+0.13
−0.12 		8.138268 — 88.73+0.18−0.17[9]° 5.70±0.17 R⊕

DS Tuc Ab is one of the few transiting planets with an age smaller than 100 Myrs. Other examples are K2-33b, V1298 Tauri b and AU Microscopii b. Of these systems DS Tuc is the brightest and it is a good target for atmospheric characterization with JWST. The planet is a super-Neptune or sub-Saturn.[8] The planet might be an inflated planet with an upper mass limit of 20 M⊕.[12] DS Tuc Ab will be observed by ESA's CHEOPS mission to characterize the planet.[17]

The planet DS Tucanae Ab has a low orbital obliquity (λ = 2.93°+0.88°
−0.87° or λ = 12°±13°). This means that the orbital plane of this planet aligns with the stellar equator of the star. This is unusual for a short period planet. Many short period planets show high orbital obliquity, which was taken as a sign of the scattering of the planet into this short period orbit. It can also be interpreted as the formation of a planet in an inner disk with an axial tilt. But these previous measurements of orbital obliquity were made for giant planets around mature stars. DS Tucanae Ab is a relatively small young planet. This suggests that DS Tucanae Ab formed in a smooth disk that was not perturbed by the stellar companion DS Tucanae B.[18][19] DS Tucanae Ab might therefore be a good target to study in-situ planet-formation of short-period planets.

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 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.
  2. ↑ Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P. et al. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars" (in en). Astronomy and Astrophysics 355: L27–L30. ISSN 0004-6361. Bibcode: 2000A&A...355L..27H. 
  3. ↑ 3.0 3.1 3.2 3.3 3.4 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.
  4. ↑ 4.0 4.1 4.2 Torres, G. (August 1988). "Visual Measurements of Southern Double Stars - Part Three" (in en). Astrophysics and Space Science 147 (2): 257–266. doi:10.1007/BF00645670. ISSN 0004-640X. Bibcode: 1988Ap&SS.147..257T. 
  5. ↑ 5.0 5.1 Samus', N. N.; Goranskii, V. P.; Durlevich, O. V.; Zharova, A. V.; Kazarovets, E. V.; Kireeva, N. N.; Pastukhova, E. N.; Williams, D. B. et al. (July 2003). "An Electronic Version of the Second Volume of the General Catalogue of Variable Stars with Improved Coordinates" (in en). Astronomy Letters 29 (7): 468–479. doi:10.1134/1.1589864. ISSN 1063-7737. Bibcode: 2003AstL...29..468S. 
  6. ↑ Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G.  Gaia DR2 record for this source at VizieR.
  7. ↑ Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G.  Gaia DR2 record for this source at VizieR.
  8. ↑ 8.00 8.01 8.02 8.03 8.04 8.05 8.06 8.07 8.08 8.09 8.10 8.11 8.12 8.13 8.14 Newton, Elisabeth R. et al. (July 2019). "TESS Hunt for Young and Maturing Exoplanets (THYME): A Planet in the 45 Myr Tucana-Horologium Association" (in en). The Astrophysical Journal Letters 880 (1): L17. doi:10.3847/2041-8213/ab2988. ISSN 0004-637X. Bibcode: 2019ApJ...880L..17N. 
  9. ↑ 9.0 9.1 9.2 Benatti, S.; Damasso, M.; Borsa, F.; Locci, D.; Pillitteri, I.; Desidera, S.; Maggio, A.; Micela, G. et al. (2021), "Constraints on the mass and on the atmospheric composition and evolution of the low-density young planet DS Tucanae a B", Astronomy & Astrophysics 650: A66, doi:10.1051/0004-6361/202140416, Bibcode: 2021A&A...650A..66B 
  10. ↑ Zuckerman, B.; Webb, R. A. (2000-06-01). "Identification of a Nearby Stellar Association in theHipparcos Catalog: Implications for Recent, Local Star Formation" (in en). The Astrophysical Journal 535 (2): 959. doi:10.1086/308897. ISSN 0004-637X. Bibcode: 2000ApJ...535..959Z. 
  11. ↑ Albright, Charlotte (14 August 2019). "Dartmouth Astronomer on Leading Discovery of a New Planet | Dartmouth News". https://news.dartmouth.edu/news/2019/08/dartmouth-astronomer-leading-discovery-new-planet. 
  12. ↑ 12.0 12.1 12.2 12.3 Benatti, S.; Nardiello, D.; Malavolta, L.; Desidera, S.; Borsato, L.; Nascimbeni, V.; Damasso, M.; D'Orazi, V. et al. (October 2019). "A possibly inflated planet around the bright young star DS Tucanae A" (in en). Astronomy & Astrophysics 630: A81. doi:10.1051/0004-6361/201935598. ISSN 0004-6361. Bibcode: 2019A&A...630A..81B. 
  13. ↑ "DS Tuc A b". https://exoplanetarchive.ipac.caltech.edu/cgi-bin/DisplayOverview/nph-DisplayOverview?objname=DS+Tuc+A+b&type=CONFIRMED_PLANET. 
  14. ↑ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html. 
  15. ↑ Torres, C. a. O.; Quast, G. R.; Silva, L. da; Reza, R. de la; Melo, C. H. F.; Sterzik, M. (2006-12-01). "Search for associations containing young stars (SACY) - I. Sample and searching method" (in en). Astronomy & Astrophysics 460 (3): 695–708. doi:10.1051/0004-6361:20065602. ISSN 0004-6361. Bibcode: 2006A&A...460..695T. 
  16. ↑ Pillitteri, I.; Argiroffi, C.; Maggio, A.; Micela, G.; Benatti, S.; Reale, F.; Colombo, S.; Wolk, S. J. (2022), "X-ray flares of the young planet host Ds Tucanae A", Astronomy & Astrophysics 666: A198, doi:10.1051/0004-6361/202244268, Bibcode: 2022A&A...666A.198P 
  17. ↑ "AO-1 Programmes - CHEOPS Guest Observers Programme - Cosmos". https://www.cosmos.esa.int/web/cheops-guest-observers-programme/ao-1-programmes. 
  18. ↑ Montet, Benjamin T.; Feinstein, Adina D.; Luger, Rodrigo; Bedell, Megan E.; Gully-Santiago, Michael A.; Teske, Johanna K.; Xuesong Wang, Sharon; Butler, R. Paul et al. (2020). "The Young Planet DS Tuc Ab has a Low Obliquity" (in en). The Astronomical Journal 159 (3): 112. doi:10.3847/1538-3881/ab6d6d. Bibcode: 2020AJ....159..112M. 
  19. ↑ Zhou, G.; Winn, J. N.; Newton, E. R.; Quinn, S. N.; Rodriguez, J. E.; Mann, A. W.; Rizzuto, A. C.; Vanderburg, A. M. et al. (2020). "A well aligned orbit for the 45 Myr old transiting Neptune DS Tuc Ab" (in en). The Astrophysical Journal 892 (2): L21. doi:10.3847/2041-8213/ab7d3c. Bibcode: 2020ApJ...892L..21Z. 



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