Eta Telescopii

Eta Telescopii (η Telescopii) is a white-hued star in the southern constellation of Telescopium. This is an A-type main sequence star with an apparent visual magnitude of +5.03. It is approximately 157 light years from Earth and is a member of the Beta Pictoris Moving Group of stars that share a common motion through space.[8] It is moving through the Galaxy at a speed of 23.7 km/s relative to the Sun.

Eta Telescopii
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Telescopium
Right ascension  19h 22m 51.20620s[1]
Declination −54° 25′ 26.1473″[1]
Apparent magnitude (V) +5.05[2]
Characteristics
Spectral type A0 Vn[3]
B−V color index +0.02[2]
Astrometry
Radial velocity (Rv)+13.0±4.2[4] km/s
Proper motion (μ) RA: +25.57[1] mas/yr
Dec.: −82.71[1] mas/yr
Parallax (π)20.74 ± 0.21[1] mas
Distance157 ± 2 ly
(48.2 ± 0.5 pc)
Absolute magnitude (MV)+1.61[5]
Details
Mass3.24[6] M☉
Radius1.61[7] R☉
Luminosity24[8] L☉
Surface gravity (log g)4.60[6] cgs
Temperature11,941±406[6] K
Rotational velocity (v sin i)330[6] km/s
Age12[8] Myr
Other designations
η Tel, CPD−54° 9339, HD 181296, HIP 95261, HR 7329, SAO 246055[9]
Database references
SIMBADdata

In 1998, imaging with the Hubble Space Telescope revealed a 12th magnitude object around 4" distant from Eta Telescopii, and calculated to be a brown dwarf of spectral type M7V or M8V with a surface temperature of around 2600 K.[10] It is located around 192 AU distant from the primary star,[8] and weighs between 20 and 50 Jupiter masses.[11]

This star has 3.24[6] times the mass of the Sun and is radiating around 24[8] times the Sun's luminosity from its outer atmosphere at an effective temperature of 11,941.[6] The age of the star is only about 12[8] million years. It is emitting an excess of infrared radiation that suggests the presence of a circumstellar disk of dust at an orbital radius of 24 AU, and an unresolved asteroid belt at 4 AU from the host star.[3] Subsequent imaging showed there were no objects of 20 Jupiter masses or greater between the disk and the brown dwarf, leading the researchers Neuhäuser and colleagues to postulate that the brown dwarf had an eccentric orbit – if 200 AU were its furthest distance from the primary, then it could come as close as 71 AU with an average distance of 136 AU.[11]

Eta Telescopii is in fact a triple star system; further away, separated by 7',[11] is the common proper motion companion HD 181327, a yellow-white main sequence star of spectral type F6V and apparent magnitude 7.0,[12] which has its own debris disk.[11] This disk has a sharply-defined inner edge at 31 AU, indicating a likely planet between 19 and 31 AU from the star.[13]

References
  1. van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357.
  2. Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99), Bibcode:1966CoLPL...4...99J.
  3. Wyatt, M.C.; et al. (July 2007), "Steady State Evolution of Debris Disks around A Stars", The Astrophysical Journal, 663 (1): 365–382, arXiv:astro-ph/0703608, Bibcode:2007ApJ...663..365W, doi:10.1086/518404.
  4. Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065.
  5. 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.
  6. David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, arXiv:1501.03154, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146. For the exceptionally high v sin i value, see the author's comments on p.600.
  7. Rhee, Joseph H.; et al. (May 2007), "Characterization of Dusty Debris Disks: The IRAS and Hipparcos Catalogs", The Astrophysical Journal, 660 (2): 1556–1571, arXiv:astro-ph/0609555, Bibcode:2007ApJ...660.1556R, doi:10.1086/509912.
  8. Smith, R.; et al. (2009), "Resolved debris disc emission around Eta Telescopii: a young solar system or ongoing planet formation?", Astronomy & Astrophysics, 493: 299–308, arXiv:0810.5087, Bibcode:2009A&A...493..299S, doi:10.1051/0004-6361:200810706.
  9. "eta Tel". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-08-08.
  10. Lowrance, Patrick J.; et al., "A Candidate Substellar Companion to HR 7329", The Astrophysical Journal, 541 (1): 390–95, arXiv:astro-ph/0005047, Bibcode:2000ApJ...541..390L, doi:10.1086/309437.
  11. Neuhäuser, R.; Ginski, C.; Schmidt, T.O.B.; Mugrauer, M. (2011), "Further Deep Imaging of HR 7329 A (η Tel A) and its Brown Dwarf Companion B", Monthly Notices of the Royal Astronomical Society, 416 (2): 1430–35, arXiv:1106.1388, Bibcode:2011MNRAS.416.1430N, doi:10.1111/j.1365-2966.2011.19139.x.
  12. "HD 181327". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-08-08.
  13. Nesvold, Erika R.; Kuchner, Marc J. (2015), "Gap Clearing by Planets in a Collisional Debris Disk", The Astrophysical Journal, 798: 10, arXiv:1410.7784, Bibcode:2015ApJ...798...83N, doi:10.1088/0004-637X/798/2/83, 83.
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