HD 169142

VLT/SPHERE image of the circumstellar disk and protoplanet candidate b around HD 169142.
Credit: ESO VLT/SPHERE - Monash University - Iain Hammond et al., adapted and mixed by Meli_thev
Observation data
Epoch J2000      Equinox J2000
Constellation Sagittarius
Right ascension 18h 24m 29.7800s[1]
Declination −29° 46′ 49.3286″[1]
Apparent magnitude (V) 8.16
Characteristics
Evolutionary stage Herbig Ae/Be star
Spectral type A9III/IVe[2]
Astrometry
Radial velocity (Rv)−3±2[3] km/s
Proper motion (μ) RA: −2.335[4] mas/yr
Dec.: −37.879[4] mas/yr
Parallax (π)8.7053 ± 0.0268 mas[4]
Distance375 ± 1 ly
(114.9 ± 0.4 pc)
Details[2]
Mass1.65 M☉
Radius1.6 R☉
Luminosity8.6 L☉
Surface gravity (log g)4.05±0.05 cgs
Temperature7650±150 K
Metallicity [Fe/H]−0.375±0.125 dex
Rotational velocity (v sin i)55±5 km/s
Age7.5±4.5 Myr
Other designations
CD−29 14904, TYC 6856-876-1, GSC 06856-00876, 2MASS J18242978-2946492[1]
Database references
SIMBADdata

HD 169142 is a single Herbig Ae/Be star. Its surface temperature is 7650±150 K. HD 169142 is depleted of heavy elements compared to the Sun, with a metallicity Fe/H index of −0.375±0.125, but is much younger at an age of 7.5±4.5 million years.[2] The star is rotating slowly and has relatively low stellar activity for a Herbig Ae/Be star.[3]

Planetary system

The Disk

The star is surrounded by a complex, rapidly evolving protoplanetary disk with two gaps. In the 1995-2005 period the disk inner edge has moved inward by 0.3 AU.[5] The dust of the disk is rich in polycyclic aromatic hydrocarbons[6] and carbon monoxide.[7]

A study using ALMA data found that the water (H2O) snow line is at around 20 astronomical units and the planet b is forming in beyond the water and carbon dioxide (CO2) snow lines, but within the carbon monoxide (CO) snow line. The CO snow line lies at around 150 AU.[8]

The study also detected a range of molecules in the disk: diazenylium (N2H+), methanol (CH3OH), [CI], deuterated hydrogen cyanide (DCN), carbon monosulfide (CS, C34S, 13CS), thioformaldehyde (H2CS), formaldehyde (H2CO), cyanoacetylene (HC3N), cyclopropenylidene (c-C3H2), sulfur monoxide (SO, previously detected) and deuterated aldehyde (DCO, previously detected). The detection of methanol in this warm disk is interpreted as a leftover from a earlier and colder stage of the disk. The methanol is now sublimating in this warmer phase. This means that complex ices can survive the disk formation process.[8]

The Planet

The annular gap and inner cavity observed in this protoplanetary disk both suggested the presence of embedded planets.[2] Several protoplanet candidates have been suggested in the literature starting from 2014.[9][10]

Nonetheless, a particular protoplanet candidate detected in 2015 and 2017 with the SPHERE instrument on the VLT appears to stand out, hereafter HD 169142 b.[11] A paper from 2023[12] confirmed that the motion of this protoplanet candidate was consistent with Keplerian motion. The object shifted with a change of the position angle of 10.2±2.8° between 2015 and 2019. The researchers point out three lines of evidence arguing in favour of this object being a protoplanet:

  1. The object is found in annular gap separating the two bright rings of the disc, as predicted in theory
  2. The protoplanet moved between 2015, 2017 and 2019 consistent with Keplerian motion of an object at a distance of about 37 astronomical units from its star.
  3. A spiral-shaped signal consistent with the expected outer spiral wake triggered by a planet in the gap, based on simulations of the system.

The researchers also found the near-infrared colors of the object are consistent with starlight scattered by dust around the protoplanet. This dust could be a circumplanetary disk or a dusty envelope around the protoplanet.[12]

A study from June 2023, using archived ALMA data found sulfur monoxide and silicon monosulfide in the disk at the position of planet b. The paper also found compact 12CO and 13CO emission at the position of the planet. Carbon monoxide and sulfur monoxide were detected in other disks in the past and they are thought to be connected to protoplanets. Silicon monosulfide on the other hand was never before detected in any other disk and can only be detected if silicates are released from nearby dust grains in massive shock waves caused by gas travelling at high velocities. It is thought that planet b is driving an outflow causing these high velocities.[13][14] Outflows from proto-jovian planets were hypothesised since 1998.[15]

Outflows are known around isolated young proto-brown dwarfs,[16] but HD 169142 b could be the first confirmed protoplanet around a star showing clear evidence of an outflow. Evidence for inflow or outflows suspected to be caused by planets exist for other disks, such as a signature in the CI gas of HD 163296.[14]

The HD 169142 planetary system
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius
b 3±2[12] MJ 37.2[12] — — 13[12]° —
protoplanetary disk 20–250[2] AU 13[17]° —

References

  1. ^ a b c "CD-29 9873". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-03-22.
  2. ^ a b c d e Quanz, Sascha P.; Avenhaus, Henning; Buenzli, Esther; Garufi, Antonio; Schmid, Hans Martin; Wolf, Sebastian (2013), "Gaps in the Hd 169142 Protoplanetary Disk Revealed by Polarimetric Imaging: Signs of Ongoing Planet Formation?", The Astrophysical Journal, 766 (1): L2, arXiv:1302.3029, Bibcode:2013ApJ...766L...2Q, doi:10.1088/2041-8205/766/1/L2, S2CID 118643209
  3. ^ a b High-resolution spectroscopy of Vega-like stars — II. Age indicators, activity and circumstellar gas
  4. ^ a b c Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  5. ^ Wagner, Kevin R.; Sitko, Michael L.; Grady, Carol A.; Swearingen, Jeremy R.; Champney, Elizabeth H.; Johnson, Alexa N.; Werren, Chelsea; Whitney, Barbara A.; Russell, Ray W.; Schneider, Glenn H.; Momose, Munetake; Muto, Takayuki; Inoue, Akio K.; Lauroesch, James T.; Hornbeck, Jeremy; Brown, Alexander; Fukagawa, Misato; Currie, Thayne M.; Wisniewski, John P.; Woodgate, Bruce E. (2014), "Variability of Disk Emission in Pre-Main Sequence and Related Stars. III. Exploring Structural Changes in the Pre-Transitional Disk in Hd 169142", The Astrophysical Journal, 798 (2): 94, arXiv:1410.8606, doi:10.1088/0004-637X/798/2/94, S2CID 118745797
  6. ^ Seok, Ji Yeon; Li, Aigen (2016), "Dust and Polycyclic Aromatic Hydrocarbon in the Pre-Transitional Disk Around Hd 169142", The Astrophysical Journal, 818 (1): 2, arXiv:1512.04992, Bibcode:2016ApJ...818....2S, doi:10.3847/0004-637X/818/1/2, S2CID 118543568
  7. ^ MacÍas, Enrique; Anglada, Guillem; Osorio, Mayra; Torrelles, José M.; Carrasco-González, Carlos; Gómez, José F.; Rodríguez, Luis F.; Sierra, Anibal (2017), "Imaging a Central Ionized Component, a Narrow Ring, and the CO Snowline in the Multigapped Disk of HD 169142", The Astrophysical Journal, 838 (2): 97, arXiv:1703.02957, Bibcode:2017ApJ...838...97M, doi:10.3847/1538-4357/aa6620, S2CID 119267132
  8. ^ a b Booth, Alice S.; Law, Charles J.; Temmink, Milou; Leemker, Margot; Macias, Enrique (2023-08-13). "Tracing snowlines and C/O ratio in a planet-hosting disk: ALMA molecular line observations towards the HD169142 disk". p. 13. arXiv:2308.07910 [astro-ph.EP].
  9. ^ Reggiani, Maddalena; Quanz, Sascha P.; Meyer, Michael R.; Pueyo, Laurent; Absil, Olivier; Amara, Adam; Anglada, Guillem; Avenhaus, Henning; Girard, Julien H.; Gonzalez, Carlos Carrasco; Graham, James; Mawet, Dimitri; Meru, Farzana; Milli, Julien; Osorio, Mayra; Wolff, Schuyler; Torrelles, Jose-Maria (2014). "Discovery of a Companion Candidate in the Hd 169142 Transition Disk and the Possibility of Multiple Planet Formation". The Astrophysical Journal. 792 (1): L23. arXiv:1408.0813. Bibcode:2014ApJ...792L..23R. doi:10.1088/2041-8205/792/1/L23. S2CID 37427761.
  10. ^ Osorio, Mayra; Anglada, Guillem; Carrasco-González, Carlos; Torrelles, José M.; Macías, Enrique; Rodríguez, Luis F.; Gómez, José F.; D'Alessio, Paola; Calvet, Nuria; Nagel, Erick; Dent, William R. F.; Quanz, Sascha P.; Reggiani, Maddalena; Mayen-Gijon, Juan M. (7 August 2014). "IMAGING THE INNER AND OUTER GAPS OF THE PRE-TRANSITIONAL DISK OF HD 169142 AT 7 mm". The Astrophysical Journal. 791 (2): L36. arXiv:1407.6549. Bibcode:2014ApJ...791L..36O. doi:10.1088/2041-8205/791/2/L36. eISSN 2041-8213. S2CID 119255686.
  11. ^ Gratton, R.; Ligi, R.; Sissa, E.; Desidera, S.; Mesa, D.; Bonnefoy, M.; Chauvin, G.; Cheetham, A.; Feldt, M.; Lagrange, A. M.; Langlois, M.; Meyer, M.; Vigan, A.; Boccaletti, A.; Janson, M.; Lazzoni, C.; Zurlo, A.; De Boer, J.; Henning, T.; d'Orazi, V.; Gluck, L.; Madec, F.; Jaquet, M.; Baudoz, P.; Fantinel, D.; Pavlov, A.; Wildi, F. (2019). "Blobs, spiral arms, and a possible planet around HD 169142". Astronomy & Astrophysics. 623: A140. arXiv:1901.06555. Bibcode:2019A&A...623A.140G. doi:10.1051/0004-6361/201834760. S2CID 118873911.
  12. ^ a b c d e Hammond, Iain; Christiaens, Valentin; Price, Daniel J.; Toci, Claudia; Pinte, Christophe; Juillard, Sandrine; Garg, Himanshi (2023-02-23). "Confirmation and Keplerian motion of the gap-carving protoplanet HD 169142 B". Monthly Notices of the Royal Astronomical Society: Letters. 522: L51–L55. arXiv:2302.11302. doi:10.1093/mnrasl/slad027.
  13. ^ "A Surprise Chemical Find by ALMA May Help Detect and Confirm Protoplanets". National Radio Astronomy Observatory. Retrieved 2023-06-27.
  14. ^ a b Law, Charles J.; Booth, Alice S.; Öberg, Karin I. (2023-06-01). "SO and SiS Emission Tracing an Embedded Planet and Compact 12CO and 13CO Counterparts in the HD 169142 Disk". Astrophysical Journal Letters. 952 (1): L19. arXiv:2306.13710. Bibcode:2023ApJ...952L..19L. doi:10.3847/2041-8213/acdfd0.
  15. ^ Quillen, A. C.; Trilling, D. E. (1998-12-01). "Do Proto-jovian Planets Drive Outflows?". The Astrophysical Journal. 508 (2): 707–713. arXiv:astro-ph/9712033. Bibcode:1998ApJ...508..707Q. doi:10.1086/306421. ISSN 0004-637X. S2CID 18444437.
  16. ^ Riaz, B.; Briceño, C.; Whelan, E. T.; Heathcote, S. (2017-07-01). "First Large-scale Herbig-Haro Jet Driven by a Proto-brown Dwarf". The Astrophysical Journal. 844 (1): 47. arXiv:1705.01170. Bibcode:2017ApJ...844...47R. doi:10.3847/1538-4357/aa70e8. ISSN 0004-637X. S2CID 119080074.
  17. ^ Dong (董若冰), Ruobing; Fung (馮澤之), Jeffrey (2017). "What is the Mass of a Gap-opening Planet?". The Astrophysical Journal. 835 (2): 146. arXiv:1612.04821. Bibcode:2017ApJ...835..146D. doi:10.3847/1538-4357/835/2/146. S2CID 118989219.
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