2018A&A...616A..19A


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.12CEST23:22:07

2018A&A...616A..19A - Astronomy and Astrophysics, volume 616A, 19-19 (2018/8-1)

The chemistry of disks around T Tauri and Herbig Ae/Be stars.

AGUNDEZ M., ROUEFF E., LE PETIT F. and LE BOURLOT J.

Abstract (from CDS):


Context. Infrared and (sub-)millimeter observations of disks around T Tauri and Herbig Ae/Be stars point to a chemical differentiation, with a lower detection rate of molecules in disks around hotter stars.
Aims. We aim to investigate the underlying causes of the chemical differentiation indicated by observations and perform a comparative study of the chemistry of T Tauri and Herbig Ae/Be disks. This is one of the first studies to compare the chemistry in the outer regions of these two types of disk.
Methods. We developed a model to compute the chemical composition of a generic protoplanetary disk, with particular attention to the photochemistry, and applied it to a T Tauri and a Herbig Ae/Be disk. We compiled cross sections and computed photodissociation and photoionization rates at each location in the disk by solving the far-ultraviolet (FUV) radiative transfer in a 1+1D approach using the Meudon PDR code and adopting observed stellar spectra.
Results. The warmer disk temperatures and higher ultraviolet flux of Herbig stars compared to T Tauri stars induce some differences in the disk chemistry. In the hot inner regions, H2O, and simple organic molecules like C2H2, HCN, and CH4 are predicted to be very abundant in T Tauri disks and even more in Herbig Ae/Be disks, in contrast with infrared observations that find a much lower detection rate of water and simple organics toward disks around hotter stars. In the outer regions, the model indicates that the molecules typically observed in disks, like HCN, CN, C2H, H2CO, CS, SO, and HCO+, do not have drastic abundance differences between T Tauri and Herbig Ae disks. Some species produced under the action of photochemistry, like C2H and CN, are predicted to have slightly lower abundances around Herbig Ae stars due to a narrowing of the photochemically active layer. Observations indeed suggest that these radicals are somewhat less abundant in Herbig Ae disks, although in any case, the inferred abundance differences are small, of a factor of a few at most. A clear chemical differentiation between both types of disks concerns ices. Owing to the warmer temperatures of Herbig Ae disks, one expects snow lines lying farther away from the star and a lower mass of ices compared to T Tauri disks.
Conclusions. The global chemical behavior of T Tauri and Herbig Ae/Be disks is quite similar. The main differences are driven by the warmer temperatures of the latter, which result in a larger reservoir or water and simple organics in the inner regions and a lower mass of ices in the outer disk.

Abstract Copyright: © ESO 2018

Journal keyword(s): astrochemistry - molecular processes - protoplanetary disks - stars: variables: T Tauri, Herbig Ae/Be

Simbad objects: 18

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Number of rows : 18

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 V* DG Tau Or* 04 27 04.6913654419 +26 06 16.041555299 13.57 13.97 10.50 12.28   K6Ve 923 1
2 V* GV Tau TT* 04 29 23.7314759229 +24 33 00.216016292 19.20         K7 271 2
3 V* DM Tau Or* 04 33 48.7335659850 +18 10 09.974471722 14.30 14.82 14.00     M2Ve 510 0
4 V* CI Tau Or* 04 33 52.0144455735 +22 50 30.093741884 14.97 15.09 13.80     K4IVe 261 1
5 V* AA Tau Or* 04 34 55.4222683130 +24 28 53.038273587 13.14 13.34 12.20     K5Ve 626 0
6 EM* LkCa 15 Or* 04 39 17.7912813350 +22 21 03.387667491   13.01 12.03 11.61   K5:Ve 552 1
7 NAME Taurus Complex SFR 04 41.0 +25 52           ~ 3479 0
8 V* GO Tau Or* 04 43 03.0761884276 +25 20 18.708294279   16.2 14.40     M2.3 151 0
9 V* DR Tau Or* 04 47 06.2152696011 +16 58 42.814250257 12.03 11.86 10.50 12.19   K5Ve 467 0
10 V* GM Aur Or* 04 55 10.9813656049 +30 21 59.375978047 14.59 14.22 13.10     K3Ve 552 0
11 V* AB Aur Ae* 04 55 45.8459978418 +30 33 04.293281305 7.20 7.16 7.05 6.96 6.70 A0Ve 932 2
12 HD 31648 Ae* 04 58 46.2654165113 +29 50 36.990341242 7.84 7.78 7.62 7.76 7.43 A5Vep 394 0
13 V* TW Hya TT* 11 01 51.9054298616 -34 42 17.031550898   11.94 10.50 10.626 9.18 K6Ve 1532 1
14 HD 97048 Ae* 11 08 03.3105687971 -77 39 17.491180130 9.03 8.76 9.00   8.64 A0Vep 458 0
15 HD 100546 Be* 11 33 25.4404858122 -70 11 41.239343121   6.71 6.30   6.64 A0VaekB8_lB 651 1
16 HD 101412 Be* 11 39 44.4562795603 -60 10 27.717502041   9.465 9.288     A3VaekA0mA0_lB 116 0
17 V* V866 Sco Or* 16 11 31.345632 -18 38 25.96200   13.98 12.63 12.81   K0e+K5e 244 0
18 HD 163296 Ae* 17 56 21.2882188601 -21 57 21.872343282 7.00 6.93 6.85 6.86 6.67 A1Vep 803 0

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2020.07.12-23:22:07

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