2019A&A...632A..46V


C.D.S. - SIMBAD4 rel 1.7 - 2020.10.31CET18:25:57

2019A&A...632A..46V - Astronomy and Astrophysics, volume 632A, 46-46 (2019/12-0)

X-shooter spectroscopy of young stars with disks. The TW Hydrae association as a probe of the final stages of disk accretion.

VENUTI L., STELZER B., ALCALA J.M., MANARA C.F., FRASCA A., JAYAWARDHANA R., ANTONIUCCI S., ARGIROFFI C., NATTA A., NISINI B., RANDICH S. and SCHOLZ A.

Abstract (from CDS):


Context. Measurements of the fraction of disk-bearing stars in clusters as a function of age indicate protoplanetary disk lifetimes ≤10Myr. However, our knowledge of the time evolution of mass accretion in young stars over the disk lifespans is subject to many uncertainties, especially at the lowest stellar masses (M*).
Aims. We investigate ongoing accretion activity in young stars in the TW Hydrae association (TWA). The age of the association (∼8-10Myr) renders it an ideal target for probing the final stages of disk accretion, and its proximity (∼50pc) enables a detailed assessment of stellar and accretion properties down to brown dwarf masses.
Methods. Our sample comprises eleven TWA members with infrared excess, amounting to 85% of the total TWA population with disks. Our targets span spectral types between M0 and M9, and masses between 0.58M and 0.02M. We employed homogeneous spectroscopic data from 300nm to 2500nm, obtained synoptically with the X-shooter spectrograph, to derive the individual extinction, stellar parameters, and accretion parameters for each object simultaneously. We then examined the luminosity of Balmer lines and forbidden emission lines to probe the physics of the star-disk interaction environment.
Results. Disk-bearing stars represent around 24% of the total TWA population. We detected signatures of ongoing accretion for 70% of our TWA targets for which accurate measurements of the stellar parameters could be derived. This implies a fraction of accretors between 13-17% across the entire TWA (that accounts for the disk-bearing and potentially accreting members not included in our survey). The spectral emission associated with these stars reveals a more evolved stage of these accretors compared to younger PMS populations studied with the same instrument and analysis techniques (e.g., Lupus): first, a large fraction (∼50%) exhibit nearly symmetric, narrow Hα line profiles; second, over 80% of them exhibit Balmer decrements that are consistent with moderate accretion activity and optically thin emission; third, less than a third exhibit forbidden line emission in [O I] 6300 Å, which is indicative of winds and outflows activity; and fourth, only one sixth exhibit signatures of collimated jets. However, the distribution in accretion rates (dMacc/dt) derived for the TWA sample closely follows that of younger regions (Lupus, Chamaeleon I, σ Orionis) over the mass range of overlap (M*∼0.1-0.3M). An overall correlation between dMacc/dt and M* is detected and best reproduced by the function dMacc/dt∝M*2.1±0.5. Conclusion. At least in the lowest M* regimes, stars that still retain a disk at ages ∼8-10Myr are found to exhibit statistically similar, albeit moderate, accretion levels as those measured around younger objects. This "slow" dMacc/dt evolution that is apparent at the lowest masses may be associated with longer evolutionary timescales of disks around low-mass stars, which is suggested by the mass-dependent disk fractions reported in the literature within individual clusters.

Abstract Copyright: © ESO 2019

Journal keyword(s): accretion - accretion disks - techniques: spectroscopic - stars: low-mass - stars: pre-main sequence - open clusters and associations: individual: TWA

VizieR on-line data: <Available at CDS (J/A+A/632/A46): list.dat fits/*>

Simbad objects: 42

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Number of rows : 42

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 NAME Taurus Complex SFR 04 41.0 +25 52           ~ 3546 0
2 NAME Orion Nebula Cluster OpC 05 35.0 -05 29           ~ 2014 1
3 NAME sigma Orionis Cluster MGr 05 38 42 -02 36.0           ~ 490 0
4 NAME ORI MOL CLOUD MoC 05 56 -01.8           ~ 866 1
5 NGC 2264 OpC 06 40 58 +09 53.7     3.9     ~ 1602 1
6 NAME eta Cha Association MGr 08 42 06 -79 01.6           ~ 312 0
7 TWA 22 LXB 10 17 26.8983656044 -53 54 26.459439803   15.69 13.96 13.72   M5 70 0
8 V* BX Ant TT* 10 18 28.6989165716 -31 50 02.826261802   13.39 11.454 11.382 9.325 M0Ve 103 0
9 V* CE Ant TT* 10 42 30.1021269333 -33 40 16.226774953   12.21 10.91   9.10 M2Ve 152 1
10 V* TW Hya TT* 11 01 51.9054298616 -34 42 17.031550898   11.94 10.50 10.626 9.18 K6Ve 1557 1
11 NAME TW Hya Association As* 11 01.9 -34 42           ~ 829 0
12 TWA 28 LM* 11 02 09.8372483500 -34 30 35.573128437     21.46 19.14 17.90 M8.3 63 0
13 NAME Cha I MoC 11 06 48 -77 18.0           ~ 987 1
14 CD-29 8887 TT* 11 09 13.8074415397 -30 01 40.070212113   12.95 11.119 10.642 8.875 M2Ve 111 0
15 TWA 3B TT* 11 10 27.8410112470 -37 31 52.748874445   14.59 13.70   8.86 M4Ve 49 0
16 TWA 3 ** 11 10 27.894072 -37 31 51.96612   13.53 12.05 11.61 9.29 M4Ve+M4Ve 200 0
17 TWA 3A TT* 11 10 27.9117558304 -37 31 51.529219753   14.04 12.57   9.10 M4Ve 187 0
18 V* V1215 Cen TT* 11 13 26.2208332352 -45 23 42.719174706     12.478   10.483 K8IVe 68 0
19 CD-34 7390A TT* 11 21 17.2193442623 -34 46 45.500772910   12.88 11.46 11.43 9.57 M1Ve 84 0
20 CD-34 7390B TT* 11 21 17.4429759333 -34 46 49.774537089   13.43 11.96 11.31 9.88 M1Ve 58 0
21 TWA 30B LM* 11 32 18.2184758367 -30 18 31.652412622         16.68 M4 33 0
22 TWA 30 Y*O 11 32 18.3109439046 -30 19 51.860228754   15.82 14.20 14.44 11.30 M5V 55 0
23 CD-26 8623B TT* 11 32 41.1729967174 -26 52 09.110626414   16.70 15.22 13.68 11.76 M5.5 66 0
24 CD-26 8623 TT* 11 32 41.2659398509 -26 51 55.961617611   13.69 12.23 11.14 9.637 M3Ve 87 0
25 TWA 26 LM* 11 39 51.1435262748 -31 59 21.473337261         15.83 M8e 97 0
26 CD-36 7429B TT* 11 48 23.7347470027 -37 28 48.519698919   15.43 14.00   11.45 M1V 66 0
27 CD-36 7429A TT* 11 48 24.2226856081 -37 28 49.112368947   12.54 11.17 10.92 9.552 K5V 107 0
28 NAME Chamaeleon Region SFR 11 55 -78.0           ~ 695 0
29 TWA 31 PM* 12 07 10.8878369580 -32 30 53.757769890   18.5   16.4   M4.2 22 0
30 TWA 27 LM* 12 07 33.4676156527 -39 32 54.016042897     19.95 17.99 15.88 M8IVe 311 0
31 TWA 40 BD* 12 07 48.3504727315 -39 00 04.493567340           L1 15 0
32 V* V1249 Cen TT* 12 15 30.7203284919 -39 48 42.605543199   13.09 11.160 10.919 9.50 M0.5 84 0
33 NAME Lower Centaurus Crux As* 12 19 -57.1           ~ 361 1
34 TWA 32 ** 12 26 51.366576 -33 16 12.54324   17.21 16.00 15.73   M6.3 26 0
35 V* V1250 Cen TT* 12 34 20.4718890806 -48 15 19.545698484   13.3 12.2   11.80 M3 34 0
36 V* V1251 Cen TT* 12 34 20.6481566532 -48 15 13.530604360   13.3 12.2   11.90 M3.5 39 0
37 TWA 29 LM* 12 45 14.1609543807 -44 29 07.737190128         18.0 M9.5p 42 0
38 2MASS J12474428-3816464 LM* 12 47 44.2863958077 -38 16 46.414130933           M9 9 0
39 NAME beta Pic Moving Group MGr 14 30 -42.0           ~ 576 0
40 NAME Lup Cloud SFR 16 03 -38.1           ~ 531 0
41 NAME Upper Sco Association As* 16 12 -23.4           ~ 1055 1
42 NAME Ophiuchus Molecular Cloud SFR 16 28 06 -24 32.5           ~ 3067 0

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2020.10.31-18:25:57

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