2022A&A...666A.189R


Query : 2022A&A...666A.189R

2022A&A...666A.189R - Astronomy and Astrophysics, volume 666A, 189 (2022/10-1)

Stellar wind properties of the nearly complete sample of O stars in the low metallicity young star cluster NGC 346 in the SMC galaxy.

RICKARD M.J., HAINICH R., HAMANN W.-R., OSKINOVA L.M., PRINJA R.K., RAMACHANDRAN V., PAULI D., TODT H., SANDER A.A.C., SHENAR T., CHU Y.-H. and GALLAGHER III J.S.

Abstract (from CDS):


Context. Massive stars are among the main cosmic engines driving the evolution of star-forming galaxies. Their powerful ionising radiation and stellar winds inject a large amount of energy in the interstellar medium. Furthermore, mass-loss (Ṁ) through radiatively driven winds plays a key role in the evolution of massive stars. Even so, the wind mass-loss prescriptions used in stellar evolution models, population synthesis, and stellar feedback models often disagree with mass-loss rates empirically measured from the UV spectra of low metallicity massive stars.
Aims. The most massive young star cluster in the low metallicity Small Magellanic Cloud galaxy is NGC 346. This cluster contains more than half of all O stars discovered in this galaxy so far. A similar age, metallicity (Z), and extinction, the O stars in the NGC 346 cluster are uniquely suited for a comparative study of stellar winds in O stars of different subtypes. We aim to use a sample of O stars within NGC 346 to study stellar winds at low metallicity.
Methods. We mapped the central 1' of NGC 346 with the long-slit UV observations performed by the Space Telescope Imaging Spectrograph (STIS) on board of the Hubble Space Telescope and complemented these new datasets with archival observations. Multi-epoch observations allowed for the detection of wind variability. The UV dataset was supplemented by optical spectroscopy and photometry. The resulting spectra were analysed using a non-local thermal equilibrium model atmosphere code (PoWR) to determine wind parameters and ionising fluxes.
Results. The effective mapping technique allowed us to obtain a mosaic of almost the full extent of the cluster and resolve stars in its core. Among hundreds of extracted stellar spectra, 21 belong to O stars. Nine of them are classified as O stars for the first time. We analyse, in detail, the UV spectra of 19 O stars (with a further two needing to be analysed in a later paper due to the complexity of the wind lines as a result of multiplicity). This more than triples the number of O stars in the core of NGC 346 with constrained wind properties. We show that the most commonly used theoretical mass-loss recipes for O stars over-predict mass-loss rates. We find that the empirical scaling between mass-loss rates (Ṁ) and luminosity (L), Ṁ ∝ L2.4, is steeper than theoretically expected by the most commonly used recipes. In agreement with the most recent theoretical predictions, we find within Ṁ ∝ Zα that α is dependent upon L. Only the most luminous stars dominate the ionisation feedback, while the weak stellar winds of O stars in NGC 346 and the lack of previous supernova explosions in this cluster restrict the kinetic energy input.

Abstract Copyright: © M. J. Rickard et al. 2022

Journal keyword(s): stars: winds, outflows - stars: individual: NGC 346 SSN18 - Magellanic Clouds - stars: evolution

Simbad objects: 28

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Number of rows : 28
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 11178 1
2 Cl* NGC 346 ELS 7 * 00 58 57.3961905528 -72 10 33.660822720 12.68 13.82 14.13   14.28 O4V((f+)) 52 0
3 Cl* NGC 346 W 4 EB* 00 59 00.0525662904 -72 10 37.962442344 11.82 12.93 13.13   13.77 O5-6V((f)) 37 0
4 Cl* NGC 346 W 3 * 00 59 00.7591806336 -72 10 28.171806492 11.46 12.61 12.80   13.63 O2III(f) 62 0
5 Cl* NGC 346 NMC 28 * 00 59 01.8187292184 -72 10 31.216864152   13.95 14.18     O5.5V((f+)) 31 0
6 Cl* NGC 346 MPG 370 * 00 59 01.835 -72 10 43.25 14.34 15.39 15.18     O9.5V 7 0
7 Cl* NGC 346 MPG 375 * 00 59 02.039 -72 10 36.31     15.594   15.826 ~ 4 0
8 Cl* NGC 346 MPG 396 * 00 59 02.92 -72 10 34.8   14.17 14.39     O7V 8 0
9 Cl* NGC 346 MPG 417 * 00 59 03.97 -72 10 51.1   14.79 15.02     O7.5V((f)) 6 0
10 Cl* NGC 346 MPG 429 * 00 59 04.260 -72 10 27.24     15.890   16.145 ~ 3 0
11 NGC 346 Cl* 00 59 04.4000 -72 10 39.000           ~ 490 0
12 Cl* NGC 346 SSN 7 s*b 00 59 04.4955841440 -72 10 24.744449712   12.37 12.57     O4If+O5-6 38 0
13 Cl* NGC 346 MPG 455 * 00 59 05.4514563072 -72 10 42.371424912   15.06 15.25     O9.5V 7 0
14 Cl* NGC 346 MPG 467 * 00 59 05.9056429752 -72 10 50.343755916 13.57 14.68 14.82   15.03 O8.5V 7 0
15 Cl* NGC 346 MPG 468 * 00 59 05.98 -72 10 29.5 13.85 14.87 15.24   15.17 O9V 5 0
16 OGLE SMC-ECL- 3932 EB* 00 59 05.984 -72 10 34.05   13.57 13.800   14.025 O8.5III 11 0
17 Cl* NGC 346 MPG 476 * 00 59 06.193 -72 10 33.56     14.562   14.757 ~ 5 0
18 Cl* NGC 346 MPG 481 * 00 59 06.316 -72 10 32.41     15.185   15.382 ~ 3 0
19 Cl* NGC 346 MPG 486 * 00 59 06.658 -72 10 28.84     16.168   16.403 ~ 3 0
20 Cl* NGC 346 NMC 17 * 00 59 06.7498587648 -72 10 41.262204828 13.05 14.19 14.33   14.60 O8V 21 0
21 Cl* NGC 346 NMC 24 * 00 59 07.3349477712 -72 10 25.381753752   14.83 15.13 15.31   O8V 8 0
22 Cl* NGC 346 MPG 499 * 00 59 07.589 -72 10 39.22     16.231   16.444 ~ 3 0
23 Cl* NGC 346 NMC 16 * 00 59 07.63 -72 10 48.3 13.99 14.93 15.09   15.31 O6V: 7 0
24 SNR B0057-72.2 SNR 00 59 27.40 -72 10 10.7   12.37 12.57     ~ 240 0
25 SK 183 * 01 29 24.5481468144 -73 33 16.345873296   13.57 13.80     O3V((f*))z+OB 17 0
26 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 7084 0
27 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 17478 0
28 NAME Local Group GrG ~ ~           ~ 8415 0

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