J/A+A/615/A40 OB stars in N206 in the LMC (Ramachandran+, 2018)
Stellar population of the superbubble N 206 in the LMC.
II. Parameters of the OB and WR stars, and the total massive star feedback.
Ramachandran V., Hamann W.-R., Hainich R., Oskinova L.M., Shenar T.,
Sander A.A.C., Todt H., Gallagher J.S.
<Astron. Astrophys., 615, A40 (2018)>
=2018A&A...615A..40R 2018A&A...615A..40R (SIMBAD/NED BibCode)
ADC_Keywords: Magellanic Clouds ; Molecular clouds ; Stars, masses ;
Radial velocities ; Rotational velocities
Keywords: stars: massive - Magellanic Clouds - stars: winds, outflows -
Hertzsprung-Russell and C-M diagrams - techniques: spectroscopic -
ISM: bubbles
Abstract:
Context. Clusters or associations of early-type stars are often
associated with a "superbubble" of hot gas. The formation of such
superbubbles is caused by the feedback from massive stars. The complex
N 206 in the Large Magellanic Cloud (LMC) exhibits a superbubble and a
rich massive star population. Aims. Our goal is to perform
quantitative spectral analyses of all massive stars associated with
the N 206 superbubble in order to determine their stellar and wind
parameters. We compare the superbubble energy budget to the stellar
energy input and discuss the star formation history of the region.
Methods. We observed the massive stars in the N 206 complex using the
multi-object spectrograph FLAMES at ESO's Very Large Telescope (VLT).
Available ultra-violet (UV) spectra from archives are also used. The
spectral analysis is performed with Potsdam Wolf-Rayet (PoWR) model
atmospheres by reproducing the observations with the synthetic
spectra. Results. We present the stellar and wind parameters of the OB
stars and the two Wolf-Rayet (WR) binaries in the N 206 complex.
Twelve percent of the sample show Oe/Be type emission lines, although
most of them appear to rotate far below critical. We found eight
runaway stars based on their radial velocity. The wind-momentum
luminosity relation of our OB sample is consistent with the
expectations. The Hertzsprung-Russell diagram (HRD) of the OB stars
reveals a large age spread (1-30Myr), suggesting different episodes of
star formation in the complex. The youngest stars are concentrated in
the inner part of the complex, while the older OB stars are scattered
over outer regions. We derived the present day mass function for the
entire N 206 complex as well as for the cluster NGC 2018. The total
ionizing photon flux produced by all massive stars in the N 206
complex is Q0~=5x1050s-1, and the mechanical luminosity of their
stellar winds amounts to Lmec=1.7x1038erg/s. Three very massive Of
stars are found to dominate the feedback among 164 OB stars in the
sample. The two WR winds alone release about as much mechanical
luminosity as the whole OB star sample. The cumulative mechanical
feedback from all massive stellar winds is comparable to the combined
mechanical energy of the supernova explosions that likely occurred in
the complex. Accounting also for the WR wind and supernovae, the
mechanical input over the last five Myr is ~=2.3x1052erg.
Conclusions. The N206 complex in the LMC has undergone star formation
episodes since more than 30Myr ago. From the spectral analyses of its
massive star population, we derive a current star formation rate of
2.2x10-3M☉/yr. From the combined input of mechanical energy
from all stellar winds, only a minor fraction is emitted in the form
of X-rays. The corresponding input accumulated over a long time also
exceeds the current energy content of the complex by more than a
factor of five. The morphology of the complex suggests a leakage of
hot gas from the superbubble.
Description:
The presented study is largely based on spectroscopic data obtained
with the Fiber Large Array Multi-Element Spectrograph (FLAMES) at
ESO-VLT. Accounting for a typical color excess of E(B-V)∼0.1-0.2mag,
implying an extinction of AV∼0.3-0.6mag, we targeted the blue hot
stars (i.e., with spectral subtypes earlier than B2V) by selecting all
sources with B-V<0.20mag and V<16mag. Therefore, for spectral types
later than B2V our sample is incomplete. Apart from this, a few blue
stars in the dense parts of the region were missed because the
allocation of the Medusa fibers is constrained by the physical size of
the fiber buttons. More details of the observations and the data
reduction are given in Paper I (Ramachandran et al.,
2018A&A...609A...7R 2018A&A...609A...7R).
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1a1.dat 37 155 Coordinates and spectral types of OB stars
in our sample (table 1 and table A1)
table3a2.dat 81 155 Stellar parameters of OB stars in N 206
(table 3 and table A2)
tablea3.dat 13 155 Ages and evolutionary masses of the OB stars
determined from isochrones
(See Sect. 7.3 for details)
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Byte-by-byte Description of file: table1a1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- N206-FS [1/234] N206-FS identification number
5- 13 F9.6 deg RAdeg Right ascension (J2000)
15- 24 F10.6 deg DEdeg Declination (J2000)
26- 37 A12 --- SpType Spectral type
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Byte-by-byte Description of file: table3a2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
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1- 3 I3 --- N206-FS [1/234] N206-FS identification number
5- 16 A12 --- SpType Spectral type
19- 22 F4.1 kK T* Stellar temperature
24- 27 F4.2 [Lsun] logL Luminosity
29- 31 F3.1 [cm/s2] logg* Surface gravity
33- 37 F5.2 [Msun/yr] logdM/dt Mass-loss rate
39- 42 F4.2 mag E(B-V) B-V colour excess
44- 48 F5.2 mag VMAG Absolute V magnitude
50- 53 F4.1 Rsun R* Stellar radius
55- 58 I4 km/s vinf Terminal velocity
60- 62 I3 km/s vsini Projected rotational velocity
64- 66 I3 km/s RV Radial velocity
68- 69 I2 Msun M* Stellar mass
71- 74 F4.1 [s-1] logQ0 Rate of hydrogen ionizing photons
76- 81 F6.2 Lsun Lmec Mechanical luminosity
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Byte-by-byte Description of file: tablea3.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- N206-FS [1/234] N206-FS identification number
5- 8 F4.1 Myr Age Age
10- 13 F4.1 Msun Mev Evolutionary mass
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History:
From electronic version of the journal
References:
Ramachandran et al., Paper I 2018A&A...609A...7R 2018A&A...609A...7R
(End) Patricia Vannier [CDS] 27-Sep-2018