J/A+A/620/A32 IRS spectra of 22 O7-B5 I-V stars (Siebenmorgen+, 2018)
Far-infrared emission of massive stars.
Siebenmorgen R., Scicluna P., Krelowski J.
<Astron. Astrophys. 620, A32 (2018)>
=2018A&A...620A..32S 2018A&A...620A..32S (SIMBAD/NED BibCode)
ADC_Keywords: Stars, O ; Stars, B-type ; Spectra, infrared
Keywords: infrared: stars - dust, extinction - stars: early-type - infrared: ISM
Abstract:
We present results of the analysis of a sample of 22 stars of spectral
types from O7 to B5 and luminosity classes I-V for which spectra from
the Infrared Spectrograph (IRS) of Spitzer are available. The IRS
spectra of these stars are examined for signs of excess infrared (IR)
emission by comparison with stellar atmospheric spectra. We find that
the spectra of half of the studied stars are dominated by excess
emission in the far-IR, including all six super- and bright giants. In
order to examine the origin of the far-IR excess, we supplement the
Spitzer data with optical high-resolution echelle spectroscopy
(λΔλ∼105), near-IR high-contrast coronagraphic
imaging taken with the SPHERE instrument at VLT with a spatial
resolution of 0.05", and WISE and Herschel photometry. In the optical
region, we detect various absorption and emission lines (Hα,
CIII, and NIII) irrespective of the far-IR excess. Pfundα and
Humphreyα lines are observed at the same time as the far-IR
excess. These lines are stronger in stars with far-IR excess than in
stars without excess. A scattered-light disk in the central r<2.5"
region of the far-IR excess stars HD149404, HD151804, and HD154368 can
be excluded from H band imaging down to a 1σ contrast of
F(r)/F*∼10-6. The far-IR excess is fit either by a free-free
component from ionized gas as for the winds of hot stars or a large
(1pc) circumstellar dust shell. The putative dust envelopes required
to explain the excess have a visual extinction as low as a few hundred
micro-mag.
Description:
High resolution optical spectra of stars with and without IR excess as
listed in Table 2. HR spectra of stars observed with UVES spectra are
available at the ESO archive.
Spectra have two columns, wavelength (Angstroem) followed by the spectrum
(relative flux in arbitrary units).
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 123 22 Spectral lines for stars with and without
far-IR excess
sp/* . 18 Individual spectra
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 A9 --- IRexcess IR excess (Excess or No excess)
11- 19 A9 --- Name Star name
22- 30 A9 --- Inst Instrument
32- 41 A10 "date" Obs.date Observation date
43- 46 I4 pc DistP ?=- Distance estimate from GAIA parallaxes
48- 51 I4 pc DistCaII ?=- Distance estimate from CaII
53- 56 I4 pc Distsp ?=- Distance estimate from spectral and
luminosity class
58- 67 A10 --- Ha Presence of Hα 6563Å
68 A1 --- n_Ha [c] Note on Ha (1)
71- 73 A3 --- CIII Presence of CIII 5596Å
75- 77 A3 --- NIII Presence of NIII 4641Å
79 A1 --- l_FPfa Limit flag on FPfa
80- 85 F6.2 10-17W/m2 FPfa Pfund α (n=6->5) 7.5um hydrogen
transition continuum subtracted line flux
87- 90 F4.2 10-17W/m2 e_FPfa ? rms uncertainty on FPfa
92- 94 I3 0.1nm EWPfa ?=- Pfund α (n=6->5) 7.5um hydrogen
transition equivalent width
96 A1 --- l_FHua Limit flag on FHua
97-101 F5.2 10-17W/m2 FHua Humphrey α (n=7->6) 12.3um hydrogen
transition continuum subtracted line flux
103-106 F4.2 10-17W/m2 e_FHua ? rms uncertainty on FHua
108-110 I3 0.1nm EWHua ?=- Humphrey α (n=7->6) 12.3um
hydrogen transition equivalent width
112-123 A12 --- FileName Name of the spectrum file in
subdirectory sp
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Note (1): Notes a s follows:
c = Out of five spectra taken between 1993-2010 only the HARPS spectrum taken
2006-03-10 shows weak Hα emission (Fig. 3).
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Byte-by-byte Description of file: sp/*
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 F12.7 0.1nm lambda ?=- Wavelength
19- 27 F9.7 --- RFlux ?=- Relative flux
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Acknowledgements:
Ralf Siebenmorgen, rsiebenm(at)eso.org
(End) Patricia Vannier [CDS] 12-Oct-2018