J/A+A/604/A78 M17 massive pms stars X-shooter spectra (Ramirez-Tannus+, 2017)
Massive pre-main-sequence stars in M17.
Ramirez-Tannus M.C., Kaper L., de Koter A., Tramper F., Bik A.,
Ellerbroek L.E., Ochsendorf B.B., Ramirez-Agudelo O.H., Sana H.
<Astron. Astrophys. 604, A78 (2017)>
=2017A&A...604A..78R 2017A&A...604A..78R (SIMBAD/NED BibCode)
ADC_Keywords: H II regions ; Stars, pre-main sequence ; YSOs ; Stars, OB ;
Spectroscopy
Keywords: stars: pre-main-sequence - stars: massive - stars: early-type -
HII regions - stars: variables: T Tauri, Herbig Ae/Be -
accretion, accretion disks
Abstract:
The formation process of massive stars is still poorly understood.
Massive young stellar objects (mYSOs) are deeply embedded in their
parental clouds; these objects are rare, and thus typically distant,
and their reddened spectra usually preclude the determination of their
photospheric parameters. M17 is one of the best-studied HII regions in
the sky, is relatively nearby, and hosts a young stellar population.
We have obtained optical to near-infrared spectra of previously
identified candidate mYSOs and a few OB stars in this region with
X-shooter on the ESO Very Large Telescope.
The large wavelength coverage enables a detailed spectroscopic
analysis of the photospheres and circumstellar disks of these
candidate mYSOs. We confirm the pre-main-sequence (PMS) nature of six
of the stars and characterise the O stars. The PMS stars have radii
that are consistent with being contracting towards the main sequence
and are surrounded by a remnant accretion disk. The observed infrared
excess and the double-peaked emission lines provide an opportunity to
measure structured velocity profiles in the disks. We compare the
observed properties of this unique sample of young massive stars with
evolutionary tracks of massive protostars and propose that these mYSOs
near the western edge of the HII region are on their way to become
main-sequence stars (∼6-20M☉) after having undergone high mass
accretion rates (dMacc/dt∼10-4-10-3M☉/yr) Their spin
distribution upon arrival at the zero age main-sequence (ZAMS) is
consistent with that observed for young B stars, assuming conservation
of angular momentum and homologous contraction.
Description:
Normalized X-shooter spectra of the PMS and OB stars in M17 studied.
The X-shooter spectra were obtained under good weather conditions with
seeing ranging from 0.5" and 1" and clear sky. With the exception of
the 2012 B289 spectrum and the 2009 B275 science verification
spectrum, the spectrograph slit widths used were 1" (UVB, 300-590nm),
0.9" (VIS, 550-1020nm), and 0.4" (NIR, 1000-2480nm), resulting in a
spectral resolving power of 5100, 8800, and 11300, respectively. The
slit widths for the 2010 B275 observations were 1.6", 0.9", and 0.9"
resulting in a resolving power of 3300, 8800, and 5600, respectively.
For the 2012 B289 observations we used the 0.8", 0.7", and 0.4" slits
corresponding to a resolving power of 6200, 11000, and 11300 for the
UVB, VIS, and NIR arms, respectively. The spectra were taken in
nodding mode and reduced using the X-shooter pipeline version 2.7.1
running under the ESO Reflex environment version 2.8.4.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 100 17 Journal of X-shooter observations
sp/* . 16 Individual normalised spectra of the studied
stars in M17
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See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
II/336 : AAVSO Photometric All Sky Survey (APASS) DR9 (Henden+, 2016)
J/ApJS/169/353 : Chandra sources in M17 (Broos+, 2007)
J/ApJ/714/L285 : YSO candidates in M17 SWex (Povich+, 2010)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- Name Object name (BNNN) as in Master's thesis of
Bumgardner (1992, thesis, Ohio State Univ.,
Columbus), Cl* NGC 6618 B NNN in Simbad
5 A1 --- n_Name [*] Note on Name (1)
6- 10 A5 --- OName Other name
12- 13 I2 --- CEN ?=- Chini et al. (1980A&A....91..186C 1980A&A....91..186C)
identification number,
Cl* NGC 6618 CEN NNN in Simbad
15- 17 I3 --- OI ? Ogura & Ishida (1976PASJ...28...35O 1976PASJ...28...35O)
identification number,
NGC 6618 NNN in Simbad
19- 20 I2 h RAh Right ascension (J2000)
22- 23 I2 min RAm Right ascension (J2000)
25- 29 F5.2 s RAs Right ascension (J2000)
31 A1 --- DE- Declination sign (J2000)
32- 33 I2 deg DEd Declination (J2000)
35- 36 I2 arcmin DEm Declination (J2000)
38- 42 F5.2 arcsec DEs Declination (J2000)
44- 49 F6.3 mag Vmag ? V magnitude
50 A1 --- r_Vmag [abc] Reference for Vmag (2)
52- 57 F6.3 mag Kmag 2MASS K magnitude (Cutri et al., 2003,
Cat. II/246)
59- 68 A10 "date" Obs.Date Observation date
70- 74 A5 --- ExpTUVB UVB arm exposure times (s)
76- 80 A5 --- ExpTVIS VIS arm exposure times (s)
82- 87 A6 --- ExpTNIR NIR arm exposure times (s)
89-100 A12 --- FileName Name of the file with spectrum,
in subdirectory sp
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Note (1): B111, B163, B164, and B253 are associated with NGC 6618
(Povich et al., 2009, Cat. J/ApJ/696/1278).
Note (2): References as follows:
a = AAVSO Photometric all sky survey (APASS) catalog:
https://www.aavso.org/apass , Cat. II/336
b = Chini et al. (1980A&A....91..186C 1980A&A....91..186C)
c = Hoffmeister et al. (2008ApJ...686..310H 2008ApJ...686..310H)
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Byte-by-byte Description of file: sp/*
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Bytes Format Units Label Explanations
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1- 24 E24.18 nm lambda Wavelength
26- 51 E26.18 --- NFlux ?=- Normalised flux
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Acknowledgements:
Maria Claudia Ramirez-Tannus, m.c.ramireztannus(at)uva.nl
(End) Maria Claudia Ramirez-Tannus [UVA], Patricia Vannier [CDS] 10-May-2017