J/A+A/654/A109 Massive YSOs VLTI observations (Koumpia+, 2021)
The first interferometric survey of massive YSOs in the K-band.
Hot dust, ionised gas, and binarity at au scales.
Koumpia E., de Wit W.-J., Oudmaijer R.D., Frost A.J., Lumsden S.,
Caratti o Garatti A., Goodwin S.P., Stecklum B., Mendigutia I., Ilee J.D.,
Vioque M.
<Astron. Astrophys. 654, A109 (2021)>
=2021A&A...654A.109K 2021A&A...654A.109K (SIMBAD/NED BibCode)
ADC_Keywords: YSOs ; Interferometry ; Spectroscopy
Keywords: stars: formation - stars: massive - techniques: interferometric -
binaries (including multiple): close - accretion, accretion disks
Abstract:
Circumstellar discs are essential for high mass star formation, while
multiplicity, in particular binarity, appears to be an inevitable
outcome since the vast majority of massive stars (>8M☉) are
found in binaries (up to 100%).
We spatially resolve and constrain the sizes of the dust and ionised
gas emission of the innermost regions towards a sample of MYSOs for
the first time, and provide high-mass binary statistics of young stars
at 2-300au scales.
We observe six MYSOs with VLTI (GRAVITY, AMBER), to resolve and
characterise the 2.2um hot dust emission originating from the inner
rim of circumstellar discs around MYSOs, and the associated Brγ
emission from ionised gas. We fit simple geometrical models to the
interferometric observables, and determine the inner radius of the
dust emission. We place MYSOs with K-band measurements in a
size-luminosity diagram for the first time, and compare our findings
to T Tauris and Herbig AeBes. We also compare the observed K-band
sizes to the sublimation radius predicted by three different disc
scenarios. Lastly, we apply binary geometries to trace close binarity
among MYSOs.
When the inner sizes of MYSOs are compared to those of lower mass
Herbig AeBe and T Tauri stars, they appear to follow a universal trend
at which the sizes scale with the square-root of the stellar
luminosity. The Brγ emission originates from a similar or
somewhat smaller and co-planar area compared to the 2.2um continuum
emission. We discuss this new finding with respect to disc-wind or jet
origin. Finally, we report an MYSO binary fraction of 17-25% at
milli-arcsecond separations (2-300au).
The size-luminosity diagram indicates that the inner regions of discs
around young stars scale with luminosity independently of the stellar
mass. At the targeted scales (2-300au), the MYSO binary fraction is
lower than what was previously reported for the more evolved main
sequence massive stars, which, if further confirmed, could implicate
the predictions from massive binary formation theories. Lastly, we
spatially resolve the crucial star/disc interface in a sample of
MYSOs, showing that au-scale discs are prominent in high-mass star
formation and similar to their low-mass equivalents.
Description:
The objective of this work is to spatially resolve and constrain the
sizes of the dust and ionised gas emission of the innermost regions
towards a sample of massive young stellar objects (MYSOs) for the
first time, and to provide high-mass binary statistics of young stars
at 2-300au scales, using direct interferometric measurements. To do
so, we analysed a set of K-band interferometric data obtained with
VLTI.
sp/*_final.fits are the reduced AAT spectra, obtained using
IRIS-2 on the AAT.
(G233.8306_final.fits, G282.2988_final.fits, G287.3716_final.fits,
G301.8147_final.fits)
fits/GRAVI*singlesciviscalibrated.fits are the reduced and calibrated
GRAVITY data, after applying GRAVITY standard pipeline recipes (as
provided by ESO, version 1.1.2). These files include the flux and
interferometric observables at the corresponding wavelength ranges.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
listsp.dat 84 4 List of AAT spectra
sp/* . 4 Individual AAT spectra
list.dat 130 16 List of GRAVITY OI-FITS files
fits/* . 16 Individual GRAVITY OI-FITS files
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Byte-by-byte Description of file: listsp.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 A9 --- Name Source name
11- 12 I2 h RAh Right ascension (J2000)
14- 15 I2 min RAm Right ascension (J2000)
17- 21 F5.2 s RAs Right ascension (J2000)
23 A1 --- DE- Declination sign (J2000)
24- 25 I2 deg DEd Declination (J2000)
27- 28 I2 arcmin DEm Declination (J2000)
30- 33 F4.1 arcsec DEs Declination (J2000)
35- 54 A20 --- FileName Name of the fits file in subdirectory sp
56- 84 A29 --- SName Simbad name
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 19 A19 "datime" Obs.date Observation date
21- 23 I3 Kibyte size Size of OI-FITS file
25- 94 A70 --- FileName Name of OI-FITS file, in subdirectory fits
96-130 A35 --- Title Title of the OI-FITS file
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Acknowledgements:
Evgenia Koumpia, ev.koumpia(at)gmail.com
(End) Patricia Vannier [CDS] 06-Aug-2021