J/A+A/592/A76 VY CMa ALMA NaCl images (Decin+, 2016)
ALMA-resolved salt emission traces the chemical footprint and inner wind
morphology of VY Canis Majoris.
Decin L., Richards A.M.S., Millar T.J., Baudry A., De Beck E., Homan W.,
Smith N., Van de Sande M., Walsh C.
<Astron. Astrophys. 592, A76 (2016)>
=2016A&A...592A..76D 2016A&A...592A..76D (SIMBAD/NED BibCode)
ADC_Keywords: Stars, supergiant ; Interferometry
Keywords: supergiants - stars: mass loss - circumstellar matter -
stars: individual: VY Canis Majoris - astrochemistry -
instrumentation: interferometers
Abstract:
At the end of their lives, most stars lose a significant amount of
mass through a stellar wind. The specific physical and chemical
circumstances that lead to the onset of the stellar wind for cool
luminous stars are not yet understood. Complex geometrical
morphologies in the circumstellar envelopes prove that various
dynamical and chemical processes are interlocked and that their
relative contributions are not easy to disentangle.
We aim to study the inner-wind structure (R<250R*) of the well-known
red supergiant VY CMa, the archetype for the class of luminous red
supergiant stars experiencing high mass loss. Specifically, the
objective is to unravel the density structure in the inner envelope
and to examine the chemical interaction between gas and dust species.
We analyse high spatial resolution (∼0.24"x0.13") ALMA Science
Verification (SV) data in band 7, in which four thermal emission lines
of gaseous sodium chloride (NaCl) are present at high signal-to-noise
ratio.
Description:
VY CMa was observed for ALMA Science Verification on 2013 16-19 August
using 16-20 12-m antennas on baselines from 0.014-2.7km. The main
objective was to map the H2O maser lines at 321 and 325GHz (Band 7)
and 658GHz (Band 9), but several thermal lines identified with various
rotational transitions of NaCl, TiO2, SO2, and SiO were also
present in the spectral setting in addition to the continuum data.
Four NaCl lines in the ground or first vibrational state are
covered in the ALMA band 7 data.
All of them are detected, albeit only two are unblended (see Table 1).
Objects:
---------------------------------------------
RA (2000) DE Designation(s)
---------------------------------------------
07 22 58.33 -25 46 03.2 VY CMa = HD 58061
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 116 4 NaCl lines in the spectral windows covered by
the ALMA observations
list.dat 134 4 List of fits files
fits/* . 4 Individual fits files
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See also:
J/ApJS/190/348 : 1mm spectral survey of IRC+10216 + VY CMa (Tenenbaum+, 2010)
J/A+A/551/A113 : VY CMa spectrum in 220.65-224.25GHz range (Kaminski+, 2013)
J/MNRAS/437/532 : VY CMa molecular line spectra (Matsuura+, 2014)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Trans Transition
13- 19 F7.3 GHz Freqlab Rest frequency
21- 26 F6.2 cm-1 Elow Lower state energy
28- 32 F5.3 s-1 A Eisntein A-values from CDMS
34- 36 I3 mJy/beam*km/s rms rms noise
38- 42 F5.3 arcsec maj Synthesized beam major axis
44- 48 F5.3 arcsec min Synthesized beam minor axis
50- 54 F5.2 deg PA Synthesized beam position angle
56-116 A61 --- Com Comment concerning line blending
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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- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 22 I3 --- Nx Number of pixels along X-axis
24- 26 I3 --- Ny Number of pixels along Y-axis
28- 29 I2 --- Nz Number of pixels along Z-axis
31- 56 A26 --- Obs.date Observation date (YYYY-MM-DDThh:mm:ss.ssssss)
58- 64 F7.3 GHz bFreq Lower value of frequency interval
66- 72 F7.3 GHz BFreq Upper value of frequency interval
74- 80 F7.5 MHz dFreq Frequency resolution
82- 86 I5 Kibyte size Size of FITS file
88-115 A28 --- FileName Name of FITS file, in subdirectory fits
117-134 A18 --- Title Title of the FITS file
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Acknowledgements:
Leen Decin, leen.decin(at)kuleuven.be
(End) Patricia Vannier [CDS] 07-Jul-2016