J/A+A/603/A67 CRL618, MWC922 and M2-9 RRL spectra (Sanchez Contreras+, 2017)
A pilot search for mm-wavelength recombination lines from emerging ionized winds
in pre-planetary nebulae candidates.
Sanchez Contreras C., Baez-Rubio A., Alcolea J., Bujarrabal V.,
Martin-Pintado J.
<Astron. Astrophys. 603, A67 (2017)>
=2017A&A...603A..67S 2017A&A...603A..67S (SIMBAD/NED BibCode)
ADC_Keywords: Planetary nebulae ; Spectroscopy ; Radio lines
Keywords: stars: AGB and post-AGB - circumstellar matter -
stars: winds, outflows - stars: mass-loss - radio lines: general -
HII regions
Abstract:
We report the results from a pilot search for radio recombination line
(RRL) emission at millimeter wavelengths in a small sample of
pre-planetary nebulae (pPNe) and young PNe (yPNe) with emerging
central ionized regions. Observations of the H30α, H31α,
H39α, H41α, H48β, H49β, H51β, and
H55γ lines at ∼1 and ∼3mm have been performed with the IRAM 30m
radio telescope. These lines are excellent probes of the dense inner
(≲150 au) and heavily obscured regions of these objects, where the
yet unknown agents for PN-shaping originate. We detected mm-RRLs in
three objects: CRL 618, MWC922, and M2-9. For CRL 618, the only pPN
with previous published detections of H41α, H35α, and
H30α emission, we find significant changes in the line profiles
indicating that current observations are probing regions of the
ionized wind with larger expansion velocities and mass-loss rate than
∼29 years ago. In the case of MWC922, we observe a drastic transition
from single-peaked profiles at 3mm (H39α and H41α) to
double-peaked profiles at 1mm (H31α and H30α), which is
consistent with maser amplification of the highest frequency lines;
the observed line profiles are compatible with rotation and expansion
of the ionized gas, probably arranged in a disk+wind system around a
∼5-10M☉ central mass. In M2-9, the mm-RRL emission appears to be
tracing a recent mass outburst by one of the stars of the central
binary system. We present the results from non-LTE line and continuum
radiative transfer models, which enables us to constrain the
structure, kinematics, and physical conditions (electron temperature
and density) of the ionized cores of our sample. We find temperatures
Te∼6000-17000K, mean densities ne∼105-108cm-3, radial density
gradients ne∝r-alphan_^ whit alphan∼2-3.5, and motions of
velocities of ∼10-30km/s in the ionized wind regions traced by these
mm-wavelength observations. We deduce mass-loss rates of
dMpAGB/dt~=10-6-10-7M☉/yr, which are significantly higher
than the values adopted by stellar evolution models currently in use
and would result in a transition from the asymptotic giant branch to
the PN phase faster than hitherto assumed.
Description:
Spectra of recombination lines at millimeter wavelengths with the IRAM
30m telescope for CRL618, MWC922 and M2-9. The intensity is presented
in Ta* (K).
Objects:
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RA (2000) DE Designation(s)
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04 42 53.64 +36 06 53.4 CRL618 = PN G166.4-06.5
18 21 16.06 -13 01 25.7 MWC922 = EM* MWC 922
17 05 37.95 -10 08 34.6 PN M2-9 = PN G010.8+18.0
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 139 24 List of spectra
fits/* . 24 Individual fits spectra
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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- 23 I4 --- Nx Number of pixels along X-axis
25- 47 A23 --- Obs.Date Observation date (YYYY-MM-DDThh:mm:ss.sss)
49- 60 E12.6 Hz bFreq Lower value of frequency interval
62- 72 E11.6 Hz BFreq Upper value of frequency interval
74- 84 E11.6 Hz dFreq Frequency resolution
86- 87 I2 Kibyte size Size of FITS file
89-104 A16 --- FileName Name of FITS file, in subdirectory fits
106-139 A34 --- Title Title of the FITS file
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Acknowledgements:
Carmen Sanchez Contreras, csanchez(at)cab.inta-csic.es
(End) Patricia Vannier [CDS] 28-Apr-2017