J/A+A/557/A104 CO observations of post-AGB stars (Bujarrabal+, 2013)
Extended rotating disks around post-AGB stars.
Bujarrabal V., Alcolea J., Van Winckel H., Santander-Garcia M.,
Castro-Carrizo A.
<Astron. Astrophys. 557, A104 (2013)>
=2013A&A...557A.104B 2013A&A...557A.104B
ADC_Keywords: Stars, late-type ; Planetary nebulae ; Carbon monoxide
Keywords: stars: AGB and post-AGB - circumstellar matter - radio lines: stars -
planetary nebulae: general
Abstract:
There is a group of binary post-AGB stars that show conspicuous near
infrared (NIR) excess, which is usually assumed to arise from hot dust
in very compact possibly rotating disks. These stars are surrounded by
significantly fainter nebulae than the standard, well studied
protoplanetary and planetary nebulae (PPNe, PNe).
We aim to identify and study extended rotating disks around these
stars and shed light on the role of disks in the formation and shaping
of planetary nebulae.
We present high-sensitivity mm-wave observations of CO lines in 24
objects of this type. The resulting CO lines are compared with
profiles expected to arise from rotating disks, from both theoretical
and observational grounds. We derive simple formulae that allow us to
determine the mass of the CO-emitting gas and estimate its extent. The
reliability and uncertainty of the methods are also widely discussed.
CO emission is detected in most observed sources, and the line
profiles show that the emissions very probably come from disks in
rotation. We derive typical values of the disk mass between 10-3
and 10-2M☉, about two orders of magnitude lower than the
(total) masses of standard PPNe. The high-detection rate (upper
limits being not very significant) clearly confirm that the NIR excess
of these stars arises from compact disks in rotation, which are likely
the inner parts of those found here. Low-velocity outflows are also
found in about eight objects with moderate expansion velocities of
∼10km/s, to be compared with the velocities of about 100km/s
often found in standard PPNe. Except for two sources with complex
profiles, the outflowing gas in our objects represents a minor nebular
component. Our simple estimates of the typical disk sizes yields
values ∼0.5-1arcsec, which is between 5x1015 and 3x1016cm.
Estimates of the linear momenta carried by the outflows, which can
only be performed in a few well studied objects, also yield moderate
values when compared to the linear momenta that can be released by the
stellar radiation pressure (contrary, again, to the case of the very
massive and fast bipolar outflows in $standard$ PPNe that are strongly
overluminous). The mass and dynamics of nebulae around various classes
of post-AGB stars differ very significantly, and we can expect the
formation of PNe with very different properties.
Description:
Spectra of CO mm-wave lines in 24 post-AGB stars are presented.
Telescopes: IRAM 30m and APEX. Lines: 12CO 1-0, 2-1, 3-2,
13CO 1-0, 2-1. The fits files contain the full spectra (all recorded
channels) calibrated Tmb units (K). The names of the fits files
include the name of the source and the line observed.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
stars.dat 131 24 Post-AGB sources observed with the 30m IRAM
and APEX telescopes (tables 1 and 2 of the paper)
list.dat 124 74 Summary of available FITS files
fits/* . 74 Individual FITS files
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See also:
J/A+A/323/469 : Optical spectra of post-AGB stars (Bakker+ 1997)
J/A+A/419/1123 : Equivalent widths of 3 post-AGB (Mooney+, 2004)
J/AJ/123/2772 : OH-selected AGB and post-AGB objects. I. (Sevenster+, 2002)
J/A+A/469/799 : Torun catalog of post-AGB and related objects (Szczerba+ 2007)
Byte-by-byte Description of file: stars.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- Tel Telescope (IRAM or APEX)
6- 20 A15 --- Name Star name
22- 23 I2 h RAh Right ascension (J2000)
25- 26 I2 min RAm Right ascension (J2000)
28- 32 F5.2 s RAs Right ascension (J2000)
34 A1 --- DE- Declination sign (J2000)
35- 36 I2 deg DEd Declination (J2000)
38- 39 I2 arcmin DEm Declination (J2000)
41- 44 F4.1 arcsec DEs Declination (J2000)
46- 51 F6.2 Jy F25um Flux at 25um
52- 56 F5.1 Jy F60um Flux at 60um
58- 62 I5 Lsun Lum Luminosity
63 A1 --- n_Lum [a] a for assumed luminosity
65- 68 I4 pc Dist Distance
70 I1 --- n_Dist [1/5] Method used for distance determination (1)
72- 78 A7 --- SpType MK spectral type
80- 82 I3 km/s Vlsr ? Local Standard of Rest (LSR) velocity
83 A1 --- u_Vlsr [?] Uncertainty flag on Vlsr
84-119 A36 --- Com Comments
121-131 A11 --- File Root part of the FITS files related to the star
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Note (1): Notes on distance estimate as follows:
1 = P-L relation for RV Tau variables
2 = Men'shchikov et al. (2002A&A...393..867M 2002A&A...393..867M)
3 = Assumed luminosity
4 = Corrected parallax (Acke et al., 2013A&A...551A..76A 2013A&A...551A..76A)
5 = Hipparcos parallax (Cat. I/239)
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Byte-by-byte Description of file: fits.dat
sl-------------------------------------------------------------------------------
Bytes Format Units Label Explanations
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1- 15 A15 --- Name Star name
17- 25 F9.5 deg RAdeg Right Ascension of center (J2000)
26- 34 F9.5 deg DEdeg Declination of center (J2000)
37- 41 I5 --- Nx [819/20737] Number of pixels along X-axis
43- 51 A9 --- Line Line observed
53- 60 F8.3 GHz Freq0 [110.201/345.796] Rest frequency of line
62- 68 F7.1 MHz bFreq [-3963/-447] Minimal frequency (from Freq0)
70- 76 F7.1 MHz BFreq [86/1900] Maximal frequency
78- 82 F5.3 MHz dFreq [0.195/1.221] Frequency resolution
84- 85 I2 Kibyte size [11/87] Size of FITS file
87-124 A38 --- FileName Name of FITS file in "fits" subdirectory
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Acknowledgements:
Valentin Bujarrabal, v.bujarrabal(at)oan.es
(End) Patricia Vannier [CDS] 14-Aug-2013