J/A+A/629/A94       CO spectra of 49 semi-regular variables   (Diaz-Luis+, 2019)

Circumstellar envelopes of semi-regular long-period variables: mass-loss rate estimates and general model fitting of the molecular gas. Diaz-Luis J.J., Alcolea J., Bujarrabal V., Santander-Garcia M., Castro-Carrizo A., Gomez-Garrido M., Desmurs J.-F. <Astron. Astrophys. 629, A94 (2019)> =2019A&A...629A..94D 2019A&A...629A..94D (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Carbon monoxide ; Spectra, radio Keywords: stars: AGB and post-AGB - circumstellar matter - stars: evolution - stars: mass-loss - radio lines: stars Abstract: We aim to study the main properties of a volume-limited unbiased sample of well characterized semi-regular variables (SRs) in order to clarify important issues that need to be further explained, such as the formation of axially symmetric planetary nebulae (PNe) from spherical circumstellar envelopes (CSEs) that takes place during the mass loss process along the AGB phase. We present new high S/N IRAM 30m observations of the 12CO J=2-1, 12CO J=1-0, and 13CO J=1-0 lines, in a volume-limited sample of SRs for which the Hipparcos distances are between 100-500 pc and declinations above -25°. We analyzed the data by characterizing the main properties of the CSEs. The 12CO J=2-1 data have been used to study the profiles, while the 12CO J=1-0 data have been used to estimate mass-loss rates for the complete sample. Moreover, the 12CO J=2-1 line has been used to determine the possible structures responsible for such profiles. We have classified the sources into four groups according to the different profiles and final gas expansion velocities. Type 1 and 2 profiles are broad and narrow symmetric lines, respectively. Type 1 profiles, furthermore, are more related to standard spherically symmetric envelopes already studied. Type 3 profiles, on the contrary, are strange profiles with very pronounced asymmetries. Type 4 profiles, finally, are those which show two different components: a narrow line profile superimposed on a broad pedestal component. We find that for sources which show this kind of profile, with two different components, the variation amplitude is very low, what means that these SRs do not have a well developed inner envelope differentiated from the outer one. Interestingly, we report a moderate correlation between mass-loss rates and 12CO J=1-0/12CO J=2-1 line intensity ratios for O-rich SRs, suggesting a different behaviour between C- and O-rich SRs. By using SHAPE+shapemol, we find a unified simple model based on an oblate spheroid, placed in different orientations, that may explain all the 12CO profiles in the sample, indicating that the gas expansion is, in general, predominantly equatorial. Moreover, in order to explain the type 4 profiles, we define an extra component which may somehow be a biconical structure or similar according to the structures already found in this kind of sources. Type 1 and 2 profiles, curiously, may also be explained by standard spherically symmetric envelopes, but often requiring anomalously low velocities. Type 3 and 4 profiles, however, need axial symmetry to be explained. We conclude that most circumstellar shells around SRs show axial, strongly non-spherical symmetry. More interferometric observations are needed in order to make firm conclusions about mass-loss processes and possible morphologies of SRs. Description: The table contains all the spectra for the 49 sources of the sample (with a blank space between them). We include the name of the source and the line (note that we are using three different lines: 12CO J=2-1, 12CO J=1-0, and 13CO J=1-0) in the first line of every dataset. Moreover, the columns contain the velocity in km/s (first column) and the main-beam brightness temperature in K (second column). File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 66 49 Main properties of the observed sample of SRs spectra.dat 53 14700 *All spectra for the 49 sources of the sample -------------------------------------------------------------------------------- Note on spectra.dat: blank line between spectra. -------------------------------------------------------------------------------- Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 10 A10 --- Star Star name 12- 13 I2 h RAh Simbad right ascension (J2000) 15- 16 I2 min RAm Simbad right ascension (J2000) 18- 19 I2 s RAs Simbad right ascension (J2000) 21 A1 --- DE- Declination sign (J2000) 22- 23 I2 deg DEd Declination (J2000) 25- 26 I2 arcmin DEm Declination (J2000) 28- 29 I2 arcsec DEs Declination (J2000) 31- 33 A3 --- Vtype [SRa SRb SRc] Variable type 35- 37 I3 d Per Period of variability 39 A1 --- SpType [CMS] Spectral type 41- 43 F3.1 mag DVmag Variation amplitude, from GCVS (Samus et al., Cat. B/gcvs) 45- 47 I3 Jy F12 IRAS 12um flux 49- 51 I3 Jy F25 IRAS 25um flux 53- 54 I2 Jy F60 IRAS 60um flux 56- 57 I2 Jy F100 IRAS 100um flux 59- 61 I3 pc DistH Distance derived from Hipparcos (van Leeuwen, 2007, Cat. I/311) parallax 63- 66 I4 pc DistG Distance derived from Gaia DR2 (Gaia Collaboration, 2018, Cat. I/345) parallax -------------------------------------------------------------------------------- Byte-by-byte Description of file: spectra.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 10 A10 --- Star Star name 13- 21 A9 --- Line Line (12CO(1-0), 12CO(2-1) or 13CO(1-0)) 32- 40 F9.4 km/s Vel Velocity 43- 53 E11.6 K Tmb Main-beam brightness temperature -------------------------------------------------------------------------------- Acknowledgements: Jose Jairo Diaz-Luis, jjairo(at)oan.es
(End) Patricia Vannier [CDS] 24-Jul-2019
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