J/A+A/686/A251 U Her and RR Aql 22GHz spectra (Winnberg+, 2024)
Water vapour masers in long-period variable stars.
III. Mira variables U Her and RR Aql.
Winnberg A., Brand J., Engels D.
<Astron. Astrophys. 686, A251 (2024)>
=2024A&A...686A.251W 2024A&A...686A.251W (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Masers ; Spectra, radio
Keywords: masers - stars: AGB and post-AGB circumstellar matter -
stars: individual: U Her - stars: individual: RR Aql
Abstract:
Water maser emission is often found in the circumstellar envelopes of
evolved stars, that is, asymptotic-giant-branch stars and red
supergiants with oxygen-rich chemistry. The H2O emission shows
strong variability in evolved stars of both of these types.
We wish to understand the reasons for the strong variability of water
masers emitted at 22GHz. In this paper we study U Her and RR Aql as
representatives of Mira variable stars.
We monitored U Her and RR Aql in the 22-GHz maser line of water vapour
with single-dish telescopes. The monitoring period covered about two
decades between 1990 and 2011, with a gap between 1997 and 2000 in the
case of RR Aql. Observations were also made in 1987 and 2015 before
and after the period of contiguous monitoring. In addition, maps of U
Her were obtained in the period 1990-1992 with the Very Large Array.
We find that the strongest emission in U Her is located in a shell
with boundaries 11-25AU. The gas-crossing time is 8.5 years. We
derive lifetimes for individual maser clouds of ≤4 years, based on
the absence of detectable line-of-sight velocity drifts of the maser
emission. The shell is not evenly filled, and its structure is
maintained over much longer timescales than those of individual maser
clouds. Both stars show brightness variability on several timescales.
The prevalent variation is periodic, following the optical variability
of the stars with a lag of 2-3 months. Superposed are irregular
fluctuations, of a few months in duration, with increased or decreased
excitation at particular locations, and long-term systematic
variations on timescales of a decade or more.
The properties of the maser emission are governed by those of the
stellar wind while traversing the H2O maser shell. Inhomogeneities
in the wind affecting the excitation conditions and prevalent beaming
directions likely cause the variations seen on timescales longer than
the stellar pulsation period. We propose the existence of long-living
regions in the shells, which maintain favourable excitation conditions
on timescales of the wind-crossing times through the shells or orbital
periods of (sub)stellar companions. The H2O maser properties in
these two Mira variables are remarkably similar to those in the
semiregular variables studied in our previous papers, regarding shell
location, outflow velocity, and lifetime. The only difference is the
regular brightness variations of the Mira variables caused by the
periodic pulsation of the stars.
Description:
The FITS files are the spectra of the 22 GHz water maser emission of U
Her (N=137) and RR Aql (N=89) as shown in Figs. C1 and C2 in Appendix
C in the paper. Flux density in Jy versus the line-of-sight velocity
relative to the LSR (V_los) in km/s.
The observations were made with the 32m Medicina antenna and the 100m
telescope at Effelsberg. The spectra were originally in CLASS-format
and were transformed to FITS via the command
'fits write name.fits /mode spectrum' in CLASS. CLASS is part of the
Grenoble GILDAS software package. The file names consist of the name
of the star, followed by a running number, and finally by the TJD
(truncated Julian Data, TJD=JD-2440000.5)
The four VLA data cubes contain the data of U Her taken at four epochs
with the Very Large Array (VLA) between Feb. 1990 and Dec. 1992. The
epochs are indicated in the names of the cubes.
Objects:
---------------------------------------------
RA (2000) DE Designation(s)
---------------------------------------------
16 25 47.47 +18 53 32.8 U Her = V* U Her
19 57 36.06 -01 53 11.3 RR Aql = V* RR Aql
---------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 91 133 Maser spectral components B-E of U Her
tablea2.dat 101 133 Maser spectral components G-M of U Her
tableb1.dat 86 89 Maser spectral components of RR Aql
list.dat 187 230 List of datacubes and spectra
fits/* . 230 Individual datacubes and spectra
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See also:
J/A+A/644/A45 : R Crt and RT Vir Medicina spectra (Brand+, 2020)
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 "date" Date Observation date
10- 14 I5 d TJD Truncated Julian date (JD-2440000.5)
16- 19 F4.2 Jy rms rms
21- 23 I3 Jy.km/s S(tot) Total flux density
25- 28 F4.2 --- phis Optical brigthness
30- 34 F5.1 km/s VlosB ?=- Vlos for B component
36 A1 --- l_SpB Limit flag on SpB
37- 40 F4.1 Jy SpB ?=- Peak flux for B component
42- 46 F5.1 km/s VlosC ?=- Vlos for C component
48 A1 --- l_VlosC Limit flag on spC
49- 52 F4.1 Jy SpC ?=- Peak flux for C component
54- 58 F5.1 km/s VlosD' ?=- Vlos for D' component
60- 63 F4.1 Jy SpD' ?=- Peak flux for D' component
65- 69 F5.1 km/s VlosD'' ?=- Vlos for D'' component
72 A1 --- l_SpD'' Limit flag on SpD''
73- 77 F5.1 Jy SpD'' ?=- Peak flux for D'' component
78 A1 --- u_SpD'' Uncertainty flag on SpD"
79- 83 F5.1 km/s VlosE ?=- Vlos for E component
84 A1 --- u_VlosE Uncertainty flag on VlosE
85 A1 --- l_SpE Limit flag on SpE
86- 90 F5.1 Jy SpE ?=- Peak flux for E component
91 A1 --- u_SpE Uncertainty flag on SpE
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 "date" Date Observation date
10- 14 I5 d TJD Truncated Julian date (JD-2440000.5)
16- 19 F4.2 Jy rms rms
21- 23 I3 Jy.km/s S(tot) Total flux density
25- 28 F4.2 --- phis Optical brigthness
30- 34 F5.1 km/s VlosG' ?=- Vlos for G' component
36 A1 --- l_SpG' Limit flag on SpG'
37- 41 F5.1 Jy SpG' ?=- Peak flux for G' component
43- 47 F5.1 km/s VlosG'' ?=- Vlos for G'' component
49 A1 --- l_VlosG'' Limit flag on spG''
50- 54 F5.1 Jy SpG'' ?=- Peak flux for G'' component
56- 60 F5.1 km/s VlosI ?=- Vlos for I component
61 A1 --- u_VlosI Uncertainty flag on VlosI
62 A1 --- l_SpI Limit flag on SpI
63- 66 F4.1 Jy SpI ?=- Peak flux for I component
68- 72 F5.1 km/s VlosK ?=- Vlos for K component
73 A1 --- u_VlosK Uncertainty flag on VlosK
74 A1 --- l_SpK Limit flag on SpK
75- 78 F4.1 Jy SpK ?=- Peak flux for K component
79 A1 --- u_SpK Uncertainty flag on SpK
80- 84 F5.1 km/s VlosE ?=- Vlos for E component
85 A1 --- u_VlosE Uncertainty flag on VlosE
86 A1 --- l_SpE Limit flag on SpE
87- 90 F4.1 Jy SpE ?=- Peak flux for E component
91 A1 --- u_SpE Uncertainty flag on SpE
92- 95 F4.1 km/s VlosM ?=- Vlos for M component
97 A1 --- l_SpM Limit flag on SpM
98-100 F3.1 Jy SpM ?=- Peak flux for M component
101 A1 --- u_SpM Uncertainty flag on SpM
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tableb1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 "date" Date Observation date
10- 14 I5 d TJD Truncated Julian date (JD-2440000.5)
16- 19 F4.2 Jy rms rms
21- 23 I3 Jy.km/s S(tot) Total flux density
25- 28 F4.2 --- phis Optical brigthness
30- 33 F4.1 km/s VlosA ?=- Vlos for A component
35 A1 --- l_SpA Limit flag on SpA
36- 40 F5.1 Jy SpA ?=- Peak flux for A component
42- 45 F4.1 km/s VlosB ?=- Vlos for B component
47 A1 --- l_VlosB Limit flag on spB
48- 52 F5.1 Jy SpB ?=- Peak flux for B component
54- 57 F4.1 km/s VlosC ?=- Vlos for C component
59 A1 --- l_SpC Limit flag on SpC
60- 64 F5.1 Jy SpC ?=- Peak flux for C component
66- 69 F4.1 km/s VlosD ?=- Vlos for D component
71 A1 --- l_SpD Limit flag on SpD
72- 75 F4.1 Jy SpD ?=- Peak flux for D component
77- 80 F4.1 km/s VlosE ?=- Vlos for E component
82 A1 --- l_SpE Limit flag on SpE
83- 86 F4.1 Jy SpE ?=- Peak flux for E component
--------------------------------------------------------------------------------
Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
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- 27 I3 --- Ny ? Number of pixels along Y-axis for
the datacubes
29- 30 I2 --- Nz ? Number of pixels along Z-axis for the
datacubes
32- 54 A23 "datime" Obs.date Observation date
56- 67 E12.6 m/s bVELO-LSR ? Lower value of VELO-LSR interval
for the datacubes
70- 80 E11.6 m/s BVELO-LSR ? Upper value of VELO-LSR interval
for the datacubes
82- 90 F9.3 m/s dVELO-LSR ? VELO-LSR resolution for the datacubes
92-103 E12.6 Hz bFREQ ? Lower value of frequency interval
for the spectra
105-116 E12.6 Hz BFREQ ? Upper value of frequency interval
for the spectra
118-126 F9.3 Hz dFREQ ? Frequency resolution for the spectra
128-132 I5 Kibyte size Size of FITS file
134-154 A21 --- FileName Name of FITS file, in subdirectory fits
156-187 A32 --- Title Title of the FITS file
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Acknowledgements:
Jan Brand, brand(at)ira.inaf.it
Dieter Engels, dengels(at)hs.uni-hamburg.de
References:
Winnberg et al., Paper I 2008A&A...482..831W 2008A&A...482..831W (RX Boo and SV Peg)
Brand et al., Paper II 2020A&A...644A..45B 2020A&A...644A..45B, Cat. J/A+A/644/A45
(R Crt and RT Vir)
(End) Patricia Vannier [CDS] 25-Mar-2024