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Vibra&onally Excited Water Emission at 658 GHz from Evolved Stars
Alain Baudry
Univ. Bordeaux, Laboratoire d’Astrophysique de Bordeaux
« Band 5 Science Workshop - Synergy with APEX/SEPIA » ESO Garching, February 1-3, 2017
Contents • First detec&ons in vibrat. excited H2O
• Why important to observe excited water • Source selec&on • APEX results at 658 GHz • First conclusions
Several collaborators – E. Humphreys, A. Richards, W. Vlemmings, M. Gray, M. WiMkowsky
C. de Breuck, F. Herpin & others
Vibra-onally Excited H2O at mm/submm λ in O-‐rich Stars
• Maser ac&on observed from 8 rotat. transi&ons in (010) & (020) excited states of the bending mode
• See e.g. review/modelling paper (Gray et al 2016) or IK Tau line survey (Velilla-‐Prieto et al 2017)
• First observa&ons of J transi&ons in v2=1 mode made with 30-‐m and APEX
• Menten & Melnick 1989, Menten et al 2006
• Powerful 658 GHz emission from 11,0-‐10,1 transi&on in v2=1, 2400 K above ground level
• First detec&on by Menten & Young (1995) with CSO in 10 out of 12 evolved stars
E (K)
J
0
2000
4000
________
________
_______ _______
E (cm-‐1)
(001) (100)
(010)
(000)
SiO v=1 1240 cm_1
H2O vibra-onal states
6.3 um
(010) state
658 GHz emiFers, many more to detect
• Addi&onal sources were detected at 658 GHz – SMA (period 2004-‐2006) at low spa&al resolu&on (≈1-‐2 arcsec)
• Hunter et al 2007, IAU Symp. #242
– HIFI aboard Herschel (≈30 arc sec) • JusManont et al 2012, O-‐rich AGB stars; Alcolea et al 2013, VY CMa
• Weak 658 emission from 2 OH/IR stars and 1 PPN
• From published literature 22 known 658 GHz sources • 16 Miras or SR and 3 Supergiants (VY CMa, VX Sgr, NML Cyg)
• Many more 658 GHz emiMers are to be discovered • Difficult because of poor atmospheric transparency & noisy Rxs
Why observe 658 GHz H2O emission? (1/2)
• Need more detec&ons to beMer understand the proper&es of this emission
• Widespread but discrete source surveys yet to be done
• Apparent maser emission s&ll ‘enigma&c’ • Can be strong up to 3000 Jy -‐not as strong as 22 GHz maser
– Useful as poten&al ALMA Band 9 phase calibrators
• Line width rather broad and asymmetric -‐a general behavior? • Time variability and polariza&on proper&es unknown
• Found in evolved stars and Orion -‐like SiO maser
Why observe 658 GHz H2O emission? (2/2)
• Exact loca&on of the emission in the CSE unknown
• Close to SiO masers? similar excita&on levels 1800 K (SiO) versus 2400 K (excited H2O) and similar velocity range
• Presumably lies within dust forma&on zone at a few R* • One first ALMA map made in VY CMa (Richards et al 2014)
– Shows aggrega&on of masers < 100-‐150 mas wrt star – Desirable to map less complex sources
• Combine 658 GHz with other maser transi&ons • To constrain CSE condi&ons on AU/sub-‐AU scales • To improve vibra&onally excited H2O modelling
» Using line intensity ra&os and line profiles
Main Goals
• Survey many O-‐rich stars to detect new 658 sources with APEX
• BeMer understand the nature of the 658 GHz maser – Later map most interes&ng sources
to this end we have:
• Built a small catalogue of poten&al new sources
• Extracted a ‘representa7ve’ sample of 10 sources from this catalog
• Used SEPIA Band 9 science verifica&on &me to perform observa&ons of this sample
• Companion project on &me variability observa&ons
A few words on mini-‐catalogue
• Based on homogeneous sample of evolved stars observed with same telescope in SiO & H2O (22 GHz) (Kim et al 2012)
• Flux density above 50 Jy • Added sources from compila&on of SiO/H2O publica&ons to improve < 0° dec. source count
• Used Parkes and SEST southern hemisphere observa&ons with same flux density limit
• Several sources not in old Benson et al compila&on
• Total of about 90 sources • Includes the 19 already known sources
DSB Observa&ons (1/2)
• Band 9 DSB receiver & 2.5 GHz Back-‐Ends • Band 9 sky freq coverage 602 – 720 GHz & IF range = 4 – 12 GHz • IF processor records 4 GHz BW <=> 2 x 2.5 GHz BEs with 1 GHz overlap
• H2O(v2=1) and 13CO(6-‐5) at 658.007 and 661.067 GHz simultaneously in LSB
• Added both polars. –polar info lost at 658 • April to July 2016, PWV = 0.45 to 0.8 mm, Integr. -me ≈ 15 –25 min/source
• Poin&ng & Reference posi&on • Beam ≈ 9 arcsec –from CO(6-‐5) • Poin&ng correc&ons & focus checked on CO sources & some&mes on planets prior to 658 GHz obs.
• Posi&on switching / Reference posi&on several beams away
DSB Observa&ons (2/2)
• 4 GHz recorded • LSB ≈ 657.5 -‐ 661.5 GHz USB ≈ 669.5 – 673.5 GHz
• Smoothed spectral resolu-on = 0.14 km/s • < 0.1 km/s resolu&on used to check for possible spikes • Some details lost with 0.5 km/s => adopt 0.14 km/s • 2 10-‐4 GHz freq uncertainty at 658 GHz <=> ≈ 0.1 km/s • Used W Hya asymm. profile to check for op&mal resolu&on
• Polariza-on info lost • Masers are owen linearly polarized; 658 GHz maser(?) • Orthogonal polars could be examined separately in strongest sources …. although
– Leakage from one polar into the other unknown – Short integra&ons => can’t es&mate intrinsic polariza&on angle
• Checked for line contamina-on from USB
PWV
____LSB____ ____USB___
PWV = 0.7 mm O3 lines USB, 669.8-‐670, 671.6-‐671.8, 672.8 GHz
O3 lines LSB 658.039, 661.4-‐661.6 GHz
JKaKc
SO2 & SO lines observed in R Dor, W Hya, IK Tau HIFI & APEX & IRAM
Danilovich et al 2016 Also present in VY CMa spectral scans
Many species observed in O-‐rich evolved stars, eg Alcolea et al, JusManont et al, Davilovich et al, Velilla Prieto et al CO CS SiO HCN HNC H2O SiS SO2 SO etc. Checked for: SO, 34SO, S18O, SO2 v=0, CO and isotopes, CS, HCN, H13CN, H2O ground & vib states, SiS v=0, SiO v=0-‐4, 29SiO in USB [669.54 673.54 GHz] 1 SO & 1 SiS lines, 2 SO2 lines with rela-vely low energy fall in USB
SO2 line at 673.067 GHz coincides with 658 GHz transi7on ≈ 3 10-‐4 GHz = 0.15 km/s SO2 detected in W Hya but it is weak -‐could model SO2 and subtract from 658 GHz H2O line
LINES in USB SO2
Coincides with 658 GHz
Observed Sources (1/2)
Source
Stellar type
RA (J2000)
Dec (J2000)
Date (2016 year)
PWV (mm)
Note
o Ce- Mira 02 19 20.79 -02 58 39.5 26 July 0.45-0.5 First detected with HIFI Normalized spetrum
R Hor Mira 02 53 52.72 -49 53 22.7 9 April 0.7-0.8 New detection
RT Eri Mira 03 34 12.48 -16 09 50.7 15 June 0.5-0.65 New detection
IK Tau Mira 03 53 28.87 +11 24 21.7 28 July 0.65 First detected with HIFI
RT Vir SR b 13 02 37.98 +05 11 08.4 28 July 0.75-0.8 New detection
R Hya Mira 13 29 42.78 -23 16 52.8 28 July 0.8 Mentioned by Hunter et al., no spectrum shown
Observed Sources (2/2)
Source
Stellar type
RA (J2000)
Dec (J2000)
Date (2016 year)
PWV (mm)
Note
W Hya Mira 13 49 02.00 -28 22 03.5 28 July 0.8 First detected by Menten & Young Detected with HIFI
RU Hya Mira 14 11 34.40 -28 53 07.4 28 July 0.75 New detection
AH Sco SR c Supergiant
17 11 17.02 -32 19 30.7 9 April 0.45-0.5 New detection
X Pav SR b 20 11 45.86 -59 56 12.8 26 July 0.4-0.45 New detection
All Sources Detected • Used observatory calibrated files and CLASS to derive TA*
– No offline opacity correc&on was tried at this stage … could increase Tpeak?
– Data obtained with old ‘pick-‐up’ mirror => exact TA*/Jy conversion factor ?
Source Type ≈ (TA*)peak (K)
≈ DV1/2 (km/s)
Note
O Ce& Mira 6 4.75 Several features/Asymm.
R Hor Mira 0.6 2.4
RT Eri Mira 0.35 3
IK Tau Mira 5.5 4.7 Asymmetric profile
RT Vir SR 1.6 8 Several features?/Asymm.
R Hya Mira 3.8 2.9 Asymmetric profile
W Hya Mira 17 4.5 Several features/Asymm.
RU Hya Mira 0.2 4.9 Weakest in sample
AH Sco Supergiant 3.2 5.8 Asymmetric pedestal
X Pav SR 0.6 6
New detec-ons
AH Sco
RT Vir
X Pav
TA* Scale
APEX
658 GHz H2O
O Ce-
HIFI JusManont et al
APEX TA* Scale
0.14 km/s resolu&on
0.017 km/s resolu&on
W Hya 28 Jul 2016 APEX
13CO (6-‐5)
Mira
W Hya
* Detec&on in Mira * Weak in W Hya, IK Tau, R Hya?
Weakly detected in R Leo, RX Boo, NML Cyg
Menten & Young
General Proper-es (1/2) • Large range of TA*
• Rela&ve intensi&es go from 1 for W Hya to 3.5 10-‐2 for R Hor and X Pav and ≈ 10-‐2 for RU Hya
• W Hya rela&vely close ≈ 100 pc while R Hor ≈ 200 pc and distance to X Pav and R U Hya is uncertain (large?)
• Strong to weak emission detected • Taking my provisional S/TA* (Jy/K) for 2016 obs. with ‘old’ mirror => Speak ≈ 3700 Jy for W Hya and ≈ 45 – 75 Jy for weakest sources in sample
• S/TA* (Jy/K) with planets could be 0.75 less => 2800 Jy for W Hya and ≈ 35 – 55 Jy for weakest sources
• Flux density comparable to first detec&ons • Menten & Young measured: 3000 Jy W Hya; weakest source 100 Jy – Flux uncertainty?
General Proper-es (2/2)
• Profiles owen asymmetric • Double line Gauss fi}ng some&mes works beMer
– Higher resolu&on does not help • DV1/2 in 2.5 -‐ 6 km/s range
– but 6 & 8 km/s for RSG AH Sco & RT Vir (several features?) – Take with care: asymmetric profile & several features ?
• Dis&nct features in o-‐Ce&, W Hya, RT Vir(?), AH Sco(?)
• 658 GHz H2O vel range close to SiO vel range • Safely conclude that 658 GHz is masing
• Strong & rela&vely narrow velocity emission => amplifica&on • First map in VY CMa confirms spa&al compactness => high Tb • Models confirm maser ac&on
ALMA maps of VY CMa Richards et al.
658 GHz shows aggrega&on of masers < 100-‐150 mas wrt star & complex picture
Recent advances in H2O modelling
• Nesterenok (2015)
• Gray, Baudry, Richards, Humphreys, Sobolev, Yates (2016)
• Gray et al sample a large parameter space (T, n, Vel) with simple models for typical late-‐type star condi&ons
– water slabs of 3 to 15 AU; models are not for specific sources
• All models predict rather strong 658 GHz emission • Some difficul&es s&ll there for a few transi&ons, however
– e.g. no emission at 67.8 GHz (v2=1) while predicted => variability? or => high H2O density needed to excite this line (tbc)
TK vs nH2O O-‐H2O fract. abundance = 3 10-‐5
Gray et al. 2015
Gain vs Tgas o-‐ and p-‐water O-‐H2O fract. abundance = 10-‐4
nH2O = 3 105 cm-‐3
Nesterenok 2015
Masers (owen) Time variable and Polarized
• Polariza&on lost here • Variability? important
• Related to: density & velocity field changes; stellar radia&on • Pumping mechanisms & satura&on
• Evidence for variability at 658 GHz? • Requires stable Rx., stable atmos. condi&ons, stable calibra&on • Compare published data ?
– Difficult with different intensity scales & flux uncertain&es – Yes we can! compare line profiles and velocity extent at different epochs
• Variability, best approach: dedicated observa&ons • Ini&ated project to monitor W Hya, RT Vir, VX Sgr & R Aql • A few observa&ons/source
Comparison of VY CMa line profiles
15 June 2016 0.17 km/s resolu&on APEX
-‐-‐-‐-‐-‐-‐-‐23 kms-‐1-‐-‐-‐-‐-‐-‐-‐ -‐30 kms-‐1-‐-‐
16 Feb 2005 0.4 km/s chann. spacing SMA Hunter et al Peak flux similar to flux in 1995
March 1995 0.9 km/s CSO Menten & Young
March 2010 1 km/s resolu&on HIFI Alcolea et al.
Tmb
S (Jy)
Comparison of W Hya line profiles
28 July 2016 0.17 km/s resolu&on this work
March 1995 0.9 km/s resolu&on Menten & Young
Nov 2005 0.4 km/s chann. spacing Hunter et al
Line Profile & Velocity Extent
• Line profile remains stable at least for VY CMa and W Hya over ≈ 20 years
• Saturated masers ? But 1 new feature seen in W Hya ? (tbc)
• V(658)peak close to V(SiO)peak v=1, J=2-‐1 – Owen close to V* -‐ but not always
– In our sample we measured • At 658: 48.5, 38, 25, 33, 17.5, -‐9.0, 41.5, -‐2.4, -‐2.5, -‐17.5 km/s • In SiO: 46.5, 35, 25, 35, 18.5, -‐9.5, 41.5, -‐5, -‐6.5, -‐19.5 km/s
– V(SiO)peak may change up to 1 km/s or more in a few months
• DVFWZI(658) tends to be correl. with DVFWZI(86 SiO) • 17 sources combining with Menten’s results; 4 RSGs included • Difficult to build a ‘clean’ diagram, but trend is there
• Above results suggest 658 GHz line excited in dust forma&on zone where SiO is observed (< a few R*)
• Largest DVFWZI(658) found in RSGs suggest shocks playing some role as suggested by VY CMa map
Concluding remarks • SEPIA Band 9 SV data provided new results, undoubtedly 658 line is widespread and masing
• more sources to be discovered + a few ALMA maps
• 658 GHz line excited in the dust forma&on zone • IR pumping & Collisions • Role of Shocks (?) cf VY CMa map
• Band 9 intensity scale s&ll provisonal • Jy/K conversion factor could be known … today/soon
• 2SB Band 9 receiver wanted on APEX & ALMA ! • Improve Tsys & Calibra&on / Cleaner line iden&fica&ons • Address &me variability ques&ons in depth
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