Simultaneous observations of the H2O and SiO masers toward the late-type stars using KVN

Transcription

1 Simultaneous observations of the H2O and SiO masers toward the late-type stars using KVN Youngjoo Yun, Se-Hyung Cho, Richard Dodson, María J. Rioja, and KVN KSP members 2016 EVN Symposium

2 Late-type stars (from AGB to PPN) low- and intermediate-mass stars (1-8 M ) SiO maser Dust layer H2O maser

3 Late-type stars (from AGB to PPN) low- and intermediate-mass stars (1-8 M ) Stellar pulsation shock wave mass-loss SiO maser Dust layer H2O maser Shock propagation Mass-loss

4 Scientific goals Spatial distributions of the different masers H 2 O and SiO masers SiO masers of different rotational states (J=1-0, J=2-1, J=3-2) SiO masers of different vibrational states (v=1, v=2, v=3) To study Physical environments of CSEs Dynamical links between the inner and outer parts of CSEs Maser-variability driven by the stellar pulsation Pumping mechanisms of the stellar masers Mass-loss processes and stellar evolution 4

5 Korean VLBI Network 5

6 KVN Four band receivers 6

7 Simultaneous observations at four frequency-bands 22 GHz H2O maser 42, 43 GHz SiO maser 86 GHz SiO maser 129 GHz SiO maser 7

8 KVN observation under SFPR scheme Target freq. Reference freq. Several degrees OK Multi-frequency simultaneous observation 8

9 Source Frequency Phase Referencing (SFPR) method For one source A M. Rioja and R. Dodson 2011 R. Dodson, M. Rioja et al High: Φ A = Φ A,GEO + Φ A,TRO + Φ A,ION + Φ A,STR + Φ A,INST + 2πn A Low: Φ A = Φ A,GEO + Φ A,TRO + Φ A,ION + Φ A,STR + Φ A,INST + 2πn A Non-dispersive errors: Φ A,TRO R Φ A,TRO 0 Φ A,GEO R Φ A,GEO 2πν/c(D ϴ A,SHIFT ) Dispersive errors: Φ A,ION R Φ A,ION = (1/R-R) Φ A,ION Φ A R Φ A = Φ A,STR 2πν/c(D ϴ A,SHIFT ) + IONO A + INST A 9

10 Source Frequency Phase Referencing (SFPR) method For one source A Φ A R Φ A = Φ A,STR 2πν/c(D ϴ A,SHIFT ) + IONO A + INST A For another source B Φ B R Φ B = Φ B,STR 2πν/c(D ϴ B,SHIFT ) + IONO B + INST B Source/Frequency referenced visibility phase: Φ A,STR + 2πν/c(D ϴ A,SHIFT D ϴ B,SHIFT ) 10

11 Schematic of data reduction using SFPR method Calibration solutions determined from the lower frequency data are transferred to the higher frequency data. 11

12 Schematic of data reduction using SFPR method R LMi R. Dodson, M. Rioja et al H2O 6(1,6)-5(2,3) SiO v=1, J=1-0 SiO v=2, J=1-0 Calibration solutions determined from the lower frequency data are transferred to the higher frequency data. 12

13 Introduction to Key Science Program (KSP) of KVN Target sources of KSP Target Reference Sep. (deg) 22/43 GHz 43/86 GHz Observation frequency 22/43/86 GHz 22/43/129 GHz Monitoring observations have been performed since August /43/86/129 GHz IK Tau J NV Aur J R Cas J R Crt J R Leo J RR Aql J V627 Cas J V1111 Oph J V1366 Aql J V2108 Oph J V5102 Sgr J VX Sgr J VY CMa J W Hya J WX Psc J χ Cyg J

14 Introduction to observations Example of KSP observations Target source: WX Psc Obs. date: (~7 hours) Fringe finder: J Position reference source: J (3.81 from TS) Scan pattern: TS (2 min.) PR (2 min.) TS (2 min.) Obs. frequencies: 22/43/86/129 GHz 14

15 Frequency setting of BBCs (base band channels) K-band: 6 IFs Q-band: 6 IFs W-band: 2 IFs D-band: 2 IFs 15

16 Frequency setting of BBCs (base band channels) K-band: 6 IFs Q-band: 6 IFs Widely separated IFs Group delay can be precisely determined. Randomly distributed IFs To avoid the frequency redundancy. W-band: 2 IFs D-band: 2 IFs 16

17 Phase transfer from LOW to HIGH frequency band From K-band From Q-band 17

18 Frequency phase transfer from K-band to Q-band Phase of K-band Phase of Q-band 18

19 Final image of H2O and SiO masers at four bands 22 GHz H2O 6(1,6)-5(2,3) 42 GHz SiO v=2, J= GHz SiO v=1, J= GHz SiO v=1, J= GHz SiO v=1, J=3-2 19

20 Final image of H2O maser (22 GHz) 20

21 Superposed map of H2O and SiO masers at four bands Location of the central star Center of the SiO maser ring Asymmetric morphology of the H2O GHz Outflow (bipolar?) motion in CSEs Spatial distribution of SiO masers Similarity and difference imply the pumping mechanisms of the SiO masers. Important information of the physical environments of the CSEs 21

22 Superposed map of SiO masers Location of the central star Center of the SiO maser ring SiO v=1 and v=2, J=1-0 masers Largely overlapped Slightly different Radiative/collisional pumping SiO v=1, J=2-1 and J=3-2 masers Different spatial distribution from 42/43 GHz SiO masers 22

23 Superposed map of H2O and SiO masers at four bands 23

24 Superposed map of H2O and SiO masers at four bands 24

25 Superposed map of H2O and SiO masers at four bands 25

26 Superposed map of H2O and SiO masers at four bands 26

27 Summary Simultaneous observations of KVN at four frequency-bands have succeeded and are now very promising for studying the stellar masers. Relative spatial distributions between the SiO masers obtained from the KVN observations can give a good evidence for the maser pumping study. Monitoring-observational results of the SiO masers and the H2O masers can be used to trace the dynamical evolution of the CSEs together with the stellar pulsation. POSTER section of #15 shows more information of this study. Come and enjoy KVN! 27