How do cool stars lose mass? How do cool stars lose mass? R R ✸ ✸ 1 1 2 2 5 5 10 10 20 20 50 50 100 100 200 200 500 500 1000 1000 Optical photosphere Optical photosphere 200 GHz 200 GHz ~ 1 ~ 1 43 GHz 43 GHz 22 GHz 22 GHz 6 GHz 6 GHz Radio Photospheres Radio Photospheres Young Red Super-Giants like Young Red Super-Giants like Ori seem to have photospheres about half as big (for Ori seem to have photospheres about half as big (for their mass) as older, cooler RSG. AGB stars are an order of magnitude smaller but their mass) as older, cooler RSG. AGB stars are an order of magnitude smaller but the location of species in their circumstellar envelopes scales similarly. The optically the location of species in their circumstellar envelopes scales similarly. The optically thick surface is seen at larger radii as the frequency decreases (Lim et al. 1998; thick surface is seen at larger radii as the frequency decreases (Lim et al. 1998; Harper et al. 2001, cartoon far left). The image left shows the 6 GHz photosphere Harper et al. 2001, cartoon far left). The image left shows the 6 GHz photosphere of of Ori has radius 115 mas (5 R Ori has radius 115 mas (5 R ✸ ✸ ), brightness temperature 1200-1300 K. Two ), brightness temperature 1200-1300 K. Two hotspots exceed 4000 K. Observations at successive frequencies from hotspots exceed 4000 K. Observations at successive frequencies from ⩾ ⩾ 200 to 5 200 to 5 GHz, at intervals of a few months – yr, will trace layers expanding at 5-20 km/s. GHz, at intervals of a few months – yr, will trace layers expanding at 5-20 km/s. Combinations of ALMA, VLA and e-MERLIN images, at Combinations of ALMA, VLA and e-MERLIN images, at ⩽ ⩽ 50-mas resolution, will 50-mas resolution, will show whether disturbances are correlated across the disc (pulsation?), or reveal show whether disturbances are correlated across the disc (pulsation?), or reveal localised differences (convection?). Contemporaneous, multi- localised differences (convection?). Contemporaneous, multi- spectral index spectral index images will show whether the hotspots are chromospheric patches. The extension images will show whether the hotspots are chromospheric patches. The extension SW may show mass loss also seen by Kervella et al. 2011 & OGorman et al. 2012. SW may show mass loss also seen by Kervella et al. 2011 & OGorman et al. 2012. Ori e-MERLIN 5.75 GHz 43-GHz Sio masers 2-4 R 43-GHz Sio masers 2-4 R ✸ (VLBA, Assaf et al. 2011) (VLBA, Assaf et al. 2011) Water Masers Water Masers 22-GHz H 22-GHz H 2 2 O masers are found at 5-25 R O masers are found at 5-25 R ✸ ✸ . RT Vir was observed 6 times in . RT Vir was observed 6 times in 10 weeks by MERLIN (left, Richards et al. 2012), showing proper motions 10 weeks by MERLIN (left, Richards et al. 2012), showing proper motions consistent with the radial expansion deduced from Doppler velocities, and consistent with the radial expansion deduced from Doppler velocities, and no rotation. This is typical for our multi-epoch studies of 9 AGB/RSG stars. no rotation. This is typical for our multi-epoch studies of 9 AGB/RSG stars. The plot below shows components fitted to VX Sgr masers form discrete The plot below shows components fitted to VX Sgr masers form discrete series, tracing physical clouds. The number density (~5x10 series, tracing physical clouds. The number density (~5x10 15 15 m m -3 -3 ) at ) at which masing is quenched determines the inner maser shell radius. which masing is quenched determines the inner maser shell radius. The size of the clouds producing 22-GHz masers is proportional to R The size of the clouds producing 22-GHz masers is proportional to R ✸ ✸ , suggesting , suggesting that they are born from the stellar surface and expand in the wind. This is that they are born from the stellar surface and expand in the wind. This is comparable to the modelled size of convection cells, 5-10% R comparable to the modelled size of convection cells, 5-10% R ✸ ✸ (Chiavassa et al. (Chiavassa et al. 2009). The clouds are at least 40x denser than the wind average, containing 2009). The clouds are at least 40x denser than the wind average, containing 20-90% of the mass in <1% volume (Richards et al. 2012). 20-90% of the mass in <1% volume (Richards et al. 2012). EVN/Global VLBI EVN/Global VLBI (above, S Per) shows (above, S Per) shows OH 1665/1667 GHz OH 1665/1667 GHz masers masers interleaving interleaving the H the H 2 2 O maser clouds. O maser clouds. OH 1612-MHz masers OH 1612-MHz masers OH masers are found out to ~200 R ✸ . All masers show an increase in expansion velocity with separation from the star (VX Sgr above left, AGB stars right, Bains et al. 2003). The wind reaches escape velocity in the H 2 O zone but continues accelerating to hundreds R ✸ , first noticed by Chapman & Cohen (1986), probably due to grain surface property changes. Magnetic field Magnetic field Maser polarization indicates a field centred on the star, strong enough to shape the wind (above left, Szymczak et al. 2001). The H 2 O maser field is aligned (Vlemmings et al. 2005); these masers are fainter around the axis (right, Murakawa et al. 2003). VX Sgr VX Sgr Masers with ALMA Masers with ALMA ALMA will resolve many SiO and H 2 O transitions simultaneously, with excitation temperatures from 100s to 1000s K (some predicted locations, left, from models by Gray 2013, Humphreys et al. 2001), tightly constraining physical conditions. Some lines straddle the main dust formation zone at ~5 R ✸ (also resolved by ALMA, along with the star) and trace interclump gas or clumps. Thermal transitions will also be imaged but maser beaming affords much higher resolution. Anita Richards (Manchester), Alain Baudry (Bordeaux), Jan Brand (Bologna), Leen Decin (Leuwen), Anita Richards (Manchester), Alain Baudry (Bordeaux), Jan Brand (Bologna), Leen Decin (Leuwen), Sandra Etoka (Hamburg), Malcolm Gray (Manchester) Graham Harper (Dublin), Liz Humphreys (ESO), Sandra Etoka (Hamburg), Malcolm Gray (Manchester) Graham Harper (Dublin), Liz Humphreys (ESO), Jeremy Lim (ASIAA), Iain MacDonald (Manchester), Eamon OGorman (Dublin), Wouter Vlemmings (Onsala) Jeremy Lim (ASIAA), Iain MacDonald (Manchester), Eamon OGorman (Dublin), Wouter Vlemmings (Onsala) IK Tau IK Tau References/Acknowledgement References/Acknowledgement Bains I. et al. 2003 MNRAS 342, 8 Chapman J.M. & Cohen R. J., 1986 MNRAS 220, 513 Chiavassa A. et al. 2009 A&A 506, 1351 Harper G. et al. 2001 ApJ, 551, 1073 Humphreys, R. VY CMa background image, HST/NASA/ESA Kervella P. et al., 2009 A&A 53, 117 Lim J. et al. 1998 Nat. 392, 575 Murakawa K. et al. 2003 MNRAS 344, 1 OGorman et al. 2012 AJ 134, 36 Richards A.M.S. et al. 2012 A&A Szymczak M. et al. 2001 A&A 371, 1012 Vlemmings W.H.T. et al. 2005 A&A 434, 1029 Water masers Water masers
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How do cool stars lose mass?How do cool stars lose mass?
RR✸✸ 11
22
55
1010
2020
5050
100100
200200
500500
10001000
Optical photosphereOptical photosphere 200 GHz 200 GHz ~ 1 ~ 1 43 GHz43 GHz 22 GHz22 GHz
6 GHz6 GHz
Radio PhotospheresRadio PhotospheresYoung Red Super-Giants likeYoung Red Super-Giants likeOri seem to have photospheres about half as big (for Ori seem to have photospheres about half as big (for their mass) as older, cooler RSG. AGB stars are an order of magnitude smaller but their mass) as older, cooler RSG. AGB stars are an order of magnitude smaller but the location of species in their circumstellar envelopes scales similarly. The optically the location of species in their circumstellar envelopes scales similarly. The optically thick surface is seen at larger radii as the frequency decreases (Lim et al. 1998; thick surface is seen at larger radii as the frequency decreases (Lim et al. 1998; Harper et al. 2001, cartoon far left). The image left shows the 6 GHz photosphere Harper et al. 2001, cartoon far left). The image left shows the 6 GHz photosphere of of Ori has radius 115 mas (5 ROri has radius 115 mas (5 R✸✸), brightness temperature 1200-1300 K. Two ), brightness temperature 1200-1300 K. Two hotspots exceed 4000 K. Observations at successive frequencies from hotspots exceed 4000 K. Observations at successive frequencies from ⩾⩾200 to 5 200 to 5 GHz, at intervals of a few months – yr, will trace layers expanding at 5-20 km/s. GHz, at intervals of a few months – yr, will trace layers expanding at 5-20 km/s. Combinations of ALMA, VLA and e-MERLIN images, at Combinations of ALMA, VLA and e-MERLIN images, at ⩽⩽50-mas resolution, will 50-mas resolution, will show whether disturbances are correlated across the disc (pulsation?), or reveal show whether disturbances are correlated across the disc (pulsation?), or reveal localised differences (convection?). Contemporaneous, multi-localised differences (convection?). Contemporaneous, multi-spectral index spectral index images will show whether the hotspots are chromospheric patches. The extension images will show whether the hotspots are chromospheric patches. The extension SW may show mass loss also seen by Kervella et al. 2011 & OGorman et al. 2012.SW may show mass loss also seen by Kervella et al. 2011 & OGorman et al. 2012.
Ori e-MERLIN 5.75 GHz
43-GHz Sio masers 2-4 R43-GHz Sio masers 2-4 R✸✸ (VLBA, Assaf et al. 2011)(VLBA, Assaf et al. 2011)
Water MasersWater Masers22-GHz H22-GHz H22O masers are found at 5-25 RO masers are found at 5-25 R✸✸. RT Vir was observed 6 times in . RT Vir was observed 6 times in 10 weeks by MERLIN (left, Richards et al. 2012), showing proper motions 10 weeks by MERLIN (left, Richards et al. 2012), showing proper motions consistent with the radial expansion deduced from Doppler velocities, and consistent with the radial expansion deduced from Doppler velocities, and no rotation. This is typical for our multi-epoch studies of 9 AGB/RSG stars. no rotation. This is typical for our multi-epoch studies of 9 AGB/RSG stars. The plot below shows components fitted to VX Sgr masers form discrete The plot below shows components fitted to VX Sgr masers form discrete series, tracing physical clouds. The number density (~5x10series, tracing physical clouds. The number density (~5x101515 m m-3-3) at ) at which masing is quenched determines the inner maser shell radius.which masing is quenched determines the inner maser shell radius.
The size of the clouds producing 22-GHz masers is proportional to RThe size of the clouds producing 22-GHz masers is proportional to R✸✸, suggesting , suggesting that they are born from the stellar surface and expand in the wind. This is that they are born from the stellar surface and expand in the wind. This is comparable to the modelled size of convection cells, 5-10% Rcomparable to the modelled size of convection cells, 5-10% R✸ ✸ (Chiavassa et al. (Chiavassa et al. 2009). The clouds are at least 40x denser than the wind average, containing 2009). The clouds are at least 40x denser than the wind average, containing 20-90% of the mass in <1% volume (Richards et al. 2012). 20-90% of the mass in <1% volume (Richards et al. 2012).
EVN/Global VLBI EVN/Global VLBI (above, S Per) shows (above, S Per) shows OH 1665/1667 GHz OH 1665/1667 GHz masers masers interleaving interleaving the Hthe H22O maser clouds. O maser clouds.
OH 1612-MHz masersOH 1612-MHz masersOH masers are found out to ~200 R✸. All masers show an increase in expansion velocity with separation from the star (VX Sgr above left, AGB stars right, Bains et al. 2003). The wind reaches escape velocity in the H2O zone but continues accelerating to hundreds R✸, first noticed by Chapman & Cohen (1986), probably due to grain surface property changes.
Magnetic fieldMagnetic fieldMaser polarization indicates a field centred on the star, strong enough to shape the wind (above left, Szymczak et al. 2001). The H2O maser field is aligned (Vlemmings et al. 2005); these masers are fainter around the axis (right, Murakawa et al. 2003).
VX SgrVX Sgr
Masers with ALMAMasers with ALMAALMA will resolve many SiO and H2O transitions simultaneously, with excitation temperatures from 100s to 1000s K (some predicted locations, left, from models by Gray 2013, Humphreys et al. 2001), tightly constraining physical conditions. Some lines straddle the main dust formation zone at ~5 R✸ (also resolved by ALMA, along with the star) and trace interclump gas or clumps. Thermal transitions will also be imaged but maser beaming affords much higher resolution.
Anita Richards (Manchester), Alain Baudry (Bordeaux), Jan Brand (Bologna), Leen Decin (Leuwen), Anita Richards (Manchester), Alain Baudry (Bordeaux), Jan Brand (Bologna), Leen Decin (Leuwen), Sandra Etoka (Hamburg), Malcolm Gray (Manchester) Graham Harper (Dublin), Liz Humphreys (ESO), Sandra Etoka (Hamburg), Malcolm Gray (Manchester) Graham Harper (Dublin), Liz Humphreys (ESO),
Jeremy Lim (ASIAA), Iain MacDonald (Manchester), Eamon OGorman (Dublin), Wouter Vlemmings (Onsala)Jeremy Lim (ASIAA), Iain MacDonald (Manchester), Eamon OGorman (Dublin), Wouter Vlemmings (Onsala)
IK TauIK Tau
References/AcknowledgementReferences/AcknowledgementBains I. et al. 2003 MNRAS 342, 8Chapman J.M. & Cohen R. J., 1986 MNRAS 220, 513 Chiavassa A. et al. 2009 A&A 506, 1351Harper G. et al. 2001 ApJ, 551, 1073Humphreys, R. VY CMa background image, HST/NASA/ESA
Kervella P. et al., 2009 A&A 53, 117Lim J. et al. 1998 Nat. 392, 575Murakawa K. et al. 2003 MNRAS 344, 1OGorman et al. 2012 AJ 134, 36 Richards A.M.S. et al. 2012 A&ASzymczak M. et al. 2001 A&A 371, 1012Vlemmings W.H.T. et al. 2005 A&A 434, 1029
Water masersWater masers
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