variable sio maser emission from v838 mon mark claussen may 16, 2006 nature of v838 mon and its...
Post on 22-Dec-2015
215 views
TRANSCRIPT
![Page 1: Variable SiO Maser Emission from V838 Mon Mark Claussen May 16, 2006 Nature of V838 Mon and its Light Echo](https://reader036.vdocuments.mx/reader036/viewer/2022062516/56649d795503460f94a5c82d/html5/thumbnails/1.jpg)
Variable SiO Maser Emission from V838 Mon
Mark Claussen
May 16, 2006
Nature of V838 Mon and its Light Echo
![Page 2: Variable SiO Maser Emission from V838 Mon Mark Claussen May 16, 2006 Nature of V838 Mon and its Light Echo](https://reader036.vdocuments.mx/reader036/viewer/2022062516/56649d795503460f94a5c82d/html5/thumbnails/2.jpg)
Main Collaborators
Howard E. Bond, STSci
Sumner Starrfield, ASU
Kevin Healy, ASU
May 16, 2006 V838 Mon Mtg
![Page 3: Variable SiO Maser Emission from V838 Mon Mark Claussen May 16, 2006 Nature of V838 Mon and its Light Echo](https://reader036.vdocuments.mx/reader036/viewer/2022062516/56649d795503460f94a5c82d/html5/thumbnails/3.jpg)
Astronomical Masers
• Mainly OH, water, SiO, methanol
• Found in several different places in the universe:– Star-forming regions
– Circumstellar shells around late-type stars
– Active Galactic Nucleii
– Supernova Remnants
– V838 Mon
• Maser emission is bright, easy to observe
• Radiative transfer is non-linear, pumping schemes not always clear, so interpretation is not easy
![Page 4: Variable SiO Maser Emission from V838 Mon Mark Claussen May 16, 2006 Nature of V838 Mon and its Light Echo](https://reader036.vdocuments.mx/reader036/viewer/2022062516/56649d795503460f94a5c82d/html5/thumbnails/4.jpg)
SiO Masers
• J = 1 0 rotational transitions in different vibrationally excited states (v = 1, 2, and 3)
• These transitions occur at a wavelength of 7mm (~43 GHz)
• Using the VLA (Very Large Array) we can obtain angular resolution ranging from 60 to 300 mas (depending upon configuration)
• Using the VLBA (Very Long Baseline Array), the angular resolution can be ~500 microarcseconds (and astrometry even better)
• Also, radio spectroscopy easily reaches 0.1 km/s spectral resolution
![Page 5: Variable SiO Maser Emission from V838 Mon Mark Claussen May 16, 2006 Nature of V838 Mon and its Light Echo](https://reader036.vdocuments.mx/reader036/viewer/2022062516/56649d795503460f94a5c82d/html5/thumbnails/5.jpg)
SiO Maser Emission from V838 Mon
• Non detection in Nov 2003
• First detected February 2005 (Deguchi et al.)
• VLA Monitoring begun in Sep 2005
• Position of SiO masers: 07h 04m 04.824s -03d 50’ 50.50” position is at least good to 10 mas, compares favorably to USNO stellar position
• Monthly since then (more or less)
• VLBA Observations October 2005, January 2006, March 2006
• Still under reduction
May 16, 2006 V838 Mon Mtg
![Page 6: Variable SiO Maser Emission from V838 Mon Mark Claussen May 16, 2006 Nature of V838 Mon and its Light Echo](https://reader036.vdocuments.mx/reader036/viewer/2022062516/56649d795503460f94a5c82d/html5/thumbnails/6.jpg)
![Page 7: Variable SiO Maser Emission from V838 Mon Mark Claussen May 16, 2006 Nature of V838 Mon and its Light Echo](https://reader036.vdocuments.mx/reader036/viewer/2022062516/56649d795503460f94a5c82d/html5/thumbnails/7.jpg)
![Page 8: Variable SiO Maser Emission from V838 Mon Mark Claussen May 16, 2006 Nature of V838 Mon and its Light Echo](https://reader036.vdocuments.mx/reader036/viewer/2022062516/56649d795503460f94a5c82d/html5/thumbnails/8.jpg)
![Page 9: Variable SiO Maser Emission from V838 Mon Mark Claussen May 16, 2006 Nature of V838 Mon and its Light Echo](https://reader036.vdocuments.mx/reader036/viewer/2022062516/56649d795503460f94a5c82d/html5/thumbnails/9.jpg)
![Page 10: Variable SiO Maser Emission from V838 Mon Mark Claussen May 16, 2006 Nature of V838 Mon and its Light Echo](https://reader036.vdocuments.mx/reader036/viewer/2022062516/56649d795503460f94a5c82d/html5/thumbnails/10.jpg)
• GBT High Velocity Search for SiO Masers (+/-350 km/s, Oct 2005)
• no detected high velocity SiO masers
• VLA Search for Water Masers (monthly check with the SiO monitoring)
• no water masers detected
• VLA Search for v=3 SiO (J=1 0) transition (March 2006)
• no v=3 masers (to a 5-sigma detection limit of 50 mJy/beam)
• VLA Radio Continuum Search at 8.4 GHz (March 2006)
• no radio continuum detected (rms 30 uJy/beam at 8.4 GHz)
May 16, 2006 V838 Mon Mtg
Other Radio Observations of V838 Mon
![Page 11: Variable SiO Maser Emission from V838 Mon Mark Claussen May 16, 2006 Nature of V838 Mon and its Light Echo](https://reader036.vdocuments.mx/reader036/viewer/2022062516/56649d795503460f94a5c82d/html5/thumbnails/11.jpg)
More Radio Observations
• VLBA Observations of SiO Masers
• Peak emission appears unresolved at 0.8 milliarcseconds resolution, but only about 50% of the flux.
• Some hint of a spatial change across the line
May 16, 2006 V838 Mon Mtg
![Page 12: Variable SiO Maser Emission from V838 Mon Mark Claussen May 16, 2006 Nature of V838 Mon and its Light Echo](https://reader036.vdocuments.mx/reader036/viewer/2022062516/56649d795503460f94a5c82d/html5/thumbnails/12.jpg)
Results of Radio Observations
• No high velocity maser emission (not in a high velocity outflow)
• No v=3 emission (no high excitation)
• No water masers --- pumping ? physical conditions ? no water molecules in the right place ?
• No radio continuum --- consistent with the possibility of ionization from B3 companion
• v=1 and v=2 masers are variable over month timescales
May 16, 2006 V838 Mon Mtg
![Page 13: Variable SiO Maser Emission from V838 Mon Mark Claussen May 16, 2006 Nature of V838 Mon and its Light Echo](https://reader036.vdocuments.mx/reader036/viewer/2022062516/56649d795503460f94a5c82d/html5/thumbnails/13.jpg)
Other places for SiO Masers
• Mira variables, late-type supergiants
• Pulsating stars
• Oxygen-rich shells harbor molecular masers:
OH, H2O, and SiO
• Masers can probe the kinematics and dynamics of the
circumstellar shell
May 16, 2006 V838 Mon Mtg
![Page 14: Variable SiO Maser Emission from V838 Mon Mark Claussen May 16, 2006 Nature of V838 Mon and its Light Echo](https://reader036.vdocuments.mx/reader036/viewer/2022062516/56649d795503460f94a5c82d/html5/thumbnails/14.jpg)
OH
H2O
SiO
100 --- 10000 AU
100s of AU
![Page 15: Variable SiO Maser Emission from V838 Mon Mark Claussen May 16, 2006 Nature of V838 Mon and its Light Echo](https://reader036.vdocuments.mx/reader036/viewer/2022062516/56649d795503460f94a5c82d/html5/thumbnails/15.jpg)
Photosphere
SiO Masers and Dust Condensation Zone
A few stellar radii
![Page 16: Variable SiO Maser Emission from V838 Mon Mark Claussen May 16, 2006 Nature of V838 Mon and its Light Echo](https://reader036.vdocuments.mx/reader036/viewer/2022062516/56649d795503460f94a5c82d/html5/thumbnails/16.jpg)
TX Cam SiO Masers(Diamond et al.)
v = 1, J=1 0 transition
Distance ~450 pcRing diameter 28 mas = 12.6 A.U.
28 mas
SiO masers lie a few stellar radii outsidethe stellar photosphere, but inside thedust condensation zone.
![Page 17: Variable SiO Maser Emission from V838 Mon Mark Claussen May 16, 2006 Nature of V838 Mon and its Light Echo](https://reader036.vdocuments.mx/reader036/viewer/2022062516/56649d795503460f94a5c82d/html5/thumbnails/17.jpg)
SiO Maser Properties in Mira Variables
• Collisional pumping / radiatve pumping ? • A few (1-2) stellar radii from the stellar surface, inside the
dust condensation zone• Number density of molecular hydrogen of 5 x 109 cm-3
• Temperature ~1500 K• Tangential amplification explains the rings• Optical, IR and SiO masers are correlated over the optical
light period• SiO masers vary in phase with near and mid-IR• Velocity extent of the maser emission ~15 km/s• Short-term variability ?• Models require the Mira pulsation to explain temporal
variability ?
May 16, 2006 V838 Mon Mtg.
![Page 18: Variable SiO Maser Emission from V838 Mon Mark Claussen May 16, 2006 Nature of V838 Mon and its Light Echo](https://reader036.vdocuments.mx/reader036/viewer/2022062516/56649d795503460f94a5c82d/html5/thumbnails/18.jpg)
V838 Mon Masers, Mira Variables, and Parallax
• At a distance of 7 – 9 kpc, maser ring about 1.8 mas in diameter; barely resolvable by VLBI
• Turn-on of masers tell us something about pumping scheme --- favors radiative
• No pulsation ? So variability may not be similar to Miras
• VLBI of SiO masers holds the possibility of a parallax measurement as well.
– 50 uas accuracy per measurement epoch, with several epochs over a year should perhaps get to a parallax with rms errors of 15 or 20 uas, depending on systematics
• Maser polarization observations may tell us something about magnetic fields
May 16, 2006 V838 Mon Mtg