1. Mass-loss rate of Redsupergiants in RSGC2 Presenter: Yuanhao Zhang 张渊皞
a RSG star V838 surrounded by dust, strong extinction
May 9, 2013

2. Question What’s the mass loss rate of red supergiant? Why RSG cluster?
key to understand the evolution of massive stars to supernovae, while late-stage massive star evolution is poorly understood.
Why RSG cluster?
Mass loss in RSG-stage is driven by radiative pressure, mass loss rate depends on luminosity, temperature and the amount of dust in the outer envelope
RSGs in the RSGC2 have similar initial mass (~14+-1 solar mass )and metallicity
Each star in the cluster represents different phase of RSG evolution
Mass loss rate depends on luminosity, temperature and the amount of dust in the outer envelope
Each star in the cluster means the different phase of RSG evolution
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3. Introduction Red Supergiant (RSG) Luminosity class I，
>10 solar mass, >1000 solar radius
Supernova
progenitors
4 known rsgcs
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4. HR diagram
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5. RSGC Red Supergiant Cluster (RSGC) Location: milky way galaxy
RSGC1(2006)(14 RSGs)
RSGC2(Stephenson )(2007)(26 RSGs)
RSGC3(2010)(8-14 RSGs)
RSGC4(Alicante 8, 2010)(8-13 RSGs)
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6. My object
RSGC2
(WISE data)
most
RSGs in MW
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7. RSGC2 in 2MASS Scutum–Centaurus Arm 6kpc
RSGC 2 J2000: 18 :39 :20 −06:01: 42
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8. Position
This slide provides the motivation for photon-counting detectors in low light applications.
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9. Candidates
I choose five typical RSGs in the cluster with different spectral types
D2: maser emission, (suggest extreme mass loss)
M7I (Ignacio Negueruela et al. 2013)
D5: M5I
D9, M3.5Iab
D11:M2.5I
D72:M0I
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10. Goal of Observing Program
Use spectra of 26 RSGs to identify the effective temperature, spectral type, radial velocity and other properties of these stars.
Calculate the mass loss rate at each spectral type
This slide provides the motivation for photon-counting detectors in low light applications.
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11. Observations & Data Telescope: Keck (D=10m) NIRSPEC-7(1.9-2.4 microns)
(Kudritzki ,13)
High Resolution:17,000
Integration time: 20s
SNR: ~50
2 MASS, WISE photometry
This slide provides the motivation for photon-counting detectors in low light applications.
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12. Reduction Example:D2 Spat map Spec map Arc light Nod pair
Davies et al. 2007
Example:D2
Spat map
Spec map
Arc light
Nod pair
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13. 2018/11/28

14. Flat field
Noble gas
Arc light
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15. Calibration Calibration lamp line lists OH Sky line lists Argon Neon
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16. IDL REDSPEC package
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17. reduction
Davies et al. 2007
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18. Finding the temperature and spectral type through spectra
The relationship between spectral type and the equivalent width of the CO bandhead feature microns
microns
(Wallace&Hinkle(1996b,1997))
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19. Research the final state of RSGs
Mass loss rate
10-4 solar mass /year (Van loon et al. 2005)
Mass loss rate depends on luminosity, temperature and the amount of dust in the outer envelope
Van loon et al. 2005
Knapp&Morris 1986
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20. photometry
Reddening
luminosity
Davies et al.2007
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21. Use Model
DUSTY
 radiation from some source (star, galactic nucleus, etc.) viewed after processing by a dusty region.
Dust property: chemical component, grain size, dust temperature
(working on the code)
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22. Discussion & Analysis
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23. Assume These RSGs are identical star but at different stage, we will be able to research these massive stars’ final destination。
If mass of RSG is a function of spectral type, trace the life of RSG stage
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24. Future direction
1. plot all the spectra of the 26 RSGs in the cluster and compare with other clusters (hopefully)
2. Use model to find out the mass loss rate more accurately
3. Find higher resolution spectra of the cluster and observe in far infrared
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25. Reference Ben Davies et al. 2007,APJ,671:781-801
Ben Davies & Don F. Figer et al., 2008,APJ
M. Jura & M. Morris, 1985, APJ,292:
G. R. Knapp & Mark Morris, 1985, APJ, 292:
J. Th. Van Loon et al.,2005,A&A 438:
Ivezic, Z.,Nenkova, M., 1999, user manual for DUSTY
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26. Thanks
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