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

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 2018/11/28

Introduction Red Supergiant (RSG) Luminosity class I， >10 solar mass, >1000 solar radius Supernova progenitors 4 known rsgcs 2018/11/28

HR diagram 2018/11/28

RSGC Red Supergiant Cluster (RSGC) Location: milky way galaxy RSGC1(2006)(14 RSGs) RSGC2(Stephenson 2 1990 )(2007)(26 RSGs) RSGC3(2010)(8-14 RSGs) RSGC4(Alicante 8, 2010)(8-13 RSGs) 2018/11/28

My object RSGC2 (WISE data) most RSGs in MW 2018/11/28

RSGC2 in 2MASS Scutum–Centaurus Arm 6kpc RSGC 2 J2000: 18 :39 :20 −06:01: 42 2018/11/28

Position This slide provides the motivation for photon-counting detectors in low light applications. 2018/11/28

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 2018/11/28

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. 2018/11/28

Observations & Data Telescope: Keck (D=10m) NIRSPEC-7(1.9-2.4 microns) (Kudritzki 2006-5-7 2006-8-12,13) 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. 2018/11/28

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 2018/11/28

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Flat field Noble gas Arc light 2018/11/28

Calibration Calibration lamp line lists OH Sky line lists Argon Neon 2018/11/28

IDL REDSPEC package 2018/11/28

reduction Davies et al. 2007 2018/11/28

Finding the temperature and spectral type through spectra The relationship between spectral type and the equivalent width of the CO bandhead feature.2.293 microns 2.288-2.293 microns (Wallace&Hinkle(1996b,1997)) 2018/11/28

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 2018/11/28

photometry Reddening luminosity Davies et al.2007 2018/11/28

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) 2018/11/28

Discussion & Analysis 2018/11/28

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 2018/11/28

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 2018/11/28

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,292:487-493 G. R. Knapp & Mark Morris, 1985, APJ, 292:640-669 J. Th. Van Loon et al.,2005,A&A 438:273-289 Ivezic, Z.,Nenkova, M., 1999, user manual for DUSTY 2018/11/28

Thanks 2018/11/28