scholarly journals First detection of X-ray line emission from Type IIn supernova 1978K with XMM-Newton’s RGS

2020 ◽  
Vol 72 (2) ◽  
Author(s):  
Yuki Chiba ◽  
Satoru Katsuda ◽  
Takashi Yoshida ◽  
Koh Takahashi ◽  
Hideyuki Umeda
Keyword(s):  
Mass Loss ◽  
Surface Composition ◽  
Massive Stars ◽  
Line Emission ◽  
Asymptotic Giant Branch ◽  
High Mass ◽  
Expansion Velocity ◽  
X Ray ◽  
Elemental Abundances ◽  
High Mass Loss

Abstract We report on robust measurements of elemental abundances of the Type IIn supernova SN 1978K, based on the high-resolution X-ray spectrum obtained with the Reflection Grating Spectrometer (RGS) onboard XMM-Newton. The RGS clearly resolves a number of emission lines, including N Ly$\alpha$, O Ly$\alpha$, O Ly$\beta$, Fe xvii, Fe xviii, Ne He$\alpha$, and Ne Ly$\alpha$ for the first time from SN 1978K. The X-ray spectrum can be represented by an absorbed, two-temperature thermal emission model, with temperatures of $kT \sim 0.6$ keV and 2.7 keV. The elemental abundances are obtained to be N $=$$2.36_{{-0.80}}^{{+0.88}}$, O $=$$0.20 \pm {0.05}$, Ne $=$$0.47 \pm {0.12}$, Fe $=$$0.15_{{-0.02}}^{{+0.01}}$ times the solar values. The low metal abundances except for N show that the X-ray emitting plasma originates from the circumstellar medium blown by the progenitor star. The abundances of N and O are far from the CNO-equilibrium abundances expected for the surface composition of a luminous blue variable, and resemble the H-rich envelope of less massive stars with masses of 10–25$\, M_{\odot }$. Together with other peculiar properties of SN 1978K, i.e., a low expansion velocity of 500–1000 km s$^{-1}$ and SN IIn-like optical spectra, we propose that SN 1978K is a result of either an electron-capture SN from a super asymptotic giant branch star, or a weak Fe core-collapse explosion of a relatively low-mass ($\sim \! \! 10\, M_{\odot }$) or high-mass ($\sim$20–25$\, M_{\odot }$) red supergiant star. However, these scenarios cannot naturally explain the high mass-loss rate of the order of $\dot{M} \sim 10^{-3}\, M_{\odot }\:{\rm yr^{-1}}$ over $\gtrsim$1000 yr before the explosion, which is inferred by this work as well as many other earlier studies. Further theoretical studies are required to explain the high mass-loss rates at the final evolutionary stages of massive stars.

scholarly journals Circumstellar environment of the M-type AGB star R Doradus

2018 ◽  
Vol 615 ◽  
pp. A8 ◽  
Author(s):  
E. De Beck ◽  
H. Olofsson
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Line Emission ◽  
Asymptotic Giant Branch ◽  
Emission Lines ◽  
High Mass ◽  
Spectral Features ◽  
High Mass Loss ◽  
Spectral Scan

Context. Our current insights into the circumstellar chemistry of asymptotic giant branch (AGB) stars are largely based on studies of carbon-rich stars and stars with high mass-loss rates. Aims. In order to expand the current molecular inventory of evolved stars we present a spectral scan of the nearby, oxygen-rich star R Dor, a star with a low mass-loss rate (~2 × 10−7 M⊙ yr−1). Methods. We carried out a spectral scan in the frequency ranges 159.0–321.5 GHz and 338.5–368.5 GHz (wavelength range 0.8–1.9 mm) using the SEPIA/Band-5 and SHeFI instruments on the APEX telescope and we compare it to previous surveys, including one of the oxygen-rich AGB star IK Tau, which has a high mass-loss rate (~5 ×10−6 M⊙ yr−1). Results. The spectrum of R Dor is dominated by emission lines of SO2 and the different isotopologues of SiO. We also detect CO, H2O, HCN, CN, PO, PN, SO, and tentatively TiO2, AlO, and NaCl. Sixteen out of approximately 320 spectral features remain unidentified. Among these is a strong but previously unknown maser at 354.2 GHz, which we suggest could pertain to H2SiO, silanone. With the exception of one, none of these unidentified lines are found in a similarly sensitive survey of IK Tau performed with the IRAM 30 m telescope. We present radiative transfer models for five isotopologues of SiO (28SiO, 29SiO, 30SiO, Si17O, Si18O), providing constraints on their fractional abundance and radial extent. We derive isotopic ratios for C, O, Si, and S and estimate that, based on our results for 17O/18O, R Dor likely had an initial mass in the range 1.3–1.6 M⊙, in agreement with earlier findings based on models of H2O line emission. From the presence of spectral features recurring in many of the measured thermal and maser emission lines we tentatively identify up to five kinematical components in the outflow of R Dor, indicating deviations from a smooth, spherical wind.

scholarly journals Observational connections between LBV’s and other stars, with emphasis on Wolf-Rayet stars

1989 ◽  
Vol 113 ◽  
pp. 229-240
Author(s):  
A. F. J. Moffat ◽  
L. Drissen ◽  
C. Robert
Keyword(s):  
Mass Loss ◽  
Massive Stars ◽  
Underlying Mechanism ◽  
High Mass ◽  
Strong Line ◽  
Essential Step ◽  
High Mass Loss ◽  
Loss Rates ◽  
R Domain

Abstract.We suggest that the LBV mechanism is an essential step to “force” massive stars (M(ZAMS) ≥ 40M⊙) to finally enter the Wolf-Rayet (W-R) domain in the Hertzsprung-Russel diagram (HRD). Just as massive supergiants showincreasingvariability as theyapproachthe Humphreys-Davidson (H-D)instability limit (horizontally in the HRD diagram), so the W-R stars showdecreasingvariability as theyrecede fromthe H-D limit (at first horizontally into the WNL domain, then, with their high mass loss rates, plunging irreversably downwards as ever hotter, smaller and fainter, strong-line W-R stars). Among the W-R stars, the luminous WNL subtypes (especially WN8) are the most variable, probably as a consequence of blob ejection in the wind. The underlying mechanism which triggers this ejection is possibly related to wind instabilities and may thus be quite different from the source of variability in luminous supergiants or LBV’s in quiescence, where photospheric effects dominate.

scholarly journals Luminous Blue Variables, cool hypergiants and some impostors in the H-R diagram

2003 ◽  
Vol 212 ◽  
pp. 38-46
Author(s):  
Roberta M. Humphreys
Keyword(s):  
Magnetic Fields ◽  
Mass Loss ◽  
Surface Activity ◽  
Massive Star ◽  
Massive Stars ◽  
High Mass ◽  
Luminous Blue Variables ◽  
Star Evolution ◽  
High Mass Loss ◽  
Massive Star Evolution

Current observations of the S Dor/LBVs and candidates and the implications for their important role in massive star evolution are reviewed. Recent observations of the cool hypergiants are altering our ideas about their evolutionary state, their atmospheres and winds, and the possible mechanisms for their asymmetric high mass loss episodes which may involve surface activity and magnetic fields. Recent results for IRC+10420, ρ Cas and VY CMa are highlighted. S Dor/LBVs in eruption, and the cool hypergiants in their high mass loss phases with their optically thick winds are not what their apparent spectra and temperatures imply; they are then ‘impostors’ on the H-R diagram. The importance of the very most massive stars, like η Carinae and the ‘supernovae impostors’ are also discussed.

scholarly journals The O stars: optical review

1979 ◽  
Vol 83 ◽  
pp. 1-22
Author(s):  
J. B. Hutchings
Keyword(s):  
Neutron Star ◽  
Interstellar Medium ◽  
Mass Loss ◽  
Large Fraction ◽  
Significant Fraction ◽  
High Mass ◽  
X Ray ◽  
The Galaxy ◽  
High Mass Loss ◽  
Rough Outline

I would like to start with a quick overview of the O stars - their significance and role in the galaxy and in astrophysics - just to remind ourselves of why we are here and what we hope to talk about. In Table 1 I show a rough outline of the contribution of O stars to what happens in the galaxy as a whole. Because of their extreme luminosity, they contribute a large fraction of the radiation of the galaxy, while forming a very tiny group of objects and mass. Because of their short lifetime they are a population that has gone through 104 generations in the life of the galaxy. Their high mass loss rates may account for a large fraction of the new matter injected into the interstellar medium, and they probably power some significant fraction of the hard X-ray sources in the galaxy, by virtue of the fact that a companion can become a neutron star a) without disrupting the binary and b) while the companion is still a mass losing O star.

Millimetre Observations of Evolved Stars

1996 ◽  
Vol 13 (2) ◽  
pp. 185-186
Author(s):  
Jessica M. Chapman
Keyword(s):  
Mass Loss ◽  
Stellar Atmosphere ◽  
Asymptotic Giant Branch ◽  
High Mass ◽  
Circumstellar Envelope ◽  
Agb Stars ◽  
Circumstellar Envelopes ◽  
Evolved Stars ◽  
High Mass Loss ◽  
Transfer Momentum

Radio emission at centimetre and millimetre wavelengths provides a powerful tool for studying the circumstellar envelopes of evolved stars. These include stars on the asymptotic giant branch (AGB), post-AGB stars and a small number of massive M-type supergiant stars. The AGB stars and M-type supergiants are characterised by extremely high mass-loss rates. The mass loss in such an evolved star is driven by radiation pressure acting on grains which form in the outer stellar atmosphere. The grains are accelerated outwards and transfer momentum to the gas through grain–gas collisions. The outflowing dust and gas thus form an expanding circumstellar envelope through which matter flows from the star to the interstellar medium, at a typical velocity of 15 km s−1. For a recent review of circumstellar mass loss see Chapman, Habing & Killeen (1995).

scholarly journals Effects of a stochastic initial mass function on the upper main sequence band

1981 ◽  
Vol 59 ◽  
pp. 293-296
Author(s):  
C. Chiosi ◽  
L. Greggio
Keyword(s):  
Mass Loss ◽  
Effective Temperature ◽  
Main Sequence ◽  
Massive Stars ◽  
Mass Function ◽  
Initial Mass Function ◽  
High Mass ◽  
Initial Mass ◽  
Sequence Band ◽  
High Mass Loss

The theoretical (Mb versus Log Te) HR diagram for the brightest galactic OB stars shows an upper boundary for the luminosity, which is characterized by a decreasing luminosity with decreasing effective temperature (Humphreys and Davidson, 1979). The existence of this limit was interpreted by Chiosi et al. (1978) as due to the effect of mass loss by stellar wind on the evolution of most massive stars in core H-burning phase. In fact, evolutionary models calculated at constant mass cover a wider and wider range in effective temperature as the initial mass increases during the main sequence phase. On the contrary, sufficiently high mass-loss rates make the evolutionary sequences of most massive stars (M 60⩾Mʘ) shrink toward the zero age main sequence whenever, due to mass loss, CNO processed material is brought to the surface (Chiosi et al., 1978; de Loore et al., 1978; Maeder, 1980).

scholarly journals The Wolf-Rayet Connection - Luminous Blue Variables and Evolved Supergiants

1991 ◽  
Vol 143 ◽  
pp. 485-498
Author(s):  
Roberta M. Humphreys
Keyword(s):  
Mass Loss ◽  
Massive Stars ◽  
Physical Characteristics ◽  
High Mass ◽  
Luminous Blue Variables ◽  
Ir Stars ◽  
High Mass Loss ◽  
Stage 1 ◽  
And Behavior

The physical characteristics and behavior of evolved massive stars in three different mass ranges are reviewed with application to whether they may eventually evolve to the WR stage 1. >40-50 M⊙ as LBV's, 2. ∼30-40 M⊙ as cool hypergiant-OH/IR stars and 3. ∼10-30 M⊙ as red supergiant-OH/IR stars. I emphasize the importance of the relatively short but high mass loss phases as LBV's and as OH/IR stars in determining the fate of massive stars from 10 to 100 M⊙.

scholarly journals On the nature of OH/IR stars

1985 ◽  
Vol 106 ◽  
pp. 131-132
Author(s):  
Dieter Engels
Keyword(s):  
Mass Loss ◽  
Line Emission ◽  
Optical Emission ◽  
Central Star ◽  
Asymptotic Giant Branch ◽  
High Mass ◽  
Radial Pulsation ◽  
Intermediate Mass ◽  
Ir Stars ◽  
Loss Rates

OH/IR stars are the infrared counterparts of galactic OH maser sources which show a characteristic double-peaked emission-line profile. Their strong radio emission can be detected at large distances, making them excellent tracers of distribution and kinematics of evolved stars in the Milky Way. The OH maser profile is typical for line emission from an expanding circumstellar shell. The circumstellar shells of OH/IR stars absorb the optical emission of the central star nearly completely and reemit the energy in the infrared. Having luminosities ~ 105 L⊙ and energy distributions peaking around 10μm, they may make a major contribution to the interstellar radiation field beyond 5μm. With mass loss rates of 10-5 to 10-4 M⊙/yr they lose several solar masses in a few hundred thousand years. OH/IR stars are therefore important objects for recycling stellar matter into the interstellar medium.Progress has been made in understanding the nature of OH/IR stars. They are Mira-like large-amplitude variables with periods up to 5 years long. It is proposed that they are stars of intermediate mass (2–10 M⊙) on the asymptotic giant branch (AGB). They have not only larger masses than Mira variables proper, but also longer periods of pulsation and larger mass loss rates. As a result optically thick circumstellar dust shells are formed, which prevent the detection of these more massive Mira-like variables at optical wavelengths. Radial pulsation (Mira variability) is thus thought to occur for all intermediate-mass stars in the course of their evolution on the AGB. In view of their high mass-loss rates, these stars may be key objects in the study of the formation of planetary nebulae.

scholarly journals Binary post-AGB stars

1997 ◽  
Vol 180 ◽  
pp. 313-318 ◽  
Author(s):  
L.B.F.M. Waters ◽  
C. Waelkens ◽  
H. Van Winckel
Keyword(s):  
Mass Loss ◽  
Central Star ◽  
Asymptotic Giant Branch ◽  
High Mass ◽  
Agb Stars ◽  
Chemical Abundances ◽  
Intermediate Mass Stars ◽  
High Mass Loss ◽  
Complicating Factors ◽  
Circumstellar Environment

Low and intermediate mass stars leave the Asymptotic Giant Branch (AGB) when the mass in their H-rich envelope is less than about 0.01 M⊙, and the high mass loss drops several orders of magnitude. The central star rapidly evolves to the left part of the HR diagram along a track of constant luminosity (e.g. Schönberner 1983). In principle the evolution of the central star to higher Teff and the expansion and cooling of the AGB remnant are easy to calculate. In practice several complicating factors arise which make it much more difficult to predict the morphology and properties of post-AGB stars, such as binarity, post-AGB mass loss and aspherical AGB mass loss. Binarity of post-AGB stars affects the morphology of the circumstellar environment, and it affects evolutionary timescales and surface chemical abundances of the components in the system. This review discusses some properties of binary post-AGB stars.

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