scholarly journals On the observational behaviour of the highly polarized Type IIn supernova SN 2017hcc

2019 ◽  
Vol 488 (3) ◽  
pp. 3089-3099
Author(s):  
Brajesh Kumar ◽  
Chakali Eswaraiah ◽  
Avinash Singh ◽  
D K Sahu ◽  
G C Anupama ◽  
...  
Keyword(s):  
Loss Rate ◽  
Mass Loss Rate ◽  
Surrounding Medium ◽  
Broad Band ◽  
Polarization Data ◽  
Intrinsic Polarization ◽  
V Band ◽  
Gaia Dr2 ◽  
Luminous Blue Variable ◽  
Narrow Emission

ABSTRACT We present the results based on photometric (Swift UVOT), broad-band polarimetric (V and Rbands) and optical spectroscopic observations of the Type IIn supernova (SN) 2017hcc. Our study is supplemented with spectropolarimetric data available in literature for this event. The post-peak light-curve evolution is slow (∼0.2 mag 100 d−1 in b band). The spectrum of ∼+27 d shows a blue continuum with narrow emission lines, typical of a Type IIn SN. Archival polarization data along with the Gaia DR2 distances have been utilized to evaluate the interstellar polarization (ISP) towards the SN direction which is found to be PISP = 0.17 ± 0.02 per cent and θISP = 140° ± 3°. To extract the intrinsic polarization of SN 2017hcc, both the observed and the literature polarization measurements were corrected for ISP. We noticed a significant decline of ∼3.5 per cent (V band) in the intrinsic level of polarization spanning a period of ∼2 months. In contrast, the intrinsic polarization angles remain nearly constant at all epochs. Our study indicates a substantial variation in the degree of asymmetry in either the ejecta and/or the surrounding medium of SN 2017hcc. We also estimate a mass-loss rate of $\dot{M}$ = 0.12 M⊙ yr−1 (for v$\mathrm{ w}$ = 20 km s−1) which suggests that the progenitor of SN 2017hcc is most likely a luminous blue variable.

scholarly journals Surface brightness fluctuations, tracers of stellar mass-loss?

2009 ◽  
Vol 5 (S262) ◽  
pp. 48-51
Author(s):  
Rosa A. González-Lópezlira ◽  
Gustavo Bruzual-A. ◽  
Stéphane Charlot ◽  
Javier Ballesteros-Paredes ◽  
Laurent Loinard
Keyword(s):  
Mass Loss ◽  
Stellar Population ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Broad Band ◽  
Global Changes ◽  
Agb Stars ◽  
Near Ir ◽  
Surface Brightness Fluctuations ◽  
Order Of Magnitude

AbstractWe present optical and IR integrated colors and SBF magnitudes, computed from stellar population synthesis models that include emission from the dusty envelopes surrounding mass-loosing TP-AGB stars. We explore the effects of varying the mass-loss rate by one order of magnitude around the fiducial value, modifying accordingly both the stellar parameters and the output spectra of the TP-AGB stars plus their dusty envelopes. We compare these models to optical and near-IR data of single AGB stars and Magellanic star clusters. Neither broad-band colors nor SBF measurements in the optical or the near-IR can discern global changes in the mass-loss rate of a stellar population. However, we predict that mid-IR SBF measurements can pick out such changes, and actually resolve whether a relation between metallicity and mass-loss exists.

scholarly journals Catching a star before explosion: the luminous blue variable progenitor of SN 2015bh

2018 ◽  
Vol 617 ◽  
pp. A115 ◽  
Author(s):  
I. Boian ◽  
J. H. Groh
Keyword(s):  
Loss Rate ◽  
Mass Loss Rate ◽  
Core Collapse ◽  
Late Time ◽  
High Wind ◽  
Hole Formation ◽  
Remarkable Case ◽  
Core Collapse Supernova ◽  
Luminous Blue Variable ◽  
Significant Attention

In this paper we analyse the pre-explosion spectrum of SN2015bh by performing radiative transfer simulations using the CMFGEN code. This object has attracted significant attention due to its remarkable similarity to SN2009ip in both its pre- and post-explosion behaviour. They seem to belong to a class of events for which the fate as a genuine core-collapse supernova or a non-terminal explosion is still under debate. Our CMFGEN models suggest that the progenitor of SN2015bh had an effective temperature between 8700 and 10 000 K, had a luminosity in the range ≃1.8−4.74 × 106 L⊙, contained at least 25% H in mass at the surface, and had half-solar Fe abundances. The results also show that the progenitor of SN2015bh generated an extended wind with a mass-loss rate of ≃6 × 10−4 to 1.5 × 10−3 M⊙ yr−1 and a velocity of 1000km s−1. We determined that the wind extended to at least 2.57 × 1014 cm and lasted for at least 30 days prior to the observations, releasing 5 × 10−5 M⊙ into the circumstellar medium. In analogy to 2009ip, we propose that this is the material that the explosive ejecta could interact at late epochs, perhaps producing observable signatures that can be probed with future observations. We conclude that the progenitor of SN2015bh was most likely a warm luminous blue variable of at least 35 M⊙ before the explosion. Considering the high wind velocity, we cannot exclude the possibility that the progenitor was a Wolf–Rayet (WR) star that inflated just before the 2013 eruption, similar to HD5980 during its 1994 episode. If the star survived, late-time spectroscopy may reveal either a similar luminous blue variable (LBV) or a WR star, depending on the mass of the H envelope before the explosion. If the star exploded as a genuine supernova (SN), 2015bh would be a remarkable case of a successful explosion after black hole formation in a star with a possible minimum mass 35 M⊙ at the pre-SN stage.

scholarly journals X-ray spectral diagnostics of activity in massive stars

2010 ◽  
Vol 6 (S272) ◽  
pp. 348-353 ◽  
Author(s):  
David H. Cohen ◽  
Emma E. Wollman ◽  
Maurice A. Leutenegger
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Broad Band ◽  
Variable Structure ◽  
Spectral Energy ◽  
X Rays ◽  
X Ray ◽  
Spectral Diagnostics ◽  
Loss Rates

AbstractX-rays give direct evidence of instabilities, time-variable structure, and shock heating in the winds of O stars. The observed broad X-ray emission lines provide information about the kinematics of shock-heated wind plasma, enabling us to test wind-shock models. And their shapes provide information about wind absorption, and thus about the wind mass-loss rates. Mass-loss rates determined from X-ray line profiles are not sensitive to density-squared clumping effects, and indicate mass-loss rate reductions of factors of 3 to 6 over traditional diagnostics that suffer from density-squared effects. Broad-band X-ray spectral energy distributions also provide mass-loss rate information via soft X-ray absorption signatures. In some cases, the degree of wind absorption is so high, that the hardening of the X-ray SED can be quite significant. We discuss these results as applied to the early O stars ζ Pup (O4 If), 9 Sgr (O4 V((f))), and HD 93129A (O2 If*).

scholarly journals The enigmatic binary system HD 5980

2019 ◽  
Vol 486 (1) ◽  
pp. 725-742 ◽  
Author(s):  
D John Hillier ◽  
Gloria Koenigsberger ◽  
Yaël Nazé ◽  
Nidia Morrell ◽  
Rodolfo H Barbá ◽  
...  
Keyword(s):  
Mass Loss ◽  
Emission Line ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Phase Dependence ◽  
Wind Speeds ◽  
Line Intensities ◽  
Orbital Phase ◽  
Emission Line Spectrum ◽  
Luminous Blue Variable

Abstract The Small Magellanic Cloud multiple system HD 5980 contains a luminous blue variable (LBV) that underwent a major eruption in 1994, and whose current spectrum is that of a hydrogen-rich Wolf–Rayet (WR) star. Since the eruption, the wind mass-loss rate has been declining while wind speeds have been steadily increasing. Observations obtained in 2014 when Star A (the LBV) eclipses Star B indicate that the fitted mass-loss rate and luminosity have reached the lowest values ever determined for such spectra: $\dot{M}$  = 4.5 × 10−5$\mathrm{M}_\odot \, \hbox{yr}^{-1}$, L  = 1.7 × 106 L⊙. In addition, the radius of the LBV’s continuum-emitting region is similar to that derived from the eclipse light curves of the late 1970s. Hence, it appears to have attained a similar ‘low’ state to that of the late 1970s. While a good fit to the emission spectrum is obtained using a cmfgen model, there are discrepancies in the UV. In particular, the extent of the observed absorption profiles is ∼1000 km s−1 greater than predicted by the emission-line intensities. Further, HST UV observations obtained in 2016, when Star A is eclipsed by Star B, show unusual P Cygni profiles that are not easily explained. Surprisingly the 2016 emission-line spectrum is similar to that at the opposite eclipse obtained in 2014. The complex UV profiles are likely to arise as a consequence of the dynamics of the wind–wind collision and radiative braking, both of which will cause significant departures from spherical symmetry, and have a strong orbital phase dependence. However, other scenarios, such as intrinsically aspherical winds, cannot be ruled out.

scholarly journals The Most Luminous Star Formation Regions in the Galaxy

1987 ◽  
Vol 115 ◽  
pp. 143-143 ◽  
Author(s):  
D. T. Jaffe ◽  
R. Genzel ◽  
D. A. Harper ◽  
A. I. Harris ◽  
P.T.P. Ho
Keyword(s):  
Star Formation ◽  
High Velocity ◽  
Massive Star ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Broad Band ◽  
Physical Conditions ◽  
Velocity Flow ◽  
The Galaxy ◽  
Star Formation Regions

We present new far-IR and submillimeter broad-band and spectroscopic results on the dense and very luminous cores of massive star formation regions. The best-studied region, W51, contains one core around the source IRS2 and another around W51 MAIN. Our earlier submillimeter continuum mapping has shown that these two cores are very massive (2-4 × 104 M⊙) and have average densities of nH2 ∼ 105 over their inner parsec. New far-IR maps show that both cores are very luminous (L(MAIN) ∼2 × 106 L⊙; L(IRS2) ∼4x106 L⊙). Observations of the (1,1) and (2,1) transitions of NH3, indicate high kinetic temperatures (200-400 K) for the quiescent gas in the inner several arc seconds (0.1 pc) of both cores. Spectroscopy of the 370 μm J = 7 → 6 and 163 μm J = 16 → 15 transitions of CO toward the cores allows us to characterize the hot high velocity material seen previously on the H2O maser transitions and not readily visible in the low J transitions of CO. The high velocity flow in IRS2 is ∼ 60 times more massive than the very similar outflow in the ∼ 30 times less luminous Orion/KL core. The mass loss rate is ∼ 30 times greater than in Orion. Additional observations of W49 allow us to draw a few general conclusions about the most luminous star formation regions in our galaxy: (1) The luminous cores are 102-103 more massive than the Orion core with the same density. (2) Outflows and warm regions in these cores have physical conditions similar to those in their less luminous counterparts but far more mass is involved in the flows.

Detection of tidal tails around the open cluster M 67 using principal component analysis

2020 ◽  
Vol 72 (3) ◽  
Author(s):  
Xinhua Gao
Keyword(s):  
Principal Component Analysis ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Open Cluster ◽  
Principal Component ◽  
Mass Range ◽  
Component Analysis ◽  
Gaussian Mixture ◽  
Tidal Tails ◽  
Gaia Dr2

Abstract In this paper we present an investigation of tidal tails around the old open cluster M 67 using Gaia-DR2. We identify likely extra-tidal stars around M 67 using principal component analysis (PCA) and a Gaussian mixture model (GMM). We find 1618 stars closely related to M 67, 85 of which are likely extra-tidal stars. We find clear evidence for the existence of two well-defined tidal tails emerging from M 67. The tidal tails extend out to projected distances of at least ${2{^{\circ}_{.}}5}$ (∼39 pc), which is more than twice as large as the tidal radius of the cluster. Based on LAMOST-DR5 data, we confirm that 13 extra-tidal stars have radial velocities and metallicities similar to those of the cluster. Furthermore, we also confirm that the extra-tidal stars cover a wide mass range of 0.2–1.1 M⊙, and nearly half the extra-tidal stars are less than 0.57 M⊙. The total mass of the extra-tidal stars is determined to be about 55 M⊙. We estimate a mass-loss rate of ∼2.8 M⊙ Myr−1 for M 67. Possible origins of these extra-tidal stars are discussed.

scholarly journals Modelling spectra of MN112

2020 ◽  
Vol 496 (4) ◽  
pp. 5455-5462
Author(s):  
A Kostenkov ◽  
S Fabrika ◽  
O Sholukhova ◽  
A Sarkisyan ◽  
D Bizyaev
Keyword(s):  
Loss Rate ◽  
Spectroscopic Analysis ◽  
Mass Loss Rate ◽  
Chemical Abundances ◽  
Strong Emission ◽  
Non Local ◽  
Hydrogen Lines ◽  
Best Fit ◽  
Calar Alto ◽  
Luminous Blue Variable

ABSTRACT MN112 is a Galactic luminous blue variable (LBV) candidate with a circumstellar nebula. P Cygni was the first LBV discovered, and was recorded during major eruptions in the 17th century. The stars have similar spectra with strong emission hydrogen lines, He i, N ii, Si ii, and Fe iii lines. We present the results of spectroscopic analysis and modelling of MN112 spectra. We obtained the main stellar parameters and chemical abundances of MN112 and compared them with those of P Cygni. Atmosphere models were calculated using the non-local thermodynamic equilibrium radiative transfer code cmfgen. We have used spectra of MN112 obtained with the 3.5-m telescope at the Observatory of Calar Alto and 3.5-m ARC telescope at the Apache Point Observatory. P Cygni spectra were taken with the 6-m BTA telescope. We have found the best fit of the observed spectrum with the model at temperature $T_{\text{eff}}= 15\, 200$ K, clumping-corrected mass-loss rate $\dot{M}f^{-0.5}=5.74 \times 10^{-5}\, \mathrm{M}_{\odot }\text{yr}^{-1}$, filling factor f = 0.1, luminosity $L=5.77 \times 10^5\, \mathrm{L}_{\odot }$ for MN112. The ratio of helium to hydrogen He/H is 0.27 (by the number of atoms) with nitrogen overabundance (XN/X⊙ = 6.8) and an underabundance of carbon (XC/X⊙ < 0.1).

scholarly journals Current day mass loss rate for Luminous Blue Variable IRAS 18576+0341

2005 ◽  
Vol 437 (1) ◽  
pp. L1-L5 ◽  
Author(s):  
G. Umana ◽  
C. S. Buemi ◽  
C. Trigilio ◽  
P. Leto
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Luminous Blue Variable

scholarly journals Investigation of faint galactic carbon stars from the First Byurakan Spectral Sky Survey. IV. GAIA DR2 data

2020 ◽  
pp. 206-210
Author(s):  
G. R. Kostandyan
Keyword(s):  
Galactic Halo ◽  
Galactic Plane ◽  
Broad Band ◽  
Absolute Magnitude ◽  
Asymptotic Giant Branch ◽  
V Band ◽  
Sky Survey ◽  
Magnitude Diagram ◽  
Absolute Magnitudes ◽  
Gaia Dr2

The second Gaia data release (Gaia DR2) data are used to analyze and estimate some important parameters for 127 carbon (C) type stars (56 are late N - type Asymptotic Giant Branch (AGB) C stars, 71 are early type CH giants) detected on the First Byurakan Spectral Sky Survey (FBS) low-resolution (lr) spectral plates. Gaia DR2 G broad band magnitudes are in the range 9.4m < G < 18.2m. for FBS C stars. Radial velocities (RV) is available for 75 C stars out of 127. For 9 objects RV is greater than 200 km/s. Absolute magnitudes in V band are estimated for 18 FBS C stars, having luminosity data, from which 17 are CH giants. They are in the range between -3.5m ≤ MV < +0.5m. For FBS 1918+869 absolute magnitude MV = -3.4(±0.2)m, which is typical for N type AGB C stars. Having distance estimations, the Hertzsprung-Russell diagram (HRD, or color - absolute magnitude diagram) was constructed for C stars. All FBS detected C stars are giants and AGB stars in the Galactic Halo. They are not far than 14 kpc from the Sun and 8 kpc from the Galactic plane.

scholarly journals Wray 15-906: a candidate luminous blue variable discovered with WISE, Herschel, and SALT

2020 ◽  
Vol 498 (4) ◽  
pp. 5093-5108
Author(s):  
O V Maryeva ◽  
V V Gvaramadze ◽  
A Y Kniazev ◽  
L N Berdnikov
Keyword(s):  
Mass Loss ◽  
Mass Loss Rate ◽  
Stellar Atmosphere ◽  
Wide Field ◽  
Single Star ◽  
V Band ◽  
Spectroscopic Monitoring ◽  
Open Star ◽  
Binary Evolution ◽  
Luminous Blue Variable

ABSTRACT We present the results of study of the Galactic candidate luminous blue variable Wray 15-906, revealed via detection of its infrared circumstellar shell (of ≈2 pc in diameter) with the Wide-field Infrared Survey Explorer and the Herschel Space Observatory. Using the stellar atmosphere code cmfgen and the Gaia parallax, we found that Wray 15-906 is a relatively low-luminosity, $\log (L/\rm \, L_\odot)\approx 5.4$, star of temperature of 25 ± 2 kK, with a mass-loss rate of ${\approx}3\times 10^{-5} \, \rm \, M_\odot \, {\rm yr}^{-1}$, a wind velocity of $280\pm 50 \, {\rm \, km\, s^{-1}}$, and a surface helium abundance of 65 ± 2 per cent (by mass). In the framework of single-star evolution, the obtained results suggest that Wray 15-906 is a post-red supergiant star with initial mass of ${\approx}25 \, \rm \, M_\odot$ and that before exploding as a supernova it could transform for a short time into a WN11h star. Our spectroscopic monitoring with the Southern African Large Telescope does not reveal significant changes in the spectrum of Wray 15-906 during the last 8 yr, while the V-band light curve of this star over years 1999–2019 shows quasi-periodic variability with a period of ≈1700 d and an amplitude of ≈0.2 mag. We estimated the mass of the shell to be $2.9\pm 0.5 \, \rm \, M_\odot$ assuming the gas-to-dust mass ratio of 200. The presence of such a shell indicates that Wray 15-906 has suffered substantial mass-loss in the recent past. We found that the open star cluster C1128−631 could be the birth place of Wray 15-906 provided that this star is a rejuvenated product of binary evolution (a blue straggler).

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