[ITAL]HUBBLE SPACE TELESCOPE[/ITAL][ITAL]Hubble Space Telescope[/ITAL] Observations of the Wolf-Rayet Nebula NGC 6888

Moore, B. D.; Hester, J. J.; Scowen, Paul A.

doi:10.1086/301389

Cited by 35 publications

(39 citation statements)

References 20 publications

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“…1. In fact, as it can be seen in Figure 2 of Moore et al (2000), the position of our aperture no. 2 corresponds to a tiny filament embedded in the [O iii]-dominated tenuous gas.…”

Section: Ngc 6888mentioning

confidence: 52%

The chemical composition of Galactic ring nebulae around massive stars

Esteban

Mesa‐Delgado

Morisset

et al. 2016

Mon. Not. R. Astron. Soc.

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We present deep spectra of ring nebulae associated with Wolf-Rayet (WR) and O-type stars: NGC 6888, G2.4+1.4, RCW 58, S 308, NGC 7635 and RCW 52. The data have been taken with the 10m Gran Telescopio Canarias and the 6.5m Clay Telescope. We extract spectra of several apertures in some of the objects. We derive C 2+ and O 2+ abundances from faint recombination lines in NGC 6888 and NGC 7635, permitting to derive their C/H and C/O ratios and estimate the abundance discrepancy factor (ADF) of O 2+ . The ADFs are larger than the typical ones of normal H ii regions but similar to those found in the ionised gas of star-forming dwarf galaxies. We find that chemical abundances are rather homogeneous in the nebulae where we have spectra of several apertures: NGC 6888, NGC 7635 and G2.4+1.4. We obtain very high values of electron temperature in a peripheral zone of NGC 6888, finding that shock excitation can reproduce its spectral properties. We find that all the objects associated with WR stars show N enrichment. Some of them also show He enrichment and O deficiency as well as a lower Ne/O than expected, this may indicate the strong action of the ON and NeNa cycles. We have compared the chemical composition of NGC 6888, G2.4+1.4, RCW 58 and S 308 with the nucleosynthesis predicted by stellar evolution models of massive stars. We find that non-rotational models of stars of initial masses between 25 and 40 M ⊙ seem to reproduce the observed abundance ratios of most of the nebulae.

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“…1. In fact, as it can be seen in Figure 2 of Moore et al (2000), the position of our aperture no. 2 corresponds to a tiny filament embedded in the [O iii]-dominated tenuous gas.…”

Section: Ngc 6888mentioning

confidence: 52%

The chemical composition of Galactic ring nebulae around massive stars

Esteban

Mesa‐Delgado

Morisset

et al. 2016

Mon. Not. R. Astron. Soc.

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“…The ALMA observations also provide critical constraints on the the FS peak frequency, the peak flux, and the jet break time, as the centimeter-band data exhibit significant variability likely due to extreme scintillation. however, the precise degree to which this mechanism is operational and effective for GRB progenitors remains an open question (Weaver et al 1977;Marston 1997;Moore et al 2000;Ramirez-Ruiz et al 2001;Chevalier et al 2004;Krause et al 2013;Smith 2014;Margutti et al 2017). We note that all observed instances of detectable RS emission, without exception, have been in low-density environments ranging from n 5 10 0 5…”

Section: Energy Injection and Rsmentioning

confidence: 82%

First ALMA Light Curve Constrains Refreshed Reverse Shocks and Jet Magnetization in GRB 161219B

Laskar

Alexander

Berger

et al. 2018

ApJ

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We present detailed multiwavelength observations of GRB 161219B at z=0.1475, spanning the radio to X-ray regimes, and the first Atacama Large Millimeter/submillimeter Array (ALMA) light curve of a γ-ray burst (GRB) afterglow. The centimeter-and millimeter-band observations before 8.5 days require emission in excess of that produced by the afterglow forward shock (FS). These data are consistent with radiation from a refreshed reverse shock (RS) produced by the injection of energy into the FS, signatures of which are also present in the X-ray and optical light curves. We infer a constant-density circumburst environment with an extremely low density, n 3 10 cm 0 4 3 »´--, and show that this is a characteristic of all strong RS detections to date. The Karl G. Lansky Very Large Array (VLA) observations exhibit unexpected rapid variability on roughlyminute timescales, indicative of strong interstellar scintillation. The X-ray, ALMA, and VLA observations together constrain the jet break time, t 32 jet » days, yielding a wide jet opening angle of 13 jet q » , implying beaming-corrected γ-ray and kinetic energies of E 4.9 10 48 »ǵ erg and E 1.3 10 K 50»´erg, respectively. Comparing the RS and FS emission, we show that the ejecta are only weakly magnetized, with relative magnetization, R 1 B » , compared to the FS. These direct, multifrequency measurements of a refreshed RS spanning the optical to radio bands highlight the impact of radio and millimeter data in probing the production and nature of GRB jets.

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“…The variable mass loss from massive stars during their evolution is known to create a structured wind bubble around the star (and its possible binary companion) with a dense shell at the interface with the ISM (e.g., Moore et al 2000). The typical radius of the swept-up shell nebula around a WRs at the end of its life is R M v n t 100(˙) 6. .…”

Section: Resultsmentioning

confidence: 99%

Dust in the Wind: The Role of Recent Mass Loss in Long Gamma-Ray Bursts

Margutti

Guidorzi

Lazzati

et al. 2015

ApJ

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We study the late-time (t 0.5 > days) X-ray afterglows of nearby (z 0.5 < ) long gamma-ray bursts (GRBs) with Swift and identify a population of explosions with slowly decaying, super-soft (photon index 3x Γ > ) X-ray emission that is inconsistent with forward shock synchrotron radiation associated with the afterglow. These explosions also show larger-than-average intrinsic absorption (NH 6 10 cm> × − ) and prompt γ-ray emission with extremely long duration (T 1000 90 > s). The chance association of these three rare properties (i.e., large, , super-soft x Γ , and extreme duration) in the same class of explosions is statistically unlikely. We associate these properties with the turbulent mass-loss history of the progenitor star that enriched and shaped the circumburst medium. We identify a natural connection between NH x i , , x Γ , and T 90 in these sources by suggesting that the latetime super-soft X-rays originate from radiation reprocessed by material lost to the environment by the stellar progenitor before exploding (either in the form of a dust echo or as reprocessed radiation from a long-lived GRB remnant), and that the interaction of the explosionʼs shock/jet with the complex medium is the source of the extremely long prompt emission. However, current observations do not allow us to exclude the possibility that super-soft X-ray emitters originate from peculiar stellar progenitors with large radii that only form in very dusty environments.

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[ITAL]HUBBLE SPACE TELESCOPE[/ITAL][ITAL]Hubble Space Telescope[/ITAL] Observations of the Wolf-Rayet Nebula NGC 6888

Cited by 35 publications

References 20 publications

The chemical composition of Galactic ring nebulae around massive stars

The chemical composition of Galactic ring nebulae around massive stars

First ALMA Light Curve Constrains Refreshed Reverse Shocks and Jet Magnetization in GRB 161219B

Dust in the Wind: The Role of Recent Mass Loss in Long Gamma-Ray Bursts

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