Die noodsaaklikheid van ’n ander paradigma vir Suid-Afrikaanse sosiologie

Smith, Hanna

doi:10.1080/02580144.1986.10558335

Cited by 2 publications

(2 citation statements)

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“…A qualitatively similar asymmetric blue bump in Hα has been seen at different speeds in several SNe IIn (Smith et al 2012a(Smith et al ,b, 2015Fransson et al 2014), and is usually attributed bipolar or perhaps disk-like geometry in the shock interaction. A corresponding red bump is usually assumed to be weaker or absent due to extinction by dust or occultation by the opaque SN photosphere.…”

Section: Asymmetry In the Ejectasupporting

confidence: 58%

The Persistent Eruption of UGC 2773-OT: finally, a decade-long extragalactic Eta Carinae analogue

Smith

Andrews

Mauerhan

et al. 2015

Mon. Not. R. Astron. Soc.

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While supernova (SN) impostors resemble the Great Eruption of η Carinae in the sense that their spectra show narrow H lines and they have typical peak absolute magnitudes of −13 to −14 mag, most extragalactic events observed so far are quite different from η Car in duration. Their bright phases typically last for ∼100 d or less, rather than persisting for several years. The transient object UGC 2773-OT (discovered in 2009) had a similar peak absolute magnitude to other SN impostors, but with a gradual 5-yr prediscovery rise. In the ∼6 yr since discovery, it has faded very slowly (0.26 mag yr −1 ). Overall, we suggest that its decade-long eruption is so far the best known analog of η Car's 19th century eruption. We discuss extensive spectroscopy of the ongoing eruption. The spectra show interesting changes in velocity and line shape that we discuss in detail, including an asymmetric Hα emission line that we show is consistent with the ejection of a bipolar nebula that could be very much like the Homunculus of η Car. Moreover, changes in the line width, line profile, blue excess emission resembling that of Type IIn supernovae, and the intensity of Hα suggest the presence of strong circumstellar interaction in the eruption at late times. This supports the hypothesis that the extended plateau of η Car's eruption may have been powered by shock interaction as well. One interesting difference compared to η Car, however, is that UGC 2773-OT so far does not exhibit the repeated brief spikes in luminosity that have been associated with binary periastron events.

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Section: Asymmetry In the Ejectasupporting

confidence: 58%

The Persistent Eruption of UGC 2773-OT: finally, a decade-long extragalactic Eta Carinae analogue

Smith

Andrews

Mauerhan

et al. 2015

Mon. Not. R. Astron. Soc.

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“…In the same analysis, Smith et al (2016) also showed that line emission from the present-day bipolar nebula around η Car shows a similar blue emission bump. An asymmetric blue bump in Hα has also been seen at faster speeds in several SNe IIn (Smith et al 2012a(Smith et al ,b, 2015Fransson et al 2014), usually attributed to bipolar or perhaps disk-like geometry in the shock interaction. A corresponding red bump is usually assumed to be weaker or absent owing to extinction by dust or occultation by the opaque SN ejecta.…”

Section: Spectroscopic Evolutionmentioning

confidence: 90%

Massive star mergers and the recent transient in NGC 4490: a more massive cousin of V838 Mon and V1309 Sco

Smith

Andrews

Dyk

et al. 2016

Mon. Not. R. Astron. Soc.

119

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The Galactic transient V1309 Sco was the result of a merger in a low-mass star system, while V838 Mon was thought to be a similar merger event from a more massive B-type progenitor. In this paper we study a recent optical and infrared (IR) transient discovered in the nearby galaxy NGC 4490 named NGC 4490-OT2011 (NGC 4490-OT hereafter), which appeared similar to these merger events (unobscured progenitor, irregular multi-peaked light curve, increasingly red colour, similar optical spectrum, IR excess at late times), but which had a higher peak luminosity and longer duration in outburst. NGC 4490-OT has less in common with the class of SN 2008S-like transients. A progenitor detected in pre-eruption Hubble Space Telescope (HST) images, combined with upper limits in the IR, requires a luminous and blue progenitor that has faded in late-time HST images. The same source was detected by Spitzer and ground-based data as a luminous IR (2-5 µm) transient, indicating a transition to a self-obscured state qualitatively similar to the evolution seen in other stellar mergers and in luminous blue variables. The post-outburst dust-obscured source is too luminous and too warm at late times to be explained with an IR echo, suggesting that the object survived the event. The luminosity of the enshrouded IR source is similar to that of the progenitor. Compared to proposed merger events, the more massive progenitor of NGC 4490-OT seems to extend a correlation between stellar mass and peak luminosity, and may suggest that both of these correlate with duration. We show that spectra of NGC 4490-OT and V838 Mon also resemble light-echo spectra of η Car, prompting us to speculate that η Car may be an extreme extension of this phenomenon.

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Die noodsaaklikheid van ’n ander paradigma vir Suid-Afrikaanse sosiologie

Cited by 2 publications

References 0 publications

The Persistent Eruption of UGC 2773-OT: finally, a decade-long extragalactic Eta Carinae analogue

The Persistent Eruption of UGC 2773-OT: finally, a decade-long extragalactic Eta Carinae analogue

Massive star mergers and the recent transient in NGC 4490: a more massive cousin of V838 Mon and V1309 Sco

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