A disrupted molecular torus around Eta Carinae as seen in 12CO with ALMA

Smith, Nathan; Ginsburg, Adam; Bally, John

doi:10.1093/mnras/stx3050

Cited by 27 publications

(48 citation statements)

References 72 publications

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“…Regarding the latter, one possible channel to sculpt such a CSM feature is from an eccentric binary system undergoing eruptive mass loss. We directly observe similar dense bipolar CSM regions in evolved stars like η Carinae (Davidson & Humphreys 1997;Smith et al 2007Smith et al , 2018 and Betelgeuse (Kervella et al 2018), as well as indirectly in SN imposters like UGC2773-OT and SN 2009ip (e.g., Smith et al 2010;Mauerhan et al 2014;Reilly et al 2017), or type IIn SNe such as SN 2012ab (Bilinski et al 2018), and of course SN 1987A, which is the clearest example of a SN evolving into a bipolar bubble. We return to this point in §4.2 and §4.3…”

Section: Two Distinct Shocksmentioning

confidence: 52%

The exceptional X-ray evolution of SN 1996cr in high resolution

Quirola-Vásquez

Bauer

Dwarkadas

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We present X-ray spectra spanning 18 years of evolution for SN 1996cr, one of the five nearest SNe detected in the modern era. Chandra HETG exposures in 2000, 2004, and 2009 allow us to resolve spectrally the velocity profiles of Ne, Mg, Si, S, and Fe emission lines and monitor their evolution as tracers of the ejecta-circumstellar medium (CSM) interaction. To explain the diversity of X-ray line profiles, we explore several possible geometrical models. Based on the highest signal-to-noise 2009 epoch, we find that a polar geometry with two distinct opening angle configurations and internal obscuration can successfully reproduce all of the observed line profiles. The best fit model consists of two plasma components: (1) a mildly absorbed (2×10 21 cm −2 ), cooler (≈2 keV) with high Ne, Mg, Si, and S abundances associated with a wide polar interaction region (half-opening angle ≈58 • ); (2) a moderately absorbed (2×10 22 cm −2 ), hotter ( > ∼ 20 keV) plasma with high Fe abundances and strong internal obscuration associated with a narrow polar interaction region (half-opening angle ≈20 • ). We extend this model to seven further epochs with lower signal-to-noise ratio and/or lower spectral-resolution between 2000-2018, yielding several interesting trends in absorption, flux, geometry and expansion velocity. We argue that the hotter and colder components are associated with reflected and forward shocks, respectively, at least at later epochs. We discuss the physical implications of our results and plausible explosion scenarios to understand the X-ray data of SN 1996cr.

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Section: Two Distinct Shocksmentioning

confidence: 52%

The exceptional X-ray evolution of SN 1996cr in high resolution

Quirola-Vásquez

Bauer

Dwarkadas

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…Artigau et al (2011) argue that this "Butterfly" nebula (Chesneau et al 2005) is not a coherent physical structure or equatorial torus but spatially separate clumps and filaments ejected at different times. Radial velocity information from ALMA observations support the general picture that the loops are a pinched torus in the orbital plane, perpendicular to the Homunculus lobes (Smith et al 2018). The direction of the pinched material matches periastron/apastron orientation (Madura et al 2013) and the companion may have played a role in disrupting the torus soon after its ejection.…”

Section: Resolved Dusty Circumstellar Structuresmentioning

confidence: 61%

“…A. Mehner et al: Mid-infrared evolution of η Car from 1968to 2018 Appendix A: Mid-IR images with VISIR in 2018…”

mentioning

confidence: 99%

Mid-infrared evolution of η Carinae from 1968 to 2018

Mehner

Wit

Asmus

et al. 2019

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Eta Car is one of the most luminous and massive stars in our Galaxy and is the brightest mid-infrared (mid-IR) source in the sky, outside our solar system. Since the late 1990s the central source has dramatically brightened at ultraviolet and optical wavelengths. This might be explained by a decrease in circumstellar dust extinction. We aim to establish the mid-IR flux evolution and further our understanding of the star's ultraviolet and optical brightening. Mid-IR images from 8 − 20 µm were obtained in 2018 with VISIR at the Very Large Telescope. Archival data from 2003 and 2005 are retrieved from the ESO Science Archive Facility and historical records are collected from publications. We present the highest angular resolution mid-IR images of η Car to date at the corresponding wavelengths (≥ 0.22 ). We reconstruct the mid-IR evolution of the spectral energy distribution of the spatially integrated Homunculus nebula from 1968 to 2018 and find no long-term changes. Eta Car's bolometric luminosity has been stable over the past five decades. We do not observe a long-term decrease in the mid-IR flux densities that could be associated with the brightening at ultraviolet and optical wavelengths, but circumstellar dust must be declining in our line-of-sight only. Short-term flux variations within about 25% of the mean levels could be present.

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“…The connection to any model for the Great Eruption is evident when we consider the relative orientation of the torus compared to the currently observed eccentric binary system. Namely, the direction of apastron in the eccentric binary seen today is also to the northwest (Madura et al 2012), toward the middle of the gap in the torus (Smith et al 2018a). This suggests that the wide eccentric companion seen today had roughly the same orbital orientation during the lead up to the Great Eruption (i.e.…”

Section: 7mentioning

confidence: 94%

“…This torus has been discussed by numerous authors, the history of which is summarized by Smith (2012). More recently, high-resolution observations of 12 CO 2-1 with the Atacama Large Millimeter Array (ALMA) have revealed new clues to the structure of the equatorial ejecta (Smith et al 2018a). The CO emission shows a toroidal structure with a size similar to previous IR data, but the density structure of the CO torus departs strongly from azimuthal symmetry.…”

Section: 7mentioning

confidence: 99%

Light echoes from the plateau in Eta Carinae’s Great Eruption reveal a two-stage shock-powered event

Smith

Andrews

Rest

et al. 2018

Monthly Notices of the Royal Astronomical Society

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We present multi-epoch photometry and spectroscopy of a light echo from η Carinae’s 19th century Great Eruption. This echo's light curve shows a steady decline over a decade, sampling the 1850s plateau of the eruption. Spectra show the bulk outflow speed increasing from ∼150 km s−1 at early times, up to ∼600 km s−1 in the plateau. Later phases also develop remarkably broad emission wings indicating mass accelerated to more than 10 000 km s−1. Together with other clues, this provides direct evidence for an explosive ejection. This is accompanied by a transition from a narrow absorption line spectrum to emission lines, often with broad or asymmetric P Cygni profiles. These changes imply that the pre-1845 luminosity spikes are distinct from the 1850s plateau. The key reason for this change may be that shock interaction with circumstellar material (CSM) dominates the plateau. The spectral evolution of η Car closely resembles that of the decade-long eruption of UGC 2773-OT, which had clear signatures of shock interaction. We propose a two-stage scenario for η Car’s eruption: (1) a slow outflow in the decades before the eruption, probably driven by binary interaction that produced a dense equatorial outflow, followed by (2) explosive energy injection that drove CSM interaction, powering the plateau and sweeping slower CSM into a fast shell that became the Homunculus. We discuss how this sequence could arise from a stellar merger in a triple system, leaving behind the eccentric binary seen today. This gives a self-consistent scenario that may explain interacting transients across a wide range of initial mass.

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A disrupted molecular torus around Eta Carinae as seen in 12CO with ALMA

Cited by 27 publications

References 72 publications

The exceptional X-ray evolution of SN 1996cr in high resolution

The exceptional X-ray evolution of SN 1996cr in high resolution

Mid-infrared evolution of η Carinae from 1968 to 2018

Light echoes from the plateau in Eta Carinae’s Great Eruption reveal a two-stage shock-powered event

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