TY - JOUR
T1 - Exceptionally fast ejecta seen in light echoes of Eta Carinae's Great Eruption
AU - Smith, Nathan
AU - Rest, Armin
AU - Andrews, Jennifer E.
AU - Matheson, Tom
AU - Bianco, Federica B.
AU - Prieto, Jose L.
AU - James, David J.
AU - Chris Smith, R.
AU - Strampelli, Giovanni Maria
AU - Zenteno, A.
N1 - Funding Information:
NS’s research on Eta Carinae’s light echoes and related LBV-like eruptions received support from NSF grants AST-1312221 and AST-1515559. Support for JLP is provided in part by FONDECYT through the grant 1151445 and by the Ministry of Economy, Development, and Tourism’s Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics, MAS. DJJ gratefully acknowledges support from the National Science Foundation, award AST-1440254.
Funding Information:
This paper includes data gathered with the 6.5m Magellan Telescopes located at Las Campanas Observatory, Chile. Based, in part, on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CON-ICYT (Chile), Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina), and Ministério da Ciência, Tecnologia e Inovac¸ão (Brazil) (Program GS-2014B-Q-24).
Funding Information:
We thank an anonymous referee for a careful reading of the manuscript and constructive comments.We acknowledge contributions of additional collaborators who helped with imaging observations to discover and monitor light echoes, as well as for discussions and contributions to proposals for telescope time for this and related projects: the Carnegie Supernova Project, Alejandro Clocchiatti, Steve Margheim, Doug Welch, and Nolan Walborn. In particular, Nolan Walborn provided helpful comments on the manuscript just weeks before he passed away, which occurred while this paper was under review. His contributions to massive star research have been tremendous, and his unique insight will be sorely missed. NS's research on Eta Carinae's light echoes and related LBVlike eruptions received support from NSF grants AST-1312221 and AST-1515559. Support for JLP is provided in part by FONDECYT through the grant 1151445 and by the Ministry of Economy, Development, and Tourism'sMillennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics, MAS. DJJ gratefully acknowledges support from the National Science Foundation, award AST-1440254. This paper includes data gathered with the 6.5m Magellan Telescopes located at Las Campanas Observatory, Chile. Based, in part, on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina), and Ministério da Cîencia, Tecnologia e Inovação (Brazil) (Program GS-2014B-Q-24).
Publisher Copyright:
© 2018 The Author(s).
PY - 2018/10
Y1 - 2018/10
N2 - In our ongoing study of η Carinae's light echoes, there is a relatively bright echo that has been fading slowly, reflecting the 1845-1858 plateau phase of the eruption. A separate paper discusses its detailed evolution, but here we highlight one important result: the Hα line in this echo shows extremely broad emission wings that reach -10 000 km s-1 to the blue and + 20 000 km s-1 to the red. The line profile shape is inconsistent with electron scattering wings, so the broad wings indicate high-velocity outflowing material. To our knowledge, these are the fastest outflow speeds ever seen in a non-terminal massive star eruption. The broad wings are absent in early phases of the eruption in the 1840s, but strengthen in the 1850s. These speeds are two orders of magnitude faster than the escape speed from a warm supergiant, and 5-10 times faster than winds from O-type or Wolf-Rayet stars. Instead, they are reminiscent of fast supernova ejecta or outflows from accreting compact objects, profoundly impacting our understanding of η Car and related transients. This echo views η Car from latitudes near the equator, so the high speed does not trace a collimated polar jet aligned with the Homunculus. Combined with fast material in the Outer Ejecta, it indicates a wide-angle explosive outflow. The fast material may constitute a small fraction of the total outflowing mass, most of which expands at ~600 km s-1. This is reminiscent of fast material revealed by broad absorption during the pre-supernova eruptions of SN 2009ip.
AB - In our ongoing study of η Carinae's light echoes, there is a relatively bright echo that has been fading slowly, reflecting the 1845-1858 plateau phase of the eruption. A separate paper discusses its detailed evolution, but here we highlight one important result: the Hα line in this echo shows extremely broad emission wings that reach -10 000 km s-1 to the blue and + 20 000 km s-1 to the red. The line profile shape is inconsistent with electron scattering wings, so the broad wings indicate high-velocity outflowing material. To our knowledge, these are the fastest outflow speeds ever seen in a non-terminal massive star eruption. The broad wings are absent in early phases of the eruption in the 1840s, but strengthen in the 1850s. These speeds are two orders of magnitude faster than the escape speed from a warm supergiant, and 5-10 times faster than winds from O-type or Wolf-Rayet stars. Instead, they are reminiscent of fast supernova ejecta or outflows from accreting compact objects, profoundly impacting our understanding of η Car and related transients. This echo views η Car from latitudes near the equator, so the high speed does not trace a collimated polar jet aligned with the Homunculus. Combined with fast material in the Outer Ejecta, it indicates a wide-angle explosive outflow. The fast material may constitute a small fraction of the total outflowing mass, most of which expands at ~600 km s-1. This is reminiscent of fast material revealed by broad absorption during the pre-supernova eruptions of SN 2009ip.
KW - Circumstellar matter
KW - Outflows
KW - Stars: evolution
KW - Stars: winds
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U2 - 10.1093/MNRAS/STY1479
DO - 10.1093/MNRAS/STY1479
M3 - Article
AN - SCOPUS:85055332728
SN - 0035-8711
VL - 480
SP - 1457
EP - 1465
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 2
ER -