Hostname: page-component-586b7cd67f-t7czq Total loading time: 0 Render date: 2024-11-26T00:02:19.754Z Has data issue: false hasContentIssue false

The wind-wind collision hole in eta Car

Published online by Cambridge University Press:  28 July 2017

A. Damineli
Affiliation:
Inst. de Astron., Geofísica e Ciências Atmosféricas, Univ. de São Paulo, R. do Matão 1226, São Paulo 05508-900, Brazil email: [email protected]
M. Teodoro
Affiliation:
Astroph. Sci. Division, Code 660, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA USRA, 7178 Columbia, MD 20146, USA
N. D. Richardson
Affiliation:
Ritter Observ., Depart. of Phys. and Astr., The University of Toledo, Toledo, OH 43606-3390, USA
T. R. Gull
Affiliation:
Astroph. Sci. Division, Code 660, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
M. F. Corcoran
Affiliation:
Astroph. Sci. Division, Code 660, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA USRA, 7178 Columbia, MD 20146, USA
K. Hamaguchi
Affiliation:
Astroph. Sci. Division, Code 660, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA USRA, 7178 Columbia, MD 20146, USA
J. H. Groh
Affiliation:
School of Physiscs, Trinity College Dublin, The Un. of Dublin, Dublin 2, Ireland
G. Weigelt
Affiliation:
Max-Planck-Institut for Radioastronomy, Auf dem Hügel 69, D-53121 Bonn, Germany
D. J. Hillier
Affiliation:
Depart. of Phys. and Astr., Univ. of Pittsburgh, 3941 O’Hara Street, Pittsburgh, PA 15260, USA
C. Russell
Affiliation:
Astroph. Sci. Division, Code 660, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
A. Moffat
Affiliation:
Départ. de Physique, Univ. de Montréal, CP 6128, Succursale: Centre-Ville, Montréal, QC, H3C 3J7, Canada
K. R. Pollard
Affiliation:
Department of Physics and Astronomy, University of Canterbury, Chirstchurch, New Zealand
T. I. Madura
Affiliation:
San Jose State University, Depart. of Physics and Astronomy, San Jose, CA, USA
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

Eta Carinae is one of the most massive observable binaries. Yet determination of its orbital and physical parameters is hampered by obscuring winds. However the effects of the strong, colliding winds changes with phase due to the high orbital eccentricity. We wanted to improve measures of the orbital parameters and to determine the mechanisms that produce the relatively brief, phase-locked minimum as detected throughout the electromagnetic spectrum. We conducted intense monitoring of the He ii λ4686 line in η Carinae for 10 months in the year 2014, gathering ~300 high S/N spectra with ground- and space-based telescopes. We also used published spectra at the FOS4 SE polar region of the Homunculus, which views the minimum from a different direction. We used a model in which the He ii λ4686 emission is produced by two mechanisms: a) one linked to the intensity of the wind-wind collision which occurs along the whole orbit and is proportional to the inverse square of the separation between the companion stars; and b) the other produced by the ‘bore hole’ effect which occurs at phases across the periastron passage. The opacity (computed from 3D SPH simulations) as convolved with the emission reproduces the behavior of equivalent widths both for direct and reflected light. Our main results are: a) a demonstration that the He ii λ4686 light curve is exquisitely repeatable from cycle to cycle, contrary to previous claims for large changes; b) an accurate determination of the longitude of periastron, indicating that the secondary star is ‘behind’ the primary at periastron, a dispute extended over the past decade; c) a determination of the time of periastron passage, at ~4 days after the onset of the deep light curve minimum; and d) show that the minimum is simultaneous for observers at different lines of sight, indicating that it is not caused by an eclipse of the secondary star, but rather by the immersion of the wind-wind collision interior to the inner wind of the primary.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2017 

References

Corcoran, M. F., Hamaguchi, K., Pittard, J.M. et al. 2010 ApJ, 725, 1528 CrossRefGoogle Scholar
Damineli, A., 1996, ApJ (Letters), 460, L49 CrossRefGoogle Scholar
Damineli, A., Conti, P. S., Lopes, D. F., 1997, New Astron., 2, 107 CrossRefGoogle Scholar
Damineli, A., et al., 2008, MNRAS, 384, 1649 CrossRefGoogle Scholar
Davidson, K., Humphreys, R. M., 1997, ARAA, 35, 1 CrossRefGoogle Scholar
Duncan, R.A. & Whithe, S.M. 2003, 2003, MNRAS, 338, 425 CrossRefGoogle Scholar
Fahed, R., et al., 2011, MNRAS, 418, 2 CrossRefGoogle Scholar
Gull, T., et al., 2009, MNRAS, 396, 1308 CrossRefGoogle Scholar
Gull, T., et al., 2016, MNRAS, 462, 3196 CrossRefGoogle Scholar
Hillier, D. J., Davidson, K., Ishibashi, K., Gull, T., 2001, ApJ, 553, 837 CrossRefGoogle Scholar
Ishibashi, K., Corcoran, M. F., et al. 1999, ApJ, 524, 983 CrossRefGoogle Scholar
Madura, T. I., Owocki, S. P. 2010, RMAA, 38, 52 Google Scholar
Madura, T. I., et al., 2013, MNRAS, 436, 3820 CrossRefGoogle Scholar
Mehner, A., et al., 2015, A&A, 578, 122 Google Scholar
Prieto, et al., 2014 ApJ, 787, L8 CrossRefGoogle Scholar
Smith, N., 2006, AJ, 644, 1151 CrossRefGoogle Scholar
Steffen, W., et al., 2014, MNRAS, 442, 3316 CrossRefGoogle Scholar
Steiner, J. E., Damineli, A., 2004, ApJ (Letters), 612, L133 CrossRefGoogle Scholar
Teodoro, M., et al., 2012, ApJ, 746, 73 CrossRefGoogle Scholar
Teodoro, M., Damineli, A., et al. 2016, ApJ, 819, 131 CrossRefGoogle Scholar
Weigelt, G., et al., 2016, A&A, 594, 106 Google Scholar