$\mathsf{\eta}$ Car: the optical features at the 2003.5 low-excitation event

Genderen, A. M. van; Sterken, C.; Allen, William H.; Liller, W.

doi:10.1051/0004-6361:20031675

Cited by 17 publications

(12 citation statements)

References 13 publications

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“…In HST data, observations at t = −5 d and +12 d showed the lowest brightness, in agreement with their data. Other aspects of the 2009 event are consistent with broad-band optical and infrared observations of past events (Fernández-Lajús et al 2003;van Genderen et al 2003;Whitelock et al 2004;Fernández-Lajús et al 2010). The star began brightening at an accelerated rate about 40 to 50 days prior to the onset of the event.…”

Section: Light Curve Of the Star 2008-2011supporting

confidence: 78%

Critical Differences and Clues in Eta Car's 2009 Event,

Mehner

Davidson²,

Martin

et al. 2011

ApJ

105

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We monitored Eta Carinae with HST WFPC2 and Gemini GMOS throughout the 2009 spectroscopic event, which was expected to differ from its predecessor in 2003). Here we report major observed differences between events, and their implications. Some of these results were quite unexpected. (1) The UV brightness minimum was much deeper in 2009. This suggests that physical conditions in the early stages of an event depend on different parameters than the "normal" inter-event wind. Extra mass ejection from the primary star is one possible cause. (2) The expected He II λ4687 brightness maximum was followed several weeks later by another. We explain why this fact, and the timing of the λ4687 maxima, strongly support a "shock breakup" hypothesis for X-ray and λ4687 behavior as proposed 5-10 years ago. (3) We observed a polar view of the star via light reflected by dust in the Homunculus nebula. Surprisingly, at that location the variations of emission-line brightness and Doppler velocities closely resembled a direct view of the star; which should not have been true for any phenomena related to the orbit. This result casts very serious doubt on all the proposed velocity interpretations that depend on the secondary star's orbital motion. (4) Latitude-dependent variations of H I, He I and Fe II features reveal aspects of wind behavior during the event. In addition, we discuss implications of the observations for several crucial unsolved problems.

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Section: Light Curve Of the Star 2008-2011supporting

confidence: 78%

Critical Differences and Clues in Eta Car's 2009 Event,

Mehner

Davidson²,

Martin

et al. 2011

ApJ

105

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“…First proposed by Damineli, Conti & Lopes (1997), it is now widely accepted that Eta Car is a massive, colliding‐wind binary system with a high eccentricity ( e ∼ 0.9; Corcoran 2005) and an orbital period of 2022.7 ± 1.3 d (Damineli et al 2008b). This scenario is supported by multi‐wavelength observations in X‐rays (Corcoran et al 1997, 2001, 2010; Pittard et al 1998; Ishibashi et al 1999; Pittard & Corcoran 2002; Corcoran 2005; Hamaguchi et al 2007; Henley et al 2008), ultraviolet (UV; Smith et al 2004; Iping et al 2005; Madura & Groh 2012), optical (Damineli et al 2000, 2008a,b; Fernández‐Lajús et al 2003, 2009, 2010; van Genderen et al 2003, 2006; Steiner & Damineli 2004; Nielsen et al 2007; Mehner et al 2011; Teodoro et al 2012), near‐infrared (IR; Feast, Whitelock & Marang 2001; Whitelock et al 2004; Gull et al 2009; Groh et al 2010a,b) and radio wavelengths (Duncan & White 2003; Abraham et al 2005a).…”

Section: Introductionmentioning

confidence: 87%

On the influence of the companion star in Eta Carinae: 2D radiative transfer modelling of the ultraviolet and optical spectra★

Groh

Hillier

Madura

et al. 2012

Monthly Notices of the Royal Astronomical Society

132

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We present two‐dimensional (2D) radiative transfer modelling of the Eta Carinae binary system accounting for the presence of a wind–wind collision (WWC) cavity carved in the optically thick wind of the primary star. By comparing synthetic line profiles with spectra obtained with the Hubble Space Telescope/Space Telescope Imaging Spectrograph near apastron, we show that the WWC cavity has a strong influence on multi‐wavelength diagnostics. This influence is regulated by the modification of the optical depth in the continuum and spectral lines. We find that Hα, Hβ and Fe ii lines are the most affected by the WWC cavity, since they form over a large volume of the stellar wind of the primary. These spectral lines depend on latitude and azimuth since, according to the orientation of the cavity, different velocity regions of a spectral line are affected. For 2D models with orientation corresponding to orbital inclination angle and longitude of periastron , the blueshifted and zero‐velocity regions of the line profiles are the most affected by the cavity. These orbital orientations are required to simultaneously fit the ultraviolet (UV) and optical spectrum of Eta Car around apastron, for a half‐opening angle of the cavity in the range of 50°–70°. We find that the excess P Cygni absorption seen in Hα, Hβ and optical Fe ii lines in 1D spherical models becomes much weaker or absent in the 2D cavity models, in agreement with the observations. The observed UV spectrum of Eta Car is strongly dominated by absorption of Fe ii lines that are superbly reproduced by our 2D models when the presence of the low‐density WWC cavity is taken into account. Small discrepancies still remain, as the P Cygni absorption of Hγ and Hδ is overestimated by our 2D models at apastron. We suggest that photoionization of the wind of the primary by the hot companion star is responsible for the weak absorption seen in these lines. Our cmfgen models indicate that the primary star has a mass‐loss rate of 8.5 × 10−4 M⊙ yr−1 and wind terminal velocity of 420 km s−1 around the 2000–2001 apastron.

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“…Variations in the continuum flux are easily derived from existing photometry, since we need only relative changes, avoiding complications involved in magnitude standardization. Color variations along the event are negligible in the optical window (at wavelengths longer than the Balmer jump), as indicated by the B − V colour index (Lajús et al 2003; van Genderen et al 2003). The problem is that the amplitude of the variations depends on the aperture used to extract the magnitudes, and the ones of published photometry do not match the slit aperture used to record the spectra.…”

Section: The Composite Morphology Of the Eventmentioning

confidence: 99%

A multispectral view of the periodic events in η Carinae

Damineli

Hillier

Corcoran

et al. 2008

Monthly Notices RAS

134

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A full description of the 5.5‐yr low excitation events in η Carinae is presented. We show that they are not as simple and brief as previously thought, but a combination of two components. The first, the slow variation component, is revealed by slow changes in the ionization level of circumstellar matter across the whole cycle and is caused by gradual changes in the wind–wind collision shock‐cone orientation, angular opening and gaseous content. The second, the collapse component, is restricted to around the minimum, and is due to a temporary global collapse of the wind–wind collision shock. High‐energy photons (E > 16 eV) from the companion star are strongly shielded, leaving the Weigelt objects at low‐ionization state for more than six months. High‐energy phenomena are sensitive only to the collapse, low energy only to the slow variation and intermediate energies to both components. Simple eclipses and mechanisms effective only near periastron (e.g. shell ejection or accretion on to the secondary star) cannot account for the whole 5.5‐yr cycle. We find anti‐correlated changes in the intensity and the radial velocity of P Cygni absorption profiles in Fe iiλ6455 and He iλ7065 lines, indicating that the former is associated to the primary and the latter to the secondary star. We present a set of light curves representative of the whole spectrum, useful for monitoring the next event (2009 January 11).

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$\mathsf{\eta}$ Car: the optical features at the 2003.5 low-excitation event

Cited by 17 publications

References 13 publications

Critical Differences and Clues in Eta Car's 2009 Event,

Critical Differences and Clues in Eta Car's 2009 Event,

On the influence of the companion star in Eta Carinae: 2D radiative transfer modelling of the ultraviolet and optical spectra★

A multispectral view of the periodic events in η Carinae

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