Carinae's Brightness Variations Since 1998:<i>Hubble Space Telescope</i>Observations of the Central Star

Martin, John; Koppelman, M. D.

doi:10.1086/382716

Cited by 44 publications

(65 citation statements)

References 14 publications

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“…This is also true for previous events (Steiner & Damineli 2004). a Earlier results can be found in (Martin & Koppelman 2004;Martin et al 2006bMartin et al , 2010.…”

Section: Unsolved Problemssupporting

confidence: 53%

“…We have monitored the brightness changes of the central star in several band-passes with photometry from HST ACS/HRC and WFPC2 images and STIS spectra since 1998 (Martin & Koppelman 2004;Martin et al 2006bMartin et al , 2010. During the 2009 event we monitored the brightness of the central star with the HST WFPC2 camera using the F255W and F336W filters.…”

Section: Hst Photometry With Wfpc2 and Stismentioning

confidence: 99%

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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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“…This is also true for previous events (Steiner & Damineli 2004). a Earlier results can be found in (Martin & Koppelman 2004;Martin et al 2006bMartin et al , 2010.…”

Section: Unsolved Problemssupporting

confidence: 53%

Section: Hst Photometry With Wfpc2 and Stismentioning

confidence: 99%

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

Mehner

Davidson²,

Martin

et al. 2011

ApJ

105

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“…In addition to the overall increase in its brightness, the central source is now much brighter than in the past and is increasingly contributing a greater fraction of the observed optical flux. In 8 yr, HST observations reveal that the central region became brighter by about 2 mag (Martin & Koppelman 2004). Superimposed on the longer-term trend is the imprint of the binary with its 5.5 yr period (e.g., Whitelock et al 2004;van Genderen et al 2006;Fernández-Lajús et al 2010;Mehner et al 2014), as well as more random variations.…”

Section: The Luminosity Of Hcarinaementioning

confidence: 98%

η Carinae's Dusty Homunculus Nebula from Near-infrared to Submillimeter Wavelengths: Mass, Composition, and Evidence for Fading Opacity

Morris

Gull

Hillier

et al. 2017

ApJ

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Infrared observations of the dusty, massive Homunculus Nebula around the luminous blue variable η Carinae are crucial to characterize the mass-loss history and help constrain the mechanisms leading to the great eruption. We present the 2.4-670 μm spectral energy distribution, constructed from legacy Infrared Space Observatory observations and new spectroscopy obtained with the Herschel Space Observatory. Using radiative transfer modeling, we find that the two best-fit dust models yield compositions that are consistent with CNO-processed material, with iron, pyroxene and other metal-rich silicates, corundum, and magnesium-iron sulfide in common. Spherical corundum grains are supported by the good match to a narrow 20.2 μm feature. Our preferred model contains nitrides AlN and Si 3 N 4 in low abundances. Dust masses range from 0.25 to 0.44tot in both cases, due to an expected high Fe gas-to-dust ratio. The bulk of dust is within a ´ 5 7 central region. An additional compact feature is detected at 390 μm. We obtain L IR = 2.96×10 6  L , a 25% decline from an average of mid-IR photometric levels observed in 1971-1977. This indicates a reduction in circumstellar extinction in conjunction with an increase in visual brightness, allowing 25%-40% of optical and UV radiation to escape from the central source. We also present an analysis of 12 CO and 13 CO J=5-4 through 9-8 lines, showing that the abundances are consistent with expectations for CNO-processed material. The [ 12 C II] line is detected in absorption, which we suspect originates in foreground material at very low excitation temperatures.

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“…Since the spectroscopic event might in principle result from a mass-shell ejection by the primary star (Zanella et al 1984;Davidson et al 1999;Smith et al 2003a;Martin & Koppelman 2004), it is also called a shell-ejection event.…”

Section: Introductionmentioning

confidence: 99%

Accretion by the Secondary in η Carinae During the Spectroscopic Event. I. Flow Parameters

Soker

2005

ApJ

120

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We examine the influence of the gravity of the companion (the secondary) to the massive primary star Carinae on the winds blown by the primary and the secondary. The two winds collide with each other after passing through two respective shock waves, and escape the system while strongly emitting in the X-ray band. While during most of the 5.5 yr orbital period the companion's gravity has a negligible effect on the winds, we find that near periastron the companion's gravity may significantly influence the flow, and the companion might accrete from the primary's wind under certain circumstances. Near periastron passage, the collision region of the two winds may collapse onto the secondary star, a process that could substantially reduce the X-ray luminosity. We suggest that such an accretion process produces the long, almost flat, X-ray minimum in Car.

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Carinae's Brightness Variations Since 1998:Hubble Space TelescopeObservations of the Central Star

Cited by 44 publications

References 14 publications

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

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

η Carinae's Dusty Homunculus Nebula from Near-infrared to Submillimeter Wavelengths: Mass, Composition, and Evidence for Fading Opacity

Accretion by the Secondary in η Carinae During the Spectroscopic Event. I. Flow Parameters

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