Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userA hot transient outflow from eta Carinae
184
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
eta Carinae is a stellar binary system with a period of 5.54 years. It harbors one of the brightest and most massive stars in our galaxy. This paper presents spectroscopic evidence for a fast (up to 2,000 km/s) X-ray outflow of ionized gas launched from eta Carinae just before what is believed to be the binary periastron (point of smallest binary separation). The appearance of this high-velocity component, just as the irregular flares in the X-ray light curve, can not be explained by the simple continuous binary wind interaction, adding to the intrigue of the eta Carinae system.
rate research
Read More
We present critical, long-wavelength observations of Eta Carinae in the submillimetre using SCUBA on the JCMT at 850 and 450 um to confirm the presence of a large mass of warm dust around the central star. We fit a two-component blackbody to the IR-submm spectral energy distribution and estimate between 0.3-0.7 solar masses of dust exists in the nebula depending on the dust absorption properties and the extent of contamination from free-free emission at the SCUBA wavelengths. These results provide further evidence that Eta Carinaes circumstellar nebula contains > 10 solar masses of gas, although this may have been ejected on a longer timescale than previously thought.
Recently Supernova 2006gy was noted as the most luminous ever recorded, with a total radiated energy of ~10^44 Joules. It was proposed that the progenitor may have been a massive evolved star similar to eta Carinae, which resides in our own galaxy at a distance of about 2.3 kpc. eta Carinae appears ready to detonate. Although it is too distant to pose a serious threat as a normal supernova, and given its rotation axis is unlikely to produce a Gamma-Ray Burst oriented toward the Earth, eta Carinae is about 30,000 times nearer than 2006gy, and we re-evaluate it as a potential superluminous supernova. We find that given the large ratio of emission in the optical to the X-ray, atmospheric effects are negligible. Ionization of the atmosphere and concomitant ozone depletion are unlikely to be important. Any cosmic ray effects should be spread out over ~10^4 y, and similarly unlikely to produce any serious perturbation to the biosphere. We also discuss a new possible effect of supernovae, endocrine disruption induced by blue light near the peak of the optical spectrum. This is a possibility for nearby supernovae at distances too large to be considered dangerous for other reasons. However, due to reddening and extinction by the interstellar medium, eta Carinae is unlikely to trigger such effects to any significant degree.
We present preliminary results of our analysis on the long-term variations observed in the optical spectrum of the LBV star Eta Carinae. Based on the hydrogen line profiles, we conclude that the physical parameters of the primary star did not change in the last 15 years.
Eta Carinae was observed by FUSE through the LWRS (30 arcsec x30 arcsec) and HIRS (1.25 arcsec x 20 arcsec) apertures in March and April 2004. There are significant differences between the two spectra. About half of the LWRS flux appears to be due to two B-type stars near the edge of the LWRS aperture, 14 arcsec from eta Carinae. The HIRS spectrum (LiF1 channel) therefore reveals the intrinsic FUV spectrum of eta Carinae without this stellar contamination. The HIRS spectrum contains strong interstellar H2 having high rotational excitation (up to J=8). Most of the atomic species with prominent ISM features (C II, Fe II, Ar I, P II, etc) also have strong blue-shifted absorption to v= ~ -580 km/s that is associated with expanding debris from the 1840 eruption.
The interacting binary Eta Carinae remains one of the most enigmatic massive stars in our Galaxy despite over four centuries of observations. In this work, its light curve from the ultraviolet to the near-infrared is analysed using spatially resolved HST observations and intense monitoring at the La Plata Observatory, combined with previously published photometry. We have developed a method to separate the central stellar object in the ground-based images using HST photometry and applying it to the more numerous ground-based data, which supports the hypothesis that the central source is brightening faster than the almost-constant Homunculus. After detrending from long-term brightening, the light curve shows periodic orbital modulation ($Delta V$ $sim$ 0.6 mag) attributed to the wind-wind collision cavity as it sweeps around the primary star and it shows variable projected area to our line-of-sight. Two quasi-periodic components with time scales of 2-3 and 8-10 yr and low amplitude, $Delta V$ $<$ 0.2 mag, are superimposed on the brightening light-curve, being the only stellar component of variability found, which indicates minimal stellar instability. Moreover, the light curve analysis shows no evidence of `shell ejections at periastron. We propose that the long-term brightening of the stellar core is due to the dissipation of a dusty clump in front of the central star, which works like a natural coronagraph. Thus, the central stars appear to be more stable than previously thought since the dominant variability originates from a changing circumstellar medium. We predict that the brightening phase, due mainly to dust dissipation, will be completed around 2032 $pm$ 4 yr, when the star will be brighter than in the 1600s by up to $Delta V$ $sim$ 1 mag.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
