Unusual Line Profile Research Articles

Explaining the unusual line profiles of SN 2006gy

Origin of enigmatic line profiles of extremely luminous type IIn supernova SN~2006gy on day 96 is explored. Among conceivable possibilities the most preferred is the model that suggests holes in the optically thick cool dense shell (CDS). The line radiation emitted at the inner side of the opaque CDS escapes through the holes thus producing unusual line profile with the emission shifted redward. The holes could emerge as a result of a vigorous Rayleigh-Taylor instability leading to the CDS fragmentation. The model light curve with the CDS fragmentation is shown to be consistent with the SN~2006gy bolometric light curve.

HIGH-VELOCITY LINE FORMING REGIONS IN THE TYPE Ia SUPERNOVA 2009ig

We report measurements and analysis of high-velocity (> 20,000 km/s) and photospheric absorption features in a series of spectra of the Type Ia supernova (SN) 2009ig obtained between -14d and +13d with respect to the time of maximum B-band luminosity. We identify lines of Si II, Si III, S II, Ca II and Fe II that produce both high-velocity (HVF) and photospheric-velocity (PVF) absorption features. SN 2009ig is unusual for the large number of lines with detectable HVF in the spectra, but the light-curve parameters correspond to a slightly overluminous but unexceptional SN Ia (M_B = -19.46 mag and Delta_m15 (B) = 0.90 mag). Similarly, the Si II lambda_6355 velocity at the time of B-max is greater than "normal" for a SN Ia, but it is not extreme (v_Si = 13,400 km/s). The -14d and -13d spectra clearly resolve HVF from Si II lambda_6355 as separate absorptions from a detached line forming region. At these very early phases, detached HVF are prevalent in all lines. From -12d to -6d, HVF and PVF are detected simultaneously, and the two line forming regions maintain a constant separation of about 8,000 km/s. After -6d all absorption features are PVF. The observations of SN 2009ig provide a complete picture of the transition from HVF to PVF. Most SN Ia show evidence for HVF from multiple lines in spectra obtained before -10d, and we compare the spectra of SN 2009ig to observations of other SN. We show that each of the unusual line profiles for Si II lambda_6355 found in early-time spectra of SN Ia correlate to a specific phase in a common development sequence from HVF to PVF.

DETECTION OF A WHITE DWARF COMPANION TO THE WHITE DWARF SDSSJ125733.63+542850.5

SDSSJ125733.63+542850.5 (hereafter SDSSJ1257+5428) is a compact white dwarf binary from the Sloan Digital Sky Survey that exhibits high-amplitude radial velocity variations on a period of 4.56 hours. While an initial analysis suggested the presence of a neutron star or black-hole binary companion, a follow-up study concluded that the spectrum was better understood as a combination of two white dwarfs. Here we present optical spectroscopy and ultraviolet fluxes which directly reveal the presence of the second white dwarf in the system. SDSSJ1257+5428's spectrum is a composite, dominated by the narrow-lined spectrum from a cool, low gravity white dwarf (Teff ~6300K, log g = 5 to 6.6) with broad wings from a hotter, high-mass white dwarf companion (11,000 to 14,000K; ~ 1Msun). The high-mass white dwarf has unusual line profiles which lack the narrow central core to Halpha that is usually seen in white dwarfs. This is consistent with rapid rotation with v sin i = 500 to 1750km/s, although other broadening mechanisms such as magnetic fields, pulsations or a helium-rich atmosphere could also be contributory factors. The cool component is a puzzle since no evolutionary model matches its combination of low gravity and temperature. Within the constraints set by our data, SDSSJ1257+5428 could have a total mass greater than the Chandrasekhar limit and thus be a potential Type Ia supernova progenitor. However, SDSSJ1257+5428's unusually low mass ratio q ~ 0.2 suggests that it is more likely that it will evolve into an accreting double white dwarf (AM CVn star).

In situ X-ray powder diffraction analysis of the microstructure of activated iron catalysts for ammonia synthesis

The formation of the iron species catalysing the synthesis of ammonia was followed by in situ X-ray powder diffraction. It was shown that a complex sequence of reactions during the activation process (reduction of the magnetite precursor) leads to a metastable form of α-iron. A detailed examination of the diffraction lines of iron helped to elucidate the question, why “ammonia iron” is so much superior to “normal iron”. Unusual line profiles were observed which could be controlled by changing the reaction conditions. Platelet crystallites of defective alpha-iron form the outer shell of isotropic bulk iron particles which represent the main body of the catalyst material. A shoulder at higher d values of the Fe(110) reflection points to the formation of an iron/nitrogen phase during catalytic action. The crystallographic observations are in line with previous data on paracrystallinity, but their interpretation is of a different nature. The structural effects of oxygen poisoning were investigated. It is shown, why the poisoning is detrimental for the catalytic performance and how the speculation could arise that this effect may be beneficial for the reaction.

Unusually broad x-ray emission lines:Lγ2,3(L1N2,3) spectra ofSn50,Te52, andI53

The $L{\ensuremath{\gamma}}_{2,3}({L}_{1}{N}_{2,3}$) x-ray emission spectra from $_{50}\mathrm{Sn}$, $_{52}\mathrm{Te}$, and $_{53}\mathrm{I}$, excited by direct electron bombardment, were measured with a double-crystal monochromator. The spectral profiles are similar to their $4p$ energy-level-region x-ray photoelectron spectra (XPS), with base widths of about 50 eV. The origin of these unusual line profiles is attributed to many-body effects in their final states which are comparable to their respective XPS final states.