Physical and Rheological Properties of Nitroso Rubbers

Ball, George L.; Wilson, H S; Salyer, I. O.; Gil'man, L. M.; Pustinger, J. V.

doi:10.21236/ad0461425

Cited by 13 publications

(16 citation statements)

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“…Since it is usually assumed that the acceleration of particles in SNe is due to the Fermi process (e.g. Ball & Kirk 1995, we show here that our finding of a low-energy cutoff is consistent with such a process acting in SN1993J. The minimum energy of electrons that can be efficiently accelerated is γ min,e = (m p /m e )(v A /cµ) (Eilek & Hughes 1991; but see also Ellison et al 2000, who argue that nonlinear effects in shocks can lead to acceleration of particles from a thermal pool), where m p and m p are the protron and electron mass, respectively, v A is the The data is as in Fig.…”

Section: Resultsmentioning

confidence: 99%

The role of synchrotron self-absorption in the late radio emission from SN 1993J

Pérez-Torres

Alberdi

Marcaide

2001

A&A

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Abstract. The standard model for radio supernovae considers that the observed synchrotron radio emission arises from the high-energy shell that results from the strong interaction between the expanding supernova ejecta and the circumstellar medium. This emission is considered to be only partially absorbed by ionized thermal electrons in the circumstellar wind of the progenitor star. Based on a study of the radio light curves of the type II supernova SN1993J, we present evidence of synchrotron self-absorption. Our modeling of the radio light curves requires a large initial magnetic field, of about 30 Gauss, and the existence of an (initially) highly-relativistic population of electrons. We also show that while at early epochs the dominant absorption mechanism is external absorption by thermal electrons, at late epochs and long wavelengths the dominant absorption mechanism is synchrotron self-absorption. Consequently, the spectral turnover takes place at much shorter wavelengths than expected in the standard model, and at long wavelengths (≥90 cm at current epochs) the flux predictions depart substantially from those of the standard model.

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Section: Resultsmentioning

confidence: 99%

The role of synchrotron self-absorption in the late radio emission from SN 1993J

Pérez-Torres

Alberdi

Marcaide

2001

A&A

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“…NAIP images were analysed with a combination of isodata clustering47 and maximum likelihood analysis48 to categorize each pixel into a preset number of classes. The higher resolution WI images were overlaid with these classes to determine which classes constituted water and vegetation.…”

Section: Methodsmentioning

confidence: 99%

Spatially integrative metrics reveal hidden vulnerability of microtidal salt marshes

et al. 2017

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Salt marshes are valued for their ecosystem services, and their vulnerability is typically assessed through biotic and abiotic measurements at individual points on the landscape. However, lateral erosion can lead to rapid marsh loss as marshes build vertically. Marsh sediment budgets represent a spatially integrated measure of competing constructive and destructive forces: a sediment surplus may result in vertical growth and/or lateral expansion, while a sediment deficit may result in drowning and/or lateral contraction. Here we show that sediment budgets of eight microtidal marsh complexes consistently scale with areal unvegetated/vegetated marsh ratios (UVVR) suggesting these metrics are broadly applicable indicators of microtidal marsh vulnerability. All sites are exhibiting a sediment deficit, with half the sites having projected lifespans of less than 350 years at current rates of sea-level rise and sediment availability. These results demonstrate that open-water conversion and sediment deficits are holistic and sensitive indicators of salt marsh vulnerability.

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“…Although NGC 891 has not undergone a starburst, it is an actively star-forming galaxy, which was not at least documented by the explosion of SN1986J in its southern half (e.g. Ball & Kirk 1995). García-Burillo et al (1992) and García-Burillo & Guélin (1995) have mapped the CO(2-1) and the CO(1-0) lines in this galaxy using the 30 m telescope on Pico Veleta.…”

Section: Ngc 891mentioning

confidence: 99%

Warm gas in central regions of nearby galaxies

Dumke

Nieten²,

Thuma³

et al. 2001

A&A

100

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Abstract.We have mapped the CO(3-2) line emission from several nearby galaxies, using the Heinrich-HertzTelescope on Mt. Graham, Arizona. Unlike earlier observations, our investigation is not restricted to starburst galaxies, but includes twelve galaxies of various types and in different stages of star forming activity. Furthermore, we have not only observed the central positions of these objects, but have obtained maps of the extended CO(3-2) emission, with a typical map extent of 2 to 3 arcmin in each direction. Our observations show that this extended mapping is necessary to reveal spatial changes of the ISM properties within the galaxies. In this paper we present the data sets and some data analysis. We compare the galaxies in view of their morphology and excitation conditions, using line ratios, luminosities and other properties, like the extent of the CO(3-2) emission. The main results of this CO(3-2) survey are: 1. In none of the observed objects the emission is confined to the nucleus, as claimed in some earlier publications. CO(3-2) emission can be detected for some objects to the same extent as the CO(2-1) and the CO(1-0) lines. 2. The emission is more concentrated to the vicinity of star forming structures (nuclear regions and spiral arms) than the lower CO transitions for most of the observed objects. This is shown by decreasing (3-2)/(1-0) line intensity ratios from the very centres towards larger radii. The (deconvolved) sizes of the central emission peaks in the CO(3-2) line vary from about 300 pc up to 3 kpc. 3. The CO(3-2) luminosity is stronger in objects that contain a nuclear starburst or morphological peculiarities. The total power emitted in the CO(3-2) line from the central regions (i.e. excluding spiral arms/outer disk) is highest in the starburst galaxies NGC 2146, M 82, NGC 3628, and in the spiral galaxy M 51. When comparing the total power normalized to the size of the emission region, the starburst galaxies M 82 and NGC 253 show the highest values (about three times higher than most other objects), while NGC 278 and NGC 4631 show the lowest. 4. With the present spatial resolution, the line ratios R3,1 seem to be independent of Hubble type, color or luminosity. Most galaxies with enhanced central star formation ("starbursts") show line ratios of the integrated intensities of R3,1 ∼ 1.3 in the very centre and ∼1.0 at a radius of about 1 kpc. Objects with a ring-like (or double-peak if seen edge-on) molecular gas distribution (NGC 253, M 82, and NGC 4631) show lower ratios. The two galaxies that have CO(3-2) emission distributed over their spiral arms (NGC 891 and M 51) show very low line ratios despite their high infrared luminosities. This result suggests that CO emission in these objects reflects a large amount of molecular gas, but not enhanced star forming activity. 5. Starburst galaxies show CO(3-2) emission also in their disks. The line intensities are higher than that of normal galaxies. This suggests that even if a starburst is a localized phenomenon, it is related to different...

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Physical and Rheological Properties of Nitroso Rubbers

Cited by 13 publications

References 0 publications

The role of synchrotron self-absorption in the late radio emission from SN 1993J

The role of synchrotron self-absorption in the late radio emission from SN 1993J

Spatially integrative metrics reveal hidden vulnerability of microtidal salt marshes

Warm gas in central regions of nearby galaxies

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