IRAS studies of galactic supershells

Using IRAS Skyflux images and a new catalog of OB stars in the Cygnus region, a complete infrared supershell surrounding the Cyg OB1 Association was identified. This supershell is seen as a conspicuous, well-defined 2 deg x 5 deg region deficient of IR emission, with a limb-brightened edge and dimensions of about 50 x 130 pc at 1.5 kpc. The shell's elongated morphology is consistent with OB-star subclustering over the approximately 10(exp 6) yr age of the bubble. With a parent star cluster still visible (10 O stars between 25 and 45 solar mass, 3 - 4 Wolf-Rayet stars, and the possibility of 3 - 5 more massive stars that died as supernovae) the Cyg OB1 supershell is an excellent object for studying the formation and evolution of Galactic supershells. A discrepancy between the less than or equal to 1 Myr bubble age estimated from its size and the 5 Myr cluster turnoff age (45 solar mass) may require non-coeval massive star formation to explain the number of post-main-sequence stars and limit the number of past supernovae

Interstellar gas and dust in the young cluster IC 348

We have completed a multiband absorption- and emission-line study of a star embedded in the young cluster IC 348, to determine the environmental effect of star formation on the interstellar medium (ISM) local to the region. The hottest and youngest star in IC 348 is BD+31°643, a B5 V star which samples the inner bright nebular region. The nearby star o Per, which lies only 8 to the north and is thought to lie beyond IC 348, samples the gas and dust which has not been processed by very recent star formation. We speculate that the ISM throughout the region was originally the same as that currently seen toward o Per, but now the contrasting environmental conditions due to the recent star formation have led to marked differences in the atomic, molecular, and dust characteristics of IC 348. These contrasts include what we have termed a ``composite\u27\u27 UV extinction curve for BD+31°643, evidence for enhanced density and enhanced depletions within IC 348 and very different molecular abundances in the interstellar sightline to BD+31°643. Toward BD+31°643, we find a higher column density of CH, but lower CN and very much higher CH + than measured toward o Per. We conclude that the physical and chemical state of the gas and dust has been altered by local processes and conditions within IC 348. The characteristics of the ISM in IC 348, via our study of the star BD+31°643, closely resemble those seen toward Oph, another sight line passing through a bright nebular region. However, the stars are not as hot in IC 348 as in Ophiuchus, so their effect on the local ISM is not as severe

Interstellar gas and dust in the young cluster IC 348

We have completed a multiband absorption- and emission-line study of a star embedded in the young cluster IC 348, to determine the environmental effect of star formation on the interstellar medium (ISM) local to the region. The hottest and youngest star in IC 348 is BD+31°643, a B5 V star which samples the inner bright nebular region. The nearby star o Per, which lies only 8 to the north and is thought to lie beyond IC 348, samples the gas and dust which has not been processed by very recent star formation. We speculate that the ISM throughout the region was originally the same as that currently seen toward o Per, but now the contrasting environmental conditions due to the recent star formation have led to marked differences in the atomic, molecular, and dust characteristics of IC 348. These contrasts include what we have termed a ``composite\u27\u27 UV extinction curve for BD+31°643, evidence for enhanced density and enhanced depletions within IC 348 and very different molecular abundances in the interstellar sightline to BD+31°643. Toward BD+31°643, we find a higher column density of CH, but lower CN and very much higher CH + than measured toward o Per. We conclude that the physical and chemical state of the gas and dust has been altered by local processes and conditions within IC 348. The characteristics of the ISM in IC 348, via our study of the star BD+31°643, closely resemble those seen toward Oph, another sight line passing through a bright nebular region. However, the stars are not as hot in IC 348 as in Ophiuchus, so their effect on the local ISM is not as severe

Thermodynamics of the Solar Corona and Evolution of the Solar Magnetic Field as Inferred from the Total Solar Eclipse Observations of 2010 July 11

We report on the first multi-wavelength coronal observations, taken simultaneously in white light, Hα 656.3 nm, Fe IX 435.9 nm, Fe X 637.4 nm, Fe XI 789.2 nm, Fe XIII 1074.7 nm, Fe XIV 530.3 nm, and Ni XV 670.2 nm, during the total solar eclipse of 2010 July 11 from the atoll of Tatakoto in French Polynesia. The data enabled temperature differentiations as low as 0.2 × 106 K. The first-ever images of the corona in Fe IX and Ni XV showed that there was very little plasma below 5 × 105 K and above 2.5 × 106 K. The suite of multi-wavelength observations also showed that open field lines have an electron temperature near 1× 106 K, while the hottest, 2× 106 K, plasma resides in intricate loops forming the bulges of streamers, also known as cavities, as discovered in our previous eclipse observations. The eclipse images also revealed unusual coronal structures, in the form of ripples and streaks, produced by the passage of coronal mass ejections and eruptive prominences prior to totality, which could be identified with distinct temperatures for the first time. These trails were most prominent at 106 K. Simultaneous Fe X 17.4 nm observations from Proba2/SWAP provided the first opportunity to compare Fe X emission at 637.4 nm with its extreme-ultraviolet (EUV) counterpart. This comparison demonstrated the unique diagnostic capabilities of the coronal forbidden lines for exploring the evolution of the coronal magnetic field and the thermodynamics of the coronal plasma, in comparison with their EUV counterparts in the distance range of 1-3 R ☉. These diagnostics are currently missing from present space-borne and ground-based observatories