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The Interstellar Matter in the Direction of the Supernova Remnant G296.5+10.0 and the Central X-Ray Source 1E 1207.4-5209
G296.5+10.0 is a high Galactic latitude supernova remnant (SNR), with abilateral morphology in radio and X-rays. The compact X-ray source 1E1207.4-5209, classified as a radio-quiet neutron star, is located veryclose to the remnant's center. We report on a survey of the H Idistribution in a region of sky, 3.5dx3.5d, around the remnant, usingthe Australia Telescope Compact Array with a spatial resolution of about3.5? and a velocity resolution of 0.82 km s-1. The H Idistribution is quite smooth, with no obvious large-scale features thatcan explain the SNR bilateral morphology based on external factors.There are, however, three clouds that we do associate directly with theremnant. Optical filaments outline two smaller features, which appear tohave been overtaken by the shock front and are cooling radiatively.Also, a high-velocity cloud gives a lower limit of ~35 km s-1to the expansion velocity of the shock into the H I gas and a lowerlimit of ~2x1049 ergs for the kinetic energy injected by thesupernova explosion into the surrounding interstellar medium. Weestimate a distance to the SNR of d=2.1+1.8-0.8kpc and a total mass of at least 1900 Msolar of associated HI gas. A hole in the H I column density is observed at the same positionof the compact X-ray source 1E 1207.4-5209. This H I hole is at the sameradial velocity as G296.5+10.0. We argue that this result constitutesconcrete evidence that 1E 1207.4-5209 and G296.5+10.0 are physicallyassociated.
| A homogeneous catalog of new UBV and H-beta photometry of B- and A-type stars in and around the Scorpius-Centaurus OB association
B- and A-type stars in and near the Sco-Cen OB association areinvestigated with UBV and H-beta photometry to acquire data relevant tothe luminosity function of Sco-Cen. The measurements generally consistof two 10-s integrations of U, B, V, (W, N) filters, and theobservations are corrected iteratively for atmospheric extinction andinstrumental response. The data presented give the mean V magnitude,mean B-V, mean U-B, and the estimated uncertainties for these values.The catalog provides a homogeneous catalog of data for a large fieldwith stellar objects delineating membership to the association Sco-Cenand that affect the luminosity function of the aggregate.
| An Einstein Observatory SAO-based catalog of B-type stars
About 4000 X-ray images obtained with the Einstein Observatory are usedto measure the 0.16-4.0 keV emission from 1545 B-type SAO stars fallingin the about 10 percent of the sky surveyed with the IPC. Seventy-fourdetected X-ray sources with B-type stars are identified, and it isestimated that no more than 15 can be misidentified. Upper limits to theX-ray emission of the remaining stars are presented. In addition tosummarizing the X-ray measurements and giving other relevant opticaldata, the present extensive catalog discusses the reduction process andanalyzes selection effects associated with both SAO catalog completenessand IPC target selection procedures. It is concluded that X-rayemission, at the level of Lx not less than 10 exp 30 ergs/s, is quitecommon in B stars of early spectral types (B0-B3), regardless ofluminosity class, but that emission, at the same level, becomes lesscommon, or nonexistent, in later B-type stars.
| Walraven photometry of nearby southern OB associations
Homogeneous Walraven (VBLUW) photometry is presented for 5260 stars inthe regions of five nearby southern OB associations: Scorpio Centaurus(Sco OB2), Orion OB1, Canis Major OB1, Monoceros OB1, and Scutum OB2.Derived V and (B - V) in the Johnson system are included.
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