Coronal C[TSUP]+3[/TSUP] in the Large Magellanic Cloud: Evidence for a Hot Halo

Abstract

Based on the detection of C IV absorption in five Large Magellanic Cloud (LMC) stars observed with the Goddard High-Resolution Spectrograph on the Hubble Space Telescope, we present the first unambiguous evidence that C+ 3 exists in the LMC away from regions where it could have been locally produced. We can exclude that this C+ 3 is associated with hot early-type stars or active regions. Significant differences between the Hα and C+ 3 velocities toward our probes indicate that H+ and C+ 3 are not cospatial. Large column density variations show that the distribution of C+ 3 is not uniform. The properties of the LMC C IV lines are similar but not identical to those found for the Milky Way: 45 km s−1 versus 73 km s−1 for the average FWHM, (8-12) × 1013 cm−2 versus (9-16) × 1013 cm−2 for the average column density. The Hα versus C IV velocity differences and the similarity of the properties of the LMC and Milky Way C IV absorption suggest that at least some of the C+ 3 in the LMC is in a hot corona and that it has been produced by processes similar to those in the Milky Way. Our results show the feasibility of detecting high-ionization absorption in faint LMC stars, but more observations will be necessary before we can understand the distribution and properties of 105 K gas in the LMC.