Engineering topics

Boggs, Don

Publications and source records attributed to Boggs, Don.

3 records

NASA NTRS1990

Ultraviolet gas absorption and dust extinction toward M8

Interstellar absorption lines are analyzed using high-resolution IUE spectra of 11 stars in the young cluster NGC 6530 located in the M8 region. High-velocity clouds at -35 km/s and -60 km/s are seen toward all cluster stars. The components arise in gases that are part of large interstellar bubbles centered on the cluster and driven by stellar winds of the most luminous members. Absorption lines of species of different ionization states are separated in velocity. The velocity stratification is best explained as a 'champagne' flow of ionized gas away from the cluster. The C IV/Si IV ratios toward the hotter cluster members are consistent with simple photoionization models if the gas-phase C/Si ratio is increased by preferential accretion onto dust grains. High ion column densities in the central cluster decline with distance from W93, suggesting that radiation from a hot source near W93 has photoionized gas in the central cluster.

Boggs, Don↗

NASA NTRS1989

Ultraviolet extinction differences within NGC 6530

Ultraviolet extinction curves are presented for 14 stars in the very young cluster NGC 6530. The variation of the short-wavelength extinction is consistent with that expected based on random errors alone, although the weakest extinction is found only toward the cluster center. Variations significantly larger than the measurement uncertainty are found in the area, width, and central peak position of the 2200 A extinction bump. These parameters are largest in the cluster center and decrease systematically outwards. Physical processes capable of modifying the grains in the H II region containing the cluster are discussed.

Boggs, Don↗

NASA NTRS1989

Effects of SN 1987A on the interstellar medium around it

It is shown that the interstellar spectrum from SN 1987A in the LMC shows a rather strong component in C IV and Si IV, and possibly a weak component in N V, at a velocity of about 300 + or - 10 Km/s. In the spectra of the neighboring stars HD38268 and R123, a component at this velocity is only seen in low-ionization lines, not in the C IV, or N V lines. The possibility is studied that SN 1987A ionized a measurable fraction of this 300 Km/s cloud within less than one day since the Si IV, C IV, and possibly, N V interstellar lines are seen only about one day after the first light from the supernova explosion was detected. This may be the case, but only if the supernova temperature at outburst was larger than 50,000 K, depending on the density assumed for the interstellar cloud. Also, H and He must have been preionized once.

Bohm-Vitense, Erika↗