Results 21 to 30 of about 35,694,720 (305)

High resolution measurements and modeling of auroral hydrogen emission line profiles [PDF]

, 2003
Measurements in the visible wavelength range at high spectral resolution (1.3 A° ) have been made at Longyearbyen, Svalbard (15.8 E,78.2 N) during an interval of intense proton precipitation.
Frey, H.U., H. U. Frey, D. Lummerzheim, Galand, M., Lummerzheim, D., S. C. Robertson, Robertson, SC, Frey, HU, Peticolas, L.M., Lummerzheim, D, Furniss, I, Baumgardner, J, M. Mendillo, Lanchester, B.S., J. Baumgardner, Baumgardner, J., Rees, M.H., I. Furniss, Lanchester, BS, Robertson, S. C., Furniss, I., M. Galand, Peticolas, L. M., Mendillo, M., Galand, M, B. S. Lanchester, Rees, MH, M. H. Rees, Peticolas, LM, Rees, M. H., L. M. Peticolas, Robertson, S.C., Lanchester, B. S., Mendillo, M, Frey, H. U.   +34 more
core   +2 more sources

The profile of the hydrogen H_β emission line in proton aurora [PDF]

Journal of Geophysical Research: Space Physics, 2001
Models of hydrogen‐proton transport in proton aurora predict the line profile of the hydrogen emissions from specified incident proton precipitation. We are using a model that includes collisional angular redistribution which leads to upward moving proton and hydrogen fluxes.
D. Lummerzheim, M. Galand
openaire   +1 more source

Hαemission-line stars in molecular clouds [PDF]

Astronomy & Astrophysics, 2014
We present a deep survey of Halpha emission-line stars in the M42 region using wide-field objective prism films. A total of 1699 Halpha emission-line stars were identified, of which 1025 were previously unknown, within an area of 5.5 x 5.5 degrees centred on the Trapezium Cluster.
Pettersson, Bertil, Armond, Tina, Reipurth, Bo   +2 more
openaire   +3 more sources

A slitless spectroscopic survey for Hαemission-line objects in SMC clusters [PDF]

Astronomy and Astrophysics, 2010
This paper checks on the roles of metallicity and evolutionary age in the appearance of the so-called Be phenomenon. Slitless CCD spectra were obtained covering the bulk of the Small Magellanic Cloud. For Halpha line emission twice as strong as the ambient continuum, the survey is complete to spectral type B2/B3 on the main sequence. About 8120 spectra
Martayan, Christophe, Baade, Dietrich, Fabregat, Juan   +2 more
openaire   +4 more sources

Origins of the H, He I, and Ca II Line Emission in Classical T Tauri Stars [PDF]

Monthly Notices of the Royal Astronomical Society, 2010
We perform local excitation calculations to obtain line opacities and emissivity ratios and compare them with observed properties of H, He I, O I, Ca II, and Na I lines to determine the density, temperature, and photon ionization rate. We find that UV photoionization is the most probable excitation mechanism for generating the He I 10830 opacities that
Kwan, John, Fischer, William
openaire   +3 more sources

Broad-line region geometry from multiple emission lines in a single-epoch spectrum [PDF]

The broad-line region (BLR) of active galactic nuclei (AGNs) traces gas close to the central supermassive black hole (BH). Recent reverberation mapping (RM) and interferometric spectro-astrometry data have enabled detailed investigations of the BLR ...
Gillessen, S., Cao, Y., Sturm, E., Davies, R., Eisenhauer, F., Schreiber, N.M. Förster, Ott, T., Shimizu, T., Tacconi, L.J., Kuhn, L., Santos, D.J.D., Netzer, H., Dexter, J., Man, A.W.S., Genzel, R., Feuchtgruber, H., Hönig, S., Shangguan, J., Lutz, D., Rabien, S.   +19 more
core   +3 more sources

Detection of an H$\alpha$ Emission Line on a Quasar, RX J1759.4$+$6638, at Z = 4.3 with AKARI [PDF]

Publications of the Astronomical Society of Japan, 2007
We report on the detection of an H$\alpha$ emission line in the low-resolution spectrum of a quasar, RX J1759.4$+$6638, at a redshift of 4.3 with the Infrared Camera (IRC) onboard AKARI. This is the first spectroscopic detection of an H$\alpha$ emission line in a quasar beyond $z =$ 4. The overall spectral energy distribution (SED) of RX J1759.4$+$6638
Oyabu, Shinki, Wada, Takehiko, Ohyama, Youichi, Matsuhara, Hideo, Takagi, Toshinobu, Nakagawa, Takao, Onaka, Takashi, Fujishiro, Naofumi, Ishihara, Daisuke, Ita, Yoshifusa, Kataza, Hirokazu, Kim, Woojung, Matsumoto, Toshio, Murakami, Hiroshi, Sakon, Itsuki, Tanabe, Toshihiko, Uemizu, Kazunori, Ueno, Munetaka, Usui, Fumihiko, Watarai, Hidenori, Haze, Kanae   +20 more
openaire   +2 more sources

Hαemission line spectroscopy in NGC 330

Astronomy & Astrophysics, 2001
We perform an observational test on global oscillations in Be star circumstellar disks in the metal deficient environment of the SMC. According to the hybrid model of disk oscillations early-type Be stars require an optically thin line force to establish a density wave.
Hummel, W., Gassler, W., Muschielok, B., Schink, H., Nicklas, H., Conti, G., Mattaini, E., Keller, S., Mantel, K. H., Appenzeller, I., Rupprecht, G., Seifert, W., Stahl, O., Tarantik, K.   +13 more
openaire   +2 more sources

Doppler-shift oscillations in the H i Lyαcoronal emission line: spectroscopic signature of propagating kink waves? [PDF]

Astronomy & Astrophysics, 2014
n ...
Mancuso, S., Raymond, J. C.
openaire   +1 more source

Intense molecular emission from the Lagoon nebula, M8 [PDF]

, 1997
The discovery is reported of the second strongest source of mm and submm wavelength CO line emission, towards M8, the Lagoon Nebula in Sagittarius. The ~31 M⊙ molecular core has dimensions ~0.2 x 0.3pc and is centred on the O7V star Herschel 36 (H36 ...
McCutcheon, W. H., Tothill, N. F. H., McCaughrean, Mark J., Matthews, H. E., Huldtgren, M., White, Glenn J.   +5 more
core   +3 more sources