The ORFEUS II Echelle Spectrometer: 
Instrument description, performance and data reduction

Barnstedt, J.; Kappelmann, N.; Appenzeller, I.; Fromm, A.; Gölz, M.; Grewing, M.; Gringel, W.; Haas, Christian; Hopfensitz, W.; Krämer, G.; Krautter, J.; Lindenberger, A.; Mandel, H.; Widmann, H.

doi:10.1051/aas:1999156

Cited by 30 publications

(21 citation statements)

References 7 publications

(7 reference statements)

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“…The echelle spectrograph on board orfeus produces spectra between 900 and 1400Å with a spectral resolution of 30 km s −1 (see Barnstedt et al 1999). Thus interstellar absorption lines of molecular hydrogen H 2 (and also of O vi) became accessible.…”

Section: Gas In Front Of the Lmcmentioning

confidence: 99%

ORFEUS echelle spectra: Molecular hydrogen in disk, IVC, and HVC gas in front of the LMC

Bluhm

Boer

Marggraf

et al. 2001

A&A

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Abstract. In front of the LMC molecular hydrogen is found in absorption near 0 km s −1 , being local disk gas, near +60 km s −1 in an intermediate velocity cloud, and near +120 km s −1 , being a high velocity halo cloud. The nature of the gas is discussed based on four Orfeus far UV spectra of LMC stars and including data from the ground and from the IUE satellite. The local gas is cool and, given a span of sight lines of only 2.5• , rather fluffy. The fractional abundance of H2 varies from log f = log[N (H2)/(2 · N(H2) + N(H i))] = −5.4 to −3.3. Metal depletions (up to −1.7 dex for Fe) are typical for galactic disk gas. In the intermediate and high velocity gas an apparent underabundance of neutral oxygen points to an ionization level of the gas of about 90 %. H2 is detected in intermediate and high velocity gas towards HD 269546. In the intermediate velocity gas we find an H2 column density of log (N ) 15.6. The H2 excitation indicates that the line of sight samples a cloud at a temperature below 150 K. Column densities are too small to detect the higher UV pumped excitation levels. The high velocity H2 (log(N ) 15.6) is highly excited and probably exposed to a strong radiation field. Its excitation temperature exceeds 1000 K. Due to the radial velocity difference between the halo gas and the Milky Way disk, the unattenuated disk radiation is available for H2 excitation in the halo. We do not find evidence for an intergalactic origin of this gas; a galactic as well as a Magellanic Cloud origin is possible.

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Section: Gas In Front Of the Lmcmentioning

confidence: 99%

ORFEUS echelle spectra: Molecular hydrogen in disk, IVC, and HVC gas in front of the LMC

Bluhm

Boer

Marggraf

et al. 2001

A&A

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“…This spectrum has a good signal to noise ratio and the spectral resolution achieved is somewhat higher than the claimed resolution of λ/∆λ = 10.000 (Barnstedt et al 1999).…”

Section: Introductionmentioning

confidence: 81%

“…The two echelle images were coadded and then the standard extraction procedure was applied (Barnstedt et al 1999) without any smoothing. An additional radial velocity correction of −10 km s −1 was applied, which corrects the wavelength scale for the fact that the star was not absolutely centered in the entrance diaphragm of the telescope.…”

Section: Data Reduction and Line Identificationmentioning

confidence: 99%

The ORFEUS II Echelle spectrum of HD 93521: A reference for interstellar molecular hydrogen

Barnstedt

Gringel

Kappelmann

et al. 2000

Astron. Astrophys. Suppl. Ser.

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Abstract. During the second flight of the ORFEUS-SPAS mission in November/December 1996, the Echelle spectrometer was used extensively by the Principal and Guest Investigator teams as one of the two focal plane instruments of the ORFEUS telescope. The spectrum of HD 93521 was obtained during this mission with a total integration time of 1740 s. This spectrum shows numerous sharp interstellar absorption lines. We identified 198 lines of molecular hydrogen including at least 7 lines with a high velocity component. Also most of the 67 identified interstellar metal lines are visible with a high velocity component.We present plots of the complete ORFEUS II Echelle spectrum together with tables of all identified interstellar absorption lines including all 14 detectable H I lines. In addition several identified stellar lines, partially with narrow absorption components, and stellar wind lines are given in a separate table.

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“…Characteristics of these stars are shown in Table 1. The procedures for data extraction and Ñux calibration are described in Barnstedt et al (1999).…”

Section: Observations and Data Reductionmentioning

confidence: 99%

“…1990 ;Barnstedt et al 1999) and (Kra mer directly derive the conversion factor along the line of X CO sight to HD 94473, for which published CO emission data are available (Keto & Myers 1986). …”

Section: Introductionmentioning

confidence: 99%

ORFEUS IIEchelle Observations of Molecular Hydrogen in the Galactic Halo

Ryu

Dixon

Hurwitz

et al. 2000

ApJ

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The far-ultraviolet spectra of HD 219188, HD 94473, and HD 18100, three early-type stars in the Galactic halo, were obtained with the echelle spectrometer on the ORFEUS II telescope in 1996 November. We derive column densities for the rotational levels up to J@@ \ 6 and estimate excitation tem-H 2 peratures and dissociation rates for the clouds toward HD 219188 and HD 94473. The results H 2 indicate that strong radiation Ðelds might exist near these clouds, but these radiation Ðelds do not seem to act as major heating sources. No signiÐcant absorption is seen toward HD 18100. The correlation H 2 between our column densities and published extinction maps conÐrms that the molecular clouds are H 2 associated with dust clouds that lie between the observed stars and the Sun. We estimate the conversion factor between and W (12CO) to be cm~2 (K km s~1)~1 for the clouds along N(H 2 ) X CO \ 4^2 ] 1019 the line of sight to HD 94473, consistent with previous estimates to within a factor of a few.

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The ORFEUS II Echelle Spectrometer: Instrument description, performance and data reduction

Cited by 30 publications

References 7 publications

ORFEUS echelle spectra: Molecular hydrogen in disk, IVC, and HVC gas in front of the LMC

ORFEUS echelle spectra: Molecular hydrogen in disk, IVC, and HVC gas in front of the LMC

The ORFEUS II Echelle spectrum of HD 93521: A reference for interstellar molecular hydrogen

ORFEUS IIEchelle Observations of Molecular Hydrogen in the Galactic Halo

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