A high-resolution optical spectrograph for the Thirty Meter Telescope: design and performance

Osterman, Steve; Froning, Cynthia S.; Beasley, Matthew; Green, James; Béland, S.

doi:10.1117/12.672333

Cited by 49 publications

(57 citation statements)

References 7 publications

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“…The G160M spectra provide a velocity resolution of v D~17 km s −1 (R = 16,000-21,000) with seven pixels per resolution element, while the G230L spectra provide a resolution of v D~120 km s −1 (R = 2100-3200) (Osterman et al 2011;Green et al 2012).…”

Section: Hst Observationsmentioning

confidence: 99%

Magnetospheric Accretion in Close Pre-Main-Sequence Binaries

Ardila

Jonhs-Krull

Herczeg

et al. 2015

ApJ

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The transfer of matter between a circumbinary disk and a young binary system remains poorly understood, obscuring the interpretation of accretion indicators. To explore the behavior of these indicators in multiple systems, we have performed the first systematic time-domain study of young binaries in the ultraviolet. We obtained far-and near-ultraviolet HST/COS spectra of the young spectroscopic binaries DQ Tau and UZ Tau E. Here we focus on the continuum from 2800 to 3200 Å and on the C IV doublet (λλ1548.19, 1550.77 Å) as accretion diagnostics. Each system was observed over three or four consecutive binary orbits, at phases ∼0, 0.2, 0.5, and 0.7. Those observations are complemented by ground-based U-band measurements. Contrary to model predictions, we do not detect any clear correlation between accretion luminosity and phase. Further, we do not detect any correlation between C IV flux and phase. For both stars the appearance of the C IV line is similar to that of single Classical T Tauri Stars (CTTSs), despite the lack of stable long-lived circumstellar disks. However, unlike the case in single CTTSs, the narrow and broad components of the C IV lines are uncorrelated, and we argue that the narrow component is powered by processes other than accretion, such as flares in the stellar magnetospheres and/or enhanced activity in the upper atmosphere. We find that both stars contribute equally to the narrow component C IV flux in DQ Tau, but the primary dominates the narrow component C IV emission in UZ Tau E. The C IV broad component flux is correlated with other accretion indicators, suggesting an accretion origin. However, the line is blueshifted, which is inconsistent with its origin in an infall flow close to the star. It is possible that the complicated geometry of the region, as well as turbulence in the shock region, are responsible for the blueshifted line profiles.

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Section: Hst Observationsmentioning

confidence: 99%

Magnetospheric Accretion in Close Pre-Main-Sequence Binaries

Ardila

Jonhs-Krull

Herczeg

et al. 2015

ApJ

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“…The HST program ID is 12173. A description of the COS spectrograph was given by Osterman et al (2011) and Green et al (2012). Details of the observations are given in Table 2.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

Far-Ultraviolet Observations of Outflows From Infrared-Luminous Galaxies

Leitherer¹,

Chandar²,

Tremonti³

et al. 2013

ApJ

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We obtained medium-resolution ultraviolet (UV) spectra between 1150 and 1450 Å of the four UV-bright, infraredluminous starburst galaxies IRAS F08339+6517, NGC 3256, NGC 6090, and NGC 7552 using the Cosmic Origins Spectrograph on board the Hubble Space Telescope. The selected sightlines toward the starburst nuclei probe the properties of the recently formed massive stars and the physical conditions in the starburst-driven galactic superwinds. Despite being metal-rich and dusty, all four galaxies are strong Lyα emitters with equivalent widths ranging between 2 and 13 Å. The UV spectra show strong P Cygni-type high-ionization features indicative of stellar winds and blueshifted low-ionization lines formed in the interstellar and circumgalactic medium. We detect outflowing gas with bulk velocities of ∼400 km s −1 and maximum velocities of almost 900 km s −1 . These are among the highest values found in the local universe and comparable to outflow velocities found in luminous Lyman-break galaxies at intermediate and high redshift. The outflow velocities are unlikely to be high enough to cause escape of material from the galactic gravitational potential. However, the winds are significant for the evolution of the galaxies by transporting heavy elements from the starburst nuclei and enriching the galaxy halos. The derived mass outflow rates of ∼100 M yr −1 are comparable to or even higher than the star formation rates. The outflows can quench star formation and ultimately regulate the starburst as has been suggested for high-redshift galaxies.

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“…In this Paper we present new UV absorption observations of three local DA white dwarfs using the Cosmic Origins Spectrograph on the HST (Osterman et al 2011). By combining these data with archival spectra gained with the FUSE satellite, and by carefully comparing the velocity shifts derived from a consistent set of low and high UV ion profiles recorded along each of the three sight-lines, we attempt to discriminate between the possible photospheric, circumstellar or interstellar origin of high ionization absorption features seen in these DA spectra.…”

Section: Introductionmentioning

confidence: 99%

High ions towards white dwarfs: circumstellar line shifts and stellar temperature

Lallement

Welsh

Barstow

et al. 2011

A&A

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Aims. Our aim is to gain new insights into highly ionized gas towards nearby hot white dwarfs (WDs). The detection of absorption lines of highly ionized interstellar (IS) species in their spectra is the main diagnostic tool of the hot IS gas phase. This requires disentangling IS ions from photospheric or circumstellar (CS) ions, and thus their simultaneous study. This is particularly timely due to the recent discovery of infra-red emitting disks around WDs and the recognition that accretion from those disks can explain the presence of photospheric heavy ions, thus opening the exciting prospect of measuring the composition of extra-solar disks and planetary systems. Methods. We present far UV spectra of three nearby white dwarfs recorded with the Cosmic Object Spectrograph on board the HST. Absorption lines of several ions at various ionization stages are detected, and we investigate their origin by means of their kinematical properties, in combination with previous measurements with the FUSE satellite. We supplement with these new results a large set of archival white dwarfs UV data and we analyze the line shifts. Results. Interstellar CIV, SiIV, NV and OVI ions are likely detected at distance from the Plane towards WD1040+492 (230 pc), but within 100 parsecs there are no detections of IS ions. Small absorptions generated at cloud-hot gas interfaces may be present but are within our detection limit. The main result is the detection of the CIV, SiIV and NV counterparts to the redshifted OVI lines measured towards WD2257-073 and WD1040+492. Based on their velocities, they very likely trace absorbing circumstellar material, extending earlier results. More surprisingly, CS absorption is also detected at small redshift towards WD1942+499, and potentially towards WD2257-073. Comparisons of the COS CIII and CIV data with atmospheric models preclude a stellar origin for these features. We thus present first evidence for a temporal variability of the CS lines and for a case of double absorption. Overall these results demonstrate the ubiquity of CS absorptions and favor a large interval of CS line shifts. Based on the compilation of OVI, CIV, SiIV and NV data from IUE, FUSE, GHRS, STIS, and COS, we derive an anti-correlation between the stellar temperature and the high ion velocity shift w.r.t. to the photosphere, with positive (resp. negative) velocity shifts for the cooler (resp. hotter) white dwarfs. This trend probably reflects more than a single process, however such a dependence on the WD's temperature again favors a CS origin for a very large fraction of those ion absorptions, and a form of balance between radiation pressure and gravitation. This is consistent with ubiquitous evaporation of orbiting dusty material. In view of these results, ion measurements close to the photospheric or the IS velocity should be interpreted with caution, especially for stars at intermediate temperatures. While tracing CS gas, they may be erroneously attributed to photospheric material or to the ISM, explaining the difficulty...

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A high-resolution optical spectrograph for the Thirty Meter Telescope: design and performance

Cited by 49 publications

References 7 publications

Magnetospheric Accretion in Close Pre-Main-Sequence Binaries

Magnetospheric Accretion in Close Pre-Main-Sequence Binaries

Far-Ultraviolet Observations of Outflows From Infrared-Luminous Galaxies

High ions towards white dwarfs: circumstellar line shifts and stellar temperature

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