Aa. Sandqvist

Low upper limits on the O2 abundance from the Odin satellite

For the first time, a search has been conducted in our Galaxy for the 119 GHz transition connecting to the ground state of O2, using the Odin satellite. Equipped with a sensitive 3 mm receiver (Tsy ...

A spectral line survey of Orion KL in the bands 486-492 and 541-577 GHz with the Odin satellite - II. Data analysis

Aims. We investigate the physical and chemical conditions in a typical star forming region, including an unbiased search for new molecules in a spectral region previously unobserved. Methods. Due to its proximity, the Orion KL region offers a unique laboratory of molecular astrophysics in a chemically rich, massive star forming region. Several ground-based spectral line surveys have been made, but due to the absorption by water and oxygen, the terrestrial atmosphere is completely opaque at frequencies around 487 and 557 GHz. To cover these frequencies we used the Odin satellite to perform a spectral line survey in the frequency ranges 486−492 GHz and 541−577 GHz, filling the gaps between previous spectral scans. Odin’s high main beam efficiency, ηmb = 0.9, and observations performed outside the atmosphere make our intensity scale very well determined. Results. We observed 280 spectral lines from 38 molecules including isotopologues, and, in addition, 64 unidentified lines. A few U-lines have interesting frequency coincidences such as ND and the anion SH − . The beam-averaged emission is dominated by CO, H2O, SO2 ,S O, 13 CO and CH3OH. Species with the largest number of lines are CH3OH, (CH3)2O, SO2, 13 CH3OH, CH3CN and NO. Six water lines are detected including the ground state rotational transition 11,0–10,1 of o-H2O, its isotopologues o-H 18 Oa nd o-H 17 O, the Hot Core tracing p-H2O transition 62,4–71,7 ,a nd the 2 0,2–11,1 transition of HDO. Other lines of special interest are the 10–0 0 transition of NH3 and its isotopologue 15 NH3. Isotopologue abundance ratios of D/H, 12 C/ 13 C, 32 S/ 34 S, 34 S/ 33 S, and 18 O/ 17 O are estimated. The temperatures, column densities and abundances in the various subregions are estimated, and we find very high gas-phase abundances of H2O, NH3 ,S O 2, SO, NO, and CH3OH. A comparison with the ice inventory of ISO sheds new light on the origin of the abundant gas-phase molecules.

The Odin satellite - II. Radiometer data processing and calibration

The radiometer on-board the Odin satellite comprises four different sub-mm receivers covering the 486-581 GHz frequency range and one fixed frequency 119 GHz receiver. Two auto-correlators and one ...

Observations of the Circumstellar Water 110→101 and Ammonia 10→00 Lines in IRC +10216 by the Odin Satellite

Submillimeter lines of H2O and NH3 have been detected in the carbon star IRC +10216 (CW Leo) with the Odin submillimeter satellite. The detection of the J = 110 → 101 557 GHz line of ortho-H2O confirms the earlier detection in the same source with SWAS. The detection of the JK = 10 → 00 572 GHz line represents the first observation of the ground-state rotational transition of NH3 in a stellar envelope. By fitting a molecular line transfer model to the observed lines, we derive an ortho-H2O abundance of 2.4 × 10-6, which is consistent with estimates from the SWAS observation. The derived ortho-NH3 abundance of 1 × 10-6 relative to H2 is significantly higher than those derived from 24 GHz inversion transitions and is slightly higher than those from vibrational transitions in the infrared band. The high H2O and NH3 abundances in the carbon-rich star IRC +10216 underscore shortcomings in the conventional gas-phase LTE and non-LTE chemical models.

W hya through the eye of odin : Satellite observations of circumstellar submillimetre H2O line emission

We present Odin observations of the AGB star W Hya in the ground-state transition of ortho-H2O, 110 − 101 ,a t 557 GHz. The line is clearly of circumstellar origin. Radiative transfer modelling of the water lines observed by Odin and ISO results in a mass-loss rate of (2.5 ± 0.5) × 10 −7 Myr −1 , and a circumstellar H2O abundance of (2.0 ± 1.0) × 10 −3 . The inferred mass-loss rate is consistent with that obtained from modelling the circumstellar CO radio line emission, and also with that obtained from the dust emission modelling combined with a dynamical model for the outflow. The very high water abundance, higher than the cosmic oxygen abundance, can be explained by invoking an injection of excess water from evaporating icy bodies in the system. The required extra mass of water is quite small, on the order of ∼0.1 M⊕.

First detection of NH3 (10 -g 00) from a low mass cloud core. On the low ammonia abundance of the rho Oph A core

Odin has successfully observed the molecular core rho Oph A in the 572.5 GHz rotational ground state line of ammonia, NH3 (JK = 10 -> 00). The interpretation of this result makes use of compleme ...

Circumstellar water vapour in M-type AGB stars: constraints from H2O(110-101) lines obtained with Odin

Context. A detailed radiative transfer code has been previously used to model circumstellar ortho-H2O line emission towards six M-type asymptotic giant branch stars using Infrared Space Observatory ...

A spectral line survey of Orion KL in the bands 486–492 and 541–577 GHz with the Odin satellite - I. The observational data

Aims. Spectral line surveys are useful since they allow identification of new molecules and new lines in uniformly calibrated data sets. The subsequent multi-transition analysis will provide improved knowledge of molecular abundances, cloud temperatures and densities, and may also reveal previously unsuspected blends of molecular lines, which otherwise may lead to erroneous conclusions. Nonetheless, large portions of the sub-millimetre spectral regime remain unexplored due to severe absorptions by H2 Oa nd O 2 in the terrestrial atmosphere. The purpose of the measurements presented here is to cover wavelength regions at and around 0.55 mm – regions largely unobservable from the ground. Methods. Using the Odin astronomy/aeronomy satellite, we performed the first spectral survey of the Orion KL molecular cloud core in the bands 486–492 and 541–576 GHz with rather uniform sensitivity (22–25 mK baseline noise). Odin’s 1.1 m size telescope, equipped with four cryo-cooled tuneable mixers connected to broad band spectrometers, was used in a satellite position-switching mode. Two mixers simultaneously observed different 1.1 GHz bands using frequency steps of 0.5 GHz (25 h each). An on-source integration time of 20 h was achieved for most bands. The entire campaign consumed ∼1100 orbits, each containing one hour of serviceable astro-observation. Results. We identified 280 spectral lines from 38 known interstellar molecules (including isotopologues) having intensities in the range 80 to 0.05 K. An additional 64 weak lines remain unidentified. Apart from the ground state rotational 11,0–10,1 transitions of ortho-H2O, H 18 Oa nd H 17 O, the high energy 62,4–71,7 line of para-H2 O( Eu = 867 K) and the HDO(20,2–11,1) line have been observed, as well as the 10–01 lines from NH3 and its rare isotopologue 15 NH3. We suggest assignments for some unidentified features, notably the new interstellar molecules ND and SH − . Severe blends have been detected in the line wings of the H 18 O, H 17 Oa nd 13 CO lines changing the true linewidths of the outflow emission.

Wide-band observations of the 557 GHz water line in Mars with Odin

The Odin satellite, thanks to the versatility of its receiver and spectrometer system, is well suited for the study of wide planetary submillimetre lines. In June and November 2003, the H2O line at 557 GHz was observed in the Mars atmosphere over a total bandwidth of 4 GHz. The wings of the line are detected up to the nearby continuum, which provides constraints on the disc-averaged vertical thermal profile and atmospheric water mixing ratio. In parallel, a sensitive search for the O2 line at 487 GHz was undertaken in June. This search was negative with a 3 σ upper limit of 4% on the absorption line depth, which is twice the expected signal. This observation, however, provides information on the continuum of Mars. In November the CO J(5-4) and the H 18 O lines were also detected in parallel and provide additional constraints on the temperature profile and mixing ratios. Surface water mixing ratios of 2-3×10 −4 are inferred, corresponding to column densities in the range of 10-15 precipitable

Odin observations of the Galactic centre in the 118-GHz band Upper limit to the O2 abundance

Odin observations of the Galactic centre in the 118-GHz band. Upper limit to the O2 abundance