| 1. |
- Cordiner, M. A., et al.
(författare)
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On the Nature of the Enigmatic Object IRAS 19312+1950: A Rare Phase of Massive Star Formation?
- 2016
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Ingår i: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 828:1
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Tidskriftsartikel (refereegranskat)abstract
- IRAS 19312+1950 is a peculiar object that has eluded firm characterization since its discovery, with combined maser properties similar to an evolved star and a young stellar object (YSO). To help determine its true nature, we obtained infrared spectra of IRAS 19312+1950 in the range 5–550 μm using the Herschel and Spitzer space observatories. The Herschel PACS maps exhibit a compact, slightly asymmetric continuum source at 170 μm, indicative of a large, dusty circumstellar envelope. The far-IR CO emission line spectrum reveals two gas temperature components: ≈0.22 solar masses of material at 280 ± 18 K, and ≈1.6 solar masses of material at 157 ± 3 K. The O i 63 μm line is detected on-source but no significant emission from atomic ions was found. The HIFI observations display shocked, high-velocity gas with outflow speeds up to 90 km/s along the line of sight. From Spitzer spectroscopy, we identify ice absorption bands due to H2O at 5.8 μm and CO2 at 15 μm. The spectral energy distribution is consistent with a massive, luminous (~2 × 10^4 solar luminosities) central source surrounded by a dense, warm circumstellar disk and envelope of total mass ~500–700 solar masses, with large bipolar outflow cavities. The combination of distinctive far-IR spectral features suggest that IRAS 19312+1950 should be classified as an accreting, high-mass YSO rather than an evolved star. In light of this reclassification, IRAS 19312+1950 becomes only the fifth high-mass protostar known to exhibit SiO maser activity, and demonstrates that 18 cm OH maser line ratios may not be reliable observational discriminators between evolved stars and YSOs.
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| 2. |
- Cordiner, M. A., et al.
(författare)
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Organic chemistry of low-mass star-forming cores I: 7 mm spectroscopy of Chamaeleon MMS1
- 2012
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Ingår i: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 744, s. 131-
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Tidskriftsartikel (refereegranskat)abstract
- Observations are presented of emission lines from organic molecules at frequencies 32-50 GHz in the vicinity of Chamaeleon MMS1. This chemically rich dense cloud core harbors an extremely young, very low luminosity protostellar object and is a candidate first hydrostatic core. Column densities are derived and emission maps are presented for species including polyynes, cyanopolyynes, sulphuretted carbon chains, and methanol. The polyyne emission peak lies about 5000 AU from the protostar, whereas methanol peaks about 15,000 AU away. Averaged over the telescope beam, the molecular hydrogen number density is calculated to be 106 cm–3 and the gas kinetic temperature is in the range 5-7 K. The abundances of long carbon chains are very large and are indicative of a non-equilibrium carbon chemistry; C6H and HC7N column densities are 5.9+2.9 –1.3 × 1011 cm–2 and 3.3+8.0 –1.5 × 1012 cm–2, respectively, which are similar to the values found in the most carbon-chain-rich protostars and prestellar cores known, and are unusually large for star-forming gas. Column density upper limits were obtained for the carbon-chain anions C4H– and C6H–, with anion-to-neutral ratios [C4H–]/[C4H]
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| 3. |
- Janczewska, Izabella, et al.
(författare)
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Clinical application of the multigene analysis test in discriminating between ulcerative colitis and Crohn's disease : a retrospective study
- 2012
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Ingår i: Scandinavian journal of gastroenterology. - : Informa UK Limited. - 1502-7708 .- 0036-5521. ; 47:2, s. 162-9
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Methods. The newly described - multigene analysis test (DiBiCol) identifying 7 inflammatory bowel disease (IBD)-specific genes in colonic mucosal biopsy differentiating between ulcerative colitis (UC) and Crohn's disease (CD) with active inflammation - is a new addition to existing methods with a higher stated sensitivity and specificity. Method biopsy material from 78 patients with a complicated course diagnosed as most probably UC in 38, CD in 18 and inflammatory bowel disease unclassified (IBDU) in 22 were investigated by DiBiCol. Results. DiBiCol showed a pattern consistent with CD in 13 patients with UC and led to change of diagnosis in 3 patients and a strong suggestion of CD in 8 patients. A total of 2 patients remained as UC. DiBiCol showed a pattern of UC in 4 patients of 18 with CD leading to a changing of diagnosis to UC in 3 patients, but the fourth remained as CD. In 22 patients with IBDU DiBiCol showed a pattern consistent with UC in 7 cases and with CD in 13 cases. A new evaluation 1 year after the DiBiCol allowed the assessment of clinical diagnosis in 10 patients confirmed in 9 of 10 patients by DiBiCol. In patients with acute flare of colitis the clinical diagnosis corresponded in 10 of 12 UC and in 5 of 6 CD cases. Summary. Adopting the DiBiCol test led to a change of the primary diagnosis in a significant number of patients with the initial diagnosis of UC and CD and suggested a clinically probable diagnosis in most of the patients with IBDU and in those with an acute flare of colitis.
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| 4. |
- Persson, Carina, 1964, et al.
(författare)
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Ortho-to-para ratio of NH2. Herschel-HIFI observations of ortho- and para-NH2 rotational transitions towards W31C, W49N, W51 and G34.3+0.1
- 2016
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 586, s. Art Nr. A128-
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Tidskriftsartikel (refereegranskat)abstract
- We have used the Herschel-HIFI instrument to observe both nuclear spin symmetries of amidogen (NH2) towards the high-mass star-forming regions W31C (G10.6-0.4), W49N (G43.2-0.1), W51 (G49.5-0.4) and G34.3+0.1. The aim is to investigate the ratio of nuclear spin types, the ortho-to-para ratio (OPR), of NH2. The excited NH2 transitions are used to construct radiative transfer models of the hot cores and surrounding envelopes in order to investigate the excitation and possible emission of the ground state rotational transitions of ortho-NH2 N_(K_a,K_c} J=1_(1,1) 3/2 - 0_(0,0) 1/2 and para-NH2 2_(1,2) 5/2 - 1_(0,1) 3/2$ used in the OPR calculations. Our best estimate of the average OPR in the envelopes lie above the high temperature limit of three for W49N, specifically 3.5 with formal errors of \pm0.1, but for W31C, W51, and G34.3+0.1 we find lower values of 2.5\pm0.1, 2.7\pm0.1, and 2.3\pm0.1, respectively. Such low values are strictly forbidden in thermodynamical equilibrium since the OPR is expected to increase above three at low temperatures. In the translucent interstellar gas towards W31C, where the excitation effects are low, we find similar values between 2.2\pm0.2 and 2.9\pm0.2. In contrast, we find an OPR of 3.4\pm0.1 in the dense and cold filament connected to W51, and also two lower limits of >4.2 and >5.0 in two other translucent gas components towards W31C and W49N. At low temperatures (T \lesssim 50 K) the OPR of H2 is 20-25 K, depending on time, and values above three at lower temperatures.
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| 5. |
- Persson, Carina, 1964, et al.
(författare)
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Upper limits to interstellar NH+ and para-NH2- abundances. Herschel-HIFI observations towards Sgr B2 (M) and G10.6-0.4 (W31C)
- 2014
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 567, s. Art. no. A130-
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Tidskriftsartikel (refereegranskat)abstract
- The understanding of interstellar nitrogen chemistry has improved significantly with recent results from the Herschel Space Observatory. To set even better constraints, we report here on deep searches for the NH+ ground state rotational transition J=1.5-0.5 of the ^2Pi_1/2 lower spin ladder, with fine-structure transitions at 1013 and 1019 GHz, and the para-NH2- 1_1,1-0_0,0 rotational transition at 934 GHz towards Sgr B2(M) and G10.6-0.4 using Herschel-HIFI. No clear detections of NH+ are made and the derived upper limits are
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| 6. |
- Wirström, Eva, 1977, et al.
(författare)
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15N fractionation in star-forming regions and Solar System objects
- 2015
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Ingår i: Proceedings of the International Astronomical Union. - 1743-9213 .- 1743-9221. ; 11:A29A, s. 271-274
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Konferensbidrag (refereegranskat)abstract
- We briefly review what is currently known of 14N/15N ratios in interstellar molecules. We summarize the fractionation ratios measured in HCN, HNC, CN, N2 and NH3, and compare these to theoretical predictions and to the isotopic inventory of cometary volatiles.
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