71 research outputs found
Time variation in the molecular infrared spectrum of IRS 46
No full textEarly Spitzer-IRS observations of the young star IRS 46 revealed strong absorption bands of gas-phase C2H2, HCN and CO2. These provided the first observational test of chemical models in the planet-forming zone of a circumstellar disk as well as a direct measure of the temperature and density. Subsequently, the same molecules have been observed in absorption toward the young star GV Tau and in emission (together with hot abundant H2O and OH) toward a number of T Tauri stars. However, follow-up Spitzer-IRS observations of IRS 46 at 5 epochs taken during 2008 and 2009 show dramatic changes of the mid-IR properties. The mid-IR continuum and the strength of hot water emission lines (previously not identified) have increased while the absorption features have strongly decreased in strength. At the same time no significant changes are observed in the molecular spectrum of GV Tau. Starting with the parameters of the SED model as presented in the original paper by Lahuis et al. 2006, we use the proptoplanetary disk model ProDiMo to model the chemical composition of the inner few AU of the IRS 46 disk. In addition ProDiMo is used to investigate the nature of the changes observed in the mid-IR spectra of IRS 46 and to test if an outburst event (akin EX Lupi) can explain the observed changes
Assessing the impact of spectral fringes on astronomical line fluxes
No full textThe following report aims to provide an initial approach to the user for quantifying the diverse methods for correcting the fringes within astronomical spectra. This study is developed as part of the Master thesis conducted at the Aerospace Engineering Faculty of Delft University of Technology. Determining the composition of the environment in space has always been a key feature for understanding it. Perceiving what cannot be seen by the human eye on images was realized by means of spectrometers, combined with focal plane detectors. Spectral features depicted on the delivered spectra provide scientists with vital information on the observed entities. However, further analysis showed that multi-beam interference of the light spectrumoccurred within this instrumentation, misleading the results. This physical principle, also called as the Fabry-Pérot principle, generates fringes, that appeared to be present in many space telescope instruments such as the STIS, SWS/LWS, Spitzer IS, HIFI and the MRS. Therefore, the need to find a reliable solution for correcting these fringes has been a key requirement within the astronomy, especially for the future spectrometers and dedicated detectors to be sent in space on board the JamesWebb Space Telescope in 2019...Aerospace Engineerin
Time variation in the molecular infrared spectrum of IRS 46
No full textEarly Spitzer-IRS observations of the young star IRS 46 revealed strong absorption bands of gas-phase C2H2, HCN and CO2. These provided the first observational test of chemical models in the planet-forming zone of a circumstellar disk as well as a direct measure of the temperature and density. Subsequently, the same molecules have been observed in absorption toward the young star GV Tau and in emission (together with hot abundant H2O and OH) toward a number of T Tauri stars. However, follow-up Spitzer-IRS observations of IRS 46 at 5 epochs taken during 2008 and 2009 show dramatic changes of the mid-IR properties. The mid-IR continuum and the strength of hot water emission lines (previously not identified) have increased while the absorption features have strongly decreased in strength. At the same time no significant changes are observed in the molecular spectrum of GV Tau. Starting with the parameters of the SED model as presented in the original paper by Lahuis et al. 2006, we use the proptoplanetary disk model ProDiMo to model the chemical composition of the inner few AU of the IRS 46 disk. In addition ProDiMo is used to investigate the nature of the changes observed in the mid-IR spectra of IRS 46 and to test if an outburst event (akin EX Lupi) can explain the observed changes
H(2)O and OH gas in the terrestrial planet-forming zones of protoplanetary disks
No full textWe present detections of numerous 10-20 mu m H(2)O emission lines from two protoplanetary disks around the T Tauri stars AS 205A and DR Tau, obtained using the InfraRed Spectrograph on the Spitzer Space Telescope. Followup 3-5 mu m Keck NIRSPEC data confirm the presence of abundant water and spectrally resolve the lines. We also detect the P4.5 (2.934 mu m) and P9.5 (3.179 mu m) doublets of OH and (12)CO/(13)CO nu = 1 -> 0 emission in both sources. Line shapes and LTE models suggest that the emission from all three molecules originates between similar to 0.5 and 5 AU, and so will provide a new window for understanding the chemical environment during terrestrial planet formation. LTE models also imply significant columns of H(2)O and OH in the inner disk atmospheres, suggesting physical transport of volatile ices either vertically or radially, while the significant radial extent of the emission stresses the importance of a more complete understanding of nonthermal excitation processes
H_2O and OH gas in the terrestrial planet-forming zones of protoplanetary disks
No full textWe present detections of numerous 10-20 μm H_2O emission lines from two protoplanetary disks around the T Tauri stars AS 205A and DR Tau, obtained using the InfraRed Spectrograph on the Spitzer Space Telescope. Follow-up 3-5 μm Keck NIRSPEC data confirm the presence of abundant water and spectrally resolve the lines. We also detect the P4.5 (2.934 μm) and P9.5 (3.179 μm) doublets of OH and ^(12)CO/^(13)CO v = 1 → 0 emission in both sources. Line shapes and LTE models suggest that the emission from all three molecules originates between ~0.5 and 5 AU, and so will provide a new window for understanding the chemical environment during terrestrial planet formation. LTE models also imply significant columns of H_2O and OH in the inner disk atmospheres, suggesting physical transport of volatile ices either vertically or radially, while the significant radial extent of the emission stresses the importance of a more complete understanding of nonthermal excitation processes
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