TY - JOUR AB - Context. The generation of spatially resolved count spectra and of cubes of count maps at different energies via imaging spectroscopy is one of the main goals of solar hard X-ray missions based on Fourier imaging. Thus, so far, for these telescopes, this goal has been realized via the generation of either count maps that are independently reconstructed in the different energy channels or electron flux maps reconstructed via a deconvolution of the approximate forms for the bremsstrahlung cross-section. Aims. Our aim is to introduce a regularized imaging spectroscopy method (RIS), whereby the regularization implemented in the count space imposes a smoothing constraint across contiguous energy channels, without the need for computing any deconvolution of the bremsstrahlung effect. Methods. STIX records imaging data, while computing the visibilities in the spatial frequency domain. Our RIS is a sequential scheme in which part of the information coded in the image is reconstructed at a specific energy channel and transferred to the reconstruction process at a contiguous channel via a visibility interpolation computed by means of variably scaled kernels (VSKs). Results. In the case of STIX visibilities recorded during the November 11, 2022 flaring event, we show that RIS is able to generate hard X-ray maps, whose morphology is seen to smoothly evolve from one energy channel to the contiguous one; accordingly, from these maps, it is possible to infer spatially resolved count spectra characterized by a notable numerical stability. We also show that the performance of this approach is robust with respect to both the image reconstruction method and the count energy channel utilized to trigger the sequential process. Conclusions. We conclude that RIS is not only an appropriate, but also an effective and necessary approach to constructing image cubes from STIX visibilities that are characterized by smooth behavior across count energies. Thus, it allows for the generation of numerically stable (and, thus, physically reliable) local count spectra. AU - Volpara, A.* AU - Lupoli, A.* AU - Filbir, F. AU - Perracchione, E.* AU - Maria Massone, A.* AU - Piana, M.* C1 - 73378 C2 - 57031 CY - 17, Ave Du Hoggar, Pa Courtaboeuf, Bp 112, F-91944 Les Ulis Cedex A, France TI - RIS: Regularized imaging spectroscopy for STIX on board Solar Orbiter. JO - Astron. Astrophys. VL - 694 PB - Edp Sciences S A PY - 2025 SN - 0004-6361 ER - TY - JOUR AB - Supernovae (SNs) are an important source of energy in the interstellar medium. Young remnants of supernovae (SNRs) exhibit peak emission in the X-ray region, making them interesting objects for X-ray observations. In particular, the supernova remnant SN1006 is of great interest due to its historical record, proximity, and brightness. Thus, it has been studied with a number of X-ray telescopes. Improving X-ray imaging of this and other remnants is an important but challenging task, as it often requires multiple observations with different instrument responses to image the entire object. Here, we use Chandra observations to demonstrate the capabilities of Bayesian image reconstruction using information field theory (IFT). Our objective is to reconstruct denoised, deconvolved, and spatio-spectral resolved images from X-ray observations and to decompose the emission into different morphologies, namely, diffuse and point-like. Further, we aim to fuse data from different detectors and pointings into a mosaic and quantify the uncertainty of our result. By utilizing prior knowledge on the spatial and spectral correlation structure of the diffuse emission and point sources, this method allows for the effective decomposition of the signal into these two components. In order to accelerate the imaging process, we introduced a multi-step approach, in which the spatial reconstruction obtained for a single energy range is used to derive an informed starting point for the full spatio-spectral reconstruction. We applied this method to 11 Chandra observations of SN1006 from 2008 and 2012, providing a detailed, denoised, and decomposed view of the remnant. In particular, the separated view of the diffuse emission ought to provide new insights into the complex, small-scale structures in the center of the remnant and at the shock front profiles. For example, our analysis reveals sharp X-ray flux increases by up to two orders of magnitude at the shock fronts of SN1006. AU - Westerkamp, M.* AU - Eberle, V.* AU - Guardiani, M.* AU - Frank, P.* AU - Platz, L.I. AU - Arras, P.* AU - Knollmüller, J.* AU - Stadler, J.* AU - Enblin, T.* C1 - 70611 C2 - 55631 CY - 17, Ave Du Hoggar, Pa Courtaboeuf, Bp 112, F-91944 Les Ulis Cedex A, France TI - The first spatio-spectral Bayesian imaging of SN1006 in X-rays. JO - Astron. Astrophys. VL - 684 PB - Edp Sciences S A PY - 2024 SN - 0004-6361 ER - TY - JOUR AB - The gamma-ray sky as seen by the Large Area Telescope (LAT) on board the Fermi satellite is a superposition of emissions from many processes. To study them, a rich toolkit of analysis methods for gamma-ray observations has been developed, most of which rely on emission templates to model foreground emissions. Here, we aim to complement these methods by presenting a template-free spatio-spectral imaging approach for the gamma-ray sky, based on a phenomenological modeling of its emission components. It is formulated in a Bayesian variational inference framework and allows a simultaneous reconstruction and decomposition of the sky into multiple emission components, enabled by a self-consistent inference of their spatial and spectral correlation structures. Additionally, we formulated the extension of our imaging approach to template-informed imaging, which includes adding emission templates to our component models while retaining the "data-drivenness"of the reconstruction. We demonstrate the performance of the presented approach on the ten-year Fermi LAT data set. With both template-free and template-informed imaging, we achieve a high quality of fit and show a good agreement of our diffuse emission reconstructions with the current diffuse emission model published by the Fermi Collaboration. We quantitatively analyze the obtained data-driven reconstructions and critically evaluate the performance of our models, highlighting strengths, weaknesses, and potential improvements. All reconstructions have been released as data products. AU - Platz, L.I. AU - Knollmüller, J.* AU - Arras, P.* AU - Frank, P.* AU - Reinecke, M.* AU - Jüstel, D. AU - Enßlin, T.A.* C1 - 69085 C2 - 53849 CY - 17, Ave Du Hoggar, Pa Courtaboeuf, Bp 112, F-91944 Les Ulis Cedex A, France TI - Multicomponent imaging of the Fermi gamma-ray sky in the spatio-spectral domain. JO - Astron. Astrophys. VL - 680 PB - Edp Sciences S A PY - 2023 SN - 0004-6361 ER - TY - JOUR AB - Context. Carbonaceous chondrites are sources of information on the origin of the Solar System. Their organic content is conventionally classified as soluble (SOM) and insoluble organic matter (IOM), where the latter represents the majority. Aims. In this work, our objectives are to identify possible relations between soluble and insoluble organic matter generated in laboratory experiments and to extrapolate the laboratory analog findings to soluble and insoluble organic matter of meteorites to test their connection. Methods. Using laboratory experiments, processes possibly linking IOM analog (IOMA) to SOM analog (SOMA) precursors are investigated by assuming that dense molecular ices are one of the sources of organic matter in the Solar System. Each organic fraction is analyzed by laser desorption coupled to a Fourier transform ion cyclotron resonance mass spectrometer on a comprehensive basis. Results. SOMA and IOMA significantly differ in their chemical fingerprints, and particularly in their aromaticity, O/C, and N/C elemental ratios. Using an innovative molecular network, the SOMAaIOMA transition was tested, revealing connection between both classes. This new network suggests that IOMA is formed in two steps: a first generation IOMA based on precursors from SOMA, while a second IOMA generation is formed by altering the first IOMA generation. Finally, using the same analytical technique, the molecular content of IOMA and that of the Paris IOM are compared, showing their molecular similarities for the first time. The molecular network application to the Paris SOM and IOM demonstrates that a possible connection related to photochemical ice processing is present, but that the overall history of IOM formation in meteorites is much more complex and might have been affected by additional factors (e.g., aqueous alteration). Conclusions. Our approach provides a new way to analyze the organic fraction of extraterrestrial material, giving new insights into the evolution of organic matter in the Solar System. AU - Danger, G.* AU - Ruf, A.* AU - Javelle, T.* AU - Maillard, J.* AU - Vinogradoff, V.* AU - Afonso, C.* AU - Schmitz-Afonso, I.* AU - Remusat, L.* AU - Gabelica, Z.* AU - Schmitt-Kopplin, P. C1 - 67146 C2 - 52280 CY - 17, Ave Du Hoggar, Pa Courtaboeuf, Bp 112, F-91944 Les Ulis Cedex A, France TI - The transition from soluble to insoluble organic matter in interstellar ice analogs and meteorites. JO - Astron. Astrophys. VL - 667 PB - Edp Sciences S A PY - 2022 SN - 0004-6361 ER - TY - JOUR AB - Context. Sulfur (S) is of prime interest in the context of (astro)chemical evolution and habitability. However, the origin of S-bearing organic compounds in the Solar System is still not well constrained.Aims. We carried out laboratory experiments to test whether complex organosulfur compounds can be formed when surfaces of icy Solar System bodies are subject to high-energy S ions.Methods. Non-S-bearing organic residues, formed during the processing of astrophysical H2O:CH3OH:NH3-bearing ice analogs, were irradiated with 105 keV-S7+ ions at 10 K and analyzed by high-resolving FT-ICR-MS. The resulting data were comprehensively analyzed, including network analysis tools.Results. Out of several thousands of detected compounds, 16% contain at least one sulfur atom (organosulfur (CHNOS) compounds), as verified via isotopic fine structures. These residue-related organosulfur compounds are different from those formed during the S ion irradiation of ices at 10 K. Furthermore, insoluble, apolar material was formed during the sulfur irradiation of residues. Potential organosulfur precursors (CHNO molecules) were identified by means of molecular networks.Conclusions. This evidence of organosulfur compounds formed by sulfur irradiation of organic residues sheds new light onto the rich and complex scope of pristine organosulfur chemistry in the Solar System, presented in the context of current and future space missions. These results indicate that the space weathering of Solar System bodies may lead to the formation of organosulfur compounds. AU - Ruf, A.* AU - Bouquet, A.* AU - Schmitt-Kopplin, P. AU - Boduch, P.* AU - Mousis, O.* AU - Danger, G.* C1 - 63671 C2 - 51496 CY - 17, Ave Du Hoggar, Pa Courtaboeuf, Bp 112, F-91944 Les Ulis Cedex A, France TI - Sulfur ion irradiation experiments simulating space weathering of Solar System body surfaces Organosulfur compound formation. JO - Astron. Astrophys. VL - 655 PB - Edp Sciences S A PY - 2021 SN - 0004-6361 ER - TY - JOUR AB - Aims. We search for frozen water and its processing around young stellar objects (YSOs of class I/II). We try to detect potential, regional differences in water ice evolution within YSOs, which is relevant to understanding the chemical structure of the progenitors of protoplanetary systems and the evolution of solid materials. Water plays an important role as a reaction bed for rich chemistry and is an indispensable requirement for life as known on Earth. Methods. We present our analysis of NAOS-CONICA/VLT spectroscopy of water ice at 3 mu m for the T Tauri star YLW16A in the rho Ophiuchi molecular cloud. We obtained spectra for different regions of the circumstellar environment. The observed absorption profiles are deconvolved with the mass extinction profiles of amorphous and crystallized ice measured in laboratory. We take into account both absorption and scattering by ice grains. Results. Water ice in YLW16A is detected with optical depths of between tau = 1.8 and tau = 2.5. The profiles that are measured can be fitted predominantly by the extinction profiles of small grains (0.1 mu m-0.3 mu m) with a small contribution from large grains (<10%). However, an unambiguous trace of grain growth cannot be found. We detected crystallized water ice spectra that have their origin in different regions of the circumstellar environment of the T Tauri star YLW16A. The crystallinity increases in the upper layers of the circumstellar disk, while only amorphous grains exist in the bipolar envelope. As in studies of silicate grains in T Tauri objects, the higher crystallinity in the upper layers of the outer disk regions implies that water ice crystallizes and remains crystallized close to the disk atmosphere where water ice is shielded against hard irradiation. AU - Schegerer, A.A. AU - Wolf, S.* C1 - 1032 C2 - 27379 TI - Spatially resolved detection of crystallized water ice in a T Tauri object. JO - Astron. Astrophys. VL - 517 PB - EDP Sciences PY - 2010 SN - 0004-6361 ER - TY - JOUR AB - Aims. High-energy irradiation of circumstellar material might impact the structure and the composition of a protoplanetary disk and hence the process of planet formation. In this paper, we present a study of the possible influence of stellar irradiation, indicated by X-ray emission, on the crystalline structure of circumstellar dust. Methods. The dust crystallinity is measured for 42 class II T Tauri stars in the Taurus star-forming region using a decomposition fit of the 10 mu m silicate feature, measured with the spitzer IRS instrument. Since the sample includes objects with disks of various evolutionary stages, we further confine the target selection, using the age of the objects as a selection parameter. Results. We correlate the X-ray luminosity and the X-ray hardness of the central object with the crystalline mass fraction of the circumstellar dust and find a significant anti-correlation for 20 objects within an age range of approx. 1 to 4.5 Myr. We postulate that X-rays represent the stellar activity and consequently the energetic ions of the stellar winds which interact with the circumstellar disk. We show that the fluxes around 1 AU and ion energies of the present solar wind are sufficient to amorphize the upper layer of dust grains very efficiently, leading to an observable reduction of the crystalline mass fraction of the circumstellar, sub-micron sized dust. This effect could also erase other relations between crystallinity and disk/star parameters such as age or spectral type. AU - Glauser, A.M.* AU - Güdel, M.* AU - Watson, D.M.* AU - Henning, T.* AU - Schegerer, A.A. AU - Wolf, S.* AU - Audard, M.* AU - Baldovin-Saavedra, C.* C1 - 1566 C2 - 27196 SP - 247-257 TI - Dust amorphization in protoplanetary disks. JO - Astron. Astrophys. VL - 508 IS - 1 PB - EDP Sciences PY - 2009 SN - 0004-6361 ER - TY - JOUR AB - The aim of this study is to enhance our knowledge of the characteristics and distribution of the circumstellar dust associated with the individual components of the young hierarchical triple system T Tau. Methods. To reach this goal, observations in the N-band (8-13 mu m) with the two-telescope interferometric instrument MIDI at the VLTI were performed. For the northern component of the T Tau system, projected baseline lengths of 43 m, 62 m, and 85 m were used. For the southern binary projected baseline lengths of equivalent resolution could be utilised. Our study is based on both the interferometric and the spectrophotometric measurements and is supplemented by new visual and infrared photometry. Also, the phases were investigated to determine the dominating mid-infrared source in the close southern binary. The data were fit with the help of a sophisticated physical disc model. This model utilises the radiative transfer code MC3D that is based on the Monte-Carlo method. Results. Extended mid-infrared emission is found around all three components of the system. Simultaneous fits to the photometric and interferometric data confirm the picture of an almost face-on circumstellar disc around T Tau N. Towards this star, the silicate band is seen in emission. This emission feature is used to model the dust content of the circumstellar disc. Clear signs of dust processing are found. Towards T Tau S, the silicate band is seen in absorption. This absorption is strongly pronounced towards the infrared companion T Tau Sa as can be seen from the first individual N-band spectra for the two southern components. Our fits support the previous suggestion that an almost edge-on disc is present around T Tau Sa. This disc is thus misaligned with respect to the circumstellar disc around T Tau N. The interferometric data indicate that the disc around T Tau Sa is oriented in the north-south direction, which favours this source as launching site for the east-western jet. We further determine from the interferometric data the relative positions of the components of the southern binary in the N-band. We find good agreement with recent position measurements in the near-infrared. AU - Ratzka, T.* AU - Schegerer, A.A. AU - Leinert, C.* AU - Ábrahám, P.* AU - Henning, T.* AU - Herbst, T.M.* AU - Köhler, R.* AU - Wolf, S.* AU - Zinnecker, H.* C1 - 543 C2 - 26292 SP - 623-646 TI - Spatially resolved mid-infrared observations of the triple system T Tauri. JO - Astron. Astrophys. VL - 502 IS - 2 PB - Edp Sciences S A PY - 2009 SN - 0004-6361 ER - TY - JOUR AB - We investigate the nature of the innermost regions with radii of several AUs of seven circumstellar disks around pre-main-sequence stars, T Tauri stars in particular. Our object sample contains disks apparently at various stages of their evolution. Both single stars and spatially resolved binaries are considered. In particular, we search for inner disk gaps as proposed for several young stellar objects (YSOs). When analyzing the underlying dust population in the atmosphere of circumstellar disks, the shape of the 10 ?m feature should additionally be investigated. Methods: We performed interferometric observations in N band (8-13 ?m) with the Mid-Infrared Interferometric Instrument (MIDI) at the Very Large Telescope Interferometer (VLTI) using baseline lengths of between 54 m and 127 m. The data analysis is based on radiative-transfer simulations using the Monte Carlo code MC3D by modeling simultaneously the spectral energy distribution (SED), N band spectra, and interferometric visibilities. Correlated and uncorrelated N band spectra are compared to investigate the radial distribution of the dust composition of the disk atmosphere. Results: Spatially resolved mid-infrared (MIR) emission was detected in all objects. For four objects (DR Tau, RU Lup, S CrA N, and S CrA S), the observed N band visibilities and corresponding SEDs could be simultaneously simulated using a parameterized active disk-model. For the more evolved objects of our sample, HD 72106 and HBC 639, a purely passive disk-model provides the closest fit. The visibilities inferred for the source RU Lup allow the presence of an inner disk gap. For the YSO GW Ori, one of two visibility measurements could not be simulated by our modeling approach. All uncorrelated spectra reveal the 10 ?m silicate emission feature. In contrast to this, some correlated spectra of the observations of the more evolved objects do not show this feature, indicating a lack of small silicates in the inner versus the outer regions of these disks. We conclude from this observational result that more evolved dust grains can be found in the more central disk regions. AU - Schegerer, A.A. AU - Wolf, S.* AU - Hummel, C.A.* AU - Quanz, S.P.* AU - Richichi, A.* C1 - 993 C2 - 26326 SP - 367-383 TI - Tracing the potential planet-forming regions around seven pre-main-sequence stars. JO - Astron. Astrophys. VL - 502 IS - 1 PB - ESO PY - 2009 SN - 0004-6361 ER -