Structures in circumbinary disks: Prospects for observability

During the past decade circumbinary disks have been discovered around various young binary stars. Hydrodynamical calculations indicate that the gravitational interaction between the central binary star and the surrounding disk results in global perturbations of the disk density profile. We study the observability of characteristic large-scale disk structures resulting from the binary-disk interaction in the case of close binary systems. We derived the structure of circumbinary disks from smoothed-particle hydrodynamic simulations. Subsequently, we performed radiative transfer simulations to obtain scattered light and thermal reemission maps. We investigated the influence of the binary mass ratio, the inclination of the binary orbit relative to the disk midplane, and the eccentricity of the binary orbit on observational quantities. We find that ALMA will allow tracing asymmetries of the inner edge of the disk and potentially resolving spiral arms if the disk is seen face-on. For an edge-on orientation, ALMA will allow detecting perturbations in the disk density distribution through asymmetries in the radial brightness profile. Through the asymmetric structure of the disks, areas are formed with a temperature $2.6$ times higher than at the same location in equivalent unperturbed disks. The time-dependent appearance of the density waves and spiral arms in the disk affects the total re-emission flux of the object by a few percent.Comment: 8 pages, 9 figures, to appear in A&

Observability of large-scale structures in circumstellar disks and analysis of their origin

Zirkumstellare Scheiben sind die Geburtsstätte von Planetensystemen. Sie bestehen zu einem überwiegenden Teil aus Gas und etwa 1% Staub und bilden sich im Zuge der Sternentstehung. Gerade die seit Kurzem möglichen Beobachtungen dieser Objekte mit ALMA bringen immer mehr ans Licht, dass es sich bei zirkumstellaren Scheiben um hoch dynamische Objekte mit großskaligen Strukturen in der Materialverteilung handelt. Inzwischen sind viele Wechselwirkungsmechanismen vorgeschlagen worden, die solche Strukturen erklären können. Allerdings ist es auch notwendig, die Beobachtbarkeit dieser theoretischen Mechanismen im Detail zu untersuchen, um ein Werkzeug zur Interpretation realer Messungen zur Hand zu haben. Besonders eignet sich hierfür ein dreiteiliges Vorgehen, bei dem zunächst die Störung der Scheibendichtestruktur in Hydrodynamiksimulationen beschrieben wird. Im nächsten Schritt werden dann Strahlungstransport-Simulationen auf der Grundlage dieser Dichteverteilungen durchgeführt und hierauf aufbauend Beobachtungen mit ausgewählten Instrumenten simuliert. Im Rahmen dieser Arbeit werden die charakteristischen Strukturen, die durch Planet-Scheibe-, Binärsystem-Scheibe- und Magnetfeld-Scheibe-Wechselwirkung in der Dichteverteilung der zirkumplanetaren, beziehungsweise zirkumbinären Scheibe entstehen, auf diese Weise untersucht. Dabei liegt ein besonderes Augenmerk auf simulierten ALMA-Beobachtungen im (sub)mm-Wellenlängenbereich. Dennoch werden auch andere Bereiche des elektromagnetischen Spektrums in die Analyse mit einbezogen, da erst durch die Kombination von Multiwellenlängen-Beobachtungen wirklich Ursachen für Scheibenstrukturen erkannt werden können. Dies ist vor allem deshalb wichtig, da es ein Ergebnis der Arbeit ist, dass ALMA für alle berücksichtigten Wechselwirkungsmechanismen tatsächlich charakteristische Strukturen beobachten kann, diese sich aber trotz unterschiedlicher Ursache derart ähneln können, dass eine Unterscheidung nicht möglich ist. So ist im Rahmen der durchgeführten Untersuchungen eine Unterscheidung der Auswirkung von Magnetfeld-Scheibe- und Planet-Scheibe-Wechselwirkung erst durch die Detektion der direkten Abstrahlung des Planeten möglich. Es werden die Bedingungen erforscht und angegeben, unter denen die planetare Abstrahlung detektiert werden kann und welche Rückschlüsse aus einer solchen Messung auf die Eigenschaften des Planeten möglich sind. Zudem zeigt sich, dass der Staub in einer zirkumstellaren Scheibe in Abhängigkeit seiner Größe eine Verteilung besitzt, die große Unterschiede zur Verteilung der Gasmoleküle besitzt. Da dieser aber für die Kontinuumsabstrahlung im (sub)mm-Wellenlängenbereich verantwortlich ist, können gerade die durch ihn erzeugten Strukturen besonders gut beobachtet werden. Das entworfene Modell zeigt hierbei große, augenscheinliche Ähnlichkeit zu einer ALMA-Beobachtung von HL Tau. Insgesamt zeigt die Arbeit allerdings, dass die Vielfalt der Ursachen für Strukturen in zirkumstellaren Scheiben so groß ist, dass ein Rückschluss von der Beobachtung einer Struktur auf die tatsächliche Ursache nicht eindeutig ist.Circumstellar disks are expected to be the birthplace of planetary systems. They predominantly consist of gas, with about 1% dust, and they are a byproduct of star formation. Since its inauguration, ALMA has revealed, that these objects are highly dynamical and show large scale structures in their distribution of matter. Meanwhile, several interactions have been proposed to create these structures. However, it is necessary to explore the observability of the theoretical models in detail to provide a means to interpret real measurements. In particular, a three step method is appropriate for this purpose. First, the interaction processes have to be investigated in hydrodynamical simulations of the disk density profiles. Second, on the basis of these density profiles, follow-up radiative transport calculations must be performed and finally the observability for selected instruments must be predicted from the radiative transfer outcome. This thesis investigates characteristic large scale disk structures resulting from planet-disk, binary-disk and magnetic-field-disk interactions. It focuses on predicting ALMA observations in the (sub)mm wavelength range. However, the rest parts of the electro-magnetic spectrum will also be included in the investigation, because only with a combination of multi-wavelength observations it is feasible to determine the origin of a disk structure. In particular, one key result of the thesis is that ALMA is able to observe the characteristic structures of each considered interaction process, but these could appear very similar although the origin is different. Within the parameter space considered, magnetic-field-disk and planet-disk interaction can only be distinguished on the basis of the direct radiation of the planetary source. The conditions under which it is possible to detect the planetary radiation are investigated, along with what one can learn from a measurement of this radiation about the properties of the planet. In addition, the decoupling of the motion of sufficiently large dust particles from that of the gas is explored, which leads to a distribution of these particles totally different from the distribution of the gas molecules in the disk. These large dust particles dominate the thermal continuum emission of a circumstellar disk in the (sub)mm range. Thus, structures in the distribution of large particles are particularly easy to observe with ALMA. Our model shows a qualitative similarity to the recent ALMA observation of HL Tau. In general, this thesis shows that there is a large variety of disk structures and origins. Therefore, tracing from observed disk structures back to their origins is ambiguous

Tracing large-scale structures in circumstellar disks with ALMA

Planets are supposed to form in circumstellar disks. The gravitational potential of a planet perturbs the disk and leads to characteristic structures, i.e. spiral waves and gaps, in the disk's density profile. We perform a large-scale parameter study of the observability of these planet-induced structures in circumstellar disks with ALMA. On the basis of HD and MHD simulations, we calculated the disk temperature structure and (sub)mm images of these systems. These were used to derive simulated ALMA images. Because appropriate objects are frequent in Taurus, we focused on a distance of 140pc and a declination of 20{\deg}. The explored range of star-disk-planet configurations consists of 6 HD simulations (including magnetic fields and different planet masses), 9 disk sizes, 15 total disk masses, 6 different central stars, and two different grain size distributions. On almost all scales and in particular down to a scale of a few AU, ALMA is able to trace disk structures induced by planet-disk interaction or by the influence of magnetic fields on the wavelength range between 0.4 and 2.0mm. In most cases, the optimum angular resolution is limited by the sensitivity. However, within the range of typical masses of protoplanetary disks (0.1-0.001Msun) the disk mass has a minor impact on the observability. It is possible to resolve disks down to 2.67e-6Msun and trace gaps induced by a planet with M_p/M_s = 0.001 in disks with 2.67e-4Msun with a signal-to-noise ratio greater than three. The central star has a major impact on the observability of gaps, as well as the considered maximum grainsize of the dust in the disk. In general, it is more likely to trace planet-induced gaps in our MHD models, because gaps are wider in the presence of magnetic fields. We also find that zonal flows resulting from MRI create gap-like structures in the disk's re-emission radiation, which are observable with ALMA.Comment: 17 pages, 21 figure

Planet-induced disk structures: A comparison between (sub)mm and infrared radiation

Young giant planets, which are embedded in a circumstellar disk, will significantly perturb the disk density distribution. This effect can potentially be used as an indirect tracer for planets. We investigate the feasibility of observing planet-induced gaps in circumstellar disks in scattered light. We perform 3D hydrodynamical disk simulations combined with subsequent radiative transfer calculations in scattered light for different star, disk, and planet configurations. The results are compared to those of a corresponding study for the (sub)mm thermal re-emission. The feasibility of detecting planet-induced gaps in scattered light is mainly influenced by the optical depth of the disk and therefore by the disk size and mass. Planet-induced gaps are in general only detectable if the photosphere of the disks is sufficiently disturbed. Within the limitations given by the parameter space here considered, we find that gap detection is possible in the case of disks with masses below $\sim 10^{-4\dots-3} \, \rm M_\odot$. Compared to the disk mass that marks the lower Atacama Large (Sub)Millimeter Array (ALMA) detection limit for the thermal radiation re-emitted by the disk, it is possible to detect the same gap both in re-emission and scattered light only in a narrow range of disk masses around $\sim 10^{-4} \, \rm M_\odot$, corresponding to $16\%$ of cases considered in our study.Comment: 4 pages, 6 figure

Tracing Planets in Circumstellar Discs

Planets are assumed to form in circumstellar discs around young stellar objects. The additional gravitational potential of a planet perturbs the disc and leads to characteristic structures, i.e. spiral waves and gaps, in the disc density profile. We perform a large-scale parameter study on the observability of these planet-induced structures in circumstellar discs in the (sub)mm wavelength range for the Atacama Large (Sub)Millimeter Array (ALMA). On the basis of hydrodynamical and magneto-hydrodynamical simulations of star-disc-planet models we calculate the disc temperature structure and (sub)mm images of these systems. These are used to derive simulated ALMA maps. Because appropriate objects are frequent in the Taurus-Auriga region, we focus on a distance of 140 pc and a declination of ≈ 20°. The explored range of star-disc-planet configurations consists of six hydrodynamical simulations (including magnetic fields and different planet masses), nine disc sizes with outer radii ranging from 9 AU to 225 AU, 15 total disc masses in the range between 2.67·10-7 M⊙ and 4.10·10-2 M⊙, six different central stars and two different grain size distributions, resulting in 10 000 disc models. At almost all scales and in particular down to a scale of a few AU, ALMA is able to trace disc structures induced by planet-disc interaction or the influence of magnetic fields in the wavelength range between 0.4...2.0 mm. In most cases, the optimum angular resolution is limited by the sensitivity of ALMA. However, within the range of typical masses of protoplane tary discs (0.1 M⊙...0.001 M⊙) the disc mass has a minor impact on the observability. At the distance of 140 pc it is possible to resolve discs down to 2.67·10-6 M⊙ and trace gaps in discs with 2.67·10-4 M⊙ with a signal-to-noise ratio greater than three. In general, it is more likely to trace planet-induced gaps in magneto-hydrodynamical disc models, because gaps are wider in the presence of magnetic fields [1]. We also find, that zonal flows resulting from magneto-rotational instability (MRI) create gap-like structures in the disc re-emission radiation which are observable with ALMA. Through the unprecedented resolution and sensitivity of ALMA in the (sub)mm wavelength range the expected detailed observations of planet-disc interaction and global disc structures will deepen our understanding of the planet formation and disc evolution process. This article presents a summary of the study published by [2]

Tracing Planets in Circumstellar Discs

Planets are assumed to form in circumstellar discs around young stellar objects. The additional gravitational potential of a planet perturbs the disc and leads to characteristic structures, i.e. spiral waves and gaps, in the disc density profile. We perform a large-scale parameter study on the observability of these planet-induced structures in circumstellar discs in the (sub)mm wavelength range for the Atacama Large (Sub)Millimeter Array (ALMA). On the basis of hydrodynamical and magneto-hydrodynamical simulations of star-disc-planet models we calculate the disc temperature structure and (sub)mm images of these systems. These are used to derive simulated ALMA maps. Because appropriate objects are frequent in the Taurus-Auriga region, we focus on a distance of 140 pc and a declination of ≈ 20°. The explored range of star-disc-planet configurations consists of six hydrodynamical simulations (including magnetic fields and different planet masses), nine disc sizes with outer radii ranging from 9 AU to 225 AU, 15 total disc masses in the range between 2.67·10-7 M⊙ and 4.10·10-2 M⊙, six different central stars and two different grain size distributions, resulting in 10 000 disc models. At almost all scales and in particular down to a scale of a few AU, ALMA is able to trace disc structures induced by planet-disc interaction or the influence of magnetic fields in the wavelength range between 0.4...2.0 mm. In most cases, the optimum angular resolution is limited by the sensitivity of ALMA. However, within the range of typical masses of protoplane tary discs (0.1 M⊙...0.001 M⊙) the disc mass has a minor impact on the observability. At the distance of 140 pc it is possible to resolve discs down to 2.67·10-6 M⊙ and trace gaps in discs with 2.67·10-4 M⊙ with a signal-to-noise ratio greater than three. In general, it is more likely to trace planet-induced gaps in magneto-hydrodynamical disc models, because gaps are wider in the presence of magnetic fields [1]. We also find, that zonal flows resulting from magneto-rotational instability (MRI) create gap-like structures in the disc re-emission radiation which are observable with ALMA. Through the unprecedented resolution and sensitivity of ALMA in the (sub)mm wavelength range the expected detailed observations of planet-disc interaction and global disc structures will deepen our understanding of the planet formation and disc evolution process. This article presents a summary of the study published by [2]

Role of the default mode resting-state network for cognitive functioning in malignant glioma patients following multimodal treatment

Background: Progressive cognitive decline following multimodal neurooncological treatment is a common observation in patients suffering from malignant glioma. Alterations of the default-mode network (DMN) represent a possible source of impaired neurocognitive functioning and were analyzed in these patients. Methods: Eighty patients (median age, 51 years) with glioma (WHO grade IV glioblastoma, n = 57; WHO grade III anaplastic astrocytoma, n = 13; WHO grade III anaplastic oligodendroglioma, n = 10) and ECOG performance score 0-1 underwent resting-state functional MRI (rs-fMRI) and neuropsychological testing at a median interval of 13 months (range, 1-114 months) after initiation of therapy. For evaluation of structural and metabolic changes after treatment, anatomical MRI and amino acid PET using O-(2-[F-18]fluoroethyl)-L-tyrosine (FET) were simultaneously acquired to rs-fMRI on a hybrid MR/PET scanner. A cohort of 80 healthy subjects matched for gender, age, and educational status served as controls. Results: The connectivity pattern within the DMN (12 nodes) of the glioma patients differed significantly from that of the healthy subjects but did not depend on age, tumor grade, time since treatment initiation, presence of residual/recurrent tumor, number of chemotherapy cycles received, or anticonvulsive medication. Small changes in the connectivity pattern were observed in patients who had more than one series of radiotherapy. In contrast, structural tissue changes located at or near the tumor site (including resection cavities, white matter lesions, edema, and tumor tissue) had a strong negative impact on the functional connectivity of the adjacent DMN nodes, resulting in a marked dependence of the connectivity pattern on tumor location. In the majority of neurocognitive domains, glioma patients performed significantly worse than healthy subjects. Correlation analysis revealed that reduced connectivity in the left temporal and parietal DMN nodes was associated with low performance in language processing and verbal working memory. Furthermore, connectivity of the left parietal DMN node also correlated with processing speed, executive function, and verbal as well as visual working memory. Overall DMN connectivity loss and cognitive decline were less pronounced in patients with higher education. Conclusion: Personalized treatment strategies for malignant glioma patients should consider the left parietal and temporal DMN nodes as vulnerable regions concerning neurocognitive outcome

Oncologic Outcome and Immune Responses of Radiotherapy with Anti-PD-1 Treatment for Brain Metastases Regarding Timing and Benefiting Subgroups

SIMPLE SUMMARY: Immune checkpoint inhibitors (ICIs) and radiotherapy (RT) are widely used for patients with brain metastasis (BM). To evaluate markers for treatment response and find a treatment concept which has the best outcome effects, we analyzed data of 93 patients with BM from different cancer types. Predictive markers for survival were good performance status, melanoma as cancer type, low metastasis volume, normal inflammatory blood parameters, and a stereotactic radiotherapy concept with high doses. We found that the best survival outcome can be achieved with the concurrent use of RT and ICI. Concurrent treatment was particularly beneficial in patients with low inflammatory status and more and larger metastases, and when high doses cannot be administered. In concurrently treated patients, therapeutic response was often delayed compared to sequential treatment. Specific immune responses such as pseudoprogression and abscopal effects were induced by concurrent treatment and associated with prolonged survival. ABSTRACT: While immune checkpoint inhibitors (ICIs) in combination with radiotherapy (RT) are widely used for patients with brain metastasis (BM), markers that predict treatment response for combined RT and ICI (RT-ICI) and their optimal dosing and sequence for the best immunogenic effects are still under investigation. The aim of this study was to evaluate prognostic factors for therapeutic outcome and to compare effects of concurrent and non-concurrent RT-ICI. We retrospectively analyzed data of 93 patients with 319 BMs of different cancer types who received PD-1 inhibitors and RT at the University Hospital Cologne between September/2014 and November/2020. Primary study endpoints were overall survival (OS), progression-free survival (PFS), and local control (LC). We included 66.7% melanoma, 22.8% lung, and 5.5% other cancer types with a mean follow-up time of 23.8 months. Median OS time was 12.19 months. LC at 6 months was 95.3% (concurrent) vs. 69.2% (non-concurrent; p = 0.008). Univariate Cox regression analysis detected following prognostic factors for OS: neutrophil-to-lymphocyte ratio NLR favoring 3 cm(3) (p = 0.007), other cancer types than melanoma (p = 0.006), anti-CTLA4-naïve patients (p < 0.001), low NLR (p = 0.039), steroid intake ≤4 mg (p = 0.042). Specific immune responses, such as abscopal effects (AbEs), pseudoprogression (PsP), or immune-related adverse events (IrAEs), occurred more frequently with concurrent RT-ICI and resulted in better OS. Other toxicities, including radionecrosis, were not statistically different in both groups. The concurrent application of RT and ICI, the ECOG-PS, cancer type, and PTV had an independently prognostic impact on OS. In concurrently treated patients, treatment response (LC) was delayed and specific immune responses (AbE, PsP, IrAE) occurred more frequently with longer OS rates. Our results suggest that concurrent RT-ICI application is more beneficial than sequential treatment in patients with low pretreatment inflammatory status, more and larger BMs, and with other cancer types than melanoma

First Millimeter Detection of the Disk around a Young, Isolated, Planetary-mass Object

International audienceOTS44 is one of only four free-floating planets known to have a disk. We have previously shown that it is the coolest and least massive known free-floating planet (∼12 {M}{Jup}) with a substantial disk that is actively accreting. We have obtained Band 6 (233 GHz) ALMA continuum data of this very young disk-bearing object. The data show a clear unresolved detection of the source. We obtained disk-mass estimates via empirical correlations derived for young, higher-mass, central (substellar) objects. The range of values obtained are between 0.07 and 0.63 {M}\oplus (dust masses). We compare the properties of this unique disk with those recently reported around higher-mass (brown dwarfs) young objects in order to infer constraints on its mechanism of formation. While extreme assumptions on dust temperature yield disk-mass values that could slightly diverge from the general trends found for more massive brown dwarfs, a range of sensible values provide disk masses compatible with a unique scaling relation between {M}{dust} and M * through the substellar domain down to planetary masses

Predicting IDH genotype in gliomas using FET PET radiomics

Mutations in the isocitrate dehydrogenase (IDH mut) gene have gained paramount importance for the prognosis of glioma patients. To date, reliable techniques for a preoperative evaluation of IDH genotype remain scarce. Therefore, we investigated the potential of O-(2-[F-18]fluoroethyl)-L-tyrosine (FET) PET radiomics using textural features combined with static and dynamic parameters of FET uptake for noninvasive prediction of IDH genotype. Prior to surgery, 84 patients with newly diagnosed and untreated gliomas underwent FET PET using a standard scanner (15 of 56 patients with IDH mut) or a dedicated high-resolution hybrid PET/MR scanner (11 of 28 patients with IDH mut). Static, dynamic and textural parameters of FET uptake in the tumor area were evaluated. Diagnostic accuracy of the parameters was evaluated using the neuropathological result as reference. Additionally, FET PET and textural parameters were combined to further increase the diagnostic accuracy. The resulting models were validated using cross-validation. Independent of scanner type, the combination of standard PET parameters with textural features increased significantly diagnostic accuracy. The highest diagnostic accuracy of 93% for prediction of IDH genotype was achieved with the hybrid PET/MR scanner. Our findings suggest that the combination of conventional FET PET parameters with textural features provides important diagnostic information for the non-invasive prediction of the IDH genotype