T Tauri Research Articles

Additional value of tau protein measurement in the diagnosis of Creutzfeldt-Jakob disease.

Since the definite diagnosis of Creutzfeldt-Jakob disease (CJD) can currently only be provided by autopsy, there is a special need for fine diagnostic tools in live patients to achieve accurate diagnosis as early as possible. The aim of this study was to perform a preliminary retrospective analysis on the utility of the measurement of total Tau (tTau) and some other biomarkers from the cerebrospinal fluid (CSF) of patients with rapidly progressive dementia in the diagnostic work up of CJD. Beside the assessment of relevant clinical data and the findings of electroencephalography and brain magnetic resonance imaging, the presence of 14-3-3 protein and the levels of tTau were determined by Western blot technique and enzyme-linked immunosorbent assay from the CSF of 19 patients diagnosed with rapidly progressive dementia between the period of 2004-2017 at the Department of Neurology, University of Szeged. This preliminary study provided 100% sensitivity for 14-3-3, and interestingly, only 40% specificity to support the clinical diagnosis of CJD. Regarding tTau, the sensitivity values were calculated to be 100% or 83%, whereas the specificity values were 71% or 86%, depending on the applied cut-off levels. The poor specificity of 14-3-3 is not in line with literature data and may be the result of the small number of patients in the cohort with non-prion disease, predominantly consisting of disorders with considerable tissue damage, whereas tTau presented good sensitivity and specificity values. The combined application of these and novel chemical biomarkers may increase both sensitivity and specificity to a desired level.

Correlations between Alzheimer's Disease Cerebrospinal Fluid Biomarkers and Cerebral Glucose Metabolism after 12 Months of Phenserine Treatment.

New therapeutic strategies in Alzheimer's disease (AD) are focused on targeting amyloid-β (Aβ) to modify the underlying cause of the disease rather than just the symptoms. The aim of this study was to investigate the long-term effects of treatment with the anti-Aβ compound phenserine on (i) cerebrospinal fluid (CSF) biomarkers for Aβ and tau pathology and (ii) brain metabolism as assessed by the regional cerebral metabolic rate for glucose (rCMRglc), using positron emission tomography. Twenty patients with mild AD were included in the study and after 12 months treatment with phenserine, CSF Aβ40 and α- and β-secretase-cleaved soluble amyloid-β protein precursor (sAβPP) levels had significantly increased and rCMRglc had stabilized. Levels of CSF Aβ40 and sAβPP correlated positively with rCMRglc and cognition while CSF Aβ42 levels, the Aβ42/40 ratio, P-tau, and T-tau correlated negatively with rCMRglc and cognition. In summary, long-term phenserine treatment resulted in increased levels of CSF Aβ40, sAβPPα, and sAβPPβ, which positively correlated with improvements in rCMRglc and cognition. The study illustrates the value of using biomarkers in the CSF and brain for evaluation of drug effects.

CSF Biomarkers and AD Prediction

Several reports have been made of the value of the CSF markers amyloid-beta1-42 (Aβ[42]), total tau protein (T-tau), and tau protein phosphorylated at

Photoevaporation of protoplanetary discs – II. Evolutionary models and observable properties

We present a new model for protoplanetary disc evolution. This model combines viscous evolution with photoevaporation of the disc. However, in a companion paper we have shown that at late times such models must consider the effect of stellar radiation directly incident on the inner disc edge, and here we model the observational implications of this process. We find that the entire disc is dispersed on a time-scale of the order of 10 5 yr after a disc lifetime of a few Myr, consistent with observations of T Tauri (TT) stars. We use a simple prescription to model the spectral energy distribution of the evolving disc, and demonstrate that the model is consistent with observational data across a wide range of wavelengths. We also note that the model predicts a short ‘inner hole’ phase in the evolution of all TT discs, and make predictions for future observations at mid-infrared and millimetre wavelengths.

The Enigmatic HH 255

ABSTRACTTo gain insight into the nature of the peculiar Herbig‐Haro object HH 255 (also called Burnham's nebula), we use previously published observations to derive information about the emission‐line fluxes as a function of position within HH 255 and compare them with the well‐studied and relatively well behaved bow shock HH 1. There are some qualitative similarities in the Hα and [O iii] λ5007 lines in both objects. However, in contrast to the expectation of the standard bow‐shock model, the fluxes of the [O i] λ6300, [S ii] λ6731, and [N ii] λ6583 lines are essentially constant along the axis of the flow, while the electron density decreases, over a large distance within HH 255. We also explore the possibility that HH 255 represents the emission behind a standing or quasi‐stationary shock. The shock faces upwind, and we suggest, using theoretical arguments, that it may be associated with the collimation of the southern outflow from T Tauri. Using a simplified magnetohydrodynamic simulation to illustrate the basic concept, we demonstrate that the existence of such a shock at the north edge of HH 255 could indeed explain its unusual kinematic and ionization properties. Whether or not such a shock can explain the detailed emission‐line stratification remains an open question.

Analysis of correlations between polarimetric and photometric characteristics of young stars

We present the results of the investigation of correlations between the polarimetric and photometric characteristics of a sample (496 objects) of young Herbig Ae/Be (HAEBE) stars and T Tauri (TT) stars. It is shown that, for 85% of the sample stars there is a gen- eral relation between the degree of optical polarization and the infrared colour index (V L)obs and the colour excess E(V L) due to the contribution of a circumstellar dust shell. Polarimetric data were also compared with the value of v sini to search for a possible correlation between the polarization and an inclination of circumstellar disks. Polarimetric data as well as IR excesses are considered and compared for dierent subgroups of young stars namely: HAEBE and TT stars with Algol{like minima of bright- ness (26 objects), Vega{type stars and post HAEBE stars (114 objects) and young solar{type stars (58 objects). For statistical purposes the data for young stars were com- pared with those collected for dierent groups of evolved objects such as: classical Be stars (300 objects), Mira Ceti stars (39 objects), early{type supergiants from the Serkowski et al. (1975) catalogue (120 objects) and main sequence (MS) stars within 50 pc from the Sun from the Leroy (1993) catalogue (68 objects). The value of polar- ization is discussed in context with the stages of evolution of circumstellar shells which were established by compari- son of spectral energy distribution in the far IR (using the IRAS data). It is shown that most young stars have sta- tistically larger value of polarization in comparison with the stars which are on a stage of evolution close to MS. We are able to contend that the changes in polarimetric behaviour of young stars are connected with evolution of their circumstellar shells.

A Deep Long‐Slit Spectroscopic Study of the Two Bipolar Outflows from the T Tauri Binary System

We present results of a new deep, high-resolution, long-slit spectroscopic study of the extended nebular line emission around the young binary T Tauri. The deduced position-velocity diagrams of the [O I], [N II], and [S II] lines have been used to investigate in great detail the complex geometric and kinematic structure of the mass outflows from the stellar binary components T Tau N and T Tau S. A large number of distinct extended outflow components, each of them characterized by its specific spatio-kinematic properties, has been identified. In addition to the brighter components (A, B, C, D, E, and F) already described in detail by Bohm & Solf, we have detected several much fainter components (G, H, I, J, K, and L), some of them extending up to ~40'' from the central binary. The new data confirm the existence of two separate bipolar outflow systems associated with the binary: one of them oriented near the east-west direction and probably originating from the visible binary component T Tau N, the other one oriented near the north-south direction and probably originating from the infrared binary component T Tau S. In the east-west outflow, so far considered to be represented only by blueshifted components (B, F, and H) west of T Tau N, we have detected for the first time an indication for a redshifted faint counterjet (G) east of T Tau, corresponding to the known HH 155 jet (H). In the north-south outflow, so far considered to be represented only by two components (C and D) near the central source (≤3''), two additional, rather faint components (I and J) have been detected, which are located farther out (8''-15'') on opposite sides of the source. Both faint components present rather low velocities of opposite sign but rather large velocity dispersions of about 75-100 km s-1 (FWHM). Using a biconical model for the outflow geometry, we have derived an inclination angle of 79° with respect to the line of sight for the bipolar axis and deduced typical velocities of ~91 and ~280 km s-1 in the faint outer regions (I and J) and the bright inner regions (C and D) of the north-south outflow, respectively. We have compared the kinematic state (mean radial velocity and velocity dispersion) of the hot (partially) ionized gas of the outflows from the binary T Tau deduced from our forbidden line observations with that of the warm molecular gas determined from the v = 1-0 S(1) line of H2 observations by T. M. Herbst and coworkers. In principal, the [S II] and H2 emission regions refer to very different spatial regions of the outflows, and hence the kinematic states of the two regions do not have to be coupled to each other. In particular, it is expected that the velocity dispersion derived from the [S II] lines is much larger than that from the H2 lines. These expectations are generally fulfilled by the observations, except for the core region of Burnham's nebula (component E) where the velocity dispersions of both the forbidden and H2 lines are approximately the same. These findings as well as other enigmatic properties of Burnham's nebula reported earlier are not yet understood.

Wind-Disk-Ambient Cloud Interactions in the Near Environment of T Tauri

view Abstract Citations (48) References (57) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Wind-Disk-Ambient Cloud Interactions in the Near Environment of T Tauri Herbst, T. M. ; Robberto, M. ; Beckwith, S. V. W. Abstract Fabry-Perot images of the near environment of T Tauri taken in the 2.122μm, υ = 1-0 S(1) quadrupole emission line of molecular hydrogen reveal a complex system of interlocking loops and arcs within 15" of the central stars. Long slit echelle spectra in the S(1) transition at several position angles indicate that the kinematics of the gas is also complex. To the north of T Tau, the redshift of the H2 line increases linearly with distance. Lower resolution spectra covering the entire K and H photometric bands reveal shock excited H2 and Fe II throughout the region. Model fits to the molecular lines point to a constant or slightly decreasing excitation temperature with distance from the stars. The interaction with the ambient molecular cloud of two, almost perpendicular outflow systems can explain the complex molecular hydrogen morphology of T Tau. Orbital motion may produce the apparent curvature of the structures. The NW-SE outflow probably energizes Burnharn's Nebula to the south of the stars. This region contains several molecular hydrogen arcs resembling bow shocks opening back toward T Tau. Similar arcs, seen in previously published [S II] images, lie interior to the H2, signalling the presence of a magnetic precursor to the shocks. The radial velocities and velocity dispersion in Burnham's Nebula remain enigmatic, however. Spatially resolved near- and mid-infrared photometry of the binary reveals evidence for circumstellar disks in both stars. These disks may collimate the outflows responsible for the H2, [S II], and [Fe II] structures. The spectral energy distribution of the infrared companion has a strong silicate absorption near 10μm, while the primary shows the silicate feature in emission. This result resolves earlier contradictory observations, some of which showed little or no Si emission in the primary. After subtraction of a model photosphere plus disk, the companion's absorption feature appears somewhat wider than the primary's emission line, consistent with optical depth or particle size effects expected from the photometric properties of the stars. The model stellar radius of the visible primary, coupled with published V sin i observations, imply an inclination of the T Tauri system of l9°. Publication: The Astronomical Journal Pub Date: August 1997 DOI: 10.1086/118508 Bibcode: 1997AJ....114..744H Keywords: STARS: PRE-MAIN SEQUENCE; CIRCUMSTELLAR MATTER; ISM: KINEMATICS AND DYNAMICS full text sources ADS | data products SIMBAD (5)

Are Both Stars in a Classic T Tauri Binary Classic T Tauri Stars?

Large near-IR color excesses and emission-line spectra indicate the presence of optically thick circumstellar accretion disks and active boundary layers in young stars. We investigate whether this classic T Tauri (TT) behavior is found in one or both members of a binary system previously identified as a TT on the basis of the unresolved light. We consider the angularly resolved Brγ and, in one case, Na I, spectra of four close (13-26) TT systems. We also take into account the angularly resolved near-IR (K-L) colors of eight additional young binaries with separations between 03 and 25. We find that for all 12 systems, both components show, or have shown in the history of their observation, evidence for TT behavior. We demonstrate that this cannot be the result of random pairing of a population of single TT and weak-lined T Tauri (WT) stars. We speculate that the result that inner, AU-sized disks tend to survive for a similar length of time in both components of a close (03-26) binary suggests that a circumbinary envelope effectively regulates the common evolution of the inner disks.

The Gas-Phase Abundances of Heavy Elements and the Destruction of Dust Grains in Herbig-Haro Shock waves

view Abstract Citations (24) References (36) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Gas-Phase Abundances of Heavy Elements and the Destruction of Dust Grains in Herbig-Haro Shock waves Beck-Winchatz, Bernhard ; Bohm, Karl-Heinz ; Noriega-Crespo, Alberto Abstract The gas-phase abundance ratios Fe/S and Fe/O have been determined for the Herbig-Haro objects HH 1, HH 7, HH 11, HH 43A, and HH 255 (Burnham's Nebula) from a fairly large number of forbidden emission lines. For HH 1, the ratio Ni/S has been determined as well. Our objective was to investigate whether Fe and Ni are depleted by dust formation in the line-emitting regions as is typical for normal (neutral or molecular) interstellar regions, or whether the observed matter has gone through sufficiently fast shock waves so that the dust grains have been destroyed and Fe and Ni have gone back into the gas phase. Using observationally determined electron temperatures and densities we have solved the statistical equilibrium equations for Fe+, Fe++, S+, 00, 0+, O++, and Ni+ and calculated the intensities of the respective emissions lines. For Fe+ a large number of new collision strengths has recently become available which enabled us to include a much greater number of transitions in our calculations than has previously been possible. For HH 1 and HH 7 both ratios Fe/S and Fe/O agree very well with the solar abundance ratios. For HH 11, the more reliable ratio Fe/S is also very close to the solar value, while the less reliable ratio Fe/O is somewhat higher. For HH 43A both abundance ratios suggest an Fe depletion by a factor 2-3 but the result is considered somewhat uncertain. The results for Burnham's Nebula also indicate a depletion of Fe (by a factor of ∼3) and are more reliable. We conclude that this object has undergone a dust formation and shock wave history which is quite different from that of HH 1, HH 7, and HH 11. The Ni/S abundance ratio determined for HH 1 is a factor ∼10 larger than the solar value. The results for the different observed [Ni II] lines are quite consistent. This situation has been found in other gaseous nebulae as well and is still enigmatic. Publication: The Astronomical Journal Pub Date: January 1996 DOI: 10.1086/117787 Bibcode: 1996AJ....111..346B Keywords: STARS: PRE-MAIN SEQUENCE; ISM: JETS AND OUTFLOWS; ISM: KINEMATICS AND DYNAMICS; SHOCK WAVES full text sources ADS | data products SIMBAD (5)

THE GAS-PHASE IRON ABUNDANCE IN HERBIG-HARO OBJECTS

ABSTRACT The gas phase abundance ratios Fe/S and Fe/O have been determined for the Herbig-Haro objects HH1, HH7, HH11, HH43A, and "Burnham's Nebula" (HH255). It is the purpose of this study to decide whether a sizeable fraction of the Fe in these HH objects is still bound in dust grains or whether the observed matter has gone through sufficiently fast shock waves so that the dust grains have been essentially destroyed and most of the iron has gone back into the gas phase. We have determined the abundance ratios using statistical equilibrium calculations for the ions Fe+, S+, and O+. (These are the most abundant ions of the elements in question.) Abundance determinations have been made using homogeneous models of the HH objects for which electron temperatures and densities have been determined observationally from forbidden line ratios. The results show that the Fe/S ratio in the objects HH1, HH7, HH11 and HH43A agrees very well with the population I abundance ratio. Only Burnham's Nebula (HH255) shows an Fe/S ratio which is about 3 times lower indicating a shock wave history which is quite different from that of the other HH objects.

Star-disc boundary layers in cataclysmic variables and T Tauri stars

La nature de l'interaction dans la couche limite entre un disque d'accretion et l'etoile centrale est etudiee. Des criteres simples sont etablis afin d'estimer la profondeur dans l'etoile pour laquelle l'interaction disque-etoile se developpe de maniere significative. Ces criteres sont appliques a une variete de systemes de disques d'accretion et les consequences observationnelles pour les variables cataclysmiques et les etoiles de type T Tauri sont discutees

Spatially resolved spectra of HH1 and Burnham's nebula in the range lambda of between about 3700 A and 10830 A

Spatially resolved spectra of HH1 and Burnham's nebula in the range lambda of between about 3700 A and 10830 A

The effects of reddening correction on the interpretation of spectrophotometry of Burnham's Nebula and H-H objects

L'analyse et l'interpretation des donnees spectrophotometriques sont presentees pour la nebuleuse de Burnham dans l'etendue 3200 A≤λ≤11000 A, l'aspect critique de l'interpretation residant dans la determination et l'application des corrections du rougissement interstellaire. On demontre qu'il est imperatif que la courbe d'extinction utilisee pour corriger le rougissement soit la meme que celle utilisee pour calculer l'exces de couleur E(B-V). Ainsi, si la courbe interstellaire moyenne est utilisee pour deriver E(B-V) et une autre courbe, telle θ Ori, pour corriger le rougissement, des erreurs peuvent resulter au niveau des comparaisons entre des regions separees de longueurs d'onde, telles les regions optiques et UV. Un re-examen des donnees optiques et UV pour HH 2 en utilisant la meme courbe θ Ori pour calculer E(B-V) et corriger le rougissement permet de resoudre l'ecart associe aux flux optiques et UV

The atmospheres of T Tauri stars. I - High-resolution calibrated observations of moderately active stars

La nature variable et complexe des etoiles T Tauri necessite un traitement theorique propre pour leurs atmospheres, avec une information spectrale pour plusieurs resolutions et longueurs d'ondes. L'ensemble des donnees recueillies a permis d'obtenir les types spectraux, corrections de rougissement, vitesses radiales d'etoiles T Tauri. D'apres les positions dans le diagramme HR, on determine la masse, rayon, et gravite de surface pour chaque objet

Further evidence for rotational modulation of the light from T Tauri stars

Observations photometriques UBVRI de cinq etoiles T Tauri: BP, DN, GK, GI et RY Tau. Informations sur les regions d'emission chaudes qui produisent apparemment plus de variabilite de type T Tauri et etude de la possibilite de trouver des modulations induites par rotation dans les variations lumineuses d'etoiles de ce type

The chromosphere and corona of T Tauri

Analyse des spectres de T Tauri obtenus entre novembre 1980 et mars 1982. Distribution de l'emission entre 10 4 et 10 5 K, densite des electrons. Modeles pour une atmosphere hydrostatique

Correction: T Tauri's Companion May Be a Protoplanet

Correction: T Tauri's Companion May Be a Protoplanet

T Tauri's Companion May Be a Protoplanet

T Tauri's Companion May Be a Protoplanet

Discovery of an infrared companion to T Tauri

Discovery of an infrared companion to T Tauri