Aims. The goal of this study is to investigate the small-scale magnetic fields of the two spectroscopic binary T Tauri stars V1878 Ori and V4046 Sgr. This is done to complete the observational characterisation of the surface magnetic fields of these stars because only their large-scale magnetic fields have been studied with Zeeman Doppler imaging (ZDI) so far. Methods. To investigate the small-scale magnetic fields, the differential Zeeman intensification of near-infrared Ti I lines was investigated using high-resolution archival spectra obtained with the ESPaDOnS spectrograph at the CFHT. In order to study the binary components separately, the spectra were disentangled by considering observations taken at different orbital phases. The Zeeman-intensification analysis was performed based on detailed polarised radiative transfer calculations aided by the Markov chain Monte Carlo inference, treating magnetic field filling factors and other stellar parameters that could affect the spectra as free parameters. Results. The obtained average magnetic field strengths of the components of V1878 Ori are 1.33 and 1.57 kG, respectively. Previous ZDI studies of V1878 Ori recovered about 14 and 20% of this magnetic field strength. For V4046 Sgr, the magnetic field strengths are 1.96 and 1.83 kG, respectively. In this case, about 12 and 9% of the total magnetic field strength was detected by ZDI. Conclusions. The small-scale magnetic field strengths obtained from Zeeman intensification are similar for the two components of each binary. This is in contrast to the large-scale magnetic fields obtained from ZDI investigations, performed using the same observations. While the large-scale field might look significantly different. This indicates that the efficiency of the magnetic dynamo is comparable for the components of the two binaries, because most energy is carreid by the small scale fields.
We present a large-scale study of stellar rotation for T Tauri stars in the Orion Star-Forming Complex. We use the projected rotational velocity ($v\sin(i)$) estimations reported by the APOGEE-2 collaboration as well as individual masses and ages derived from the position of the stars in the HR diagram, considering Gaia-EDR3 parallaxes and photometry plus diverse evolutionary models. We find an empirical trend for $v\sin(i)$ decreasing with age for low-mass stars ($0.4 M_{\odot} < M_{\ast} < 1.2 M_{\odot}$). Our results support the existence of a mechanism linking $v\sin(i)$ to the presence of…
Classical T Tauri stars are low-mass objects, which are still accreting material from the surrounding circumstellar disk. The accretion process is essential in the formation of Sun-like stars and in setting the properties of the disk at the time when planet formation occurs. We constructed a complex dataset in order to examine the accretion process of VW Cha, a classical T Tauri multiple system with the aim of studying the physical origin of the photometric and spectroscopic variability of the system. The TESS Space Telescope observed VW Cha between 2019 April 22 and June 19, and we complement…
The binary T Tauri system JW 566 in the Orion Molecular Cloud underwent an energetic, short-lived flare observed at submillimetre wavelengths by the SCUBA-2 instrument on 26 November 2016 (UT). The emission faded by nearly 50% during the 31 minute integration. The simultaneous source fluxes averaged over the observation are 500 +/- 107 mJy/beam at 450 microns and 466 +/- 47 mJy/beam at 850 microns. The 850 micron flux corresponds to a radio luminosity of $L_ν=8\times10^{19}$ erg/s/Hz, approximately one order of magnitude brighter (in terms of $νL_ν$) than that of a flare of the young star GMR-…
The coevolution of T Tauri stars and their surrounding protoplanetary disks dictates the timescales of planet formation. In this paper, we present magnetospheric accretion and inner disk wall model fits to NUV-NIR spectra of nine classical T Tauri stars in Orion OB1b as part of the Outflows and Disks around Young Stars: Synergies for the Exploration of ULLYSES Spectra (ODYSSEUS) Survey. Using NUV-optical spectra from the Hubble UV Legacy Library of Young Stars as Essential Standards (ULLYSES) Director's Discretionary Program and optical-NIR spectra from the PENELLOPE VLT Large Programme, we fi…
The star S CrA is a tight visual binary consisting of two classical T Tauri stars, both with outstanding spectral characteristics and brightness variations. High-resolution spectra were collected at ESO and photometric observations with the SMARTS telescope. Both stars undergo large variation in brightness caused mainly by variable foreground extinction. From the stellar parameters we conclude that the two stars are remarkably similar, and that S CrA can be regarded as a T Tauri twin. Rotational periods and inclinations are also similar. The stars differ, however, in terms of degree of veiling…
We present \emph{Herschel} PACS observations of 8 Classical T Tauri Stars in the $\sim 7-10$ Myr old OB1a and the $\sim 4-5$ Myr old OB1b Orion sub-asscociations. Detailed modeling of the broadband spectral energy distributions, particularly the strong silicate emission at 10 $μ$m, shows that these objects are (pre)transitional disks with some amount of small optically thin dust inside their cavities, ranging from $\sim 4$ AU to $\sim 90$ AU in size. We analyzed \emph{Spitzer} IRS spectra for two objects in the sample: CVSO-107 and CVSO-109. The IRS spectrum of CVSO-107 indicates the presence …
We present X-ray through submillimeter observations of the classical RV Tauri (RVb-type) variable U Mon, a post-AGB binary with a circumbinary disk (CBD). Our SMA observations indicate a CBD diameter of $\lesssim$550 au. Our XMM-Newton observations make U Mon the first RV Tauri variable detected in X-rays. The X-ray emission is characteristic of a hot plasma ($\sim$10 MK), with L$_{X}=5\times10^{30}{\rm erg}~{\rm s}^{-1}$, and we consider its possible origin from U Mon, its companion, and/or binary system interactions. Combining DASCH and AAVSO data, we extend the time-series photometric basel…
We investigate a sample of 6 Herbig Ae/Be stars belonging to the Orion OB1 association, as well as 73 low mass objects, members of the $σ$ Orionis cluster, in order to explore the angular momentum evolution at early stages of evolution, and its possible connection with main-sequence Ap/Bp magnetic stars. Using FIES and HECTOCHELLE spectra, we obtain projected rotational velocities through two independent methods. Individual masses, radii, and ages were computed using evolutionary models, distance, and cluster extinction. Under the assumption that similar physical processes operate in both, T T…
We performed a photometric and spectroscopic analysis of two RV Tauri stars GK Car and GZ Nor. Both objects are surrounded by hot circumstellar dust. Their pulsation periods, derived from ASAS photometric time series, have been used to derive their luminosities and distances via the PLC relation. In addition, for both objects, GAIA distances are available. The Gaia distances and luminosities are consistent with the values obtained from the PLC relationship. GK Car is at distance of 4.5$\pm{1.3}$ kpc and has a luminosity of 1520$\pm{840}$ L$_{\odot}$, while GZ Nor is at distance of 8.4$\pm{2.3}…
Variations of the 10 um Silicate Features in the Actively Accreting T Tauri Stars: DG Tau and XZ Tau
利用斯皮策太空望远镜上的红外光谱仪，我们观测到附近金牛座-御夫座恒星形成区中11颗活跃吸积的金牛座T星的多个时期。在第2和第3周期的1.5年中，共收集了88个低分辨率中红外光谱。这个多时期的调查结果表明，10微米的硅酸盐复杂的光谱中的两个源- DG Tau和XZ Tau -经历了显着的变化与硅酸盐的功能越来越弱和强，超过一个月和一年的时间尺度。较短的时间尺度变化的一天到一周的时间尺度内没有检测到测量通量的错误。该数据集的时间分辨率覆盖范围不足以确定变化是否是周期性的。纯发射组成模型的硅酸盐复合物在每个时代的DG头和XZ头光谱提供不良的拟合所观察到的硅酸盐功能。这些结果与以前的小组，试图只适合这些来源的单历元观测结果。简单的两个温度，两个板坯模型具有相似的成分成功地再现了所观察到的硅酸盐特征的变化。这些模型暗示了硅酸盐复合物减少的自吸收起源，而不是排放尘埃颗粒的人口组成变化。我们讨论了几种情况下产生这种变化，包括磁盘阴影，垂直混合，磁盘加热的变化，和磁盘风事件与吸积爆发。
The T Tauri stars with active accretion disks show veiled photospheric spectra. This is supposedly due to non-photospheric continuum radiated by hot spots beneath the accretion shocks at stellar surface and/or chromospheric emission lines radiated by the post-shocked gas. The amount of veiling is often considered as a measure of the mass-accretion rate. We analysed high-resolution photospheric spectra of accreting T Tauri stars LkHa 321, V1331 Cyg, and AS 353 A with the aim of clarifying the nature of the line-dependent veiling. Each of these objects shows a highly veiled, strong emission line…
The Periastron Passage of T Tauri South B as Viewed by ALMA: Millimeter Flux Variations and Dust Heating Triggered by Orbital Motion
Space Telescope Science Insitute（太空望远镜科学研究所）；Laboratoire d’Astrophysique de Bordeaux, Université de Bordeaux, CNRS（波尔多大学天体物理学实验室，法国国家科学研究中心）；The CHARA Array of Georgia State University（佐治亚州立大学CHARA阵列）；The Institut de Radioastronomie Millimétrique (IRAM)（毫米射电天文研究所）
Context. The origin of the fossil magnetic fields detected in 5 to 10% of intermediate-mass main sequence stars is still highly debated. Aims. We want to bring observational constraints to a large population of intermediate-mass pre-main sequence (PMS) stars in order to test the theory that convective-dynamo fields generated during the PMS phases of stellar evolution can occasionally relax into fossil fields on the main sequence. Methods. Using distance estimations, photometric measurements, and spectropolarimetric data from HARPSpol and ESPaDOnS of 38 intermediate-mass PMS stars, we determine…
We present results of our large scale, optical, multi-epoch photometric survey of ~180 square degrees across the Orion OB1 association, complemented with extensive follow up spectroscopy. We map and characterize in an uniform way the off-cloud, low-mass, pre-main sequence populations. We report 2064, mostly K and M-type, confirmed T Tauri members. Most (59%) are located in the OB1a subassociation, 27% in OB1b, and 14% within the confines of the A and B molecular clouds. There is significant structure in the spatial distribution of the young stars. We characterize two new clusterings of T Tauri…
In the framework of the GIARPS High-resolution Observations of T Tauri stars (GHOsT) project, we aim to characterize the atomic and molecular winds in a sample of classical T Tauri stars (CTTs) of the Taurus-Auriga region. We analyzed the flux calibrated [OI] 630 nm and $\rm H_2$ 2.12 $\rm μm$ lines in a sample of 36 CTTs observed at the Telescopio Nazionale Galileo with the HARPS and GIANO spectrographs. We decomposed the line profiles into different kinematic Gaussian components and focused on the most frequently detected component, the narrow low-velocity (v$\rm_p < 20$ $\rm km$ $\rm s^{-1}…
The mass-accretion rate, Macc, is a crucial parameter for the study of the evolution of accretion disks around young low-mass stellar objects (YSOs) and for planet formation studies. The Taurus star forming region (SFR) is rich in pre-main sequence (PMS) stars, most of them of the T Tauri class. A variety of methodologies have been used in the past to measure mass accretion in samples of YSOs in Taurus, but despite being a general benchmark for star formation studies, a comprehensive and systematic analysis of the Taurus T Tauri population, where the stellar and accretion properties are derive…
While protoplanetary disks often appear to be compact and well-organized in millimeter continuum emission, CO spectral line observations are increasingly revealing complex behavior at large distances from the host star. We present deep ALMA maps of the $J=2-1$ transition of $^{12}$CO, $^{13}$CO, and C$^{18}$O, as well as the $J=3-2$ transition of DCO$^+$, toward the T Tauri star RU Lup at a resolution of $\sim0.3''$ ($\sim50$ au). The CO isotopologue emission traces four major components of the RU Lup system: a compact Keplerian disk with a radius of $\sim120$ au, a non-Keplerian ``envelope-li…
We search for signatures of a distant planet around the two-million-year-old classical T-Tauri star CI Tau hosting a hot Jupiter candidate (M_{p} sin{i} ~ 8.1 M_{Jupiter}) in an eccentric orbit (e ~0.3). To probe the existence of an outer perturber, we reanalyzed 1.3 mm dust continuum observations of the protoplanetary disk around CI Tau obtained by the Atacama Large Millimeter/submillimeter Array. We found a gap structure at ~0".8 in CI Tau's disk. Our visibility fitting assuming an axisymmetric surface brightness profile suggested that the gap is located at a deprojected radius of 104.5+/-1.…
The prevalence of short-period super-Earths that are independent of host metallicity challenges the theoretical construction of their origin. We propose that dust trapping in the global pressure bump induced by magnetospheric truncation in evolved protoplanetary discs (PPDs) around T Tauri stars offers a promising formation mechanism for super-Earths, where the host metallicity is already established. To better understand this planet forming scenario, we construct a toy inner disc model and focus on the evolution of dust trapped in the bump, taking into account the supply from drifting pebbles…
We summarize Hubble Space Telescope (HST) UV observations of the weak-lined T Tauri star (wTTS) PDS 70 obtained with the Space Telescope Imaging Spectrograph (STIS). These observations provide the first far-UV (FUV) and near-UV (NUV) spectra of PDS 70. Ground-based observations have so far revealed two formative giant planets orbiting in a wide gap in its circumstellar disk. Both the star and young planets are thought to still be accreting. The HST spectra provide new insight into physical conditions in the star's outer atmosphere and circumstellar environment. The spectra are dominated by chr…
PDS 70 is a $\sim$5 Myr old star with a gas and dust disc in which several proto-planets have been discovered. We present the first UV detection of the system along with X-ray observations taken with the \textit{Neil Gehrels Swift Observatory} satellite. PDS 70 has an X-ray flux of 3.4$\times 10^{-13}$ erg cm$^{-2}$ s$^{-1}$ in the 0.3-10.0 keV range, and UV flux (U band) of 3.5$\times 10^{-13}$ erg cm$^{-2}$ s$^{-1}$ . At the distance of 113.4 pc determined from Gaia DR2 this gives luminosities of 5.2$\times 10^{29}$ erg s$^{-1}$ and 5.4$\times 10^{29}$ erg s$^{-1}$ respectively. The X-ray lu…
Many population studies have been performed with the Atacama Large Millimeter/submillimeter Array (ALMA) to understand the bulk properties of protoplanetary disks around young stars. The studied populations mostly consisted of G, K & M stars, with relatively few more massive Herbig stars. With GAIA updated distances, now is a good time to use ALMA archival data for a Herbig disk population study and take an important step forward in our understanding of planet formation. This work determines the masses and sizes of all Herbig dust disks observed with ALMA to date out to 450 pc. These masses an…
