Podcasts about t tauri

Juno reveals a surprise about the interior of Jupiter's volcanic moon Io, and the OG young variable star T Tauri is getting ready to fade from view thanks to its dusty neighbors to the south. Speaking of dust, that's what gets kicked up when comets collide, and a new survey examines the cometary belts around dozens of star systems, providing a detailed look at the outer reaches of exoplanetary systems. Join us for all this, sample return stumpers, and Top Quark trivia.

Astronomy Daily - The Podcast: S04E21In this episode of Astronomy Daily, host Anna dives into a range of exciting developments from the world of space exploration. From China's ambitious satellite projects to NASA's poignant Day of Remembrance, we cover the stories that are shaping our understanding of the cosmos.Highlights:- China's Thousand Sails Mega Constellation: Discover the latest launch of 18 satellites as part of China's ambitious Internet Constellation project, aiming for a staggering 14,000 satellites in orbit by 2025.- NASA's Day of Remembrance: Reflect on the lives lost in space exploration as NASA honors the crews of Apollo 1, Challenger, and Columbia, emphasizing the importance of safety in future missions.- SpaceX's Direct to Cell Technology: Learn about SpaceX's groundbreaking beta test for a system that allows mobile phones to connect directly to Starlink satellites, potentially revolutionizing global communications.- T Tauri's Great Dimming: Explore the remarkable celestial event as T Tauri, a young star system, begins a dimming phase that could last a century, offering unique insights into planetary formation.- Boeing's Starliner Challenges: Get the latest on Boeing's CST-100 Starliner program as the company faces financial setbacks and uncertainty regarding its future operational missions.- Upcoming NASA Missions: Excitement builds for NASA's ambitious missions in 2025, including the Sphere X Space Observatory and the Lunar Trailblazer, aimed at enhancing our understanding of the universe and the Moon.For more cosmic updates, visit our website at astronomydaily.io. Join our community on social media by searching for #AstroDailyPod on Facebook, X, YouTubeMusic, Tumblr, and TikTok. Share your thoughts and connect with fellow space enthusiasts. Don't forget to subscribe to the podcast on Apple Podcasts, Spotify, iHeartRadio, or wherever you get your podcasts.Thank you for tuning in. This is Anna signing off. Until next time, keep looking up and stay curious about the wonders of our universe.00:00 - Astronomy Daily brings you the latest in space and astronomy news00:50 - China's Thousand Sails Mega Constellation project successfully launches 18 satellites03:30 - NASA honors the brave crews lost in space exploration during Day of Remembrance06:10 - SpaceX prepares to test its innovative direct to cell technology09:40 - T Tauri enters a dimming phase that could last a century12:20 - Boeing faces challenges with the Starliner program and future missions15:00 - Upcoming NASA missions set to launch in 2025✍️ Episode ReferencesNASA[NASA](https://www.nasa.gov)SpaceX[SpaceX](https://www.spacex.com)Boeing[Boeing](https://www.boeing.com)China National Space Administration[CNSA](http://www.cnsa.gov.cn)Astronomy Daily[Astronomy Daily](https://www.astronomydaily.io)Become a supporter of this podcast: https://www.spreaker.com/podcast/astronomy-daily--5648921/support.

La tertulia semanal en la que repasamos las últimas noticias de la actualidad científica. En el episodio de hoy: Rayos gamma de estrellas T Tauri (min 1:00); El agujero negro del centro galáctico, Sagittarius A* (21:00); El mecanismo de Anticitera y la película de Indiana Jones, parte 2 (36:30); Detectados neutrinos del LHC (1:24:00); Reorganización cortical tras lesiones de médula espinal (1:54:00); Señales de los oyentes (2:05:00)Este episodio es continuación de la parte A. Contertulios: María Ribes, Marian Martínez, Gastón Giribet, Francis Villatoro, Iván Martí Vidal, Sara Robisco, Héctor Socas. Imagen de portada realizada con Midjourney. Todos los comentarios vertidos durante la tertulia representan únicamente la opinión de quien los hace... y a veces ni eso! Hosted on Acast. See acast.com/privacy for more information.

塗粉敢會是媠--ê？當然！而且 in 閣足有路用--ê。金牛座分子雲 內底有幾若粒足光 ê 恆星，毋過內底 ê 烏暗塗粉 是閣較 吸引人注意。這寡四湠 ê 塗粉 有波湧 kah 波紋，予這幅媠圖內底敢若有幾若隻 塗粉 兔仔。毋過閣較重要 ê 是，in 代表講這區 ê 星際間氣體 是厚甲會產生 重力收縮，形成恆星。這張相片 ê 中心有較淺色 ê 星雲，是去予厝邊恆星照予光--ê。這毋但是一个有名 ê 星雲 in 兜，嘛是有名 ê 少年懸質量恆星 in 兜。恆星、T Tauri 星、星雲、kah Hind 變光星雲 ê 光度變化攏足大--ê。毋過 in ê 光度變化無一定發生 tī 仝一个時間，所以這區才會遮爾神祕遮爾趣味。T Tauri 星 kah 類似 ê 恆星 攏去予天文學家 當做 類太陽 恆星。In 較少年，無到幾若百萬歲遐爾老，猶 tī lih 恆星 形成 ê 早期階段。這張相片差不多有 4 度 闊，內底 ê 天體離 昴宿 星團無蓋遠，相片內底 ê 塗粉區離咱有 400 光年 遠。 ——— 這是 NASA Astronomy Picture of the Day ê 台語文 podcast 原文版：https://apod.nasa.gov/ 台文版：https://apod.tw/ 今仔日 ê 文章： https://apod.tw/daily/20230321/ 影像：Vikas Chander 音樂：高小糕 GaoXiaoGao 聲優：阿錕 翻譯：An-Li Tsai (NCU) 原文：https://apod.nasa.gov/apod/ap230321.html Powered by Firstory Hosting

Tema: Plan de observación de nebulosas los predecesores estelares, nebulosas oscuras, protoestrellas de tipo T Tauri y Herbig Ae/Be Enlaces: Web: Astrodidacta. Imágenes que ayudaran a la comprensión de los temas tratados Correo: astrodidacta2020@gmail.com Derechos de Música: Faster Does It de Kevin MacLeod cuenta con una licencia Creative Commons Atribución 4.0. https://creativecommons.org/licenses/by/4.0/ Fuente: http://incompetech.com/music/royalty-free/index.html?isrc=USUAN1100794 Artista: http://incompetech.com/ Derechos de Imagen 51 Ophiuchii. Aladin

Determining Dust Properties in Protoplanetary Disks: SED-derived Masses and Settling With ALMA by Anneliese Rilinger et al. on Wednesday 30 November We present spectral energy distribution (SED) modeling of 338 disks around T Tauri stars from eleven star-forming regions, ranging from $sim$0.5 to 10 Myr old. The disk masses we infer from our SED models are typically greater than those reported from (sub)mm surveys by a factor of 1.5-5, with the discrepancy being generally higher for the more massive disks. Masses derived from (sub)mm fluxes rely on the assumption that the disks are optically thin at all millimeter wavelengths, which may cause the disk masses to be underestimated since the observed flux is not sensitive to the whole mass in the disk; SED models do not make this assumption and thus yield higher masses. Disks with more absorbing material should be optically thicker at a given wavelength; which could lead to a larger discrepancy for disks around massive stars when the disk temperature is scaled by the stellar luminosity. We also compare the disk masses and degree of dust settling across the different star-forming regions and find that disks in younger regions have more massive disks than disks in older regions, but a similar degree of dust settling. Together, these results offer potential partial solutions to the "missing" mass problem: disks around T Tauri stars may indeed have enough material to form planetary systems, though previous studies have underestimated the mass by assuming the disks to be optically thin; these planetary systems may also form earlier than previously theorized since significant dust evolution (i.e., settling) is already apparent in young disks. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.16732v1

A search for thermal gyro-synchrotron emission from hot stellar coronae by Walter W. Golay et al. on Tuesday 29 November We searched for thermal gyro-synchrotron radio emission from a sample of five radio-loud stars whose X-ray coronae contain a hot ($T_e>10^7$ K) thermal component. We used the JVLA to measure Stokes I and V/I spectral energy distributions (SEDs) over the frequency range 15--45 GHz, determining the best-fitting model parameters using power-law and thermal gyro-synchrotron emission models. The SEDs of the three chromospherically active binaries (Algol, UX Arietis, HR 1099) were well-fit by a power-law gyro-synchrotron model, with no evidence for a thermal component. However, the SEDs of the two weak-lined T Tauri stars (V410 Tau, HD 283572) had a circularly polarized enhancement above 30 GHz that was inconsistent with a pure power-law distribution. These spectra were well-fit by summing the emission from an extended coronal volume of power-law gyro-synchrotron emission and a smaller region with thermal plasma and a much stronger magnetic field emitting thermal gyro-synchrotron radiation. We used Bayesian inference to estimate the physical plasma parameters of the emission regions (characteristic size, electron density, temperature, power-law index, and magnetic field strength and direction) using independently measured radio sizes, X-ray luminosities, and magnetic field strengths as priors, where available. The derived parameters were well-constrained but somewhat degenerate. The power-law and thermal volumes in the pre-main-sequence stars are probably not co-spatial, and we speculate they may arise from two distinct regions: a tangled-field magnetosphere where reconnection occurs and a recently discovered axisymmetric toroidal magnetic field, respectively. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.11440v2

A search for thermal gyro-synchrotron emission from hot stellar coronae by Walter W. Golay et al. on Monday 28 November We searched for thermal gyro-synchrotron radio emission from a sample of five radio-loud stars whose X-ray coronae contain a hot ($T_e>10^7$ K) thermal component. We used the JVLA to measure Stokes I and V/I spectral energy distributions (SEDs) over the frequency range 15--45 GHz, determining the best-fitting model parameters using power-law and thermal gyro-synchrotron emission models. The SEDs of the three chromospherically active binaries (Algol, UX Arietis, HR 1099) were well-fit by a power-law gyro-synchrotron model, with no evidence for a thermal component. However, the SEDs of the two weak-lined T Tauri stars (V410 Tau, HD 283572) had a circularly polarized enhancement above 30 GHz that was inconsistent with a pure power-law distribution. These spectra were well-fit by summing the emission from an extended coronal volume of power-law gyro-synchrotron emission and a smaller region with thermal plasma and a much stronger magnetic field emitting thermal gyro-synchrotron radiation. We used Bayesian inference to estimate the physical plasma parameters of the emission regions (characteristic size, electron density, temperature, power-law index, and magnetic field strength and direction) using independently measured radio sizes, X-ray luminosities, and magnetic field strengths as priors, where available. The derived parameters were well-constrained but somewhat degenerate. The power-law and thermal volumes in the pre-main-sequence stars are probably not co-spatial, and we speculate they may arise from two distinct regions: a tangled-field magnetosphere where reconnection occurs and a recently discovered axisymmetric toroidal magnetic field, respectively. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.11440v2

A search for thermal gyro-synchrotron emission from hot stellar coronae by Walter W. Golay et al. on Monday 28 November We searched for thermal gyro-synchrotron radio emission from a sample of five radio-loud stars whose X-ray coronae contain a hot ($T_e>10^7$ K) thermal component. We used the JVLA to measure Stokes I and V/I spectral energy distributions (SEDs) over the frequency range 15--45 GHz, determining the best-fitting model parameters using power-law and thermal gyro-synchrotron emission models. The SEDs of the three chromospherically active binaries (Algol, UX Arietis, HR 1099) were well-fit by a power-law gyro-synchrotron model, with no evidence for a thermal component. However, the SEDs of the two weak-lined T Tauri stars (V410 Tau, HD 283572) had a circularly polarized enhancement above 30 GHz that was inconsistent with a pure power-law distribution. These spectra were well-fit by summing the emission from an extended coronal volume of power-law gyro-synchrotron emission and a smaller region with thermal plasma and a much stronger magnetic field emitting thermal gyro-synchrotron radiation. We used Bayesian inference to estimate the physical plasma parameters of the emission regions (characteristic size, electron density, temperature, power-law index, and magnetic field strength and direction) using independently measured radio sizes, X-ray luminosities, and magnetic field strengths as priors, where available. The derived parameters were well-constrained but somewhat degenerate. The power-law and thermal volumes in the pre-main-sequence stars are probably not co-spatial, and we speculate they may arise from two distinct regions: a tangled-field magnetosphere where reconnection occurs and a recently discovered axisymmetric toroidal magnetic field, respectively. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.11440v2

The GRAVITY Young Stellar Object survey -- IX Spatially resolved kinematics of hot hydrogen gas in the star disk interaction region of T Tauri stars by GRAVITY Collaboration et al. on Thursday 24 November Aims: We aim to spatially and spectrally resolve the Br-gamma hydrogen emission line with the methods of interferometry in order to examine the kinematics of the hydrogen gas emission region in the inner accretion disk of a sample of solar-like young stellar objects. The goal is to identify trends and categories among the sources of our sample and to discuss whether or not they can be tied to different origin mechanisms associated with Br-gamma emission in T Tauri stars, chiefly and most prominently magnetospheric accretion. Methods: We observed a sample of seven T Tauri stars for the first time with VLTI GRAVITY, recording spectra and spectrally dispersed interferometric quantities across the Br-gamma line in the NIR K-band. We use them to extract the size of the Br-gamma emission region and the photocenter shifts. To assist in the interpretation, we also make use of radiative transfer models of magnetospheric accretion to establish a baseline of expected interferometric signatures if accretion is the primary driver of Br-gamma emission. Results: From among our sample, we find that five of the seven T~Tauri stars show an emission region with a half-flux radius in the range broadly expected for magnetospheric truncation. Two of the five objects also show Br-gamma emission primarily originating from within the corotation radius, while two other objects exhibit extended emission on a scale beyond 10 R$_*$, one of them even beyond the K~band continuum half-flux radius of 11.3 R$_*$. Conclusions: We find strong evidence to suggest that for the two weakest accretors in the sample, magnetospheric accretion is the primary driver of Br-gamma radiation. The results for the remaining sources imply either partial or strong contributions coming from spatially extended emission components in the form of outflows, such as stellar or disk winds. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.13095v3

The GRAVITY Young Stellar Object survey -- IX Spatially resolved kinematics of hot hydrogen gas in the star disk interaction region of T Tauri stars by GRAVITY Collaboration et al. on Wednesday 23 November Aims: We aim to spatially and spectrally resolve the Br-gamma hydrogen emission line with the methods of interferometry in order to examine the kinematics of the hydrogen gas emission region in the inner accretion disk of a sample of solar-like young stellar objects. The goal is to identify trends and categories among the sources of our sample and to discuss whether or not they can be tied to different origin mechanisms associated with Br-gamma emission in T Tauri stars, chiefly and most prominently magnetospheric accretion. Methods: We observed a sample of seven T Tauri stars for the first time with VLTI GRAVITY, recording spectra and spectrally dispersed interferometric quantities across the Br-gamma line in the NIR K-band. We use them to extract the size of the Br-gamma emission region and the photocenter shifts. To assist in the interpretation, we also make use of radiative transfer models of magnetospheric accretion to establish a baseline of expected interferometric signatures if accretion is the primary driver of Br-gamma emission. Results: From among our sample, we find that five of the seven T~Tauri stars show an emission region with a half-flux radius in the range broadly expected for magnetospheric truncation. Two of the five objects also show Br-gamma emission primarily originating from within the corotation radius, while two other objects exhibit extended emission on a scale beyond 10 R$_*$, one of them even beyond the K~band continuum half-flux radius of 11.3 R$_*$. Conclusions: We find strong evidence to suggest that for the two weakest accretors in the sample, magnetospheric accretion is the primary driver of Br-gamma radiation. The results for the remaining sources imply either partial or strong contributions coming from spatially extended emission components in the form of outflows, such as stellar or disk winds. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.13095v3

Interpreting molecular hydrogen and atomic oxygen line emission of T Tauri disks with photoevaporative disk-wind models by Ch. Rab et al. on Tuesday 22 November Winds in protoplanetary disks play an important role in their evolution and dispersal. However, what physical process is driving the winds is still unclear (i.e. magnetically vs thermally driven), and can only be understood by directly confronting theoretical models with observational data. We use hydrodynamic photoevaporative disk-wind models and post-process them with a thermo-chemical model to produce synthetic observables for the o-H$_2$ at 2.12 micron and [OI] at 0.63 micron spectral lines and directly compare the results to a sample of observations. Our photoevaporative disk-wind model is consistent with the observed signatures of the blueshifted narrow low-velocity component (NLVC), which is usually associated with slow disk winds, for both tracers. Only for one out of seven targets that show blueshifted NLVCs does the photoevaporative model fail to explain the observed line kinematics. Our results also indicate that interpreting spectral line profiles by simple methods, such as the thin-disk approximation, to determine the line emitting region can yield misleading conclusions. The photoevaporative disk-wind models are largely consistent with the studied observational data set, but it is not possible to clearly discriminate between different wind-driving mechanisms. Further improvements to the models, such as consistent modelling of the dynamics and chemistry and detailed modelling of individual targets would be beneficial. Furthermore, a direct comparison of magnetically driven disk-wind models to the observational data set is necessary in order to determine whether or not spatially unresolved observations of multiple wind tracers are sufficient to discriminate between theoretical models. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.15486v2

Interpreting molecular hydrogen and atomic oxygen line emission of T Tauri disks with photoevaporative disk-wind models by Ch. Rab et al. on Monday 21 November Winds in protoplanetary disks play an important role in their evolution and dispersal. However, what physical process is driving the winds is still unclear (i.e. magnetically vs thermally driven), and can only be understood by directly confronting theoretical models with observational data. We use hydrodynamic photoevaporative disk-wind models and post-process them with a thermo-chemical model to produce synthetic observables for the o-H$_2$ at 2.12 micron and [OI] at 0.63 micron spectral lines and directly compare the results to a sample of observations. Our photoevaporative disk-wind model is consistent with the observed signatures of the blueshifted narrow low-velocity component (NLVC), which is usually associated with slow disk winds, for both tracers. Only for one out of seven targets that show blueshifted NLVCs does the photoevaporative model fail to explain the observed line kinematics. Our results also indicate that interpreting spectral line profiles by simple methods, such as the thin-disk approximation, to determine the line emitting region can yield misleading conclusions. The photoevaporative disk-wind models are largely consistent with the studied observational data set, but it is not possible to clearly discriminate between different wind-driving mechanisms. Further improvements to the models, such as consistent modelling of the dynamics and chemistry and detailed modelling of individual targets would be beneficial. Furthermore, a direct comparison of magnetically driven disk-wind models to the observational data set is necessary in order to determine whether or not spatially unresolved observations of multiple wind tracers are sufficient to discriminate between theoretical models. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.15486v2

Interpreting molecular hydrogen and atomic oxygen line emission of T Tauri disks with photoevaporative disk-wind models by Ch. Rab et al. on Monday 21 November Winds in protoplanetary disks play an important role in their evolution and dispersal. However, what physical process is driving the winds is still unclear (i.e. magnetically vs thermally driven), and can only be understood by directly confronting theoretical models with observational data. We use hydrodynamic photoevaporative disk-wind models and post-process them with a thermo-chemical model to produce synthetic observables for the o-H$_2$ at 2.12 micron and [OI] at 0.63 micron spectral lines and directly compare the results to a sample of observations. Our photoevaporative disk-wind model is consistent with the observed signatures of the blueshifted narrow low-velocity component (NLVC), which is usually associated with slow disk winds, for both tracers. Only for one out of seven targets that show blueshifted NLVCs does the photoevaporative model fail to explain the observed line kinematics. Our results also indicate that interpreting spectral line profiles by simple methods, such as the thin-disk approximation, to determine the line emitting region can yield misleading conclusions. The photoevaporative disk-wind models are largely consistent with the studied observational data set, but it is not possible to clearly discriminate between different wind-driving mechanisms. Further improvements to the models, such as consistent modelling of the dynamics and chemistry and detailed modelling of individual targets would be beneficial. Furthermore, a direct comparison of magnetically driven disk-wind models to the observational data set is necessary in order to determine whether or not spatially unresolved observations of multiple wind tracers are sufficient to discriminate between theoretical models. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.15486v2

Infrared variability of young solar analogs in the Lagoon Nebula by C. Ordenes-Huanca et al. on Tuesday 18 October T Tauri stars are low-mass pre-main sequence stars that are intrinsically variable. Due to the intense magnetic fields they possess, they develop dark spots on their surface that, because of rotation, introduce a periodic variation of brightness.In addition, the presence of surrounding disks could generate flux variations by variable extinction or accretion. Both can lead to a brightness decrease or increase, respectively. Here, we have compiled a catalog of light curves for 379 T Tauri stars in the Lagoon Nebula (M8) region, using VVVX survey data in the Ks-band. All these stars were already classified as pre-MS stars based on other indicators. The data presented here are spread over a period of about eight years, which gives us a unique follow-up time for these sources at this wavelength. The light curves were classified according to their degree of periodicity and asymmetry, to constrain the physical processes responsible for their variation. Periods were compared with the ones found in literature, on a much shorter baseline. This allowed us to prove that for 126 stars, the magnetically active regions remain stable for several years. Besides, our near-IR data were compared with the optical Kepler/K2 light curves, when available, giving us a better understanding of the mechanisms responsible for the brightness variations observed and how they manifest at different bands. We found that the periodicity in both bands is in fairly good agreement, but the asymmetry will depend on the amplitude of the bursts or dips events and the observation cadence. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.09242v1

Infrared variability of young solar analogs in the Lagoon Nebula by C. Ordenes-Huanca et al. on Tuesday 18 October T Tauri stars are low-mass pre-main sequence stars that are intrinsically variable. Due to the intense magnetic fields they possess, they develop dark spots on their surface that, because of rotation, introduce a periodic variation of brightness.In addition, the presence of surrounding disks could generate flux variations by variable extinction or accretion. Both can lead to a brightness decrease or increase, respectively. Here, we have compiled a catalog of light curves for 379 T Tauri stars in the Lagoon Nebula (M8) region, using VVVX survey data in the Ks-band. All these stars were already classified as pre-MS stars based on other indicators. The data presented here are spread over a period of about eight years, which gives us a unique follow-up time for these sources at this wavelength. The light curves were classified according to their degree of periodicity and asymmetry, to constrain the physical processes responsible for their variation. Periods were compared with the ones found in literature, on a much shorter baseline. This allowed us to prove that for 126 stars, the magnetically active regions remain stable for several years. Besides, our near-IR data were compared with the optical Kepler/K2 light curves, when available, giving us a better understanding of the mechanisms responsible for the brightness variations observed and how they manifest at different bands. We found that the periodicity in both bands is in fairly good agreement, but the asymmetry will depend on the amplitude of the bursts or dips events and the observation cadence. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.09242v1

GIARPS High-resolution Observations of T Tauri stars GHOsT IV Accretion properties of the Taurus-Auriga young association by M. Gangi et al. on Tuesday 11 October In the framework of the GIARPS@TNG High-resolution Observations of T Tauri stars (GHOsT) project, we study the accretion properties of 37 Classical T Tauri Stars of the Taurus-Auriga star forming region (SFR) with the aim of characterizing their relation with the properties of the central star, of jets and disk winds, and of the global disk structure, in synergy with complementary ALMA millimiter observations. We derive stellar parameters, optical veiling, accretion luminosity ($rm L_{acc}$) and mass accretion rate ($rm dot M_{acc}$) in a homogeneous and self-consistent way using high-resolution spectra acquired at the Telescopio Nazionale Galileo with the HARPS-N and GIANO spectrographs, and flux-calibrated based on contemporaneous low-resolution spectroscopic and photometric ancillary observations. The $rm L_{acc}$-$rm L_{star}$, $rm dot{M}_{acc}$-$rm M_{star}$ and $rm dot{M}_{acc}$-$rm M_{disk}$ relationships of the Taurus sample are provided and compared with those of the coeval SFRs of Lupus and Chamaeleon I. Our results demonstrate the potential of contemporaneous optical and near-infrared high-resolution spectroscopy to simultaneously provide precise measurements of stellar and accretion/wind properties of young stars. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2208.14895v2

Mixing and diffusion in protoplanetary disc chemistry by P. Woitke et al. on Monday 26 September We develop a simple iterative scheme to include vertical turbulent mixing and diffusion in ProDiMo thermo-chemical models for protoplanetary discs. The models are carefully checked for convergence toward the time-independent solution of the reaction-diffusion equations, as e.g. used in exoplanet atmosphere models. A series of five T Tauri disc models is presented where we vary the mixing parameter {alpha} mix from 0 to 0.01 and take into account (a) the radiative transfer feedback of the opacities of icy grains that are mixed upward and (b) the feedback of the changing molecular abundances on the gas temperature structure caused by exothermic reactions and increased line heating/cooling. We see considerable changes of the molecular and ice concentrations in the disc. The most abundant species (H2, CH4, CO, the neutral atoms in higher layers, and the ices in the midplane) are transported both up and down, and at the locations where these abundant chemicals finally decompose, for example by photo processes, the release of reaction products has important consequences for all other molecules. This generally creates a more active chemistry, with a richer mixture of ionised, atomic, molecular and ice species and new chemical pathways that are not relevant in the unmixed case. We discuss the impact on three spectral observations caused by mixing and find that (i) icy grains can reach the observable disc surface where they cause ice absorption and emission features at IR to far-IR wavelengths, (ii) mixing increases the concentrations of certain neutral molecules observable by mid-IR spectroscopy, in particular OH, HCN and C2H2, and (iii) mixing can change the optical appearance of CO in ALMA line images and channel maps, where strong mixing would cause the CO molecules to populate the distant midplane. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.12233v1

Jet from the enigmatic high-latitude star BP Psc and evolutionary status of its driving source by I. S. Potravnov et al. on Sunday 18 September BP Psc is an active late-type (sp:G9) star with unclear evolutionary status lying at high galactic latitude $b=-57^{circ}$. It is also the source of the well collimated bipolar jet. We present results of the proper motion and radial velocity study of BP Psc outflow based on the archival $Halpha$ imaging with the GMOS camera at 8.1-m Gemini-North telescope as well as recent imaging and long-slit spectroscopy with the SCORPIO multi-mode focal reducer at 6-m BTA telescope of SAO RAS. The 3D kinematics of the jet revealed the full spatial velocity up to $sim$140 km$cdot$s$^{-1}$ and allows us to estimate the distance to BP Psc system as $D=135pm40$ pc. This distance leads to an estimation of the central source luminosity $L_*approx1.2L_{odot}$, indicating that it is the $approx$1.3$M_{odot}$ T Tauri star with an age $tlesssim$ 7 Myr. We measured the electron density of order $N_esim10^2$ cm$^{-3}$ and mean ionization fraction $fapprox0.04$ within the jet knots and estimated upper limit of the mass-loss rate in NE lobe as $dot{M}_{out}approx1.2cdot10^{-8}M_{odot}cdot yr^{-1}$. The physical characteristics of the outflow are typical for the low-excitation YSO jets and consistent with the magnetocentrifugal mechanism of its launching and collimation. Prominent wiggling pattern revealed in $Halpha$ images allowed us to suppose the existence of a secondary substellar companion in a non-coplanar orbit and estimate its most plausible mass as $M_papprox 30M_{Jup}$. We conclude that BP Psc is one of the closest to the Sun young jet-driving systems and its origin is possibly related to the episode of star formation triggered by expanding supershells in Second Galactic quadrant. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.07727v1

Accretion and extinction variations in the low-mass pre-main sequence binary system WX Cha by Eleonora Fiorellino et al. on Monday 12 September Light curves of young star systems show photometric variability due to different kinematic, and physical processes. One of the main contributors to the photometric variability is the changing mass accretion rate, which regulates the interplay between the forming young star and the protoplanetary disk. We collected high-resolution spectroscopy in eight different epochs, as well as ground-based and space-borne multi-epoch optical and infrared photometry of WX Cha, an M0 binary system, with an almost edge-on disk (i = 87degrees) in the Chamaeleon I star-forming region. Spectroscopic observations cover 72 days, the ground-based optical monitoring covers 42 days while space-borne TESS photometry extends for 56 days. The multi-wavelength light curves exhibit quasi-periodic variability of 0.35 - 0.53 mag in the near-infrared, and of 1.3 mag in g band. We studied the variability of selected emission lines that trace the accretion, computed the accretion luminosity and the mass accretion rate using empirical relations and obtained values of the accretion luminosity between 1.6 and 3.2 Lsun and mass accretion rate between 3.31x10{-7} Msun/yr and 7.76x10^{-7} Msun/yr. Our results show that WX Cha is accreting at a rate larger than what is typical for T Tauri stars in the same star-forming region with the same stellar parameters. We theorize that this is due to the higher disk mass of WX Cha than what is usual for stars with similar stellar mass, and to the binary nature of the system. Daily changes in the accretion luminosity and in the extinction can explain the photometric variability. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.04304v1

Accretion and extinction variations in the low-mass pre-main sequence binary system WX Cha by Eleonora Fiorellino et al. on Monday 12 September Light curves of young star systems show photometric variability due to different kinematic, and physical processes. One of the main contributors to the photometric variability is the changing mass accretion rate, which regulates the interplay between the forming young star and the protoplanetary disk. We collected high-resolution spectroscopy in eight different epochs, as well as ground-based and space-borne multi-epoch optical and infrared photometry of WX Cha, an M0 binary system, with an almost edge-on disk (i = 87degrees) in the Chamaeleon I star-forming region. Spectroscopic observations cover 72 days, the ground-based optical monitoring covers 42 days while space-borne TESS photometry extends for 56 days. The multi-wavelength light curves exhibit quasi-periodic variability of 0.35 - 0.53 mag in the near-infrared, and of 1.3 mag in g band. We studied the variability of selected emission lines that trace the accretion, computed the accretion luminosity and the mass accretion rate using empirical relations and obtained values of the accretion luminosity between 1.6 and 3.2 Lsun and mass accretion rate between 3.31x10{-7} Msun/yr and 7.76x10^{-7} Msun/yr. Our results show that WX Cha is accreting at a rate larger than what is typical for T Tauri stars in the same star-forming region with the same stellar parameters. We theorize that this is due to the higher disk mass of WX Cha than what is usual for stars with similar stellar mass, and to the binary nature of the system. Daily changes in the accretion luminosity and in the extinction can explain the photometric variability. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.04304v1

We've done the baby universe, and baby galaxies, and the very first baby stars ... and *those* were a bit nasty, a bit grumpy. So this week, we're talking baby stars again, but in the modern era — stars being born now, as we speak. Mind you, just because they've got more than H and He to buiold with, doesn't mean they're any less temperamental. Emily takes use from the interstellar medium, through interstellar clouds and collapsing proto-stars, to the birth of a cute little pre-main-sequence star.Syzygy Merch! Get it at the store.Help us make Syzygy even better! Tell your friends and give us a review, or show your support on Patreon: patreon.com/syzygypodSyzygy is produced by Chris Stewart and co-hosted by Dr Emily Brunsden from the Department of Physics at the University of York.On the web: syzygy.fm | Twitter: @syzygypodThings we talk about in this episode:· The Interstellar medium and Interstellar clouds· Proto-stars and their windiness· Brown dwarfs· Main sequence stars· T Tauri stars· Herbig Ae/Be stars

Les objets de Herbig-Haro sont liés aux étoiles T Tauri. Ils sont aussi difficiles à étudier, mais c'est une étape passionnante dans la vie des étoiles...

Hi everyone...Andrew here with the show notes: In this episode we take a look at the huge success of the Blue Origin project and the disappearance of the Japanese Hitomi satellite project. What's happened to it? We report on what's known and the speculation. Do you know what a Protoplanetary Disc is? (I could barely say it...) According to Wikipedia : 'A protoplanetary disk is a rotating circumstellar disk of dense gas and dust surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star.' We discuss...and Fred clarifies. And are scientists really planning to defend earth from aliens with some sort of laser shield? Maybe...maybe not. Fred gives his opinion on this news... You can subscribe to the podcast at iTunes (please leave a review...it helps us a lot); audioBoom; Stitcher; Pocketcasts; Podcast Addict or any good podcatcher app. You can also listen to this and past episodes at our website via www.bitesz.com . Please sign up for our irregular newsletter while there. #astronomy #space #science #BlueOrigin #Hitomi Learn more about your ad choices. Visit megaphone.fm/adchoices See acast.com/privacy for privacy and opt-out information.

Transcript: The most important pre-main sequence stars are called T Tauri stars, named after the twentieth cataloged variable star in the constellation of Taurus. T Tauri stars are transitions between infrared stars in opaque cocoons or nebulae and stable stars settling for the first time onto the main sequence. The density of T Tauri stars in a rich star forming region like the Orion nebula exceeds the density of all stars in the solar neighborhood. T Tauri stars vary irregular in their brightness and are very young in the range twenty thousand to only a million years old.

Transcript: Nearly 2,000 years ago Ptolemy's Almagest, a compendium of astronomical information, contained catalogs of star names. Ancient knowledge was brought to Europe by Arab astronomers who gave names to many of the brightest stars in the sky. The Arab article is al and so we have Algol, Aldebaran, Altair, Alcor, and others. Other stars were named from myths and legends and are often given names associated with the constellation in which they reside. Thus, Alpha Centauri is the first star named in the Centaur constellation; Delta Scuti is the fourth star named in the shield constellation. Other catalogs exist too; T Tauri is the twentieth variable star in the constellation the bull. Astronomers name fainter stars by their coordinates and are given numbers rather than names, and despite what you may read in some parts of the popular press, it’s not possible to exclusively buy a star name. Star names are given by the International Astronomical Union.

Transcript: Nearly 2,000 years ago Ptolemy's Almagest, a compendium of astronomical information, contained catalogs of star names. Ancient knowledge was brought to Europe by Arab astronomers who gave names to many of the brightest stars in the sky. The Arab article is al and so we have Algol, Aldebaran, Altair, Alcor, and others. Other stars were named from myths and legends and are often given names associated with the constellation in which they reside. Thus, Alpha Centauri is the first star named in the Centaur constellation; Delta Scuti is the fourth star named in the shield constellation. Other catalogs exist too; T Tauri is the twentieth variable star in the constellation the bull. Astronomers name fainter stars by their coordinates and are given numbers rather than names, and despite what you may read in some parts of the popular press, it’s not possible to exclusively buy a star name. Star names are given by the International Astronomical Union.

Young stars close to the sun (within 100 pc) yield an interesting sample in many respects: They are relatively bright and because of their close distance we can resolve the surroundings of these stars by using adaptive optics on 8 to 10 m class telescopes (e.g. VLT or Keck). In the K-band the achievable angular resolution is about 50 mas which corresponds to 5 AU at a star closer than 100 pc; 5 AU is about the distance between the Sun and Jupiter. This possibility can be used to study surrounding material such as disks made up of gas and dust as well as stellar and substellar companions. A sample consisting of young stars in the solar vicinity and in an evolutionary stage between the classical T Tauri phase with a disk and the zero-age main sequence can be provided by the catalog of flare stars and related objects compiled by Gershberg et al. (1999) because young stars are often variable and exhibit large eruptions (flares). In a first step we need to verify that these stars are indeed young and did not come to lie above the main sequence in a Hertzsprung-Russell diagram because they are old or unresolved binaries or multiples. Therefore, we have taken spectra of 223 stars lying above the main sequence (of the 463 stars of the sample). The distances to these stars were measured (in most cases by Hipparcos) and they are located at a few to 100 pc. The goal was to detect lithium absorption at 6708 A which all young stars have in common. In addition to the detection of lithium, we want to identify other age indicators such as filling in or emission of the Halpha -, the magnesium Ib- and the calcium lines. The G- and K-type stars of the northern hemisphere were also observed with high resolution, and high signal-to-noise ratio spectroscopy to study these objects with methods of spectral synthesis analysis to determine the surface gravity, the chemical composition, and the temperature. The age determination of these 223 stars lead to a value between 10 Myr and the zero-age main sequence, they are indeed nearby and 17 stars are clearly pre-main sequence. In the course of this work, we discovered the closest pre-main sequence star (HIP 108405 A, 10+-10 Myrs at a distance of 16.1pc). The star is younger than GJ 182 (27 pc, 20+-10 Myrs) which held the record up to now. A planet with a mass of 5 MJup in orbit of a (for this sample) typical M-star, would have an apparent magnitude in the K-band of 14.5 to 17.5 mag at a distance of 16 pc. This would lead to a magnitude difference DeltaK of 8 to 11 mag between the star and the companion, which could be detected with 8 to 10 m class telescopes at a separation of 1" or a projected separation of 16 AU. All newly discovered young flare stars were imaged using NAOS/CONICA to search for distant companions. Depending on the space motion of the stars, they have to be reobserved in one or more years to distinguish comoving companions from stagnant background stars. In this work we have measured radial velocity variations of young stars for the first time using the échelle spectrograph of the Thüringer Landessternwarte. In these measurements one can see the problems of such an investigation, such as variability caused by activity and stellar spots. But one can also see that it is in principle possible to detect planets around active young stars. To verify the results and to measure longer rotation periods, we have to observe these stars for another season.

In the presented work, a population of twelve very young bona fide and candidate brown dwarfs in the ChaI star forming cloud (ChaHa1-12) was studied observationally in terms of their kinematic properties, the occurrence of multiple systems among them as well as their rotational characteristics. Based on high-resolution spectra taken for nine out of the twelve objects with UVES at the VLT, radial and rotational velocities have been measured with high accuracy. A kinematic study of the sample showed that their radial velocity dispersion is relatively small (2.2 kms). It is significantly smaller than the radial velocity dispersion of the T~Tauri stars in the field (3.6 kms) and slightly larger than that one of the surrounding molecular gas (1.2 kms). This result indicates that the studied brown dwarfs are not ejected during their formation with velocities large than ~2 kms as proposed in recent formation scenarios. The brown dwarfs may have larger 3D velocities. However, brown dwarfs ejected during the early accretion phase in directions with a significant fraction perpendicular to the line-of-sight, would have flown out of the field a long time ago. By means of time-resolved UVES spectra, a radial velocity survey for close companions to the targets was conducted. In addition, a direct imaging survey for wide companions was carried out with the WFPC camera on board the HST, with FORS at the VLT as well as with SofI at the NTT. With these two complementary search methods, a wide range of possible companion separations has been covered. For brown dwarf companions (> 13 M_Jup) to the targets, separations < 3 AU and between 50 and 1000 AU were covered. With more restricted separations (< 0.1 AU and 300-1000 AU) the surveys were sensitive also to companion masses down to 1 M_Jup. HST images of ChaHa2 hint at a binary system comprised of two approximately equal-mass companions with a separation of ~30 AU. No further indications for companions have been found in the images. Furthermore, the radial velocities of the targets turned out to be rather constant setting upper limits for the mass Msini of possible companions to 0.1 M_Jup to 2 M_Jup These findings hint at a rather low (smaller or equal 10%) multiplicity fraction of the studied brown dwarfs. Furthermore, a photometric monitoring campaign of the targets yielded the determination of rotational periods for ChaHa2, 3 and 6 in the range of 2.2 to 3.4 days. These are the first rotational periods for very young brown dwarfs and among the first for brown dwarfs at all. They are complemented by measurements of rotational velocities vsini from UVES spectra. The observations show that brown dwarfs at an age of 1-5 Myr display surface spots like T Tauri stars and are moderately fast rotators in contrast to rapidly rotating old brown dwarfs consistent with them being in an early contracting stage. A comparison with rotational periods from the literature indicates that most of the acceleration of brown dwarfs takes place in the first 30 million years or less of their lifetime.