scholarly journals Nature of Emission-Line Stars in the Outer Orion Region

1995 ◽  
Vol 148 ◽  
pp. 376-379
Author(s):  
Makoto Nakano ◽  
Peter J. McGregor
Keyword(s):  
Emission Line ◽  
Large Scale ◽  
Near Infrared ◽  
Infrared Photometry ◽  
Low Mass Stars ◽  
Strong Emission ◽  
Star Catalog ◽  
T Tauri ◽  
Low Mass ◽  
Cloud Complex

AbstractNear-infrared photometry is reported for 76 emission-line stars in outer regions of the Orion molecular cloud complex. Most of our program stars are selected from the Hα emission-line star catalog of the large-scale Kiso Schmidt survey of the Orion region. We confirm that most of the emission-line stars with strong emission detected in the Kiso survey are typical T Tauri stars with masses in the range 0.5 to 2 M⊙. Low mass stars have therefore continued to form in the outer parts of the Orion region, away from present day massive molecular clouds, until at least as recently as a few million year ago.

scholarly journals Evidence of Collective Formation of Low Mass Stars in the Dark Cloud Kh141

1987 ◽  
Vol 115 ◽  
pp. 64-66
Author(s):  
Yoshio Tomita ◽  
Hiroshi Ohtani
Keyword(s):  
Star Formation ◽  
Massive Stars ◽  
T Tauri Stars ◽  
Low Mass Stars ◽  
Dark Cloud ◽  
T Tauri ◽  
Low Mass ◽  
Cloud Complex

To find evidence for collective star formation without massive stars in the dark cloud complex Kh141 (Saito 1980), a search for T-Tauri stars has been made.

scholarly journals A LARGE-SCALE OPTICAL-NEAR-INFRARED SURVEY FOR BROWN DWARFS AND VERY LOW MASS STARS IN THE ORION OB1 ASSOCIATION

2008 ◽  
Vol 136 (1) ◽  
pp. 51-66 ◽  
Author(s):  
Juan José Downes ◽  
César Briceño ◽  
Jesús Hernández ◽  
Nuria Calvet ◽  
Lee Hartmann ◽  
...  
Keyword(s):  
Large Scale ◽  
Near Infrared ◽  
Brown Dwarfs ◽  
Low Mass Stars ◽  
Low Mass ◽  
Infrared Survey

Magnetic fields of T Tauri stars and inner accretion discs

2018 ◽  
Vol 14 (A30) ◽  
pp. 121-121
Author(s):  
Jean-Francois Donati
Keyword(s):  
Magnetic Fields ◽  
Large Scale ◽  
Near Infrared ◽  
High Sensitivity ◽  
T Tauri Stars ◽  
Accretion Discs ◽  
High Resolution Spectroscopy ◽  
T Tauri ◽  
Low Mass ◽  
The Impact

AbstractMagnetic fields play a key role in the early life of stars and their planets, as they form from collapsing dense cores that progressively flatten into large-scale accretion discs and eventually settle as young suns orbited by planetary systems. Pre-main-sequence phases, in which central protostars feed from surrounding planet-forming accretion discs, are especially crucial for understanding how worlds like our Solar System are born.Magnetic fields of low-mass T Tauri stars (TTSs) are detected through high-resolution spectroscopy and spectropolarimetry (e.g., Johns Krull 2007), whereas their large-scale topologies can be inferred from time series of Zeeman signatures using tomographic techniques inspired from medical imaging (Donati & Landstreet 2009). Large-scale fields of TTSs are found to depend on the internal structure of the newborn star, allowing quantitative models of how TTSs magnetically interact with their inner accretion discs, and the impact of this interaction on the subsequent stellar evolution (e.g., Romanova et al. 2002, Zanni & Ferreira 2013).With its high sensitivity to magnetic fields, SPIRou, the new near-infrared spectropolarimeter installed in 2018 at CFHT (Donati et al. 2018), should yield new advances in the field, especially for young embedded class-I protostars, thereby bridging the gap with radio observations.

scholarly journals Ultracool Neighbors from 2MASS

2003 ◽  
Vol 211 ◽  
pp. 201-202
Author(s):  
Kelle L. Cruz ◽  
I. Neill Reid ◽  
P. J. Lowrance ◽  
J. Davy Kirkpatrick ◽  
J. Liebert ◽  
...  
Keyword(s):  
Near Infrared ◽  
Infrared Photometry ◽  
Selection Methods ◽  
Low Mass Stars ◽  
Target List ◽  
Sky Survey ◽  
Low Mass ◽  
Initial Results ◽  
Existing Data

We present initial results of an all-sky search for cool, low-mass stars and brown dwarfs within 20 pc. We have used the near-infrared photometry provided by the 2-Micron All Sky Survey (2MASS) Second Incremental Data Release to create a target list of 1793 candidates with 6 < J < 17 and J – K > 1. Follow-up observations and existing data have enabled over 85% of the sample to be classified. Spectral types and distances have been derived for over 250 nearby dwarfs, including 39 newly discovered L dwarfs. In this poster, we discuss our selection methods and present preliminary results.

scholarly journals Stellar Rotation of T Tauri Stars in the Orion Star-forming Complex

2021 ◽  
Vol 923 (2) ◽  
pp. 177
Author(s):  
Javier Serna ◽  
Jesus Hernandez ◽  
Marina Kounkel ◽  
Ezequiel Manzo-Martínez ◽  
Alexandre Roman-Lopes ◽  
...  
Keyword(s):  
Large Scale ◽  
Rotational Velocity ◽  
T Tauri Stars ◽  
Evolutionary Models ◽  
Stellar Rotation ◽  
Low Mass Stars ◽  
Star Forming ◽  
T Tauri ◽  
Low Mass ◽  
Early Phases

Abstract 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 (0.4M ⊙ < M * < 1.2M ⊙). Our results support the existence of a mechanism linking v sin ( i ) to the presence of accreting protoplanetary disks, responsible for regulating stellar rotation on timescales of about 6 Myr, which is the timescale in which most of the T Tauri stars lose their inner disk. Our results provide important constraints to models of rotation in the early phases of evolution of young stars and their disks.

scholarly journals Understanding Formation of Young, Distributed Low-mass Stars and Clusters in the W4 Cloud Complex

2019 ◽  
Vol 157 (3) ◽  
pp. 112 ◽  
Author(s):  
Neelam Panwar ◽  
Manash R. Samal ◽  
A. K. Pandey ◽  
H. P. Singh ◽  
Saurabh Sharma
Keyword(s):  
Low Mass Stars ◽  
Low Mass ◽  
Cloud Complex

scholarly journals Multi-Wavelength High-Resolution Spectroscopy for Exoplanet Detection: Motivation, Instrumentation and First Results

Geosciences ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 289 ◽  
Author(s):  
Serena Benatti
Keyword(s):  
High Resolution ◽  
Near Infrared ◽  
Giant Planet ◽  
High Resolution Spectroscopy ◽  
M Dwarfs ◽  
Low Mass Stars ◽  
First Results ◽  
Multi Wavelength ◽  
Low Mass ◽  
Rocky Planets

Exoplanet research has shown an incessant growth since the first claim of a hot giant planet around a solar-like star in the mid-1990s. Today, the new facilities are working to spot the first habitable rocky planets around low-mass stars as a forerunner for the detection of the long-awaited Sun-Earth analog system. All the achievements in this field would not have been possible without the constant development of the technology and of new methods to detect more and more challenging planets. After the consolidation of a top-level instrumentation for high-resolution spectroscopy in the visible wavelength range, a huge effort is now dedicated to reaching the same precision and accuracy in the near-infrared. Actually, observations in this range present several advantages in the search for exoplanets around M dwarfs, known to be the most favorable targets to detect possible habitable planets. They are also characterized by intense stellar activity, which hampers planet detection, but its impact on the radial velocity modulation is mitigated in the infrared. Simultaneous observations in the visible and near-infrared ranges appear to be an even more powerful technique since they provide combined and complementary information, also useful for many other exoplanetary science cases.

scholarly journals The Frequency of YY Orionis Objects among the T Tauri Stars

1977 ◽  
Vol 42 ◽  
pp. 80-87 ◽  
Author(s):  
I. Appenzeller
Keyword(s):  
Statistical Analysis ◽  
Present Theory ◽  
T Tauri Stars ◽  
Early Evolution ◽  
Low Mass Stars ◽  
T Tauri ◽  
Uv Excess ◽  
Low Mass ◽  
Good Agreement

A list of 24 T Tauri stars belonging to the YY Orionis subclass is presented. From a statistical analysis it is estimated that at least 75% (and possibly all) UV-excess T Tauri stars are YY Orionis stars. Since about 50% of all known T Tauri stars show a strong UV-excess, the percentage of YY Orionis stars among the T Tauri stars is estimated to be 40 - 50%. This relative high percentage is in good agreement with the present theory of the formation and early evolution of low mass stars.

scholarly journals Characterising the surface magnetic fields of T Tauri stars with high-resolution near-infrared spectroscopy

2019 ◽  
Vol 630 ◽  
pp. A99 ◽  
Author(s):  
A. Lavail ◽  
O. Kochukhov ◽  
G. A. J. Hussain
Keyword(s):  
Magnetic Field ◽  
High Resolution ◽  
Magnetic Fields ◽  
Large Scale ◽  
Near Infrared ◽  
Field Measurements ◽  
T Tauri Stars ◽  
Small Scale ◽  
Surface Magnetic Field ◽  
T Tauri

Aims. In this paper, we aim to characterise the surface magnetic fields of a sample of eight T Tauri stars from high-resolution near-infrared spectroscopy. Some stars in our sample are known to be magnetic from previous spectroscopic or spectropolarimetric studies. Our goals are firstly to apply Zeeman broadening modelling to T Tauri stars with high-resolution data, secondly to expand the sample of stars with measured surface magnetic field strengths, thirdly to investigate possible rotational or long-term magnetic variability by comparing spectral time series of given targets, and fourthly to compare the magnetic field modulus ⟨B⟩ tracing small-scale magnetic fields to those of large-scale magnetic fields derived by Stokes V Zeeman Doppler Imaging (ZDI) studies. Methods. We modelled the Zeeman broadening of magnetically sensitive spectral lines in the near-infrared K-band from high-resolution spectra by using magnetic spectrum synthesis based on realistic model atmospheres and by using different descriptions of the surface magnetic field. We developped a Bayesian framework that selects the complexity of the magnetic field prescription based on the information contained in the data. Results. We obtain individual magnetic field measurements for each star in our sample using four different models. We find that the Bayesian Model 4 performs best in the range of magnetic fields measured on the sample (from 1.5 kG to 4.4 kG). We do not detect a strong rotational variation of ⟨B⟩ with a mean peak-to-peak variation of 0.3 kG. Our confidence intervals are of the same order of magnitude, which suggests that the Zeeman broadening is produced by a small-scale magnetic field homogeneously distributed over stellar surfaces. A comparison of our results with mean large-scale magnetic field measurements from Stokes V ZDI show different fractions of mean field strength being recovered, from 25–42% for relatively simple poloidal axisymmetric field topologies to 2–11% for more complex fields.

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