scholarly journals T Tauri stars and flare stars: common properties and differences

1990 ◽  
Vol 137 ◽  
pp. 209-213
Author(s):  
I. Appenzeller
Keyword(s):  
Accretion Disks ◽  
T Tauri Stars ◽  
The Other ◽  
Late Type ◽  
Physical Origin ◽  
Other Hand ◽  
T Tauri ◽  
Low Mass ◽  
Flare Stars

T Tauri stars and flare stars are both magnetically active late-type stars of low mass and low to moderate luminosities. The flares observed in these two classes of variables show similar properties and, thus, probably have the same physical origin. On the other hand, at least the majority of the classical T Tauri stars seem to be surrounded by cool, dusty (accretion) disks, which are absent or undetectable in most classical flare stars.

scholarly journals X-ray Flare Rate of T Tauri Stars in Taurus

1995 ◽  
Vol 151 ◽  
pp. 216-217
Author(s):  
R. Neuhäuser ◽  
Th. Preibisch
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
T Tauri Stars ◽  
Medium Size ◽  
Late Type ◽  
Large Sample ◽  
X Ray ◽  
T Tauri ◽  
Sky Survey ◽  
Low Mass

AbstractWe study the X-ray emission of several hundred (young, low-mass, late-type, pre-main sequence) T Tauri stars (TTS) in the Taurus T association, a nearby well-studied region of ongoing star formation. We report on X-ray emission variability of TTS as observed with the flux-limited ROSAT All-Sky Survey (RASS). Since RASS observations are spatially unbiased, we can investigate the X-ray flare rate of TTS on a large sample. We find that large flares are very rare (once per year), while medium-size flares can occur once in ∼ 40 days.

scholarly journals NMA Imaging of Envelopes and Disks around Low Mass Protostars and T Tauri Stars

1997 ◽  
Vol 182 ◽  
pp. 381-390
Author(s):  
Yoshimi Kitamura ◽  
Masao Saito ◽  
Ryohei Kawabe ◽  
Kazuyoshi Sunada
Keyword(s):  
Accretion Disks ◽  
Molecular Clouds ◽  
Protoplanetary Disks ◽  
Hierarchical Structures ◽  
T Tauri Stars ◽  
Mass Star ◽  
Low Mass Stars ◽  
Star Forming ◽  
T Tauri ◽  
Low Mass

We are intensively studying low mass star formation with the radio telescopes at Nobeyama in Japan. Using both the Nobeyama 45 m dish equipped with a 2 × 2 array receiver and the Nobeyama Millimeter Array (NMA), we can cover a very wide spatial range from overall molecular clouds down to compact protoplanetary disks. With the 45 m dish we are investigating hierarchical structures of molecular clouds including star-forming cores. With NMA we are imaging disklike structures (i.e., envelopes, accretion disks, and protoplanetary disks) around protostars and T Tauri stars. Recently, we have completed our survey for dense disklike envelopes around eleven Class 0 & I protostars by NMA. In this paper, we will present our recent results of the disklike envelopes in addition to the previous NMA results of the disks around three T Tauri stars. On the basis of the data, we will discuss the evolution of the disklike structures (dense envelopes → tenuous ones → dispersing ones → accretion disks → protoplanetary ones), and propose a new scenario for the formation of low mass stars.

scholarly journals The Possible Connexion Between T Tauri Stars and UV Ceti Stars

1957 ◽  
Vol 3 ◽  
pp. 26-30 ◽  
Author(s):  
Guillermo Haro
Keyword(s):  
T Tauri Stars ◽  
The Sun ◽  
Late Type ◽  
Dwarf Stars ◽  
Present Discussion ◽  
T Tauri ◽  
Flare Stars ◽  
Periodic Changes

As is well known, very rapid and non-periodic changes in brightness have been discovered in several late-type dwarf stars in recent years. In the vicinity of the sun, within a radius not exceeding 10 parsecs, nine or ten such objects have been found and named ‘flare’ stars because of their extraordinarily rapid variations. The prototype of these flare stars is UV Ceti. For the purpose of the present discussion, we shall call these objects ‘classical’ flare stars.

scholarly journals Very Low-Luminosity Objects in Star-Forming Regions

1998 ◽  
Vol 11 (1) ◽  
pp. 423-424
Author(s):  
Motohide Tamura ◽  
Yoichi Itoh ◽  
Yumiko Oasa ◽  
Alan Tokunaga ◽  
Koji Sugitani
Keyword(s):  
Brown Dwarfs ◽  
Mass Function ◽  
T Tauri Stars ◽  
Initial Mass Function ◽  
Formation Mechanisms ◽  
Star Forming ◽  
Star Forming Regions ◽  
T Tauri ◽  
Low Mass ◽  
Stellar Sources

Abstract In order to tackle the problems of low-mass end of the initial mass function (IMF) in star-forming regions and the formation mechanisms of brown dwarfs, we have conducted deep infrared surveys of nearby molecular clouds. We have found a significant population of very low-luminosity sources with IR excesses in the Taurus cloud and the Chamaeleon cloud core regions whose extinction corrected J magnitudes are 3 to 8 mag fainter than those of typical T Tauri stars in the same cloud. Some of them are associated with even fainter companions. Follow-up IR spectroscopy has confirmed for the selected sources that their photospheric temperature is around 2000 to 3000 K. Thus, these very low-luminosity young stellar sources are most likely very low-mass T Tauri stars, and some of them might even be young brown dwarfs.

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 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 Magnetically Driven Warping and Precession of Accretion Disks: Implications for Exotic Stellar Variabilities

2002 ◽  
Vol 187 ◽  
pp. 215-220
Author(s):  
Dong Lai
Keyword(s):  
Accretion Disks ◽  
Low Frequency ◽  
Disk Accretion ◽  
X Ray ◽  
T Tauri ◽  
Magnetic Stars ◽  
Low Mass ◽  
Inner Region ◽  
X Ray Binaries

AbstractThe inner region of the accretion disk around a magnetized star is subjected to magnetic torques that induce warping and precession of the disk. These torques arise from interactions between the stellar field and the induced electric currents in the disk. These novel magnetic effects give rise to some “exotic” stellar variabilities, and may play an important role in explaining a number of puzzling behaviors related to disk accretion onto magnetic stars, such as mHz QPOs in X-ray pulsars, long-term periodicities of X-ray binaries (including precession of jets), low-Frequency (10-50 Hz) QPO’s in low-mass X-ray binaries, and photometric variabilities of T Tauri stars.

scholarly journals Quasicyclic Light Changes in Three Low Mass T Tauri Stars

1977 ◽  
Vol 42 ◽  
pp. 66-71
Author(s):  
H. Mauder
Keyword(s):  
Variable Stars ◽  
T Tauri Stars ◽  
Emission Lines ◽  
T Tauri ◽  
Cyclic Variations ◽  
Low Mass ◽  
Photographic Survey ◽  
Objective Prism

During a photographic survey of the Chamaeleon T association in 1971/1972, evidence was found for quasiperiodic light changes of three variable stars, see Mauder and Sosna (1975). The period of 6.2 days for SY Cha is well seen, the periods of 7 days for VZ Cha and of 8 days for TW Cha are less pronounced. Intrinsic variations are present in addition to the cyclic variations. The three stars were classified by Hoffmeister (1963) as T Tauri type stars from their light variations. Objective prism spectra obtained by Henize and Mendoza (1973) confirm this classification, they found conspicuous emission lines. For SY Cha and TW Cha they got slit spectra, too, which show the typical veiling. The stars SY Cha, TW Cha and VZ Cha have been observed in the UBV system from 1974 March 12 until 1974 March 22, using the ESO standard photometer. In Figures 1 - 3 the light and colour curves are given for SY Cha, TH Cha and VZ Cha. Each point is a mean of generally 8 to 12 integrations, each integration lasting 5 seconds.

Observations of suspected low-mass post-T Tauri stars and their evolutionary status

1983 ◽  
Vol 269 ◽  
pp. 229 ◽  
Author(s):  
R. Mundt ◽  
F. M. Walter ◽  
E. D. Feigelson ◽  
U. Finkenzeller ◽  
G. H. Herbig ◽  
...  
Keyword(s):  
T Tauri Stars ◽  
Evolutionary Status ◽  
T Tauri ◽  
Low Mass
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