scholarly journals A Very Active T Tauri Star in NGC 7129

1995 ◽  
Vol 151 ◽  
pp. 223-226
Author(s):  
Evgeni Semkov
Keyword(s):  
Tauri Star ◽  
Star Forming ◽  
Dark Clouds ◽  
T Tauri ◽  
Photometric Observations ◽  
Long Time ◽  
Identification Chart ◽  
Hα Emission ◽  
Irregular Variable Star ◽  
Emission Stars

The star forming region NGC 7129 was first studied by Herbig (1960), who discovered two bright (BD+65° 1637 and LkHα234) and some weaker Hα emission stars. Subsequent investigations in this region led to the detection of five Herbig-Haro objects (Strom et al. 1974, Gyulbudaghian et al. 1978, Eiroa et al. 1992) and one T Tauri star, V350 Cep (Gyulbudaghian & Sarkissian 1977). Some non-stable stars in NGC 7129 are surrounded by reflection and cometary nebulae.Our Hα-emission survey (Semkov &: Tsvetkov 1986) revealed an interesting irregular variable star in the dark clouds near the emission nebulae. On objective prism plates the star shows very strong Hα-emission and was included in our list of such stars as No. 7. An identification chart and the coordinates can be found in Semkov (1993a). The observations reported here include long-time photographic photometry and CCD spectroscopic and photometric observations.

scholarly journals Detection of T-Tauri Star Candidates in the Canis Major Star-Forming Region and its Implications

1987 ◽  
Vol 115 ◽  
pp. 60-60
Author(s):  
Suhardja D. Wiramihardja ◽  
Tomokazu Kogure ◽  
Makoto Nakano ◽  
Shigeomi Yoshida
Keyword(s):  
Tauri Star ◽  
Schmidt Telescope ◽  
Star Forming ◽  
T Tauri ◽  
Hα Emission ◽  
Emission Stars ◽  
Photographic Photometry

We have made a survey of Hα-emission stars in the CMa R1 region with the 105cm Schmidt telescope at the Kiso Observatory. In an area of about 37 square degrees, a total of 107 Hα-emission stars (V = 6-15 mag.) was found, and, for all of them, the photographic photometry in the UBV system has been carried out.

scholarly journals Surveys for Hα Emission-Line Stars using the Bosscha Schmidt Telescope

1995 ◽  
Vol 148 ◽  
pp. 388-394
Author(s):  
Bambang Hidayat ◽  
Katsuo Ogura ◽  
Masao Shinohara
Keyword(s):  
Emission Line ◽  
Planetary Nebulae ◽  
T Tauri Stars ◽  
Schmidt Telescope ◽  
Dark Clouds ◽  
T Tauri ◽  
Hα Emission ◽  
Objective Prism ◽  
Emission Stars

According to McCarthy (1984) the objects detected in objective prism surveys for Hα emission line are a ”most unnatural“ group. Of course they consist of many natural groupings whose identities or other peculiarities could become apparent after observing them with higher dispersion and resolution spectroscopy. In some cases, however, their galactic locations and associations with other known populations, can provide a clue to their population types.The aims of the objective prism surveys using the Bosscha Schmidt telescope can be broadly categorised as follows: 1.Searches for galactic planetary nebulae in the region 240° < l < 360 °; |b| ≤ 10°, initiated by The (1968).2.Searches for T-Tauri stars in some southern dark clouds (Shinohara, Ogura & Hidayat 1989).3.Searches for variations in Hα intensities and luminous emission stars in some selected galactic regions, such as in the Puppis and Carina regions.

scholarly journals Hα emission-line stars in molecular clouds

2019 ◽  
Vol 630 ◽  
pp. A90 ◽  
Author(s):  
Bertil Pettersson ◽  
Bo Reipurth
Keyword(s):  
Molecular Clouds ◽  
Young Stellar Objects ◽  
Be Stars ◽  
Stellar Objects ◽  
Strong Concentration ◽  
Ob Stars ◽  
Star Forming ◽  
Hα Emission ◽  
Objective Prism ◽  
Emission Stars

A deep objective-prism survey for Hα emission stars towards the Canis Major star-forming clouds was performed. A total of 398 Hα emitters were detected, 353 of which are new detections. There is a strong concentration of these Hα emitters towards the molecular clouds surrounding the CMa OB1 association, and it is likely that these stars are young stellar objects recently born in the clouds. An additional population of Hα emitters is scattered all across the region, and probably includes unrelated foreground dMe stars and background Be stars. About 90% of the Hα emitters are detected by WISE, of which 75% was detected with usable photometry. When plotted in a WISE colour–colour diagram it appears that the majority are Class II YSOs. Coordinates and finding charts are provided for all the new stars, and coordinates for all the detections. We searched the Gaia-DR2 catalogue and from 334 Hα emission stars with useful parallaxes, we selected a subset of 98 stars that have parallax errors of less than 20% and nominal distances in the interval 1050 to 1350 pc that surrounds a strong peak at 1185 pc in the distance distribution. Similarly, Gaia distances were obtained for 51 OB-stars located towards Canis Major and selected with the same parallax errors as the Hα stars. We find a median distance for the OB stars of 1182 pc, in excellent correspondence with the distance from the Hα stars. Two known runaway stars are confirmed as members of the association. Finally, two new Herbig-Haro objects are identified.

scholarly journals Optical photometric variable stars towards Cygnus OB7

2019 ◽  
Vol 487 (2) ◽  
pp. 1765-1776 ◽  
Author(s):  
Somnath Dutta ◽  
Soumen Mondal ◽  
Santosh Joshi ◽  
Ramkrishna Das
Keyword(s):  
Variable Stars ◽  
T Tauri Stars ◽  
Light Curves ◽  
Main Sequence Stars ◽  
Star Forming ◽  
Rotation Rates ◽  
T Tauri ◽  
Photometric Observations ◽  
Sky Survey ◽  
Magnitude Diagram

ABSTRACT We present optical I-band light curves of the stars towards a star-forming region Cygnus OB7 from 17-night photometric observations. The light curves are generated from a total of 381 image frames with very good photometric precision. From the light curves of 1900 stars and their periodogram analyses, we detect 31 candidate variables including five previously identified. 14 out of 31 objects are periodic and exhibit the rotation rates in the range of 0.15–11.60 d. We characterize those candidate variables using optical/infrared colour–colour diagram and colour–magnitude diagram (CMD). From spectral indices of the candidate variables, it turns out that four are probably Classical T-Tauri stars (CTTSs), rest remain unclassified from present data, they are possibly field stars or discless pre-main-sequence stars towards the region. Based on their location on the various CMDs, the ages of two T Tauri Stars were estimated to be ∼5 Myr. The light curves indicate at least five of the periodic variables are eclipsing systems. The spatial distribution of young variable candidates on Planck 857 GHz (350 $\mu$m) and 2MASS (Two Micron All Sky Survey) Ks images suggest that at least two of the CTTSs are part of the active star-forming cloud Lynds 1003.

scholarly journals Disks around Young Brown Dwarfs

2003 ◽  
Vol 211 ◽  
pp. 133-136
Author(s):  
Michael C. Liu
Keyword(s):  
Brown Dwarfs ◽  
Circumstellar Disks ◽  
Disk Accretion ◽  
Low Mass Stars ◽  
Star Forming ◽  
Star Forming Regions ◽  
Planetary Mass ◽  
T Tauri ◽  
Hα Emission ◽  
Low Mass

We present some results from a systematic survey for disks around spectroscopically identified young brown dwarfs and very low mass stars. We find that ≈75% of our sample show intrinsic IR excesses, indicative of circum(sub)stellar disks. The observed excesses are well-correlated with Hα emission, consistent with a common disk accretion origin. Because the excesses are modest, conventional analyses using only IR colors would have missed most of the sources with disks. In the same star-forming regions, we find that disks around brown dwarfs and T Tauri stars are contemporaneous; assuming coevality, this demonstrates that substellar disks are at least as long-lived as stellar disks. Altogether, the frequency and properties of circumstellar disks are similar from the stellar regime down to the substellar and planetary-mass regime. This offers compelling evidence of a common origin for most stars and brown dwarfs.

scholarly journals Molecules in Dense Clouds And Protostars

1971 ◽  
Vol 2 ◽  
pp. 366-377
Author(s):  
P. G. Mezger
Keyword(s):  
Line Emission ◽  
Tauri Star ◽  
Evolutionary Stage ◽  
Solar Mass ◽  
Low Mass Stars ◽  
Dark Clouds ◽  
Physical Conditions ◽  
Dust Clouds ◽  
T Tauri ◽  
Low Mass

AbstractThis paper deals with the interpretation of molecular line emission from class I OH/H2O emission centers associated with compact HII regions and with the OH 18 cm emission from dark clouds in T-Tauri star associations. Observational evidence is presented, that class IOH/H2O emission centers represent a particular stage in the evolution of a massive star (or a group of massive stars) whereas protostars of lower mass apparently do not go through such a stage.It appears that in associations the low-mass stars are formed first and the massive O-stars are formed last. T-Tauri star associations may represent an early evolutionary stage of a star association where low-mass stars are formed. Evidence is presented that the physical conditions in some parts of the Taurus complex of dust clouds and T-Tauri stars are appropriate for the formation of single stars of about a solar mass.

scholarly journals Analysis of star-disk interaction in young stellar systems

2013 ◽  
Vol 9 (S302) ◽  
pp. 50-53
Author(s):  
Nathalia N. J. Fonseca ◽  
Silvia H. P. Alencar ◽  
Jérôme Bouvier
Keyword(s):  
Rotation Axis ◽  
Tauri Star ◽  
Infrared Light ◽  
Dynamical Interaction ◽  
Stellar Cluster ◽  
Circumstellar Material ◽  
T Tauri ◽  
Hα Emission ◽  
Profile Changes ◽  
Magnetospheric Accretion

AbstractWe present preliminary results of the study of star-disk interaction in the classical T Tauri star V354 Mon, a member of the young stellar cluster NGC 2264. As part of an international campaign of observations of NGC 2264 organized from December 2011 to February 2012, high resolution photometric and spectroscopic data of this object were obtained simultaneously with the Chandra, CoRoT and Spitzer satellites, and ground-based telescopes, such as CFHT and ESO/VLT. The optical and infrared light curves of V354 Mon show periodic brightness minima that vary in depth and width every 5.21 days rotational cycle. We found evidence that the Hα emission line profile changes according to the period of photometric variations, indicating that the same phenomenon causes both modulations. Such correlation was also identified in a previous observational campaign on the same object, where we concluded that material non-uniformly distributed in the inner part of the disk is the main cause of the photometric modulation. This assumption is supported by the fact that the system is seen at high inclination. It is believed that this distortion of the inner part of the disk results from the dynamical interaction between the stellar magnetosphere, inclined with respect to the rotation axis, and the circumstellar disk, as also observed in the classical T Tauri star AA Tau, and predicted by magnetohydrodynamic numerical simulations. A model of occultation by circumstellar material was applied to the photometric data in order to determine the parameters of the obscuring material during both observational campaigns, thus providing an investigation of its stability on a timescale of a few years. We also studied V422 Mon, a classical T Tauri star with photometric variations similar to those of V354 Mon at optical wavelengths, but with a distinct behavior in the infrared. The mechanism that produces such a difference is investigated, testing the predictions of magnetospheric accretion models.

Detection of T-Tauri Star Candidates in the Canis Major Star-Forming Region and its Implications

1987 ◽  
pp. 60-60
Author(s):  
Suhardja D. Wiramihardja ◽  
Tomokazu Kogure ◽  
Makoto Nakano ◽  
Shigeomi Yoshida
Keyword(s):  
Tauri Star ◽  
Star Forming ◽  
T Tauri

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.

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