scholarly journals Variability of young stellar objects in the star-forming region Pelican Nebula

2019 ◽  
Vol 627 ◽  
pp. A135 ◽  
Author(s):  
A. Bhardwaj ◽  
N. Panwar ◽  
G. J. Herczeg ◽  
W. P. Chen ◽  
H. P. Singh
Keyword(s):  
Main Sequence ◽  
T Tauri Stars ◽  
Young Stellar Objects ◽  
Spectral Energy ◽  
Physical Parameters ◽  
Main Sequence Stars ◽  
Stellar Objects ◽  
Star Forming ◽  
T Tauri ◽  
Optical Wavelengths

Context. Pre-main-sequence variability characteristics can be used to probe the physical processes leading to the formation and initial evolution of both stars and planets. Aims. The photometric variability of pre-main-sequence stars is studied at optical wavelengths to explore star–disk interactions, accretion, spots, and other physical mechanisms associated with young stellar objects. Methods. We observed a field of 16′ × 16′ in the star-forming region Pelican Nebula (IC 5070) at BVRI wavelengths for 90 nights spread over one year in 2012−2013. More than 250 epochs in the VRI bands are used to identify and classify variables up to V ∼ 21 mag. Their physical association with the cluster IC 5070 is established based on the parallaxes and proper motions from the Gaia second data release (DR2). Multiwavelength photometric data are used to estimate physical parameters based on the isochrone fitting and spectral energy distributions. Results. We present a catalog of optical time-series photometry with periods, mean magnitudes, and classifications for 95 variable stars including 67 pre-main-sequence variables towards star-forming region IC 5070. The pre-main-sequence variables are further classified as candidate classical T Tauri and weak-line T Tauri stars based on their light curve variations and the locations on the color-color and color-magnitude diagrams using optical and infrared data together with Gaia DR2 astrometry. Classical T Tauri stars display variability amplitudes up to three times the maximum fluctuation in disk-free weak-line T Tauri stars, which show strong periodic variations. Short-term variability is missed in our photometry within single nights. Several classical T Tauri stars display long-lasting (≥10 days) single or multiple fading and brightening events of up to two magnitudes at optical wavelengths. The typical mass and age of the pre-main-sequence variables from the isochrone fitting and spectral energy distributions are estimated to be ≤1 M⊙ and ∼2 Myr, respectively. We do not find any correlation between the optical amplitudes or periods with the physical parameters (mass and age) of pre-main-sequence stars. Conclusions. The low-mass pre-main-sequence stars in the Pelican Nebula region display distinct variability and color trends and nearly 30% of the variables exhibit strong periodic signatures attributed to cold spot modulations. In the case of accretion bursts and extinction events, the average amplitudes are larger than one magnitude at optical wavelengths. These optical magnitude fluctuations are stable on a timescale of one year.

Two New T Tauri stars and a Candidate FU Orionis Star associated with Bok Globules

1997 ◽  
Vol 163 ◽  
pp. 839-839
Author(s):  
J. L. Yun ◽  
M. Moreira
Keyword(s):  
Infrared Emission ◽  
T Tauri Stars ◽  
Emission Lines ◽  
Young Stellar Objects ◽  
Spectral Energy ◽  
Energy Distributions ◽  
Stellar Objects ◽  
T Tauri ◽  
Bok Globules ◽  
Reflection Nebulae

AbstractWe present photometric and spectroscopic evidence of two new T Tauri stars formed in the conditions of isolated small Bok globules. The spectral energy distributions of these objects display excess infrared emission, they are associated with optical reflection nebulae, and their optical spectra reveal Balmer emission lines and the Li I λ6707 Å absorption line. Additionnally, we report the discovery of what is likely to be a new FU Orionis star seen towards Bok globule CB34. The star is about 4 magnitudes brighter than it appears on the Palomar plates and is associated with the aggregate of young stellar objects forming in Bok globule CB34.

scholarly journals T Tauri Disk Lifetime in the Lupus Association

2015 ◽  
Vol 10 (S314) ◽  
pp. 191-192
Author(s):  
P. A. B. Galli ◽  
C. Bertout ◽  
R. Teixeira ◽  
C. Ducourant
Keyword(s):  
Main Sequence ◽  
T Tauri Stars ◽  
Young Stars ◽  
Main Sequence Stars ◽  
Disk Model ◽  
Star Forming ◽  
T Tauri

AbstractIn a recent study, we derived individual distances for a sample of pre-main sequence stars that define the comoving association of young stars in the Lupus star-forming region. Here, we use these new distances to investigate the mass and age distributions of Lupus T Tauri stars and derive the average disk lifetime in the Lupus association based on an empirical disk model.

scholarly journals The ASAS-SN catalogue of variable stars – VIII. ‘Dipper’ stars in the Lupus star-forming region

2020 ◽  
Vol 496 (3) ◽  
pp. 3257-3269 ◽  
Author(s):  
J W Bredall ◽  
B J Shappee ◽  
E Gaidos ◽  
T Jayasinghe ◽  
P Vallely ◽  
...  
Keyword(s):  
Main Sequence ◽  
Statistical Significance ◽  
Variable Stars ◽  
Young Stars ◽  
Light Curves ◽  
Young Stellar Objects ◽  
Circumstellar Dust ◽  
Stellar Objects ◽  
Star Forming ◽  
T Tauri

ABSTRACT Some young stellar objects such as T Tauri-like ‘dipper’ stars vary due to transient partial occultation by circumstellar dust, and observations of this phenomenon inform us of conditions in the planet-forming zones close to these stars. Although many dipper stars have been identified with space missions such as Kepler/K2, ground-based telescopes offer longer term and multiwavelength perspectives. We identified 11 dipper stars in the Lupus star-forming region in data from the All-Sky Automated Survey for SuperNovae (ASAS-SN), and further characterized these using observations by the Las Cumbres Global Observatory Telescope (LCOGT) and the Transiting Exoplanet Survey Satellite (TESS), as well as archival data from other missions. Dipper stars were identified from a catalogue of nearby young stars and selected based on the statistical significance, asymmetry, and quasi-periodicity or aperiodicity of variability in their ASAS-SN light curves. All 11 stars lie above or redwards of the zero-age main sequence and have infrared (IR) excesses indicating the presence of full circumstellar discs. We obtain reddening–extinction relations for the variability of seven stars using our combined ASAS-SN-TESS and LCOGT photometry. In all cases, the slopes are below the ISM value, suggesting larger grains, and we find a tentative relation between the slope (grain size) and the $K_\text{s}-[22 \, \mu \text{m}]$ IR colour regarded as a proxy for disc evolutionary state.

scholarly journals Circumstellar maher of young low-mass stars: Observations versus theory

1987 ◽  
Vol 122 ◽  
pp. 23-38 ◽  
Author(s):  
Claude Bertout
Keyword(s):  
T Tauri Stars ◽  
Young Stellar Objects ◽  
Low Mass Stars ◽  
Stellar Objects ◽  
Star Forming ◽  
T Tauri ◽  
Region I ◽  
Low Mass ◽  
Infrared Sources

After presenting NGC 7129 as a prototypical star-forming region, I discuss what can be learned from the radio spectra of embedded infrared sources. I then review available observational evidence for disks around young stellar objects, with emphasis on accretion disks around T Tauri stars. Finally, new results on the role of magnetic fields in the circumstellar activity of T Tauri stars are presented.

scholarly journals Luminosity functions of YSO clusters in Sh-2 255, W3 Main and NGC 7538 star forming regions

2006 ◽  
Vol 2 (S237) ◽  
pp. 458-458
Author(s):  
Devendra Ojha ◽  
Motohide Tamura ◽  
Keyword(s):  
Main Sequence ◽  
Near Infrared ◽  
Infrared Camera ◽  
Young Stellar Objects ◽  
Main Sequence Stars ◽  
Stellar Objects ◽  
Star Forming ◽  
Star Forming Regions ◽  
Luminosity Functions ◽  
Infrared Surveys

AbstractWe have conducted deep near-infrared surveys of the Sh-2 255, W3 Main and NGC 7538 massive star forming regions using simultaneous observations of the JHKs-band with the near-infrared camera SIRIUS on the UH 88-inch telescope and with SUBARU. The near-infrared surveys cover a total area of ~ 72 arcmin2 of three regions with 10-σ limiting magnitudes of ~ 19.5, 18.4 and 17.3 in J, H and Ks-band, respectively. Based on the color-color and color-magnitude diagrams and their clustering properties, the candidate young stellar objects are identified and their luminosity functions are constructed in Sh-2 255, W3 Main and NGC 7538 star forming regions. A large number of previously unreported red sources (H-K > 2) have also been detected around these regions. We argue that these red stars are most probably pre-main-sequence stars with intrinsic color excesses. The detected young stellar objects show a clear clustering pattern in each region: the Class I-like sources are mostly clustered in molecular cloud region, while the Class II-like sources are in or around more evolved optical HII regions. We find that the slopes of the Ks-band luminosity functions of Sh-2 255, W3 Main and NGC 7538 are lower than the typical values reported for the young embedded clusters, and their stellar populations are primarily composed of low mass pre-main-sequence stars. From the slopes of the Ks-band luminosity functions, we infer that Sh-2 255, W3 Main and NGC 7538 star forming regions are rather young (age ≤ 1 Myr).

scholarly journals Spectral energy distributions and structures of debris discs

2004 ◽  
Vol 202 ◽  
pp. 328-330
Author(s):  
W.R.F. Dent ◽  
M. C. Wyatt ◽  
W. S. Holland ◽  
J. S. Greaves ◽  
I. M. Coulson ◽  
...  
Keyword(s):  
Main Sequence ◽  
T Tauri Stars ◽  
Spectral Energy ◽  
Spectral Energy Distributions ◽  
Energy Distributions ◽  
Long Wavelength ◽  
T Tauri

New photometry of main-sequence debris discs has been carried out at 850 and 450/μm; the derived SEDs indicate that the dust can lie in either thin rings or radially-extended discs, as seen directly in the few nearby objects which are resolvable. All such objects are consistent with a long wavelength opacity index β of 1.0±0.2 - similar to T Tauri stars, but significantly lower than embedded objects.

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.

IUE observations of pre-main-sequence stars. I - MG II and CA II resonance line fluxes for T Tauri stars

1981 ◽  
Vol 251 ◽  
pp. 113 ◽  
Author(s):  
M. S. Giampapa ◽  
N. Calvet ◽  
C. L. Imhoff ◽  
L. V. Kuhi
Keyword(s):  
Resonance Line ◽  
Main Sequence ◽  
T Tauri Stars ◽  
Main Sequence Stars ◽  
T Tauri

scholarly journals The Infrared Companions of T Tauri Stars: Clues to the Formation and Early Evolution of Binaries

2001 ◽  
Vol 200 ◽  
pp. 265-274 ◽  
Author(s):  
Chris D. Koresko ◽  
Christoph Leinert
Keyword(s):  
T Tauri Stars ◽  
Young Stars ◽  
Early Evolution ◽  
Young Stellar Objects ◽  
Physical Status ◽  
Stellar Objects ◽  
T Tauri ◽  
Mode Of Development ◽  
Source Of Information

Infrared companions are young stellar objects with unusual properties gravitationally bound to more or less typical T Tauri stars. As such they promise to be the source of information on either a particular phase in the development of young stars or on a particular mode of development. We discuss the observed properties of infrared companions as well as attempts to explain their physical status with the aim to see how much of solid conclusion has been obtained so far.

scholarly journals The circumstellar environment of chromospherically active T Tauri stars

1987 ◽  
Vol 122 ◽  
pp. 103-104
Author(s):  
U. Finkenzeller ◽  
G. Basri
Keyword(s):  
Interstellar Extinction ◽  
T Tauri Stars ◽  
Activity Level ◽  
Young Stellar Objects ◽  
Balmer Line ◽  
Stellar Envelope ◽  
Stellar Objects ◽  
T Tauri ◽  
Type 3 ◽  
Circumstellar Environment

We discuss new spectroscopic material on 7 T Tauri stars of low to intermediate activity level which have envelopes of low optical thickness and small circumstellar/interstellar extinction. We show that difference plots between the target star and appropriate standards are a powerful tool to probe the stellar envelope structure. In our sample we find 1 object with a P Cyg type, 3 with inverse P Cyg type, and 3 with symmetrical Balmer line profiles. We conclude that the physical processes in these T Tauri stars do not differ qualitatively from the ones found in extremely active ones. In particular, the inverse P Cyg type profiles are not restricted to stars with very opaque envelopes and are possibly a much more common attribute of young stellar objects.

Sign in / Sign up

Export Citation Format

Share Document