scholarly journals MAIN-SEQUENCE STARS MASQUERADING AS YOUNG STELLAR OBJECTS IN THE CENTRAL MOLECULAR ZONE

2015 ◽  
Vol 799 (1) ◽  
pp. 53 ◽  
Author(s):  
Christine M. Koepferl ◽  
Thomas P. Robitaille ◽  
Esteban F. E. Morales ◽  
Katharine G. Johnston
Keyword(s):  
Main Sequence ◽  
Young Stellar Objects ◽  
Main Sequence Stars ◽  
Stellar Objects

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.

scholarly journals Energetics, Collimation and Propagation of Galactic Protostellar Outflows

1997 ◽  
Vol 182 ◽  
pp. 241-258 ◽  
Author(s):  
Max Camenzind
Keyword(s):  
Main Sequence ◽  
Young Stellar Objects ◽  
Rotating Stars ◽  
Main Sequence Stars ◽  
Stellar Objects ◽  
Central Object ◽  
Protostellar Jets ◽  
Bow Shocks ◽  
Low Mass ◽  
Rapidly Rotating Stars

Formation of jets in low-mass protostellar objects and young pre-main sequence stars is ultimately related to the existence of some gaseous disk around a rapidly rotating central object. This configuration has deep parallels to extragalactic systems such as radio galaxies and quasars. Rotating black holes are still thought to be the prime-mover behind the activity detected in centers of galaxies, while, in the case of protostellar jets, rapidly rotating stars and disks are responsible for the ejection of bipolar outflows. In both cases, magnetic fields are invoked for the acceleration, the collimation and propagation of these outflows. The ultimate rooting of these fields is still under debate. We discuss models where winds injected into rapidly rotating magnetospheres of the central object drive the outflows. From these considerations it follows that the jets of young stellar objects can only be produced magnetically and that their progagation is determined by their magnetic properties. Such jets have low Mach numbers ≃ 2 and their instabilities are dominated by the pinch mode. Knots closest to the source are attributed to compression by the time-dependent pinches. Multiple bow shocks occur on longer time-scales (a few thousand years) and are attributed to variations in the magnetospheric structure of the star, or the disk.

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 Long-Term Multicolour Photometry of the Young Stellar Objects FHO 26, FHO 27, FHO 28, FHO 29, and V1929 Cygni

2015 ◽  
Vol 32 ◽  
Author(s):  
S. I. Ibryamov ◽  
E. H. Semkov ◽  
S. P. Peneva
Keyword(s):  
Gulf Of Mexico ◽  
Young Stellar Objects ◽  
Main Sequence Stars ◽  
Stellar Objects ◽  
Photometric Variability ◽  
The North ◽  
Dense Molecular Cloud ◽  
Photometric Observations ◽  
All Optical

AbstractResults from long-term multicolour optical photometric observations of the pre-main-sequence stars FHO 26, FHO 27, FHO 28, FHO 29, and V1929 Cyg collected during the period from 1997 June to 2014 December are presented. The objects are located in the dense molecular cloud L935, named ‘Gulf of Mexico’, in the field between the North America and Pelican nebulae. All stars from our study exhibit strong photometric variability in all optical passbands. Using our BVRI observations and data published by other authors, we tried to define the reasons for the observed brightness variations. The presented paper is a part of our long-term photometric study of the young stellar objects in the region of ‘Gulf of Mexico’.

Oscillations in Young Stellar Objects

2002 ◽  
Vol 185 ◽  
pp. 352-353
Author(s):  
F.J.G. Pinheiro ◽  
D.F.M. Folha ◽  
M.J.P.F.G. Monteiro ◽  
M. Marconi ◽  
V. Ripepi ◽  
...  
Keyword(s):  
Light Curve ◽  
Main Sequence ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Stellar Oscillations ◽  
Pms Stars

AbstractWe report the discovery of periodicities in the light curve of the Herbig Ae star V346 Ori. We interpret these variations as the superposition of at least two signals with periods P1=42±6 min and P2=68±12 min resulting from stellar oscillations. The computation of linear non-adiabatic pulsation models for Pre-Main Sequence (PMS) stars reproduces these periods for a 1.5 M⊙ star with Teff= 7300 K and log L/L⊙= 0.74, pulsating in the fundamental and second overtones.

Pre-main-sequence stars in the stellar association N 11 in the Large Magellanic Cloud: clustering properties

2009 ◽  
Vol 5 (S266) ◽  
pp. 545-548
Author(s):  
Antonella Vallenari ◽  
Rosanna Sordo ◽  
Emanuela Chiosi
Keyword(s):  
Formation Process ◽  
Main Sequence ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Main Sequence Stars ◽  
Stellar Association ◽  
Stellar Objects ◽  
Significant Difference ◽  
Low Metallicity ◽  
Tree Method

AbstractMagellanic Clouds are of extreme importance to study the star-formation process in low-metallicity environments. Here, we discuss the clustering properties of the pre-main-sequence candidates and young embedded stellar objects in N 11, located in the Large Magellanic Cloud. Deep archival HST/ACS photometry is used to derive color–magnitude diagrams of the associations in N 11 and of the foreground field population. These data are complemented by archival infrared Spitzer data which allow detection of young embedded stellar objects. The spatial distribution of the pre-main-sequence candidates and young embedded stellar objects is discussed. The degree of clustering is derived using the minimal-spanning-tree method. No significant difference is found in clustering degree of young blue main-sequence stars and faint pre-main-sequence candidates, suggesting that they might be part of the same formation process.

scholarly journals Water masers and the near-stellar environment in YSOs

2002 ◽  
Vol 206 ◽  
pp. 27-34
Author(s):  
Mark J. Claussen
Keyword(s):  
Main Sequence ◽  
Very Long Baseline Interferometry ◽  
Angular Resolution ◽  
Young Stellar Objects ◽  
High Angular Resolution ◽  
High Luminosity ◽  
Stellar Objects ◽  
Long Baseline ◽  
Water Masers ◽  
Very High

I present a review of observations of water masers, in particular very high angular resolution of water masers using Very Long Baseline Interferometry, with which it is possible to probe the environment of young stellar objects and forming stars within only a few A.U. of the protostar, its accretion disk, and therefore the base of outflowing material. Although reference is made to some high-luminosity sources, the main thrust of the review are the water masers found toward forming objects whose mass and luminosity will be approximately that of the Sun when they reach the main sequence.

Near Infrared Mapping of Jets and Outflow Cavities Associated with Young Stellar Objects

1993 ◽  
Vol 10 (3) ◽  
pp. 203-207 ◽  
Author(s):  
W.J. Zealey ◽  
M.G. Suters ◽  
P.R. Randall
Keyword(s):  
Main Sequence ◽  
Near Infrared ◽  
High Spatial Resolution ◽  
Infrared Camera ◽  
Young Stellar Objects ◽  
General Mechanism ◽  
Stellar Objects ◽  
Hydrogen Emission ◽  
First Time

AbstractOur current understanding of Herbig-Haro objects and their relationship with outflows and Pre-Main-Sequence objects is limited. Although the general mechanism of outflows is understood, the detailed questions concerning the outflowing material’s origin and the collimation mechanisms remain largely unanswered. The role of multi-waveband observations (visible, infrared and radio) is vital to our understanding of the shock dynamics of outflows.This paper discusses high spatial resolution near infrared maps of three outflow complexes, HH34, HH46/HH47 and HH54, made using the Anglo Australian Observatory’s infrared camera, IRIS. For the first time molecular hydrogen emission is observed associated with the edges of outflow cavities. In the cases of HH46/47 and to a lesser extent HH34 molecular emission is seen coincident with highly collimated jets feeding the outflow cavities.

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