scholarly journals Measuring the physical conditions of accreting gas in T Tauri systems

2007 ◽  
Vol 3 (S243) ◽  
pp. 95-102
Author(s):  
Jeffrey S. Bary ◽  
Sean P. Matt
Keyword(s):  
Near Infrared ◽  
Young Star ◽  
Emission Lines ◽  
Line Flux ◽  
Star Forming ◽  
Physical Conditions ◽  
T Tauri ◽  
Hydrogen Emission Lines ◽  
Line Theory ◽  
Magnetospheric Accretion

AbstractHydrogen emission lines observed from T Tauri stars (TTS) are associated with the accretion/outflow of gas in these young star forming systems. Magnetospheric accretion models have been moderately successful at reproducing the shapes of several Hi emission line profiles, suggesting that the emission arises in the accretion funnels. Despite considerable effort to model and observe these emission features, the physical conditions of the gas confined to the funnel flows remain poorly constrained by observation. We conducted a mutli-epoch near-infrared spectroscopic survey of 16 actively accreting classical TTS in the Taurus-Auriga star forming region. We present an analysis of these simultaneously acquired line flux ratios of many Paschen and Brackett series emission lines, in which we compare the observed ratios to those predicted by the Case B approximation of hydrogen recombination line theory. We find that the line flux ratios for the Paschen and Brackett decrements as well as a comparison between Brγ and Paschen transitions agree well with the Case B models with T < 5000 K and ne ≈ 1010 cm−3.

Magnetospheric Accretion Models for the Hydrogen Emission Lines of T Tauri Stars

1998 ◽  
Vol 492 (2) ◽  
pp. 743-753 ◽  
Author(s):  
James Muzerolle ◽  
Nuria Calvet ◽  
Lee Hartmann
Keyword(s):  
T Tauri Stars ◽  
Emission Lines ◽  
Hydrogen Emission ◽  
T Tauri ◽  
Hydrogen Emission Lines ◽  
Magnetospheric Accretion

Probing the physical conditions surrounding young star clusters

2018 ◽  
Vol 14 (S345) ◽  
pp. 326-327
Author(s):  
Jane Gregorio-Hetem ◽  
Beatriz Fernandes ◽  
Felipe Navarete
Keyword(s):  
Near Infrared ◽  
Cluster Formation ◽  
Young Star ◽  
Star Cluster ◽  
Infrared Observations ◽  
Associated Gas ◽  
Star Forming ◽  
Physical Conditions ◽  
Ongoing Work ◽  
Young Star Clusters

AbstractThe scenario of star cluster formation can be better understood based on the detailed study of the dynamical conditions of the associated gas, clustering properties and effects of ionizing sources, among others. Some of these characteristics are explored in our ongoing work based on observations with the SOAR and T80-S telescopes. With these data we have obtained a complete multi-band photometric catalogue of selected clusters that we characterize using color-color diagrams and flux ratios. In particular, this work is focused on SOAR/Spartan (near-infrared) observations of the Canis Major star-forming region.

scholarly journals T Tauri stars: from mystery to magnetospheric accretion

2007 ◽  
Vol 3 (S243) ◽  
pp. 13-22
Author(s):  
Gibor Basri
Keyword(s):  
Angular Momentum ◽  
Physical System ◽  
Time Variable ◽  
T Tauri Stars ◽  
Emission Lines ◽  
Spectral Information ◽  
Historical Overview ◽  
Physical Conditions ◽  
T Tauri ◽  
Magnetospheric Accretion

AbstractThis is a selective historical overview of the progess in understanding T Tauri spectra. Originally they were understood to be very young, but the physical conditions (or even geometry) of the material on the star and in its surroundings were mysterious. The origin and meaning of the emission lines was largely unknown. Today we have a detailed consensus of what is happening near and on these newly forming stars. They are very magnetically active, and the stellar field is strong and extensive enough to control both the final accretion onto the star and the launching of outflows which solve the angular momentum problem during formation. Much of this consensus has emerged from spectral information, but much remains to be learned. I highlight some of the seminal breakthroughs that have led to the current picture. There are very complex and time-variable components to the entire physical system that constitutes a T Tauri star, and spectral information at various wavelengths and resolutions is crucial to making further progress.

scholarly journals Shocked Molecular Hydrogen from Star Forming Regions

1987 ◽  
Vol 115 ◽  
pp. 181-181 ◽  
Author(s):  
Adair P. Lane ◽  
John Bally
Keyword(s):  
Shock Waves ◽  
High Velocity ◽  
Molecular Hydrogen ◽  
Near Infrared ◽  
Young Stars ◽  
Emission Lines ◽  
Molecular Gas ◽  
Star Forming ◽  
Star Forming Regions ◽  
Post Shock

Near infrared (2 micron) emission lines from molecular hydrogen provide a powerful probe of the morphology and energetics of outflows associated with stellar birth. The H2 emission regions trace the location of shock waves formed when the high velocity outflow from young stars encounters dense quiescent gas. Since H2 is the dominant coolant of the hot post-shock molecular gas, the H2 lines provide a measure of the fraction of the total mechanical luminosity radiated away from the cloud.

scholarly journals A Two-Dimensional Near—Infrared Speckle Imaging Survey of T Tauri Stars in Taurus and Ophiuchus

1992 ◽  
Vol 135 ◽  
pp. 1-9
Author(s):  
A. Ghez ◽  
G. Neugebauer ◽  
K. Matthews
Keyword(s):  
Binary Stars ◽  
Near Infrared ◽  
Angular Separation ◽  
Speckle Interferometry ◽  
T Tauri Stars ◽  
Two Dimensional ◽  
Star Forming ◽  
Double Stars ◽  
Star Forming Regions ◽  
T Tauri

AbstractWe present the results of a magnitude limited (K≤8.5 mag) multiplicity survey of T Tauri stars in the two nearest star forming regions, Taurus-Auriga and Ophiuchus-Scorpius (D = 150 pc), observable from the northern hemisphere. Each of the 70 stars in the sample was imaged at 2.2 μm using two-dimensional speckle interferometry resulting in a survey sensitive to binary stars with separations ranging from 0.″09 to about 2″.5.The frequency of double stars with separation in this range is 46±8%. A division between the classical T Tauri stars and the weak-lined T Tauri stars shows no distinction. Furthermore, no difference is observed between the binary frequencies in the two star forming regions although the clouds have very different properties.Given the limited angular separation range that this survey is sensitive to, both the spectroscopic and wide binaries will be missed. The rate at which binaries are detected suggests that most, if not all, T Tauri stars have companions.

scholarly journals The origin of R CrA variability

2019 ◽  
Vol 630 ◽  
pp. A132 ◽  
Author(s):  
E. Sissa ◽  
R. Gratton ◽  
J. M. Alcalà ◽  
S. Desidera ◽  
S. Messina ◽  
...  
Keyword(s):  
Light Curve ◽  
Spectroscopic Data ◽  
Near Infrared ◽  
Progressive Increase ◽  
Emission Lines ◽  
Periodic Modulation ◽  
Star Forming ◽  
Stable Period ◽  
Total Luminosity ◽  
M Dwarf

Context. R CrA is the brightest member of the Coronet star-forming region and is the closest Herbig AeBe star with a spectrum dominated by emission lines. Its luminosity has been monitored since the end of the nineteenth century, but the origin of its variability, which shows a stable period of 65.767 ± 0.007 days, is still unknown. Aims. We studied photometric and spectroscopic data for this star to investigate the nature of the variability of R CrA. Methods. We exploited the fact that the near-infrared luminosity of the Herbig AeBe stars is roughly proportional to the total luminosity of the stars to derive the absorption, and then mass and age of R CrA. In addition, we modeled the periodic modulation of the light curve as due to partial attenuation of a central binary by a circumbinary disk. This model reproduces the observations very well. Results. We found that the central object in R CrA is a very young (1.5 ± 1.5 Myr) highly absorbed (AV = 5.47 ± 0.4 mag) binary; we obtain masses of MA = 3.02 ± 0.43 M⊙ and MB = 2.32 ± 0.35 M⊙ for the two components. We propose that the secular decrease of the apparent luminosity of R CrA is due to a progressive increase of the disk absorption. This might be related to precession of a slightly inclined disk caused by the recently discovered M-dwarf companion. This means that R CrA might be a triple system hosting a disk.

scholarly journals A Study of the Young Star V1331 CYG in a Compact Star-Forming Region

1998 ◽  
Vol 11 (1) ◽  
pp. 344-344
Author(s):  
Alisher Hojaev ◽  
Alexander Zheleznyak
Keyword(s):  
Compact Star ◽  
Young Star ◽  
Light Curves ◽  
Circumstellar Disk ◽  
Line Profiles ◽  
Periodic Process ◽  
Dark Cloud ◽  
Star Forming ◽  
T Tauri ◽  
Morphologic Analysis

The peculiar T Tauri type star V1331 Cyg = LkH 120, located in the dark cloud Lynds 984, is a FU Orionis pre-outburst candidate (McMuldroch et al., 1993). This star embedded in circumstellar bright nebulosity is also surrounded by a helix-shaped nebula originated from the star. We obtained a series of speckle images of V1331 Cyg on the standard VBR system on July 18-20, 1994 using the Zeiss 1000 1.0 m telescope of the High Altitude Maydanak Observatory in Uzbekistan. We also used the results of Johnson’s system photometry of V1331 Cyg, made simultaneously at Maydanak Observatory with a 0.6 m reflector. Images were computer processed. Surface photometry of the star and surrounding nebula was made and isophotes were constructed. Fourier analysis of light curves for V1331 Cyg has shown 36.2 day periodic process (Melnikov, priv. comm.) which could be due to the presence of a circumstellar disk. Morphologic analysis revealed a complex fine structure of nebula, consisting of many bright knots and obviously show a jet-like outflow. According to spectral observations (Chavarria K. 1981; Penston & Keavey 1977) the line profiles of V1331 Cyg are P Cyg type only; there are no detections of anti-P Cyg profiles during the last 25 years observations. This indicates a stable mass loss (on average, 10−7M⊙/yr) with mean velocities about −410 km/s.

scholarly journals V899 Mon: A Peculiar Eruptive Young Star Close to the End of Its Outburst

2021 ◽  
Vol 923 (2) ◽  
pp. 171
Author(s):  
Sunkyung Park ◽  
Ágnes Kóspál ◽  
Fernando Cruz-Sáenz de Miera ◽  
Michał Siwak ◽  
Marek Dróżdż ◽  
...  
Keyword(s):  
Loss Rate ◽  
Near Infrared ◽  
Accretion Rate ◽  
Mass Loss Rate ◽  
Young Star ◽  
Light Curves ◽  
Emission Lines ◽  
Spectroscopic Observations ◽  
Photometric Monitoring ◽  
Physical Changes

Abstract The eruptive young star V899 Mon shows characteristics of both FUors and EXors. It reached a peak brightness in 2010, then briefly faded in 2011, followed by a second outburst. We conducted multifilter optical photometric monitoring, as well as optical and near-infrared spectroscopic observations, of V899 Mon. The light curves and color–magnitude diagrams show that V899 Mon has been gradually fading after its second outburst peak in 2018, but smaller accretion bursts are still happening. Our spectroscopic observations taken with Gemini/IGRINS and VLT/MUSE show a number of emission lines, unlike during the outbursting stage. We used the emission line fluxes to estimate the accretion rate and found that it has significantly decreased compared to the outbursting stage. The mass-loss rate is also weakening. Our 2D spectroastrometric analysis of emission lines recovered jet and disk emission of V899 Mon. We found that the emission from permitted metallic lines and the CO bandheads can be modeled well with a disk in Keplerian rotation, which also gives a tight constraint for the dynamical stellar mass of 2 M ⊙. After a discussion of the physical changes that led to the changes in the observed properties of V899 Mon, we suggest that this object is finishing its second outburst.

scholarly journals Extended Hα over compact far-infrared continuum in dusty submillimeter galaxies

2020 ◽  
Vol 635 ◽  
pp. A119 ◽  
Author(s):  
Chian-Chou Chen ◽  
C. M. Harrison ◽  
I. Smail ◽  
A. M. Swinbank ◽  
O. J. Turner ◽  
...  
Keyword(s):  
Near Infrared ◽  
Far Infrared ◽  
Young Star ◽  
Spectral Energy ◽  
Star Forming ◽  
Very Large Telescope ◽  
Submillimeter Galaxies ◽  
The Difference ◽  
Using Data ◽  
Integral Field

By using data from the Atacama Large Millimeter/submillimeter Array and near-infrared (NIR) integral field spectrographs, including both Spectrograph for INtegral Field Observations in the Near Infrared and K-band Multi Object Spectrograph on the Very Large Telescope, we investigate the two-dimensional distributions of Hα and rest-frame far-infrared (FIR) continuum in six submillimeter galaxies (SMGs) at z ∼ 2. At a similar spatial resolution (∼0.″5 FWHM; ∼4.5 kpc at z = 2), we find that the half-light radius of Hα is significantly larger than that of the FIR continuum in half of the sample, and on average Hα is a median factor of 2.0 ± 0.4 larger. Having explored various ways to correct for the attenuation, we find that the attenuation-corrected Hα-based star-formation rates (SFRs) are systematically lower than the infrared (IR)-based SFRs by at least a median factor of 3 ± 1, which cannot be explained by the difference in half-light radius alone. In addition, we find that in 40% of cases the total V-band attenuation (AV) derived from energy balance modeling of the full ultraviolet (UV)-to-FIR spectral energy distributions (SEDs) is significantly higher than what is derived from SED modeling using only the UV-to-NIR part of the SEDs, and the discrepancy appears to increase with increasing total infrared luminosity. Finally, in considering all of our findings along with the studies in the literature, we postulate that the dust distributions in SMGs, and possibly also in less IR luminous z ∼ 2 massive star-forming galaxies, can be decomposed into the following three main components: the diffuse dust heated by older stellar populations, the more obscured and extended young star-forming H II regions, and the heavily obscured central regions that have a low filling factor but dominate the infrared luminosity in which the majority of attenuation cannot be probed via UV-to-NIR emissions.

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