226 Young Stellar Objects, Very Young Stars, T-Tauri Stars, H-H Objects Poster Session
226.01
Near-Infrared Variability in Young Stars with Disks
Thomas Rice1, S. J. Wolk1, C. Aspin2
1Harvard-Smithsonian Center for Astrophysics, 2University of Hawaii Institute for Astronomy.
8:00 AM - 7:00 PM
Essex Ballroom
We present the results from the analysis of 120 epoch time-series photometry of a 1 square degree region of the Lynds 1003 dark cloud in the Cygnus OB7 association. Using the Wide-Field imaging camera (WFCAM) on UKIRT we were able to obtain almost-nightly J,H,K' photometry over three observing seasons of over 100,000 stars with photometric uncertainty better than 0.02 mag in the range J=10-16 mags and better than 0.1 mag down to J=18. We have identified over 300 candidate disk-bearing YSOs from color criteria and have investigated variability and periodicity for these stars relative to the field population. We have uncovered a population of young stars whose K-band infrared excess varies significantly over our 2-year observations. We report the discovery of periodic and stochastic variables among T Tauri stars, and present rotation periods for a number of YSOs.
Part of this work was funded by the NSF REU program.
226.02
Catching the Weak T-Tauri Population in L1641 North and NGC 1980.
Ignazio Pillitteri1
1SAO.
8:00 AM - 7:00 PM
Essex Ballroom
The complex of Orion Molecular Cloud is the most interesting example of complex cloud and star forming region. With SOXS program we have obtained information on the X-ray (with XMM-Newton) and infrared (IR, with Spitzer) of the young population distributed along NGC1980 and L1641 south of the Orion Nebula Cloud. In the framework of studying dynamics and morphology of star forming regions, we have conducted an optical spectroscopic follow-up of 37 bona fide Weak-T-Tauri stars in NGC1980/L1641 North, selected on the basis of their strong X-ray emission and the absence of IR excesses in Spitzer IRAC bands. Here we present radial velocities, H-alpha and Lithium equivalent widths and discuss these in the context of their spatial distribution information obtained with IR and X-ray observations.
226.03
Accretion Variability in Young Spectroscopic Binaries
David R. Ardila1, G. Herczeg2, C. Johns-Krull3, M. Robert4
1NASA Herschel Science Center / IPAC / Caltech, 2Max Planck Institute for Extraterrestrial Physics, Germany, 3Rice University, 4University of Wisconsin at Madison.
8:00 AM - 7:00 PM
Essex Ballroom
In this project, we study circumbinary disk accretion into young binaries as a function of orbital phase. We have observed the pre-main-sequence binaries UZ Tau E (mass ratio q=0.3, e=0.33) and DQ Tau (q=1, e=0.58) in four phases, over three orbital periods, with the Hubble Space Telescope (COS), and rougly simultaneously with the NASA Infrared Telescope Facility (CSHELL), McDonald Observatory (Sandiford Echelle), and the Gemini Observatory (GNRIS). Here we present preliminary results from the HST observations. We observe dramatic variability in the CIV (1550 A) doublet in both stars and in the accretion rate as a function of phase. The DQ Tau system shows strong changes in the CIV line shape and centroid, and increased accretion at apastron, as manifested in the NUV flux. In the UZ Tau E system the CIV line develops a redshifted (~50 km/sec) emission at moments of strong accretion. The changes are not completely consistent with previous (optical) observations, as they seem dominated not by the orbital period but by stochastic changes in accretion. They serve to illuminate the geometry of the accretion flow in young binaries.
226.04
Near-infrared Variability Of Young Stellar Objects In The YSOVAR Program
Joseph L. Hora1, J. Stauffer2, M. Morales-Calderon2, J. Carpenter2, J. Bloom3, D. Starr3, YSOVAR Team
1Harvard-Smithsonian CFA, 2Caltech, 3University of California - Berkeley.
8:00 AM - 7:00 PM
Essex Ballroom
The Spitzer Young Stellar Object variability (YSOVAR) project is currently underway and to date has obtained well-sampled light curves for several star forming regions, including fields in Orion, IC 1396, Mon R2, NGC 2264, Ceph-C, L1688, IRAS 20050+2720, and GGD 12-15. The survey will eventually contain data for over 2000 YSOs, and will allow us to place constraints on the structure of the inner disks, measure the stability of hot spots on the surfaces of YSOs over a range of evolutionary stages, and determine rotational periods for a large sample of objects. As part of this project, we have obtained contemporaneous near-infrared (JHK) photometry of the fields using the PAIRITEL telescope. We have continued the near-IR monitoring to assess the stability of the YSOs over longer periods. We will present initial results from the PAIRITEL observations, including a comparison of the JHK and IRAC 3.6 and 4.5 micron variability, and the long-term behavior of the YSOs.
226.05
Inner Structure in the TW Hya Circumstellar Disk
Rachel L. Akeson1, R. Millan-Gabet1, D. Ciardi1, A. Boden2, A. Sargent2, J. Monnier3, H. McAlister4, T. ten Brummelaar4, J. Sturmann4, L. Sturmann4, N. Turner4
1NASA Exoplanet Science Institute, Caltech, 2Dept of Astronomy, Caltech, 3University of Michigan, 4CHARA, Georgia State University.
8:00 AM - 7:00 PM
Essex Ballroom
TW Hya is a nearby (50 pc) young stellar object with an estimated age of 10 Myr and signs of active accretion. Previous modeling of the circumstellar disk has shown that the inner disk contains optically thin material, placing this object in the class of "transition disks". We present new near-infrared interferometric observations of the disk material and use these data, as well as previously published, spatially resolved data at 10 microns and 7 mm, to constrain disk models based on a standard flared disk structure. Our model demonstrates that the constraints imposed by the spatially resolved data can be met with a physically plausible disk but this requires a disk containing not only an inner gap in the optically thick disk as previously suggested, but also some optically thick material within this gap. Our model is consistent with the suggestion by previous authors of a planet with an orbital radius of a few AU.
This work was conducted at the NASA Exoplanet Science Institute, California Institute of Technology.
226.06
Examining Star-Disk interactions in Pre-Main Sequence Binaries: A Submillimeter Array Survey of Taurus Multiple Star Systems
Robert J. Harris1, S. M. Andrews1
1Harvard University.
8:00 AM - 7:00 PM
Essex Ballroom
Most stars are born in multiple systems. Theory predicts that star-disk interactions in these systems preferentially strip circumstellar disk material away from the lower-mass companion, such that the ratio of the companion disk radius to orbital separation is set by the orbital parameters of the system. To test those predictions, we present a comparison of disk mass as a function of orbital separation and stellar mass ratio using a new, resolved 880 micron Submillimeter Array (SMA) imaging survey of young multiple star systems in Taurus (for stellar mass ratios > 0.1 and separations > 35 AU). We also highlight some initial results from complementary EVLA radio-wave observations of some of these disk-bearing multiple systems, and comment on how they can be used to quantify how dust coagulation in their disks compares with those around isolated stars.
226.07
The Anatomy of the Young Protostellar Outflow HH 211: Strong Evidence for CO v = 1-0 Fundamental Band Emission from Dense Gas in the Terminal Shock
Achim Tappe1, J. Forbrich1, S. Martín2, C. J. Lada1
1Harvard-Smithsonian Center for Astrophysics, 2European Southern Observatory, Chile.
8:00 AM - 7:00 PM
Essex Ballroom
We present Spitzer Space Telescope 5-37 µm spectroscopic mapping observations toward the southeastern lobe of the young protostellar outflow HH 211 (part of IC 348 in Perseus, 260 pc). The terminal shock of the outflow shows a rich atomic and molecular spectrum with emission lines from OH, H2O, HCO+, CO2, H2, HD, [Fe II], [Si II], [Ne II], [S I], and [Cl I]. The spectrum also shows a rising continuum towards 5 µm, which we interpret as unresolved emission lines from highly excited rotational levels of the CO v=1-0 fundamental band. This interpretation is confirmed by a strong excess flux observed in the Spitzer IRAC 4-5 µm channel 2 image.
We also observed the terminal outflow shock of this lobe with the Submillimeter Array (SMA) and detected pure rotational emission from CO 2-1, HCO+ 3-2, and HCN 3-2. The rotationally excited CO traces the collimated outflow and the terminal shock, whereas the vibrationally excited CO seen with Spitzer follows the continuation of the collimated outflow backbone in the terminal shock. The extremely high critical densities of the CO v=1-0 rovibrational lines indicate terminal shock jet densities larger than 107 cm-3.
The unique combination of mid-infrared, submillimeter, and previous near-infrared observations allow us to gain detailed insights into the interaction of one of the youngest known protostellar outflows with its surrounding molecular cloud. Our results help to understand the nature of some of the so-called ‘green fuzzies’ (Extended Green Objects) identified by their Spitzer IRAC channel 2 excess and association with star-forming regions. They also provide a critical observational test to models of pulsed protostellar jets.
226.08
Optical And Infrared Monitoring Of KH 15D
Holly Capelo1, W. Herbst1, C. Hamilton2
1Wesleyan Uniersity, 2Dickinson College.
8:00 AM - 7:00 PM
Essex Ballroom
We present the most recent optical and near-infrared photometric monitoring of KH15D, a pre-main sequence binary star system that undergoes occultation by a precessing high-inclination circumbinary disk. Amplitude variations in the object's periodic light curve may be accounted for by the dependence of reflectance properties of the disk on distance from the binary or by a putative third body within the system. We have acquired medium-resolution spectra intended to probe circumstellar absorption features for signatures of mineral condensates for our study of this object's proto-planetary environment.
226.09
Simultaneous Spitzer/Chandra Observation Of Young Stellar Objects In GGD 12-15 - Do X-ray Flares Produce Disk Afterglows?
Jan Forbrich1, K. R. Covey2, S. J. Wolk1, J. R. Stauffer3, R. R. A. Gutermuth4, M. Morales Calderon3, B. A. Whitney5, J. L. Hora1, B. Posselt6
1Harvard-Smithsonian CfA, 2Cornell University, 3Caltech, 4Smith College, 5Space Science Institute, 6Pennsylvania State University.
8:00 AM - 7:00 PM
Essex Ballroom
We present first results of a simultaneous 20h Spitzer/Chandra monitoring campaign of the young cluster GGD 12-15. By analyzing correlated X-ray and mid-IR variability on different timescales, we are testing 1) theoretical predictions of X-ray heating in circumstellar disks (in an analogy to reverberation mapping), and 2) whether disk accretion rates rise following stellar X-ray flares, as expected from disk accretion models. Focusing on simultaneous X-ray and mid-infrared observations and timescales of minutes to hours, this project is leveraging extensive mid-IR light curves obtained via the Spitzer Warm Mission program YSOVAR. Ancillary science includes the identification of weak-line T Tauri stars to study their mid-IR variability and the LX-rotation relation of protostars, using mid-IR periods.
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