List of Past LMA/CARMA Seminars : 01-Jan-2016 to 01-Jun-2016

Date:   Monday 11-Apr-2016
Speaker:   Dr. Will Fischer (GSFC/USRA)
Title:  Luminosity Outbursts in Orion's Protostars

Early in the era of all-sky infrared surveys, it was discovered that low-mass pr otostars are, on average, less luminous than expected if they form due to steady accretion of their envelopes over their estimated lifetimes. One solution to th is luminosity problem is episodic accretion, where the protostar is usually less luminous than average, but it undergoes stochastic bursts of accretion that are short compared to its formation period. In these events, protostars may become 10 to 100 times brighter in just months and remain bright for years. We searched for examples of episodic accretion by comparing photometry of 319 protostars fr om the Spitzer survey of Orion (2004-05) to that from WISE, the Wide-field Infra red Survey Explorer (2010). We recovered one known outburst and discovered a sec ond, extremely young example. I will discuss our photometric and spectroscopic m onitoring of these protostars and address how they contribute to our understandi ng of star formation.

Date:   Tuesday 31-May-2016
Speaker:   Dr. Isabelle Joncour (Institut de Planetologie et d'Astrophysique de Grenoble/UMD)
Title:  Unexpected ultra-wide pairs and mini-clusters in Taurus-Auriga association

Because of its proximity (140 pc), its low level of turbulence (0.2 km/s), its low stellar density (1-10 pc^-2) and its great spatial extension (10x10 deg^2), the Taurus-Auriga complex is one of the most studied star formation regions in order to derive constraints on star birth scenarios and early dynamical evolution (last observational review on Taurus Hartman 2008). Radio data have shown the richness of hierarchical intertwined gas filaments and chains of dense cores (Hacar et al 2013, Panopoulou et al 2014, Tafalla & Hacar, 2015) and recent Herschel observations have revealed a detailed picture of filaments (filament growths, Palmeirin et ap 2013), a universal filament width (0.1 pc, Andre et al 2014) and a rich population of prestellar cores (Marsh et al 2016). Those cores are believed to be the precursor of protostellar cores known to be single or multiple stars cradles. In this quiet star-forming region, stars have barely time to move far away from their birth site, thus spatial analysis of star distribution should reveal imprints of their pristine natal environment. In our work, we have used statistical and graph-theoretic framework to analyse the complete census of stellar catalog (Luhman et al, 2010) completed here by multiplicity data collected from the literature. In this talk, I will present the main results of this study: (1) the presence of a large coeval ultra-wide pairs (UWP) beyond previously known population (Kraus & Hillenbrand 2009). A majority of these UBW is biased towards high multiplicity, the shorter are their separation, the higher is the multiplicity: this points to a nested cascade fragmentation scenario for their formation (2) unexpected youngest dense star mini-clusters (NEST for Nested Elementary STructures) inside previously known loose groups (Gomez et al 1993, Kirk et al 2011) and mostly along the dust filaments. These NESTs shelter half stellar population of Taurus and 72% of the ultra-wide pairs. (3) fractal hierarchical stellar structure that connect these NESTs to the whole structure of the region. This talk opens discussions on future work using upcoming GAIA data to analyse further 3D spatial distribution and kinematics on stars an d compare to gas spatial and kinematics structure.

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