ON THE NATURE OF EXor ACCRETION EVENTS: AN INFREQUENT MANIFESTATION OF A COMMON PHENOMENOLOGY?

Journal Article · Fri Apr 20 04:00:00 EDT 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/749/2/188· OSTI ID:22020370

Lorenzetti, D; Antoniucci, S; Giannini, T; Li Causi, G; Ventura, P; Di Paola, A; Nisini, B ^[1]; Arkharov, A A; Larionov, V M ^[2]

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1. INAF-Osservatorio Astronomico di Roma, Via Frascati 33, 00040 Monte Porzio (Italy)
2. Central Astronomical Observatory of Pulkovo, Pulkovskoe Shosse 65, 196140 St. Petersburg (Russian Federation)

We present the results of a comparison between classical and newly identified EXor based on literature data and aimed at recognizing possible differences or similarities between the categories. Optical and near-IR two-color diagrams, modalities of fluctuations, and derived values of the mass accretion rates are indicative of strong similarities between the two samples. We demonstrate how the difference between the outburst and the quiescence spectral energy distribution of all EXor can be well fitted with a single blackbody, as if an additional thermal component appears during the outbursting phase. Temperatures of this additional component span between 1000 and 4500 K, while the radii of the emitting regions (assumed to be a uniform disk) span between 0.01 and 0.1 AU, sizes typical of the inner portions of the circumstellar disk. Spots persisting up to 50% of the outburst duration, not exceeding 10% of the stellar surface, and with temperatures compatible with the EXor mass accretion rates, are able to account for both the appearance of the additional thermal component and the dust sublimation in the inner structures of the disk. We also compare the EXor events with the most significant color and magnitude fluctuations of active T Tauri stars finding that (1) burst accretion phenomena should also be important for this latter class and (2) EXor events could be more frequent than those accidentally discovered. A remarkable case is that of the source V2493 Cyg, a T Tauri star recently identified as a strong outbursting object: New optical and near-IR photometric and spectroscopic data are presented in an attempt to clarify its EXor or FUor nature.

• OSTI ID: 22020370
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 749; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ACCRETION DISKS
COLOR
COSMOLOGY
DUSTS
ENERGY SPECTRA
MASS
MATTER
SUBLIMATION
T TAURI STARS