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Post Info TOPIC: V2492 Cygni
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ATel 10183: High resolution spectroscopy of the young eruptive star V2492 Cyg currently peaking at record brightness



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Blobrana


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V2492 Cyg
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ATel 10170: Significant increase in the optical brightness of V2492 Cyg



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Blobrana


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Title: Exploring the circumstellar environment of the young eruptive star V2492 Cyg
Authors: A. Kóspál, P. abrahám, J. A. Acosta-Pulido, M. J. Arévalo Morales, Z. Balog, M. I. Carnerero, E. Szegedi-Elek, A. Farkas, Th. Henning, J. Kelemen, T. Kovács, M. Kun, G. Marton, Sz. Mészáros, A. Moór, A. Pál, K. Sárneczky, R. Szakáts, N. Szalai, A. Szing, I. Tóth, N. J. Turner, K. Vida

Context. V2492 Cyg is a young eruptive star that went into outburst in 2010. The near-infrared colour changes observed since the outburst peak suggest that the source belongs to a newly defined sub-class of young eruptive stars where time-dependent accretion and variable line-of-sight extinction play a combined role in the flux changes. Aims. In order to learn about the origin of the light variations and to explore the circumstellar and interstellar environment of V2492 Cyg, we monitored the source at ten different wavelengths, between 0.55 µm and 2.2 µm from the ground, and between 3.6 µm and 160 µm from space.
Methods. We analyse the light curves and study the colour-colour diagrams via comparison with the standard reddening path. We examine the structure of the molecular cloud hosting V2492 Cyg by computing temperature and optical depth maps from the far-infrared data.
Results. We find that the shapes of the light curves at different wavelengths are strictly self-similar, and the observed variability is related to a single physical process, most likely variable extinction. We suggest that the central source is episodically occulted by a dense dust cloud in the inner disk, and -- based on the invariability of the far-infrared fluxes -- we propose that it is a long-lived rather than a transient structure. In some respects, V2492 Cyg can be regarded as a young, embedded analogue of UX Orionis-type stars.
Conclusions. The example of V2492 Cyg demonstrates that the light variations of young eruptive stars are not exclusively related to changing accretion. The variability provided information on an azimuthally asymmetric structural element in the inner disk. Such an asymmetric density distribution in the terrestrial zone may have consequences for the initial conditions of planet formation, too.

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Title: Highly Variable Extinction and Accretion in the Jet-driving Class I Type Young Star PTF 10nvg (V2492 Cyg, IRAS 20496+4354)
Authors: Lynne A. Hillenbrand, Adam A. Miller, Kevin R. Covey, John M. Carpenter, S.Bradley Cenko, Jeffrey M. Silverman, Philip Muirhead, William Fischer, Justin R. Crepp, Joshua S. Bloom, Alexei V. Filippenko

We report extensive photometry and spectroscopy of the highly variable young stellar object PTF 10nvg including optical, near-infrared, mid-infrared, and millimeter data. Following the 2010 maximum and subsequent fade, during 2011 and 2012 the source underwent additional episodes of brightening followed by several magnitude dimming events consistent with extinction variations. Further, a ~221 day period is derived; 2010 data taken when the source was near maximum brightness do not phase well to this period, however. Spectral evolution includes changes in slope and correlated changes in the prominence of TiO/VO/CO and atomic emission. These are anticorrelated with changes in forbidden emission which, along with H_2, dominate at faint epochs. Notably, night-to-night variations in several forbidden doublet strengths and ratios are observed. High-dispersion spectra in a variety of photometric states reveal line profiles for atomic species likely formed in an accretion flow and/or impact. The origin of zero-velocity Li I 6707 in emission is unknown. Forbidden line profiles are all blueshifted and likely arise from an outflow/jet. Several of these lines are also seen in a shocked region that is spatially offset from the continuum source position. Blueshifted absorption components similarly are formed in the outflow. CARMA maps resolve a spatially extended outflow in mm-wavelength CO. We attribute the observed photometric and spectroscopic behavior to rotating circumstellar disk material located at approximately 0.5-0.7 AU from the continuum source, causing the semi-periodic dimming. Occultation of the central star as well as the bright inner disk and the accretion/outflow zones renders shocked gas in the inner part of the jet amenable to observation at the faint epochs. We discuss PTF 10nvg as a source exhibiting both accretion-driven and extinction-driven phenomena.

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