N. Szalai

Publications (2)5.53 Total impact

• Article: Exploring the circumstellar environment of the young eruptive star V2492 Cyg

  Á. Kóspál, P. Ábrahám, J. A. Acosta-Pulido, M. J. Arévalo Morales, Z. Balog, M. I. Carnerero, E. Szegedi-Elek, A. Farkas, Th. Henning, J. Kelemen, [......], Sz. Mészáros, A. Moór, A. Pál, K. Sárneczky, R. Szakáts, N. Szalai, A. Szing, I. Tóth, N. J. Turner, K. Vida
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  ABSTRACT: Context. V2492 Cyg is a young eruptive star that went into outburst in 2010. The near-infrared color 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 \mu m and 2.2 \mu m from the ground and between 3.6 \mu m and 160 \mu m from space. Methods. We analyze the light curves and study the color-color 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 that 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 analog 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 also have consequences for the initial conditions of planet formation.
  01/2013;
• Source

  Available from: Attila Szing

  Article: A Peculiar Young Eruptive Star in the Dark Cloud Lynds 1340

  M. Kun, E. Szegedi-Elek, A. Moór, P. Ábrahám, J. A. Acosta-Pulido, D. Apai, J. Kelemen, A. Pál, M. Rácz, Zs. Regály, R. Szakáts, N. Szalai, and A. Szing
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  ABSTRACT: We conducted a long-term optical photometric and spectroscopic monitoring of the strongly variable, accreting young sun-like star [KOS94] HA11, associated with the dark cloud Lynds 1340 that exhibited large amplitude (5-6 mag in the I C band) brightness variations on 2-3 years timescales, flat spectral energy distribution (SED), and extremely strong (300 EW/Å 900) Hα emission. In this Letter we describe the basic properties of the star, derived from our observations between 1999 and 2011, and put into context the observed phenomena. The observed variations in the emission spectra, near-infrared colors, and SED suggest that [KOS94] HA11 (spectral type: K7-M0) is an eruptive young star, possibly similar in nature to V1647 Ori: its large-scale photometric variations are governed by variable accretion rate, associated with variations in the inner disk structure. The star recently has undergone strong and rapid brightness variations, thus its further observations may offer a rare opportunity for studying structural and chemical rearrangements of the inner disk, induced by variable central luminosity.
  The Astrophysical Journal Letters 04/2011; 733(1):L8. · 5.53 Impact Factor