THE 2008 OUTBURST OF EX Lup—SILICATE CRYSTALS IN MOTION

Juhász, A.; Dullemond, C. P.; Boekel, R. van; Bouwman, J.; Ábrahám, P.; Acosta–Pulido, J. A.; Henning, Th.; Kóspál, Á.; Sicilia‐Aguilar, A.; Jones, A. F.; Moór, A.; Mosoni, L.; Regály, Zs.; Szokoly, G. P.; Sipos, N.

doi:10.1088/0004-637x/744/2/118

Cited by 60 publications

(115 citation statements)

References 60 publications

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“…In outburst, the accretion luminosity overwhelms the stellar luminosity, so the measured rate should be more accurate. The outburst accretion rate (a few times 10 −8 M /yr; SA12; Juhász et al 2012) is high, but not extreme, for a low-mass star, which is also in agreement with a very low rate during the quiescence phases.…”

Section: Origin and Implications Of Stable Accretion Columns In Ex Lupisupporting

confidence: 71%

Accretion dynamics of EX Lupi in quiescence

Sicilia‐Aguilar¹,

Fang²,

Roccatagliata³

et al. 2015

A&A

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Context. EX Lupi is a young, accreting M0 star and the prototype of EXor variable stars. Its spectrum is very rich in emission lines, including many metallic lines with narrow and broad components. The presence of a close companion has also been proposed, based on radial velocity signatures. Aims. We use the metallic emission lines to study the accretion structures and to test the companion hypothesis. Methods. We analyse 54 spectra obtained during five years of quiescence time. We study the line profile variability and the radial velocity of the narrow and broad metallic emission lines. We use the velocity signatures of different species with various excitation conditions and their time dependency to track the dynamics associated with accretion. Results. We observe periodic velocity variations in the broad and the narrow line components, consistent with rotational modulation. The modulation is stronger for lines with higher excitation potentials (e.g. He II), which are likely produced in a confined area very close to the accretion shock. Conclusions. We propose that the narrow line components are produced in the post-shock region, while the broad components originate in the more extended, pre-shock material in the accretion column. All the emission lines suffer velocity modulation due to the rotation of the star. The broad components are responsible for the line-dependent veiling observed in EX Lupi. We demonstrate that a rotationally modulated line-dependent veiling can explain the radial velocity signature of the photospheric absorption lines, making the close-in companion hypothesis unnecessary. The accretion structure is locked to the star and very stable during the five years of observations. Not all stars with similar spectral types and accretion rates show the same metallic emission lines, which could be related to differences in temperature and density in their accretion structure(s). The contamination of photospheric signatures by accretion-related processes can be turned into a very useful tool for determining the innermost details of the accretion channels in the proximity of the star. The presence of emission lines from very stable accretion columns will nevertheless be a very strong limitation for the detection of companions by radial velocity in young stars, given the similarity of the accretion-related signatures with those produced by a companion.

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Section: Origin and Implications Of Stable Accretion Columns In Ex Lupisupporting

confidence: 71%

Accretion dynamics of EX Lupi in quiescence

Sicilia‐Aguilar¹,

Fang²,

Roccatagliata³

et al. 2015

A&A

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“…We took the difference of the quiescent and the 2010 September SED between 1.25 and 3.8 μm and dereddened it by different values in the 6−12 mag range (Covey et al 2011). We found that, irrespective of the applied dereddening, the outburst component seems to have a temperature distribution rather than a single temperature blackbody (as opposed to EX Lup or HBC 722, Juhász et al 2012;Kóspál et al 2011).…”

Section: Spectral Energy Distributionsmentioning

confidence: 79%

“…Comparing the quiescent SED with the upper envelope SED (i.e., the SED representative of the peak brightness), it is evident that an extra emission component appeared in the system that caused brightening in the whole optical-to-far-infrared regime, even at 70 μm. Such an outburst component was observed in a number of eruptive objects, such as OO Ser (Kóspál et al 2007), V1647 Ori (Muzerolle et al 2005), and EX Lup (Juhász et al 2012). Assuming that this component is located in the center of the system, it is probably reddened by both circumstellar and interstellar extinction.…”

Section: Spectral Energy Distributionsmentioning

confidence: 87%

Exploring the circumstellar environment of the young eruptive star V2492 Cygni

Kóspál

Ábrahám

Acosta–Pulido

et al. 2013

A&A

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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 μm and 2.2 μm from the ground and between 3.6 μm and 160 μm 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.

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“…Interestingly, our finding of low abundances of enstatite echoes the study of crystallization processes during the violent outburst around EX Lupi. Ábrahám et al (2009) found evidence for the production of forsterite, but not of enstatite, within the first AU of the disk, a result later on confirmed by VLTI/MIPS observation (Juhasz et al 2012). …”

Section: A90 Page 20 Of 26mentioning

confidence: 88%

Transient dust in warm debris disks

Olofsson

Juhász

Henning

et al. 2012

A&A

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Context. Debris disks trace remnant reservoirs of leftover planetesimals in planetary systems. In the past years, a handful of "warm" debris disks have been discovered in which emission in excess starts in the mid-infrared. An interesting subset of these warm debris disks shows emission features in mid-infrared spectra, which points towards the presence of μm-sized dust grains, with temperatures above hundreds K. Given the ages of the host stars, the presence of these small grains is puzzling, and raises questions about their origin and survival in time.Aims. This study focuses on determining the mineralogy of the dust around seven debris disks with evidence for warm dust, based on Spitzer/IRS spectroscopic data, to provide new insights into the origin of the dust grains. Methods. We developed and present a new radiative transfer code (Debra) dedicated to spectral energy distribution (SED) modeling of optically thin disks. The Debra code is designed such that it can simultaneously determine dust composition and disk properties. We used this code on the SEDs of seven warm debris disks, in combination with recent laboratory experiments on dust optical properties. Results. We find that most, if not all, debris disks in our sample are experiencing a transient phase, suggesting a production of small dust grains on relatively short timescales. Dust replenishment should be efficient on timescales of months for at least three sources. From a mineralogical point of view, we find that crystalline pyroxene grains (enstatite) have low abundances compared to crystalline olivine grains. The main result of our study is that we find evidence for Fe-rich crystalline olivine grains (Fe/[Mg + Fe] ∼ 0.2) for several debris disks. This finding contrasts with studies of gas-rich protoplanetary disks, where Fe-bearing crystalline grains are usually not observed. Conclusions. These Fe-rich olivine grains, and the overall differences between the mineralogy of dust in Class II disks compared to debris disks suggests that the transient crystalline dust in warm debris disk is of a new generation. We discuss possible crystallization routes to explain our results, and also comment on the mechanisms that may be responsible for the production of small dust grains.

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THE 2008 OUTBURST OF EX Lup—SILICATE CRYSTALS IN MOTION

Cited by 60 publications

References 60 publications

Accretion dynamics of EX Lupi in quiescence

Accretion dynamics of EX Lupi in quiescence

Exploring the circumstellar environment of the young eruptive star V2492 Cygni

Transient dust in warm debris disks

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