Flickering in FU Orionis

Kenyon, Scott J.; Kolotilov, E. A.; Ibragimov, M. A.; Mattei, J. A.

doi:10.1086/308515

Cited by 62 publications

(75 citation statements)

References 53 publications

(53 reference statements)

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“…For FU Ori, Kenyon et al (2000) find a non-periodic variability of 33 mmag at the V band, after removal of a 17-day period with an amplitude of 9 mmag. They use a lower sampling rate (∼few per day) but consider a multiband (UBVR) data set, and conclude that 35 mmag variations (correlated over multiple color bands) must occur on timescales <1 day, comparable to the dynamic timescale of the inner disk.…”

Section: Comparison To Other Studies Of Young Stellar Objectsmentioning

confidence: 87%

“…Observations of T Tauri stars (Stassun et al 1999;Rucinski et al 2008) and Herbig Ae/Be stars (Rucinski et al 2010) find indications of the stellar rotation and asymmetry due to a collection of hot or cool spots (Herbst et al 2007), but only sparse evidence of direct accretion processes. Additionally, pulsations and random reddening events in young stellar objects were considered in Kenyon et al (2000) but found to be unlikely as the cause of observed ∼0.03 mag variability. Finally, some evidence for hour-timescale variability has been found in short-lived excited modes in shorter-duration outbursts, EXors (Bastien et al 2011), likely more evolved sources than FUors.…”

Section: Introductionmentioning

confidence: 99%

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Variability at the Edge: Optical Near/Ir Rapid-Cadence Monitoring of Newly Outbursting Fu Orionis Object HBC 722

Green

Robertson

Baek

et al. 2013

ApJ

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We present the detection of day-timescale periodic variability in the r-band lightcurve of newly outbursting FU Orionis-type object HBC 722, taken from >42 nights of observation with the CQUEAN instrument on the McDonald Observatory 2.1 m telescope. The optical/near-IR lightcurve of HBC 722 shows a complex array of periodic variability, clustering around 5.8-day (0.044 mag amplitude) and 1.28-day (0.016 mag amplitude) periods, after removal of overall baseline variation. We attribute the unusual number of comparable strength signals to a phenomenon related to the temporary increase in accretion rate associated with FUors. We consider semirandom "flickering," magnetic braking/field compression and rotational asymmetries in the disk instability region as potential sources of variability. Assuming that the 5.8-day period is due to stellar rotation and the 1.28-day period is indicative of Keplerian rotation at the inner radius of the accretion disk (at 2 R ), we derive a B-field strength of 2.2-2.7 kG, slightly larger than typical T Tauri stars. If instead the 5.8-day signal is from a disk asymmetry, the instability region has an outer radius of 5.4 R , consistent with models of FUor disks. Further exploration of the time domain in this complicated source and related objects will be key to understanding accretion processes.

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Section: Comparison To Other Studies Of Young Stellar Objectsmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Variability at the Edge: Optical Near/Ir Rapid-Cadence Monitoring of Newly Outbursting Fu Orionis Object HBC 722

Green

Robertson

Baek

et al. 2013

ApJ

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“…FU Ori is the prototype of the FU Orionis phenomenon. While the SIMBAD database lists a spectral type of G3Iavar, Kenyon et al (2000) changed it to G0II. In contrast to Hanner et al (1998), who measured an increasing MIR flux shortward of 10 μm, the spectra of Schegerer et al (2006) and Quanz et al (2006) agree very well with ours, indicating that this object was not variable in the MIR between Dec. 2002 and Jan. 2006 (or at least that any period of variability was not observed).…”

Section: Appendix A: Comments On Individual Sourcesmentioning

confidence: 99%

Mid-IR observations of circumstellar disks

Schuetz¹,

Meeus

Sterzik³

et al. 2009

A&A

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We present new mid-infrared spectra of 15 targets (1 FU Orionis object, 4 Herbig Ae stars, 5 T Tauri stars, and 5 Vega-type stars), obtained with the TIMMI2 camera at La Silla Observatory (ESO). Three targets are members of the β Pic moving group (HD 155 555, HD 181 296, and HD 319 139). PAH bands are observed towards the T Tauri star HD 34 700 and the Herbig Ae star PDS 144 N. For HD 34 700, the band profiles indicate processed PAHs. The spectrum of the Vega-type object η Corvi (HD 109 085), for which a resolved disk at sub-mm wavelengths is known, appears stellar between 8-13 μm, but a small excess emission was reported by Spitzer observations. Similarly, no indication of circumstellar matter at mid-infrared wavelengths is found towards the Vega-like stars HD 3003, HD 80 951, HD 181 296, and, surprisingly, the T Tauri system HD 155 555. The silicate emission features of the remaining eight sources are modelled with a mixture of silicates of different grain sizes and composition. Unprocessed dust dominates FU Ori, HD 143 006, and CD-43 344. Large amorphous grains are the main dust component around HD 190 073, HD 319 139, KK Oph, and PDS 144 S. Both small grains and crystalline dust is found for the Vega-type HD 123 356, with a dominance of small amorphous grains. We show that the infrared emission of the binary HD 123 356 is dominated by its late-type secondary, but optical spectroscopy is still required to confirm the age of the system and the spectral class of the companion. For most targets, this is their first mid-infrared spectroscopic observation. We investigate trends between stellar, disk, and silicate properties and confirm correlations identified in previous studies. Several objects present an exciting potential for follow-up high-resolution disk studies.

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“…The low mass pre-main sequence star FU Orionis (hereafter, FU Ori) brightened by ∆B = 6 mag in 1936 (Herbig 1977), and subsequently has declined slowly (∼ 0.013 mag/yr; Kenyon et al 2000) to the present day. This outburst established a prototype class of variable star (FU Orionis objects, or "FUors"; Hartmann & Kenyon 1996;Hartmann 1998) that ∼10 other stars have since matched.…”

Section: Introductionmentioning

confidence: 99%

TESTING THE BINARY TRIGGER HYPOTHESIS IN FUors

Green

Kraus

Rizzuto

et al. 2016

ApJ

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We present observations of three FU Orionis objects (hereafter, FUors) with nonredundant aperturemask interferometry (NRM) at 1.59 µm and 2.12 µm that probe for binary companions on the scale of the protoplanetary disk that feeds their accretion outbursts. We do not identify any companions to V1515 Cyg or HBC 722, but we do resolve a close binary companion to V1057 Cyg that is at the diffraction limit (ρ = 58.3 ± 1.4 mas or 30 ± 5 AU) and currently much fainter than the outbursting star (∆K ′ = 3.34 ± 0.10 mag). Given the flux excess of the outbursting star, we estimate that the mass of the companion (M ∼ 0.25M ⊙ ) is similar to or slightly below that of the FUor itself, and therefore it resembles a typical T Tauri binary system. Our observations only achieve contrast limits of ∆K ′ ∼ 4 mag, and hence we are only sensitive to companions that were near or above the pre-outburst luminosity of the FUors. It remains plausible that FUor outbursts could be tied to the presence of a close binary companion. However, we argue from the system geometry and mass reservoir considerations that these outbursts are not directly tied to the orbital period (i.e., occurring at periastron passage), but instead must only occur infrequently.

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Flickering in FU Orionis

Cited by 62 publications

References 53 publications

Variability at the Edge: Optical Near/Ir Rapid-Cadence Monitoring of Newly Outbursting Fu Orionis Object HBC 722

Variability at the Edge: Optical Near/Ir Rapid-Cadence Monitoring of Newly Outbursting Fu Orionis Object HBC 722

Mid-IR observations of circumstellar disks

TESTING THE BINARY TRIGGER HYPOTHESIS IN FUors

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