High-resolution Spectroscopic Monitoring Observations of FU Orionis–type Object, V960 Mon

Ábrahám

et al. 2021

ApJ

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Among the low-mass pre-main sequence stars, a small group called FU Orionis-type objects (FUors) are notable for undergoing powerful accretion outbursts. V1057 Cyg, a classical example of an FUor, went into outburst around 1969 -1970, after which it faded rapidly, making it the fastest fading FUor known. Around 1995, a more rapid increase in fading occurred. Since that time, strong photometric modulations have been present. We present nearly 10 years of source monitoring at Piszkéstető Observatory, complemented with optical/near-infrared photometry and spectroscopy from the Nordic Optical Telescope, Bohyunsan Optical Astronomy Observatory, Transiting Exoplanet Survey Satellite, and the Stratospheric Observatory for Infrared Astronomy. Our light curves show continuation of significant quasi-periodic variability in brightness over the past decade. Our spectroscopic observations show strong wind features, shell features, and forbidden emission lines. All of these spectral lines vary with time. We also report the first detection of [S II], [N II], and [O III] lines in the star.

Section: Optical Spectroscopymentioning

confidence: 77%

A Study of the Photometric and Spectroscopic Variations of the Prototypical FU Orionis–type Star V1057 Cyg

Szabó

Ábrahám

et al. 2021

ApJ

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“…Only V346 Nor shows several H 2 emission lines similar to V899 Mon. The H 2 2.122 µm emission line was detected in the FUor V960 Mon (Park et al 2020) and in some EXors (Kóspál et al 2011a;Hodapp et al 2019Hodapp et al , 2020, however, none of the other H 2 transitions were detected.…”

Section: Molecular Hydrogen Linesmentioning

confidence: 91%

“…Na I 2.2062 µm line is blended by Si I 2.2069 µm line; therefore, we did not measure the HWHD of this line. A general trend of HWHD decreases with increasing wavelength, suggesting that these atomic lines are formed at the disk (Zhu et al 2009;Lee et al 2015;Park et al 2020).…”

Section: Permitted Atomic Linesmentioning

confidence: 96%

V899 Mon: A Peculiar Eruptive Young Star Close to the End of Its Outburst

Park

Miera

et al. 2021

ApJ

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The eruptive young star V899 Mon shows characteristics of both FUors and EXors. It reached a peak brightness in 2010, then briefly faded in 2011, followed by a second outburst. We conducted multifilter optical photometric monitoring, as well as optical and near-infrared spectroscopic observations, of V899 Mon. The light curves and color–magnitude diagrams show that V899 Mon has been gradually fading after its second outburst peak in 2018, but smaller accretion bursts are still happening. Our spectroscopic observations taken with Gemini/IGRINS and VLT/MUSE show a number of emission lines, unlike during the outbursting stage. We used the emission line fluxes to estimate the accretion rate and found that it has significantly decreased compared to the outbursting stage. The mass-loss rate is also weakening. Our 2D spectroastrometric analysis of emission lines recovered jet and disk emission of V899 Mon. We found that the emission from permitted metallic lines and the CO bandheads can be modeled well with a disk in Keplerian rotation, which also gives a tight constraint for the dynamical stellar mass of 2 M ⊙. After a discussion of the physical changes that led to the changes in the observed properties of V899 Mon, we suggest that this object is finishing its second outburst.

“…In order to estimate the rotational velocity (vsini), we convolved the stellar spectrum with a Gaussian profile to account for the rotational broadening of the lines and compared their spectra to V1515 Cyg. For this analysis, we adopted the standard stellar spectra from F8 to G8 supergiants used in Park et al (2020), which are observed with the same observing setup as V1515 Cyg. First, we averaged four spectral lines (Fe I 6141.7, Fe I 6411.6, Ca I 6439.1, and Fe I 7511.0 Å) by normalizing each peak intensity for V1515 Cyg and standard stars.…”

Section: Optical Spectroscopymentioning

confidence: 99%

A Multi-epoch, Multiwavelength Study of the Classical FUor V1515 Cyg Approaching Quiescence

Szabó

Ábrahám

et al. 2022

ApJ

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Historically, FU Orionis-type stars are low-mass, pre-main-sequence stars. The members of this class experience powerful accretion outbursts and remain in an enhanced accretion state for decades or centuries. V1515 Cyg, a classical FUor, started brightening in the 1940s and reached its peak brightness in the late 1970s. Following a sudden decrease in brightness, it stayed in a minimum state for a few months, then started brightening for several years. We present the results of our ground-based photometric monitoring complemented with optical/near-infrared spectroscopic monitoring. Our light curves show a long-term fading with strong variability on weekly and monthly timescales. The optical spectra show P Cygni profiles and broad blueshifted absorption lines, common properties of FUors. However, V1515 Cyg lacks the P Cygni profile in the Ca ii 8498 Å line, a part of the Ca infrared triplet, formed by an outflowing wind, suggesting that the absorbing gas in the wind is optically thin. The newly obtained near-infrared spectrum shows the strengthening of the CO bandhead and the FeH molecular band, indicating that the disk has become cooler since the last spectroscopic observation in 2015. The current luminosity of the accretion disk dropped from the peak value of 138 L ⊙ to about 45 L ⊙, suggesting that the long-term fading is also partly caused by the dropping of the accretion rate.