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

Abstract

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.

The Effelsberg survey of FU Orionis and EX Lupi objects

“…Instead, the non-detections may indicate that dense circumstellar envelopes have already been dispersed. For instance, the ammonia non-detection in the case of V1515 Cyg is consistent with a recent multi-wavelength SED analysis that found no clear sign of a massive circumstellar envelope (Szabó et al 2022).…”

“…The FUor class was defined by Herbig (1977) based on the common properties of FU Orionis, V1057 Cyg, and V1515 Cyg, often referred to as the classical FUors (see e.g. Clarke et al 2005;Szabó et al 2021Szabó et al , 2022. This class currently includes more than a dozen objects (e.g.…”

High Mass Inner Regions Found in Five Outbursting Sources

“…Within our small sample, there appears to be no trend in mass versus outburst classification, peak luminosity, nor most recently observed brightness (most up-to-date photometic observations for each source: Peneva et al 2009;Kopatskaya et al 2013;Ninan et al 2013;Ibryamov & Semkov 2021;Szabó et al 2022). Our two most massive sources are an FU Ori (V1057 Cyg) and EX Ori object (V2492 Cyg), which exhibit markedly different peak luminosities and time since outburst.…”

“…V1057 Cyg and V1515 Cyg, along with the namesake source FU Ori were the first three discovered and defined the class of FUOr-type objects (Herbig 1977). V1735 Cyg was discovered later and exhibited the characteristic sharp rise in luminosity followed by a slow decay with short-period modulations (Szabó et al 2022). V1647 Ori was at first categorized as an FU Ori-type object due to its extreme rise in luminosity; however, it has exhibited multiple significant outburst events since the first one was captured, and thus it has been classified as either borderline FU Ori/EX Or, or a "peculiar" source (Audard et al 2014;Connelley & Reipurth 2018;Fischer et al 2023).…”

Photometric and Spectroscopic Study of the EXor-like Eruptive Young Star Gaia19fct

“…As a result, we obtained that, except for a few random-like variations directly visible in the light curves, there is no significant variability that would last for at least a few consecutive cycles. This is reminiscent of the situation in V1057 Cyg (Szabó et al 2021) and V1515 Cyg (Szabó et al 2022), where the inner disk light is strongly reprocessed by the obscuring surrounding envelope (Szabó et al 2021).…”