Repeating Outbursts from the Young Stellar Object Gaia23bab (= SPICY 97589)

Repeating periodic eruptions of the supernova impostor SN 2000ch

We analyse photometric observations of the supernova (SN) impostor SN 2000ch in NGC 3432 covering the time since its discovery. This source was previously observed to have four outbursts in 2000-2010. Observations now reveal at least three additional outbursts in 2004-2007, and sixteen outbursts in 2010-2022. Outburst light curves are irregular and multipeaked, exhibiting a wide variety of peak magnitude, duration, and shape. The outbursts after 2008 repeat with a period of 200.7$\pm{2}$ d, while the outburst in 2000 seems to match with a shorter period. The next outburst should occur around J…

Flickering returns as RS Oph reestablishes quiescent conditions following its 2021 nova outburst

RS Oph has persistently displayed flickering at optical wavelengths when observed away from its repeating nova outbursts. During the 2006 eruption the flickering disappeared, and this repeated during the recent 2021 event. We have been monitoring RS Oph looking for the reappearance of flickering at B-band following the 2021 outburst. The flickering was still absent (sigma(B)<0.002 mag) on day +210 (counted from nova optical maximum), appeared at sigma(B)=0.008 mag on day +224, and raised to sigma(B)=0.029 mag on day +250. On following dates the amplitude remained large, although fluctuating. T…

The Gravo-Magneto Limit Cycle in Accretion Disks

Previous theoretical studies have found that repeating outbursts can occur in certain regions of an accretion disk, due to sudden transitions in time from gravitationally produced turbulence to magnetically produced turbulence. We analyze the disk evolution in a state diagram that plots the mass accretion rate versus disk surface density. We determine steady state accretion branches that involve gravitational and magnetic sources of turbulence. Using time-dependent numerical disk simulations, we show that cases having outbursts track along a nonsteady 'dead zone' branch and some steady state a…

A survey for variable young stars with small telescopes: VI -- Analysis of the outbursting Be stars NSW284, Gaia19eyy, and VES263

This paper is one in a series reporting results from small telescope observations of variable young stars. Here, we study the repeating outbursts of three likely Be stars based on long-term optical, near-infrared, and mid-infrared photometry for all three objects, along with follow-up spectra for two of the three. The sources are characterised as rare, truly regularly outbursting Be stars. We interpret the photometric data within a framework for modelling light curve morphology, and find that the models correctly predict the burst shapes, including their larger amplitudes and later peaks towar…

年轻恒星 V1741 Sgr 的 2022-2023 年吸积爆发

The 2022-2023 accretion outburst of the young star V1741 Sgr

本文通过光学与红外监测研究了年轻恒星 V1741 Sgr 在 2022-2023 年发生的 EXor 型吸积爆发，结合光谱温度变化和能谱分布分析，提出爆发由恒星表面之外的星周气体连续谱发射主导，并用气体冷却解释 TiO 吸收的出现与消失。

A peculiar interacting Be star binary in the Small Magellanic Cloud

We find that the emission line object OGLEJ005039.05-725751.4, a member of the cluster OGLE-CL SMC 64, exhibits a peculiar light curve pattern repeating with a recurrence time of 141.45 days. The light curve resembles periodic outbursts with a duty cycle of 20%. A second long-cycle of 2500 days is also detected in the photometric dataset. Two X-SHOOTER spectra obtained at minimum and maximum reveal a Be star dominating at minimum light resembling the Classical Be star 48 Lib. The larger H$α$ emission, the stronger NaD absorption and the appearance of emission in the infrared Ca II triplet at m…

利用 ZTF 和 TESS 数据表征 VY Scl CVs 中的高低吸积态

Characterising high and low accretion states in VY Scl CVs using ZTF and TESS data

本文利用 ZTF 和 TESS 数据分析了 VY Scl 激变变星的高低吸积态转换，发现系统状态分布差异，并探讨了颜色变化、周期性及现有理论模型。

Periodic Eruptive Variability of the Isolated Pre-Main Sequence Star V347 Aurigae

V347 Aurigae is associated with the small dark cloud L1438 and appears to be an isolated pre-main sequence star located at distance $d\approx$200 pc. Multi-epoch, archival photometry reveals periodic brightness variations with amplitude $V\approx2.0$ magnitudes occurring on timescales of $\sim$160 days that have persisted for decades. Regular cadence, optical imaging of the source with the Zwicky Transient Facility shows that a small reflection nebula illuminated by V347 Aur also fluctuates in brightness, at times fading completely. Multi-epoch, Keck/HIRES data suggests the presence of two dis…

FUOR 中吸积爆发起源的研究

On the origin of accretion bursts in FUORs

本文通过恒星演化代码模拟行星质量损失过程，揭示绝热行星膨胀引发失控 FUOR 爆发、超绝热行星收缩导致爆发断续的机制，并利用中红外与光学辐射的时间延迟特征区分不同爆发模型，为 FU Ori 等年轻恒星吸积爆发起源提供新解释。