Dissonance in Harmony: The UV/Optical Periodic Outbursts of ASASSN-14ko Exhibit Repeated Bumps and Rebrightenings

Huang, Shifeng; Jiang, Ning; Shen, Rong-Feng; Wang, Tinggui; Sheng, Zhenfeng

doi:10.3847/2041-8213/acffc5

Cited by 9 publications

(5 citation statements)

References 62 publications

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“…In contrast, the pTDE candidate ASASSN-14ko recently showed noticeable bumps before the main UV/ optical peaks and rebrightenings after that. This can be interpreted as a consequence of the collision between the stream debris and the extended disk in the pTDE scenario (Huang et al 2023b), which distinguishes it from AT 2023lli and other TDEs.…”

Section: Comparison With Bumps In Other Tdesmentioning

confidence: 99%

“…Most TDEs that have been discovered so far exhibit a smooth single-peak light curve in both UV and optical bands. However, some of them display a bump in the rising phase of their light curves (Holoien et al 2019;Charalampopoulos et al 2023;Faris et al 2023;Huang et al 2023b;Wang et al 2023b;Z. Lin et al 2024, in preparation).…”

Section: Introductionmentioning

confidence: 99%

“…But no definitive conclusion has been reached. The collision between stream debris and the disk was proposed to explain the early bump in recent UV/optical outbursts of the candidate for repeated partial TDE (pTDE) ASASSN-14ko (Huang et al 2023b). Furthermore, a fraction of the sources appeared to rebrighten in the optical light curve as the duration of observation increased (Jiang et al 2019;Malyali et al 2021;Chen et al 2022;Wang et al 2023c;Yao et al 2023).…”

Section: Introductionmentioning

confidence: 99%

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AT 2023lli: A Tidal Disruption Event with Prominent Optical Early Bump and Delayed Episodic X-Ray Emission

Huang,

Jiang,

Zhu

et al. 2024

ApJL

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High-cadence, multiwavelength observations have continuously revealed the diversity of tidal disruption events (TDEs), thus greatly advancing our knowledge and understanding of TDEs. In this work, we conducted an intensive optical-UV and X-ray follow-up campaign of TDE AT 2023lli and found a remarkable month-long bump in its UV/optical light curve nearly 2 months prior to maximum brightness. The bump represents the longest separation time from the main peak among known TDEs to date. The main UV/optical outburst declines as t −4.10, making it one of the fastest-decaying optically selected TDEs. Furthermore, we detected sporadic X-ray emission 30 days after the UV/optical peak, accompanied by a reduction in the period of inactivity. It is proposed that the UV/optical bump could be caused by the self-intersection of the stream debris, whereas the primary peak is generated by the reprocessed emission of the accretion process. In addition, our results suggest that episodic X-ray radiation during the initial phase of decline may be due to the patched obscurer surrounding the accretion disk, a phenomenon associated with the inhomogeneous reprocessing process. The double TDE scenario, in which two stars are disrupted in sequence, is also a possible explanation for producing the observed early bump and main peak. We anticipate that the multicolor light curves of TDEs, especially in the very early stages, and the underlying physics can be better understood in the near future with the assistance of dedicated surveys such as the deep high-cadence survey of the 2.5 m Wide Field Survey Telescope.

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Section: Comparison With Bumps In Other Tdesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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AT 2023lli: A Tidal Disruption Event with Prominent Optical Early Bump and Delayed Episodic X-Ray Emission

Huang,

Jiang,

Zhu

et al. 2024

ApJL

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“…ASASSN-14ko (Holoien et al 2014a) is another nuclear transient with a bump reported in its rising phase (Huang et al 2023). However, it displays spectra more similar to those of AGNs (Payne et al 2021) and periodicity in its outbursts (Payne et al 2021(Payne et al , 2022(Payne et al , 2023, which are not seen in the class of TDEs to which AT 2019azh belongs.…”

Section: Early Light-curve Structurementioning

confidence: 99%

Light-curve Structure and Hα Line Formation in the Tidal Disruption Event AT 2019azh

Faris,

Arcavi,

Makrygianni

et al. 2024

ApJ

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AT 2019azh is a H+He tidal disruption event (TDE) with one of the most extensive ultraviolet and optical data sets available to date. We present our photometric and spectroscopic observations of this event starting several weeks before and out to approximately 2 yr after the g-band's peak brightness and combine them with public photometric data. This extensive data set robustly reveals a change in the light-curve slope and a possible bump in the rising light curve of a TDE for the first time, which may indicate more than one dominant emission mechanism contributing to the pre-peak light curve. Indeed, we find that the MOSFiT-derived parameters of AT 2019azh, which assume reprocessed accretion as the sole source of emission, are not entirely self-consistent. We further confirm the relation seen in previous TDEs whereby the redder emission peaks later than the bluer emission. The post-peak bolometric light curve of AT 2019azh is better described by an exponential decline than by the canonical t −5/3 (and in fact any) power-law decline. We find a possible mid-infrared excess around the peak optical luminosity, but cannot determine its origin. In addition, we provide the earliest measurements of the Hα emission-line evolution and find no significant time delay between the peak of the V-band light curve and that of the Hα luminosity. These results can be used to constrain future models of TDE line formation and emission mechanisms in general. More pre-peak 1–2 days cadence observations of TDEs are required to determine whether the characteristics observed here are common among TDEs. More importantly, detailed emission models are needed to fully exploit such observations for understanding the emission physics of TDEs.

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“…Alternatively, multiple independent TDEs could be supported by an enhanced TDE rate due to the concentrated nuclear stellar profile, e.g., in post-starburst galaxies (e.g., Arcavi et al 2014;Hammerstein et al 2021;Bortolas 2022;Wang et al 2024) or galaxies with nuclear star clusters (Pfister et al 2020). Despite the challenges, several candidates for repeated pTDE have been reported, e.g., IC 3599 (Campana et al 2015), ASASSN-14ko (Payne et al 2021, 2022, 2023Huang et al 2023), Swift J023017.0+283603 (Evans et al 2023;Guolo et al 2024b), eRASSt J045650.3-203750 (Z. Liu et al 2023, AT 2018fyk (Wevers et al 2023;Pasham et al 2024), RX J133157.6-324319.7 (Hampel et al 2022Malyali et al 2023), and AT 2020vdq (Somalwar et al 2023b). The great diversity of the flaring intervals, bands, and shapes (listed in Table 2) among these sources calls for additional theoretical efforts.…”

Section: Introductionmentioning

confidence: 99%

The Unluckiest Star: A Spectroscopically Confirmed Repeated Partial Tidal Disruption Event AT 2022dbl

Lin,

Jiang,

Wang

et al. 2024

ApJL

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The unluckiest star orbits a supermassive black hole elliptically. Every time it reaches the pericenter, it shallowly enters the tidal radius and gets partially tidally disrupted, producing a series of flares. Confirmation of a repeated partial tidal disruption event (pTDE) requires not only evidence to rule out other types of transients but also proof that only one star is involved, as TDEs from multiple stars can also produce similar flares. In this Letter, we report the discovery of a repeated pTDE, AT 2022dbl. In a quiescent galaxy at z = 0.0284, two separate optical/UV flares have been observed in 2022 and 2024 with no bright X-ray, radio, or mid-infrared counterparts. Compared to the first flare, the second flare has a similar blackbody temperature of ∼26,000 K, slightly lower peak luminosity, and slower rise and fall phases. Compared to the Zwicky Transient Facility TDEs, their blackbody parameters and light-curve shapes are all similar. The spectra taken during the second flare show a steeper continuum than the late-time spectra of the previous flare, consistent with a newly risen flare. More importantly, the possibility of two independent TDEs can be largely ruled out because the optical spectra taken around the peak of the two flares exhibit highly similar broad Balmer, N iii, and possible He ii emission lines, especially the extreme ∼4100 Å emission lines. This represents the first robust spectroscopic evidence for a repeated pTDE, which can soon be verified by observing the third flare, given its short orbital period.

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Dissonance in Harmony: The UV/Optical Periodic Outbursts of ASASSN-14ko Exhibit Repeated Bumps and Rebrightenings

Cited by 9 publications

References 62 publications

AT 2023lli: A Tidal Disruption Event with Prominent Optical Early Bump and Delayed Episodic X-Ray Emission

AT 2023lli: A Tidal Disruption Event with Prominent Optical Early Bump and Delayed Episodic X-Ray Emission

Light-curve Structure and Hα Line Formation in the Tidal Disruption Event AT 2019azh

The Unluckiest Star: A Spectroscopically Confirmed Repeated Partial Tidal Disruption Event AT 2022dbl

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