Dissonance in harmony: The UV/optical periodic outbursts of ASASSN-14ko exhibit repeated bumps and rebrightenings

Abstract

ASASSN-14ko was identified as an abnormal periodic nuclear transient with a potential decreasing period. Its outbursts in the optical and UV bands have displayed a consistent and smooth "fast-rise and slow-decay" pattern since its discovery, which has recently experienced an unexpected alteration in the last two epochs, as revealed by our proposed high-cadence Swift observations. The new light curve profiles show a bump during the rising stages and a rebrightening during the declining stages, making them much broader and symmetrical than the previous ones. In the last two epochs, there is no significant difference in the X-ray spectral slope compared to the previous one, and its overall luminosity is lower than those of the previous epochs. The energy released in the early bump and rebrightening phases ($\sim 10^{50}$ erg) could be due to collision of the stripped stream from partial tidal disruption events (pTDEs) with an expanded accretion disk. We also discussed other potential explanations, such as disk instability and star-disk collisions. Further high-cadence multi-wavelength observations of subsequent cycles are encouraged to comprehend the unique periodic source with its new intriguing features.

arXiv commentAccepted for publication in ApJL, 10 pages, 6 figures

References in corpus (47)

• Astropy: A Community Python Package for Astronomy
• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• The Swift X-ray Telescope
• The Swift Ultra-Violet/Optical Telescope
• HI4PI: A full-sky HI survey based on EBHIS and GASS
• Understanding the Lomb-Scargle Periodogram
• Hydrodynamical Simulations to Determine the Feeding Rate of Black Holes by the Tidal Disruption of Stars: The Importance of the Impact Parameter and Stellar Structure
• A massive binary black-hole system in OJ287 and a test of general relativity
• Nine-hour X-ray quasi-periodic eruptions from a low-mass black hole galactic nucleus
• Multiwavelength Evidence for Quasi-periodic Modulation in the Gamma-ray Blazar PG 1553+113
• X-ray Quasi-Periodic Eruptions from two previously quiescent galaxies
• X-ray quasi-periodic eruptions from the galactic nucleus of RX J1301.9+2747
• Primary black hole spin in OJ287 as determined by the General Relativity centenary flare
• Equipotential Surfaces and Lagrangian points in Non-synchronous, Eccentric Binary and Planetary Systems
• Authenticating the Presence of a Relativistic Massive Black Hole Binary in OJ 287 Using its General Relativity Centenary Flare: Improved Orbital Parameters
• ASASSN-14ko is a Periodic Nuclear Transient in ESO 253-G003
• A milliparsec supermassive black hole binary candidate in the galaxy SDSS J120136.02+300305.5
• X-ray Quasi-periodic Eruptions driven by Star-Disc Collisions : Application to GSN069 and Probing the Spin of Massive Black Holes
• Interacting Stellar EMRIs as Sources of Quasi-Periodic Eruptions in Galactic Nuclei
• Repeating tidal disruptions in GSN 069: Long-term evolution and constraints on quasi-periodic eruptions' models
• Stellar transits across a magnetized accretion torus as a mechanism for plasmoid ejection
• Live to die another day: the rebrightening of AT2018fyk as a repeating partial tidal disruption event
• Tormund's return: Hints of quasi-periodic eruption features from a recent optical tidal disruption event
• Deciphering the extreme X-ray variability of the nuclear transient eRASSt J045650.3-203750: A likely repeating partial tidal disruption event
• Spitzer Observations of the Predicted Eddington Flare from Blazar OJ 287
• A long decay of X-ray flux and spectral evolution in the supersoft active galactic nucleus GSN 069
• Alive and kicking: A new QPE phase in GSN 069 revealing a quiescent luminosity threshold for QPEs
• Modified models of radiation pressure instability in application to 10, 10${}^5$, and 10${}^7$ $M_{\odot }$ accreting black holes
• Ultraluminous X-ray bursts in two ultracompact companions to nearby elliptical galaxies
• Monthly quasi-periodic eruptions from repeated stellar disruption by a massive black hole
• RX J1301.9+2747: A Highly Variable Seyfert Galaxy with Extremely Soft X-ray Emission
• Infrared echo and late-stage rebrightening of nuclear transient PS1-10adi: exploring Torus by tidal disruption event in active galactic nuclei
• The rebrightening of a ROSAT-selected tidal disruption event: repeated weak partial disruption flares from a quiescent galaxy?
• X-ray flares from the stellar tidal disruption by a candidate supermassive black hole binary
• Application of the disk instability model to all Quasi-Periodic Eruptions
• A simple and accurate prescription for the tidal disruption radius of a star and the peak accretion rate in tidal disruption events
• AT2019 avd: A tidal disruption event with a two-phase evolution
• Re-observing the NLS1 Galaxy RE J1034+396. II. New Insights on the Soft X-ray Excess, QPO and the Analogy with GRS 1915+105
• The Rapid X-ray and UV Evolution of ASASSN-14ko
• AT 2020wey and the class of faint and fast Tidal Disruption Events
• Fast, ultra-luminous X-ray bursts from tidal stripping of White Dwarfs by Intermediate-mass Black Holes
• Chandra, HST/STIS, NICER, Swift, and TESS Detail the Flare Evolution of the Repeating Nuclear Transient ASASSN-14ko
• Tidal disruption events from eccentric orbits and lessons learned from the noteworthy ASASSN-14ko
• Highly variable AGN from the XMM-Newton Slew Survey
• The radio detection and accretion properties of the peculiar nuclear transient AT 2019avd
• An Amusing Look at the Host of the Periodic Nuclear Transient ASASSN-14ko Reveals a Second AGN
• Angular Momentum Transfer in QPEs from Galaxy Nuclei

Cited by in corpus (11)

• The unluckiest star: A spectroscopically confirmed repeated partial tidal disruption event AT 2022dbl
• Rapid evolution of the recurrence time in the repeating partial tidal disruption event eRASSt J045650.3-203750
• Repeating Partial Tidal Encounters of Sun-like Stars Leading to their Complete Disruption
• Light-Curve Structure and Halpha Line Formation in the Tidal Disruption Event AT 2019azh
• Binary Stars Approaching Supermassive Black Holes: Tidal Break-up, Double Stellar Disruptions and Stellar Collision
• Unveiling the Cosmic Dance of Repeated Nuclear Transient ASASSN-14ko: Insights from Multiwavelength Observations
• Testing the Shock-cooling Emission Model from Star-Disk Collisions for Quasiperiodic Eruptions
• Diverse Emission Patterns from Precessing Super-Eddington Disks Formed in Tidal Disruption Events
• Repeating X-ray bursts: Interaction between a neutron star and clumps partially disrupted from a planet
• AT 2021hdr: A candidate tidal disruption of a gas cloud by a binary super massive black hole system
• Precursors in tidal disruption events: repeating, fast, and AGN-hosted TDEs