Abstract Supermassive black holes can experience super-Eddington peak mass fallback rates following the tidal disruption of a star. The theoretical expectation is that part of the infalling material ...is expelled by means of an accretion disk wind, whose observational signature includes blueshifted absorption lines of highly ionized species in X-ray spectra. To date, however, only one such ultrafast outflow (UFO) has been reported in the tidal disruption event (TDE) ASASSN–14li. Here we report on the discovery of a transient absorption-like signature in X-ray spectra of the TDE AT2020ksf/Gaia20cjk (at a redshift of z = 0.092), following an X-ray brightening ∼230 days after UV/optical peak. We find that while no statistically significant absorption features are present initially, they appear on a timescale of several days and remain detected up to 770 days after peak. Simple thermal continuum models, combined with a power-law or neutral absorber, do not describe these features well. Adding a partial-covering, low-velocity ionized absorber improves the fit at early times but fails at late times. A high-velocity ( v w ∼ 42,000 km s −1 ), ionized absorber (UFO) provides a good fit to all data. The few-day timescale of variability is consistent with expectations for a clumpy wind. We discuss several scenarios that could explain the X-ray delay, as well as the potential for larger-scale wind feedback. The serendipitous nature of the discovery could suggest a high incidence of UFOs in TDEs, alleviating some of the tension with theoretical expectations.
Abstract
Stars that interact with supermassive black holes (SMBHs) can be either completely or partially destroyed by tides. In a partial tidal disruption event (TDE), the high-density core of the ...star remains intact, and the low-density outer envelope of the star is stripped and feeds a luminous accretion episode. The TDE AT 2018fyk, with an inferred black hole mass of 10
7.7±0.4
M
⊙
, experienced an extreme dimming event at X-ray (factor of >6000) and UV (factor of ∼15) wavelengths ∼500–600 days after discovery. Here we report on the reemergence of these emission components roughly 1200 days after discovery. We find that the source properties are similar to those of the predimming accretion state, suggesting that the accretion flow was rejuvenated to a similar state. We propose that a repeated partial TDE, where the partially disrupted star is on an ∼1200 day orbit about the SMBH and periodically stripped of mass during each pericenter passage, powers its unique light curve. This scenario provides a plausible explanation for AT 2018fyk’s overall properties, including the rapid dimming event and the rebrightening at late times. We also provide testable predictions for the behavior of the accretion flow in the future; if the second encounter was also a partial disruption, then we predict another strong dimming event around day 1800 (2023 August) and a subsequent rebrightening around day 2400 (2025 March). This source provides strong evidence of the partial disruption of a star by an SMBH.
Abstract In the past 5 yr, six X-ray quasi-periodic eruption (QPE) sources have been discovered in the nuclei of nearby galaxies. Their origin remains an open question. We present Multi Unit ...Spectroscopic Explorer integral field spectroscopy of five QPE host galaxies to characterize their properties. We find that 3/5 galaxies host extended emission-line regions (EELRs) up to 10 kpc in size. The EELRs are photoionized by a nonstellar continuum, but the current nuclear luminosity is insufficient to power the observed emission lines. The EELRs are decoupled from the stars both kinematically and in projected sky position, and the low velocities and velocity dispersions (<100 km s −1 and ≲75 km s −1 , respectively) are inconsistent with being driven by active galactic nuclei (AGNs) or shocks. The origin of the EELRs is likely a previous phase of nuclear activity. QPE host galaxies share several similarities with tidal disruption event (TDE) hosts, including an overrepresentation of galaxies with strong Balmer absorption and little ongoing star formation, as well as a preference for a short-lived (the typical EELR lifetime is ∼15,000 yr), gas-rich phase where the nucleus has recently faded significantly. This suggests that QPEs and TDEs may share a common formation channel, disfavoring AGN accretion disk instabilities as the origin of QPEs. If QPEs are related to extreme mass ratio inspiral systems (EMRIs), e.g., stellar-mass objects on bound orbits about massive black holes, the high incidence of EELRs and recently faded nuclei could be used to localize the hosts of EMRIs discovered by low-frequency gravitational-wave observatories.
Aims.
The modelling of spectroscopic observations of tidal disruption events (TDEs) to date suggests that the newly formed accretion disks are mostly quasi-circular. In this work we study the ...transient event AT 2020zso, hosted by an active galactic nucleus (AGN; as inferred from narrow emission line diagnostics), with the aim of characterising the properties of its newly formed accretion flow.
Methods.
We classify AT 2020zso as a TDE based on the blackbody evolution inferred from UV/optical photometric observations and spectral line content and evolution. We identify transient, double-peaked Bowen (N
III
), He
I
, He
II,
and H
α
emission lines. We model medium-resolution optical spectroscopy of the He
II
(after careful de-blending of the N
III
contribution) and H
α
lines during the rise, peak, and early decline of the light curve using relativistic, elliptical accretion disk models.
Results.
We find that the spectral evolution before the peak can be explained by optical depth effects consistent with an outflowing, optically thick Eddington envelope. Around the peak, the envelope reaches its maximum extent (approximately 10
15
cm, or ∼3000–6000 gravitational radii for an inferred black hole mass of 5−10 × 10
5
M
⊙
) and becomes optically thin. The H
α
and He
II
emission lines at and after the peak can be reproduced with a highly inclined (
i
= 85 ± 5 degrees), highly elliptical (
e
= 0.97 ± 0.01), and relatively compact (
R
in
= several 100
R
g
and
R
out
= several 1000
R
g
) accretion disk.
Conclusions.
Overall, the line profiles suggest a highly elliptical geometry for the new accretion flow, consistent with theoretical expectations of newly formed TDE disks. We quantitatively confirm, for the first time, the high inclination nature of a Bowen (and X-ray dim) TDE, consistent with the unification picture of TDEs, where the inclination largely determines the observational appearance. Rapid line profile variations rule out the binary supermassive black hole hypothesis as the origin of the eccentricity; these results thus provide a direct link between a TDE in an AGN and the eccentric accretion disk. We illustrate for the first time how optical spectroscopy can be used to constrain the black hole spin, through (the lack of) disk precession signatures (changes in inferred inclination). We constrain the disk alignment timescale to > 15 days in AT2020zso, which rules out high black hole spin values (
a
< 0.8) for
M
BH
∼ 10
6
M
⊙
and disk viscosity
α
≳ 0.1.
Abstract
We present UV and/or optical observations and models of SN 2023ixf, a type II supernova (SN) located in Messier 101 at 6.9 Mpc. Early time (
flash
) spectroscopy of SN 2023ixf, obtained ...primarily at Lick Observatory, reveals emission lines of H
i
, He
i/ii
, C
iv
, and N
iii/iv/v
with a narrow core and broad, symmetric wings arising from the photoionization of dense, close-in circumstellar material (CSM) located around the progenitor star prior to shock breakout. These electron-scattering broadened line profiles persist for ∼8 days with respect to first light, at which time Doppler broadened the features from the fastest SN ejecta form, suggesting a reduction in CSM density at
r
≳ 10
15
cm. The early time light curve of SN 2023ixf shows peak absolute magnitudes (e.g.,
M
u
= −18.6 mag,
M
g
= −18.4 mag) that are ≳2 mag brighter than typical type II SNe, this photometric boost also being consistent with the shock power supplied from CSM interaction. Comparison of SN 2023ixf to a grid of light-curve and multiepoch spectral models from the non-LTE radiative transfer code
CMFGEN
and the radiation-hydrodynamics code
HERACLES
suggests dense, solar-metallicity CSM confined to
r
= (0.5–1) × 10
15
cm, and a progenitor mass-loss rate of
M
̇
=
10
−
2
M
⊙
yr
−1
. For the assumed progenitor wind velocity of
v
w
= 50 km s
−1
, this corresponds to enhanced mass loss (i.e.,
superwind
phase) during the last ∼3–6 yr before explosion.
Hemodialysed patients with no history of porphyria may present neurological symptoms similar to those seen in acute porphyrias. Porphyria has been associated with an increase in plasma levels of ...5-aminolevulinic acid and porphobilinogen. Our aim was to evaluate these parameters and the activities of the enzymes involved in the first steps of heme metabolism in non-porphyric hemodialysed patients. The activities of 5-aminolevulinate dehydratase and deaminase were determined in red blood cells (RBC) from 78 hemodialysed patients, before and after dialysis. Plasma levels of 5-aminolevulinic acid, porphobilinogen and zinc were also measured. These parameters were also measured in 40 volunteers to obtain controls levels. The levels of 5-aminolevulinic acid (0.98 +/- 0.09 microgram/ml) and porphobilinogen (1.32 +/- 0.13 micrograms/ml) were raised in non-porphyric patients prior to hemodialysis (P < 0.001) compared with controls (5-aminolevulinic acid 0.13 +/- 0.02 microgram/ml; porphobilinogen 0.90 +/- 0.09 microgram/ml). After dialysis there was a decrease in both 5-aminolevulinic acid (to 0.61 +/- 0.05 microgram/ml) and porphobilinogen (to 1.10 +/- 0.16 micrograms/ml) although both parameters remained higher than controls (P < 0.001). The activities of both 5-aminolevulinate dehydratase (0.550 +/- 0.095 U/ml RBC), and deaminase (54.13 +/- 9.13 U/ml RBC) were diminished in blood samples of patients before dialysis (P < 0.001) compared to controls (dehydratase 0.975 +/- 0.115 U/ml RBC; deaminase 77.32 +/- 10.00 U/ml RBC). After dialysis 5-aminolevulinate dehydratase activity was partially recovered (to 0.666 +/- 0.100 U/ml RBC) while deaminase returned to normal values (73.45 +/- 9.46 U/ml RBC). The plasma zinc concentration in hemodialysed patients (44 +/- 12 micrograms/100 ml) was significantly lower than controls (105 +/- 30 micrograms/100 ml, P < 0.001). Addition of 22.5 mM zinc to the dehydratase reaction mixture raised the activity of 5-aminolevulinate dehydratase in blood samples of hemodialysed patients taken before and after dialysis. The study reports a partial loss of activity of 5-aminolevulinate dehydratase and deaminase activities in red blood cells from non-porphyric patients undergoing hemodialysis. Since plasma zinc levels were below normal in hemodialysed patients, and the activity of 5-aminolevulinate dehydratase could be restored by the addition of zinc, it is suggested that these abnormalities in heme metabolism may be explained by altered zinc and associated antioxidant status following dialysis.
Supermassive black holes can experience super-Eddington peak mass fallback rates following the tidal disruption of a star. The theoretical expectation is that part of the infalling material is ...expelled by means of an accretion disk wind, whose observational signature includes blueshifted absorption lines of highly ionized species in X-ray spectra. To date, however, only one such ultra-fast outflow (UFO) has been reported in the tidal disruption event (TDE) ASASSN-14li. Here we report on the discovery of transient absorption-like signatures in X-ray spectra of the TDE AT2020ksf/Gaia20cjk (at a redshift of \(z\)=0.092), following an X-ray brightening \(\sim 230\) days after UV/optical peak. We find that while no statistically significant absorption features are present initially, they appear on a timescale of several days, and remain detected up to 770 days after peak. Simple thermal continuum models, combined with a power-law or neutral absorber, do not describe these features well. Adding a partial covering, low velocity ionized absorber improves the fit at early times, but fails at late times. A high velocity (v\(_w\) \(\sim\) 42000 km s\(^{-1}\), or -0.15c), ionized absorber (ultra-fast outflow) provides a good fit to all data. The few day timescale of variability is consistent with expectations for a clumpy wind. We discuss several scenarios that could explain the X-ray delay, as well as the potential for larger scale wind feedback. The serendipitous nature of the discovery could suggest a high incidence of UFOs in TDEs, alleviating some of the tension with theoretical expectations.
Las porfirias son un grupo heterogéneo de desórdenes metabólicos, hereditarios o adquiridos, que resultan de la deficiencia parcial de una de las enzimas de la biosíntesis del hemo. Existen 8 tipos ...de porfirias diferentes y su diagnóstico diferencial se realiza combinando datos clínicos, bioquímicos y en la actualidad moleculares. La Porfiria Aguda Intermitente (PAI) es causada por una deficiencia parcial de la porfobilinógeno deaminasa o PBG-D y la Porfiria Cutánea Tardía (PCT) resulta de la actividad deficiente de la uroporfirinogeno decarboxilasa (UROD). Se heredan en forma autosómica dominante con penetrancia incompleta. Las Porfirias Duales causadas por defectos en dos enzimas diferentes son muy raras, hay muy pocos casos reportados, y sólo uno confirmado molecularmente en un mismo individuo. Se estudió genéticamente una familia argentina cuyo padre fue diagnosticado bioquímicamente hace 10 años como PCT. Hace 2 años concurrió uno de los hijos con un cuadro clínico y bioquímico compatible tanto con PCT como con PAI. Se analizaron los dos genes y encontramos que heredó la mutación familiar en el gen UROD (c.10_12insA) y que es portador de la mutación IVS7+1_+4 (Surin 2001) en el gen PBGD. Se realizó segregación de alelos, analizando snps conocidos, en los padres y hermanos confirmando que es una mutación de novo. Además se encontró un snp novel para nuestra población. Éste es el primer caso reportado en nuestro país de una mutación de novo y la primera vez que se confirma molecularmente una Porfira Dual en un mismo individuo.
In the past five years, six quasi-periodic X-ray eruption (QPE) sources have been discovered in the nuclei of nearby galaxies. Their origin remains an open question. We present MUSE integral field ...spectroscopy of five QPE host galaxies to characterize their properties. We find that 3/5 galaxies host extended emission line regions (EELRs) up to 10 kpc in size. The EELRs are photo-ionized by a non-stellar continuum, but the current nuclear luminosity is insufficient to power the observed emission lines. The EELRs are decoupled from the stars both kinematically and in projected sky position, and the low velocities and velocity dispersions (\(<\) 100 km s\(^{-1}\) and \(\lesssim 75\) km s\(^{-1}\) respectively) are inconsistent with being AGN- or shock-driven. The origin of the EELRs is likely a previous phase of nuclear activity. The QPE host galaxy properties are strikingly similar to those of tidal disruption events (Wevers et al. submitted). The preference for a very short-lived (the typical EELR lifetime is \(\sim\)15000 years), gas-rich phase where the nucleus has recently faded significantly suggests that TDEs and QPEs may share a common formation channel, disfavoring AGN accretion disk instabilities as the origin of QPEs. In the assumption that QPEs are related to extreme mass ratio inspiral systems (EMRIs; stellar-mass objects on bound orbits about massive black holes), the high incidence of EELRs and recently faded nuclear activity can be used to aid in the localization of the host galaxies of EMRIs discovered by low frequency gravitational wave observatories.
