Jin-Hong Chen | Sun Yat-Sen University (original) (raw)

Papers by Jin-Hong Chen

The Astrophysical Journal, 2022

We present and analyze the optical/UV and X-ray observations of a nearby tidal disruption event (... more We present and analyze the optical/UV and X-ray observations of a nearby tidal disruption event (TDE) candidate, AT 2019azh, from ∼30 days before to ∼400 days after its early optical peak. The X-rays show a late brightening by a factor of ∼30–100 around 200 days after discovery, while the UV/opticals continuously decayed. The early X-rays show two flaring episodes of variation, temporally uncorrelated with the early UV/opticals. We found a clear sign of X-ray hardness evolution; i.e., the source is harder at early times and becomes softer as it brightens later. The drastically different temporal behaviors in X-rays and UV/opticals suggest that the two bands are physically distinct emission components and probably arise from different locations. These properties argue against the reprocessing of X-rays by any outflow as the origin of the UV/optical peak. The full data are best explained by a two-process scenario, in which the UV/optical peak is produced by the debris stream–stream co...

The Astrophysical Journal, 2022

Tidal disruption events (TDEs) can uncover the quiescent supermassive black holes (SMBHs) at the ... more Tidal disruption events (TDEs) can uncover the quiescent supermassive black holes (SMBHs) at the center of galaxies and also offer a promising method to study them. After the disruption of a star by an SMBH, the highly elliptical orbit of the debris stream will be gradually circularized due to the self-crossing, and then the circularized debris will form an accretion disk. The recent TDE candidate AT 2019avd has double peaks in its optical light curve, and the X-ray emerges near the second peak. The durations of the peaks are ∼400 and 600 days, respectively, and the separation between them is ∼700 days. We fit its spectral energy distribution and analyze its light curves in the optical/UV, mid-infrared, and X-ray bands. We find that this source can be interpreted as a two-phase scenario in which the first phase is dominated by the stream circularization, and the second phase is the delayed accretion. We use the succession of the self-crossing model and delayed accretion model to fit...

The Astrophysical Journal, 2018

There has been suggestive evidence of intermediate-mass black holes (IMBHs; 10 3−5 M e) existing ... more There has been suggestive evidence of intermediate-mass black holes (IMBHs; 10 3−5 M e) existing in some globular clusters (GCs) and dwarf galaxies, but IMBHs as a population remain elusive. As a main-sequence star passes too close by an IMBH it might be tidally captured and disrupted. We study the long-term accretion and observational consequence of such tidal disruption events. The disruption radius is hundreds to thousands of the BH's Schwarzschild radius, so the circularization of the falling-back debris stream is very inefficient due to weak general relativity effects. Due to this and a high mass fallback rate, the bound debris initially goes through a ∼10 yr long super-Eddington accretion phase. The photospheric emission of the outflow ejected during this phase dominates the observable radiation and peaks in the UV/optical bands with a luminosity of 10 erg s 42 1-. After the accretion rate drops below the Eddington rate, the bolometric luminosity follows the conventional t −5/3 powerlaw decay, and X-rays from the inner accretion disk start to be seen. Modeling the newly reported IMBH tidal disruption event candidate 3XMM J2150-0551, we find a general consistency between the data and predictions. The search for these luminous, long-term events in GCs and nearby dwarf galaxies could unveil the IMBH population.

The Astrophysical Journal, 2021

Tidal disruption events (TDEs) can uncover the quiescent black holes (BHs) at the center of galax... more Tidal disruption events (TDEs) can uncover the quiescent black holes (BHs) at the center of galaxies and also offer a promising method to study them. In a partial TDE (PTDE), the BH's tidal force cannot fully disrupt the star, so the stellar core survives and only a varied portion of the stellar mass is bound to the BH and feeds it. We calculate the event rate of PTDEs and full TDEs (FTDEs). In general, the event rate of PTDEs is higher than that of FTDEs, especially for the larger BHs. And the detection rate of PTDEs is about dozens per year by Zwicky Transient Factory (ZTF). During the circularization process of the debris stream in PTDEs, no outflow can be launched due to the efficient radiative diffusion. The circularized debris ring then experiences viscous evolution and forms an accretion disk. We calculate the light curves of PTDEs contributed by these two processes, along with their radiation temperature evolution. The light curves have double peaks and the spectra peak in UV. Without obscuration or reprocessing of the radiation by an outflow, PTDEs provide a clean environment to study the circularization and transient disk formation in TDEs.

The Astrophysical Journal, 2022

We present and analyze the optical/UV and X-ray observations of a nearby tidal disruption event (... more We present and analyze the optical/UV and X-ray observations of a nearby tidal disruption event (TDE) candidate, AT 2019azh, from ∼30 days before to ∼400 days after its early optical peak. The X-rays show a late brightening by a factor of ∼30–100 around 200 days after discovery, while the UV/opticals continuously decayed. The early X-rays show two flaring episodes of variation, temporally uncorrelated with the early UV/opticals. We found a clear sign of X-ray hardness evolution; i.e., the source is harder at early times and becomes softer as it brightens later. The drastically different temporal behaviors in X-rays and UV/opticals suggest that the two bands are physically distinct emission components and probably arise from different locations. These properties argue against the reprocessing of X-rays by any outflow as the origin of the UV/optical peak. The full data are best explained by a two-process scenario, in which the UV/optical peak is produced by the debris stream–stream co...

The Astrophysical Journal, 2022

Tidal disruption events (TDEs) can uncover the quiescent supermassive black holes (SMBHs) at the ... more Tidal disruption events (TDEs) can uncover the quiescent supermassive black holes (SMBHs) at the center of galaxies and also offer a promising method to study them. After the disruption of a star by an SMBH, the highly elliptical orbit of the debris stream will be gradually circularized due to the self-crossing, and then the circularized debris will form an accretion disk. The recent TDE candidate AT 2019avd has double peaks in its optical light curve, and the X-ray emerges near the second peak. The durations of the peaks are ∼400 and 600 days, respectively, and the separation between them is ∼700 days. We fit its spectral energy distribution and analyze its light curves in the optical/UV, mid-infrared, and X-ray bands. We find that this source can be interpreted as a two-phase scenario in which the first phase is dominated by the stream circularization, and the second phase is the delayed accretion. We use the succession of the self-crossing model and delayed accretion model to fit...

The Astrophysical Journal, 2018

There has been suggestive evidence of intermediate-mass black holes (IMBHs; 10 3−5 M e) existing ... more There has been suggestive evidence of intermediate-mass black holes (IMBHs; 10 3−5 M e) existing in some globular clusters (GCs) and dwarf galaxies, but IMBHs as a population remain elusive. As a main-sequence star passes too close by an IMBH it might be tidally captured and disrupted. We study the long-term accretion and observational consequence of such tidal disruption events. The disruption radius is hundreds to thousands of the BH's Schwarzschild radius, so the circularization of the falling-back debris stream is very inefficient due to weak general relativity effects. Due to this and a high mass fallback rate, the bound debris initially goes through a ∼10 yr long super-Eddington accretion phase. The photospheric emission of the outflow ejected during this phase dominates the observable radiation and peaks in the UV/optical bands with a luminosity of 10 erg s 42 1-. After the accretion rate drops below the Eddington rate, the bolometric luminosity follows the conventional t −5/3 powerlaw decay, and X-rays from the inner accretion disk start to be seen. Modeling the newly reported IMBH tidal disruption event candidate 3XMM J2150-0551, we find a general consistency between the data and predictions. The search for these luminous, long-term events in GCs and nearby dwarf galaxies could unveil the IMBH population.

The Astrophysical Journal, 2021

Tidal disruption events (TDEs) can uncover the quiescent black holes (BHs) at the center of galax... more Tidal disruption events (TDEs) can uncover the quiescent black holes (BHs) at the center of galaxies and also offer a promising method to study them. In a partial TDE (PTDE), the BH's tidal force cannot fully disrupt the star, so the stellar core survives and only a varied portion of the stellar mass is bound to the BH and feeds it. We calculate the event rate of PTDEs and full TDEs (FTDEs). In general, the event rate of PTDEs is higher than that of FTDEs, especially for the larger BHs. And the detection rate of PTDEs is about dozens per year by Zwicky Transient Factory (ZTF). During the circularization process of the debris stream in PTDEs, no outflow can be launched due to the efficient radiative diffusion. The circularized debris ring then experiences viscous evolution and forms an accretion disk. We calculate the light curves of PTDEs contributed by these two processes, along with their radiation temperature evolution. The light curves have double peaks and the spectra peak in UV. Without obscuration or reprocessing of the radiation by an outflow, PTDEs provide a clean environment to study the circularization and transient disk formation in TDEs.