The UV Excesses of Supernovae and the Implications for Studying Supernovae and Other Optical Transients

Supernovae (SNe), kilonovae (KNe), tidal disruption events (TDEs), optical afterglows of gamma ray bursts (GRBs), and many other optical transients are important phenomena in time-domain astronomy. Fitting the multi-band light curves (LCs) or the synthesized (pseudo-)bolometric LCs can be used to constrain the physical properties of optical transients. The (UV absorbed) blackbody module is one of the most important modules used to fit the multi-band LCs of optical transients having (UV absorbed) blackbody spectral energy distributions (SEDs). We find, however, that the SEDs of some SNe show UV excesses, which cannot be fitted by the model including a (UV absorbed) blackbody module. We construct the bolometric LCs and employ the (cooling plus) \Ni model to fit the constructed bolometric LCs, obtaining decent fits. Our results demonstrate that the optical transients showing UV excesses cannot be fitted by the multi-band models that include (UV-absorbed) blackbody module, but can be well modeled by constructing and fitting their bolometric LCs.Comment: 9 pages, 4 figures, 1 table, submitted to Ap

SN 2018gk Revisited: the Photosphere, the Central Engine, And the Putative Dust

In this paper, we perform a comprehensive study for the physical properties of SN 2018gk which is a luminous type IIb supernova (SN). We find that the early-time photospheric velocity vary from a larger value to a smaller value before the photosphere reach a temperature floor. We generalize the photosphere modulus and fit the multi-band light curves (LCs) of SN 2018gk. We find that the $^{56}$Ni mass model require $\sim0.90$ M$_\odot$ of $^{56}$Ni which is larger than the derived ejecta mass ($\sim0.10$ M$_\odot$). Alternatively, we use the magnetar plus $^{56}$Ni and the fallback plus $^{56}$Ni models to fit the LCs of SN 2018gk, finding that the two models can fit the LCs. We favor the magnetar plus $^{56}$Ni since the parameters are rather reasonable ($M_{\rm ej} =1.65$ M$_\odot$, $M_{\rm Ni}=0.05$ M$_\odot$ which is smaller than the upper limit of the value of the $^{56}$Ni mass can by synthesized by the neutrino-powered core collapse SNe $B=6.52\times10^{14}$ G which is comparable to those of luminous and superluminous SNe studied in the literature, and $P_0=10.42$ ms which is comparable to those of luminous SNe), while the validity of the fallback plus $^{56}$Ni model depends on the accretion efficiency ($\eta$). Therefore, we suggest that SN 2018gk might be a SN IIb mainly powered by a central engine. Finally, we confirm the NIR excesses of the spectral energy distributions (SEDs) of SN 2018gk at some epochs and constrain the physical properties of the putative dust using the blackbody plus dust emission model.Comment: 26 pages, 11 figures, 5 tables, Accepted for publication in Ap

Penta­aqua­(1H-benzimidazole-5,6-dicarboxyl­ato-κN 3)nickel(II) penta­hydrate

In the title mononuclear complex, [Ni(C9H4N2O4)(H2O)5]·5H2O, the NiII atom is six-coordinated by one N atom from a 1H-benzimidazole-5,6-dicarboxyl­ate ligand and by five O atoms from five water mol­ecules and displays a distorted octa­hedral geometry. Inter­molecular O—H⋯O hydrogen-bonding inter­actions among the coordinated water mol­ecules, solvent water mol­ecules and carboxyl O atoms of the organic ligand and additional N—H⋯O hydrogen bonding lead to the formation of a three-dimensional supra­molecular network

Diaqua­bis­(4-carb­oxy-2-propyl-1H-imidazole-5-carboxyl­ato-κ2 N 3,O 4)cobalt(II) N,N-dimethyl­formamide disolvate

In the title complex, [Co(C8H9N2O4)2(H2O)2]·2C3H7NO, the CoII cation (site symmetry ) is six-coordinated by two 5-carb­oxy-2-propyl-1H-imidazole-4-carboxyl­ate ligands and two water mol­ecules in a distorted octa­hedral environment. In the crystal structure, the complex mol­ecules and dimethyl­formamide solvent mol­ecules are linked by extensive O—H⋯O and N—H⋯O hydrogen bonding into sheets lying parallel to (21)

Hexaaqua­nickel(II) 4,4′-(1,2-dihy­droxy­ethane-1,2-di­yl)dibenzoate monohydrate

In the title compound, [Ni(H2O)6](C16H12O6)·H2O, the NiII cation is located on a mirror plane and is coordinated by six water mol­ecules, two of which are also located on the mirror plane, in a distorted octa­hedral geometry. The 4,4′-(1,2-dihy­droxy­ethane-1,2-di­yl)dibenzoate anion is centrosymmetric with the mid-point of the central ethane C—C bond located on an inversion center. The uncoordinated water mol­ecule is located on a mirror plane. Extensive O—H⋯O hydrogen bonding is present in the crystal structure

The Study of Dust Formation of Six Tidal Disruption Events

This paper investigates eleven (UV-)optical-infrared (IR) spectral energy distributions (SEDs) of six tidal disruption events (TDEs), which are ASASSN-14li, ASASSN-15lh, ASASSN-18ul, ASASSN-18zj, PS18kh, and ZTF18acaqdaa. We find that all the SEDs show evident IR excesses. We invoke the blackbody plus dust emission model to fit the SEDs, and find that the model can account for the SEDs. The derived masses of the dust surrounding ASASSN-14li, ASASSN-15lh, ASASSN-18ul, ASASSN-18zj, PS18kh, and ZTF18acaqdaa are respectively $\sim0.7-1.0\,(1.5-2.2)\times10^{-4}\,M_\odot$, $\sim0.6-3.1\,(1.4-6.3)\times10^{-2}\,M_\odot$, $\sim1.0\,(2.8)\times10^{-4}\,M_\odot$, $\sim0.1-1.6\,(0.3-3.3)\times10^{-3}\,M_\odot$, $\sim1.0\,(2.0)\times10^{-3}\,M_\odot$, and $\sim 1.1\,(2.9)\times10^{-3}\,M_\odot$, if the dust is graphite (silicate). The temperature of the graphite (silicate) dust of the six TDEs are respectively $\sim1140-1430\,(1210-1520)$\,K, $\sim1030-1380\,(1100-1460)$\,K, $\sim1530\,(1540)$\,K, $\sim960-1380\,(1020-1420)$\,K, $\sim900\,(950)$\,K, and $\sim1600\,(1610)$\,K. By comparing the derived temperatures to the vaporization temperature of graphite ($\sim 1900$\,K) and silicate ($\sim 1100-1500$\,K), we suggest that the IR excesses of PS18kh can be explained by both the graphite and silicate dust, the rest five TDEs favor the graphite dust while the silicate dust model cannot be excluded. Moreover, we demonstrate the lower limits of the radii of the dust shells surrounding the six TDEs are significantly larger than those of the radii of the photospheres at the first epochs of SEDs, indicating that the dust might exist before the the TDEs occurred.Comment: 13 pages, 4 figures, 4 tables, submitted to Ap

Poly[(μ4-tetra­zole-1-acetato-κ4 N 3:N 4:O:O′)silver(I)]

In the title complex, [Ag(C3H3N4O2)]n, the AgI atom is four-coordinated in a slightly distorted tetra­hedral coordination geometry by two N atoms from two tetra­zole-1-acetate (tza) ligands and two O atoms from the other two tza ligands. The tza ligand bridges two Ag atoms through the carboxyl­ate O atoms and simultaneously binds to the other two Ag atoms through the tetra­zole N atoms, forming a two-dimensional network parallel to (100)

Penta­aqua­(1H-benzimidazole-5,6-di­carboxyl­ato-κN 3)cobalt(II) penta­hydrate

In the title mononuclear complex, [Co(C9H4N2O4)(H2O)5]·5H2O, the CoII atom exhibits a distorted octa­hedral geometry involving an N atom of a 1H-benzimidazole-5,6-dicarboxyl­ate ligand and five water O atoms. A supra­molecular network is generated through inter­molecular O—H⋯O hydrogen-bonding inter­actions involving the coordinated and uncoordinated water mol­ecules and the carboxyl O atoms of the organic ligand. An inter­molecular N—H⋯O hydrogen bond is also observed