Abstract The amount of cosmic dust contributed by stellar sources in galaxies at all cosmic epochs remains a controversial topic, particularly whether or not supernovae (SNe) have an important role to play given the dust-hostile environments provided by SNe. To date, freshly-formed dust has been observed in a handful of core collapse (CC) SNe, both in the ejecta in-situ and in the interactions between the ejecta and circumstellar medium (CSM). As yet, there exists no clear observational evidence for dust formation in Type Ia SNe despite predictions of $3×10^{-4}$- $0.2$ Msun of dust forming per Ia. Here we report evidence of dust formation in the ejecta-CSM interaction in the Type Ia (SNIa) SN2018evt just three years after the explosion, characterized by a staggering rise in the mid-infrared (MIR) flux accompanied by an accelerated decline in the optical. This hypothesis is strengthened by the concurrent evolution of the profiles of the Hα emission lines. A preexisting hydrogen-rich torus which itself may be dusty before the SN explosion, provides a natural explanation of the observed data. SN 2018evt is the first SNIa with clear evidence of both dust destruction and formation in its ejecta and surroundings. The amount of the newly formed dust follows a steep power law rise of index 4 with time after the explosion. This steep rise indicates that the newly formed dust is formed in the SN ejecta, which is compressed by the shock interaction with the CSM. 

The Fall and Rise of Cosmic Dust in SN 2018evt

In this paper, we introduce \texttt{SuperLite}, an open-source Monte Carlo radiation transport code designed to produce synthetic spectra for astrophysical transient phenomena affected by circumstellar interaction. \texttt{SuperLite} utilizes Monte Carlo methods for semi-implicit, semi-relativistic radiation transport in high-velocity shocked outflows, employing multi-group structured opacity calculations. The code enables rapid post-processing of hydrodynamic profiles to generate high-quality spectra that can be compared with observations of transient events, including superluminous supernovae, pulsational pair-instability supernovae, and other peculiar transients. We present the methods employed in \texttt{SuperLite} and compare the code's performance to that of other radiative transport codes, such as \texttt{SuperNu} and CMFGEN. We show that \texttt{SuperLite} has successfully passed standard Monte Carlo radiation transport tests and can reproduce spectra of typical supernovae of Type Ia, Type IIP and Type IIn. 

Monte Carlo Radiation Transport for Astrophysical Transients Powered by Circumstellar Interaction

The scaling relation of central massive black holes (MBHs) and their host galaxies is well-studied for supermassive BHs (SMBHs, MBH ≥ 106M⊙). However, this relation has large uncertainties in the mass range of the intermediate-mass BHs (IMBHs, MBH ∼ 103–106M⊙). Since Green pea (GP) galaxies are luminous compact dwarf galaxies, which may be likely to host less massive SMBHs or even IMBHs, we systematically search for MBHs in a large sample of 2190 GP galaxies at z < 0.4, selected from LAMOST and SDSS spectroscopic surveys. Here, we report a newly discovered sample of 59 MBH candidates with broad Hα lines. This sample has a median stellar mass of 108.83±0.11M⊙ and hosts MBHs with single-epoch virial masses ranging from MBH ∼ 104.7 to 108.5M⊙ (median 105.85±0.64M⊙). Among the 59 MBH candidates, 36 have black hole masses MBH ≤ 106M⊙ (IMBH candidates), one of which even has MBH ≲ 105M⊙. We find that the MBH-M* relation of our MBH sample is consistent with the MBH-Mbulge relation for SMBHs, while is above the MBH-M* relation for MBHs in dwarf galaxies in the same mass range. Furthermore, we show that 25 MBH candidates, including 4 IMBH candidates, have additional evidence of black hole activities, assessed through various methods such as the broad-line width, BPT diagram, mid-infrared color, X-ray luminosity, and radio emission. Our studies show that it is very promising to find IMBHs in GP galaxies, and the BH sample so obtained enables us to probe the connection between the MBHs and compact dwarf galaxies in the low-redshift Universe.

Intermediate-mass black holes in Green pea galaxies (IMBH-GP) I: A candidate sample from LAMOST and SDSS

Abstract Understanding the nature of the luminous 1991T-like supernovae (SNe) is of great importance to SN cosmology as they are likely to have been more common in the early Universe. In this paper, we explore the observational properties of 1991T-like SNe to study their relationship to other luminous, slow-declining Type Ia supernovae (SNe Ia). From the spectroscopic and photometric criteria defined in Phillips et al., we identify 17 1991T-like SNe from the literature. Combining these objects with 10 1991T-like SNe from the Carnegie Supernova Project-II, the spectra, light curves, and colors of these events, along with their host galaxy properties, are examined in detail. We conclude that 1991T-like SNe are closely related in essentially all of their UV, optical, and near-infrared properties—as well as their host galaxy parameters—to the slow-declining subset of Branch core-normal SNe and to the intermediate 1999aa-like events, forming a continuum of luminous SNe Ia. The overriding difference between these three subgroups appears to be the extent to which 56 Ni mixes into the ejecta, producing the premaximum spectra dominated by Fe iii absorption, the broader UV light curves, and the higher luminosities that characterize the 1991T-like events. Nevertheless, the association of 1991T-like SNe with the rare Type Ia circumstellar material SNe would seem to run counter to this hypothesis, in which case 1991T-like events may form a separate subclass of SNe Ia, possibly arising from single-degenerate progenitor systems. 

1991T-like Supernovae*

Abstract Dust associated with various stellar sources in galaxies at all cosmic epochs remains a controversial topic, particularly whether supernovae play an important role in dust production. We report evidence of dust formation in the cold, dense shell behind the ejecta–circumstellar medium (CSM) interaction in the Type Ia-CSM supernova (SN) 2018evt three years after the explosion, characterized by a rise in mid-infrared emission accompanied by an accelerated decline in the optical radiation of the SN. Such a dust-formation picture is also corroborated by the concurrent evolution of the profiles of the Hα emission line. Our model suggests enhanced CSM dust concentration at increasing distances from the SN as compared to what can be expected from the density profile of the mass loss from a steady stellar wind. By the time of the last mid-infrared observations at day +1,041, a total amount of 1.2 ± 0.2 × 10 −2 M ⊙ of new dust has been formed by SN 2018evt, making SN 2018evt one of the most prolific dust factories among supernovae with evidence of dust formation. The unprecedented witness of the intense production procedure of dust may shed light on the perceptions of dust formation in cosmic history. 

pdf/newly-formed-dust-within-the-circumstellar-environment-of-sn-2jyxcoggtf.pdf

Newly formed dust within the circumstellar environment of SN Ia-CSM 2018evt

We applythereplica methodtoanalyze vector pre-coding, amethodtoreduce transmit powerin antenna arraycommunications, inthelimit ofaninfinite numberofdimensions ofthesignal vector. Theanalysis applies toaverygeneral class ofchannel matrices. The statistics ofthechannel matrixenterthetransmitted energy persymbol viaitsR-transform. Wespecialize ourresult toinversion ofani.i.d. channel andtwocasesofsignal pointoptimization i)2-point lattice pre-coding andii) compact relaxation. Inthetwo cases thereplica symmetric transmitted energy isfound tobe4.3dBand9.6dBabovetheorthogonal casefor asquare channel matrix, respectively.

Vector Precoding inHighDimensions: A Replica Analysis

A rare class of supernovae(SNe) is characterizedbystrong interactionbetweenthe ejecta and several solar masses of circumstellar matter (CSM) as evidenced by strong Balmer-line emission. Within the ﬁrst few weeks after the explosion, they may display spectral features similar to overluminous Type Ia SNe, while at later phase their observation properties exhibit remarkable similarities with some extreme case of Type IIn SNe that show strong Balmer lines years after the explosion. We present polarimetric observations of SN 2018evt obtained by the ESO Very Large Telescope from 172 to 219 days after the estimated time of peak luminosity to study the geometry of the CSM. The nonzero continuum polarization decreases over time, suggesting that the mass loss of the progenitor star is aspherical. The prominent H 𝛼 emission can be decomposed into a broad, time-evolving component and an intermediate-width, static component. The former shows polarized signals, and it is likely to arise from a cold dense shell (CDS) within the region between the forward and reverse shocks. The latter is signiﬁcantly unpolarized, and it is likely to arise from shocked, fragmented gas clouds in the H-rich CSM. We infer that SN 2018evt exploded inside a massive and aspherical circumstellar cloud. The symmetry axes of the CSM and the SN appear to be similar. SN 2018evt shows observational properties common to events that display strong interaction between the ejecta and CSM, implying that they share similar circumstellar conﬁgurations. Our preliminary estimate also suggests that the circumstellar environment of SN 2018evt has been signiﬁcantly enriched at a rate of ∼ 0 . 1 M ⊙ yr − 1 over a period of > 100 yr.

/pdf/the-interaction-of-supernova-2018evt-with-a-substantial-1m999bb1.pdf

The Interaction of Supernova 2018evt with a Substantial Amount of Circumstellar Matter -- An SN1997cy-like Event

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Vector Precoding inHighDimensions: A Replica Analysis

The Interaction of Supernova 2018evt with a Substantial Amount of Circumstellar Matter -- An SN1997cy-like Event