We present a multi-epoch quantitative spectroscopic analysis of the Type IIn supernova (Type IIn SN) 1994W, an event interpreted by Chugai et al. as stemming from the inter- action between the ejecta of a SN and a 0.4 Mcircumstellar shell ejected 1.5 yr before core collapse. During the brightening phase, our models suggest that the source of optical radiation is not unique, perhaps associated with an inner optically thick cold dense shell and outer op- tically thin shocked material. During the fading phase, our models support a single source of radiation, an hydrogen-rich optically thick layer with a near-constant temperature of ∼7000 K that recedes from a radius of 4.3 × 10 15 at a peak to 2.3 × 10 15 cm 40 d later. We reproduce the hybrid narrow-core broad-wing line profile shapes of SN 1994W at all times, invoking an optically thick photosphere exclusively (i.e. without any external optically thick shell). In SN 1994W, slow expansion makes scattering with thermal electrons a key escape mechanism for photons trapped in optically thick line cores, and allows the resulting broad incoherent electron-scattering wings to be seen around narrow-line cores. In SNe with larger expansion velocities, the thermal broadening due to incoherent scattering is masked by the broad profile and the dominant frequency redshift occasioned by bulk motions. Given the absence of broad lines at all times and the very low 56 Ni yields, we speculate whether SN 1994W could have resulted from an interaction between two ejected shells without core collapse. The high con- version efficiency of kinetic to thermal energy may not require a SN-like energy budget for

/pdf/sn-1994w-an-interacting-supernova-or-two-interacting-shells-531fc1gwno.pdf

SN 1994W: an interacting supernova or two interacting shells?

Prominent Fe Kα line emission is detected in the XMM‐Newton spectrum of the ultraluminous infrared galaxy Arp 220. The centroid of the line is found at an energy of 6.7 keV and the equivalent width of the line is EW ∼ 1.9 keV (at 3.5σ significance). A few other spectral features are found at various degrees of significance in the lower energy range on a hard 2.5‐ 10 keV continuum (� ∼ 1). The large EW of the Fe K line poses a problem with interpreting the hard X-ray emission as integrated X-ray binary emission. A thermal emission spectrum with a temperature of kT ∼ 7k eV modified by absorption of N H � 3 × 10 22 cm −2 , can describe the 2.5‐10 keV continuum shape and the Fe K emission. A hot bubble that is shocked internally in a starburst region would have a similar temperature and gives a good explanation for the observed X-ray properties with a high star formation rate. An ensemble of radio supernovae in a dense environment, as suggested from VLBI imaging, could be another possibility, if such powerful supernovae are produced continuously at a high rate. However, the apparent lack of emission from X-ray binaries is incompatible with the high supernova rate (∼2 SNe yr −1 ) required by both interpretations. Highly photoionized, low-density gas illuminated by a hidden Compton-thick active galactic nucleus is a possible alternative for the hard X-ray emission, which can be tested by examining whether radiative recombination continua from highly ionized Ca and Fe are present in better quality data from a forthcoming observation. Ke yw ords: galaxies: individual: Arp 220 ‐ X-rays: galaxies.

/pdf/fe-k-emission-in-the-ultraluminous-infrared-galaxy-arp-220-3ons9lpa13.pdf

Fe K emission in the ultraluminous infrared galaxy Arp 220

We have used the Chandra X-Ray Observatory to resolve spatially and spectrally the X-ray emission from the Circinus galaxy. We report here on the nature of the X-ray emission from the off-nuclear point sources associated with the disk of Circinus, which make up ≈34% of the total 0.5–10 keV emission. We find that many of the serendipitous X-ray sources are concentrated along the optical disk of the galaxy, although few have optical counterparts within 1'' of their X-ray positions down to limiting magnitudes of mV = 23–25. At the distance of Circinus (≈3.8 Mpc), their intrinsic 0.5–10 keV luminosities range from ≈2 × 1037 ergs s-1 to ≈4 × 1039 ergs s-1. One-fourth of the sources are variable over the duration of the 67 ks observation, and spectral fitting of these off-nuclear sources shows a diverse range of spectral properties. The overall characteristics of the point sources suggest that most are X-ray binaries and/or ultraluminous supernova remnants within Circinus. We are able to analyze the two strongest off-nuclear sources in greater detail and find both to have remarkable properties. The average X-ray luminosities of the two sources are 3.7 × 1039 ergs s-1 and 3.4 × 1039 ergs s-1. The former displays large and periodic flux variations every 7.5 hr and is well fitted by a multicolor blackbody accretion disk model with Tin = 1.35 keV, properties consistent with an eclipsing 50 M⊙ black hole binary. The latter appears to be a young supernova remnant, as it coincides with a nonthermal radio counterpart and an Hα-detected H II region. This source exhibits both long-term (≈4 yr) X-ray variability and a 6.67–6.97 keV iron emission-line blend with a 1.6 keV equivalent width. These two objects further support the notion that super-Eddington X-ray sources in nearby galaxies can be explained by a mixture of intermediate-mass black holes in X-ray binaries and young supernova remnants.

A Chandra Study of the Circinus Galaxy Point-Source Population

Near-infrared observations are presented for five Type IIn supernovae (SN 1995N, SN 1997ab, SN 1998S, SN 1999Z, and SN 1999el) that exhibit strong infrared excesses at late times (t 100 days). H- and K-band emission from these objects is dominated by a continuum that rises toward longer wavelengths. The data are interpreted as thermal emission from dust, probably situated in a preexisting circumstellar nebula. The IR luminosities implied by single-temperature blackbody fits are quite large, 1041-1042 ergs s-1, and the emission evolves slowly, lasting for years after maximum light. For SN 1995N, the integrated energy release via IR dust emission was ≈0.5-1 × 1050 ergs. A number of dust heating scenarios are considered, the most likely being an infrared echo powered by X-ray and UV emissions from the shock interaction with a dense circumstellar medium.

/pdf/extraordinary-late-time-infrared-emission-of-type-iin-41697iky16.pdf

Extraordinary Late-Time Infrared Emission of Type IIn Supernovae

The X-ray emission from the circumstellar interaction in type II supernovae with a dense circumstellar medium is calculated. In type IIL and type IIn supernovae, mass loss rates are generally high enough for the region behind the reverse shock to be radiative, producing strong radiation, particularly in X-rays. We present a model for the emission from the cooling region in the case of a radiative reverse shock. Under the assumption of a stationary flow, a hydrodynamic model is combined with a time-dependent ionization balance and multilevel calculations. The applicability of the steady state approximation is discussed for various values of the ejecta density gradient and different sets of chemical composition. We show how the emerging spectrum strongly depends on the reverse shock velocity and the composition of the shocked gas. We discuss differences between a spectrum produced by this model and a single-temperature spectrum. Large differences are found especially for the line emission, which can seriously affect abundance estimates. We also illustrate the effects of absorption in the cool shocked ejecta. The applicability of our model to various types of supernovae is discussed.

/pdf/x-ray-emission-from-radiative-shocks-in-type-ii-supernovae-17ncrg53pw.pdf

X-ray emission from radiative shocks in type II supernovae

We report on multi-epoch X-ray observations of the Type IIn (narrow emissionline) supernova SN 1995N with the ROSAT and ASCA satellites. The January 1998ASCA X-ray spectrum is well ﬁtted by a thermal bremsstrahlung (kT ∼ 10 keV,N H ∼ 6 × 10 20 cm −2 ) or power-law (α ∼ 1.7, N H ∼ 10 21 cm −2 ) model. The X-raylight curve shows evidence for signiﬁcant ﬂux evolution between August 1996 and Jan-uary 1998: the count rate from the source decreased by 30% between our August 1996and August 1997 ROSAT observations, and the X-ray luminosity most likely increasedby a factor of ∼2 between our August 1997 ROSAT and January 1998 ASCA obser-vations, although evolution of the spectral shape over this interval is not ruled out.The high X-ray luminosity, L X ∼ 10 41 ergs s −1 , places SN 1995N in a small groupof Type IIn supernovae with strong circumstellar interaction, and the evolving X-rayluminosity suggests that the circumstellar medium is distributed inhomogeneously.Key words: supernovae: individual: SN 1995N – X–rays: stars – stars: circumstel-lar matter

The X‐ray spectrum and light curve of Supernova 1995N

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

S. Uno

Author Tools

Chat about Author

Papers

The X‐ray spectrum and light curve of Supernova 1995N