We analyzed light curves of seven relatively slower novae, PW Vul, V705 Cas, GQ Mus, RR Pic, V5558 Sgr, HR Del, and V723 Cas, based on an optically thick wind theory of nova outbursts. For fast novae, free-free emission dominates the spectrum in optical bands rather than photospheric emission and nova optical light curves follow the universal decline law. Faster novae blow stronger winds with larger mass loss rates. Since the brightness of free-free emission depends directly on the wind mass loss rate, faster novae show brighter optical maxima. In slower novae, however, we must take into account photospheric emission because of their lower wind mass loss rates. We calculated three model light curves of free-free emission, photospheric emission, and the sum of them for various WD masses with various chemical compositions of their envelopes, and fitted reasonably with observational data of optical, near-IR (NIR), and UV bands. From light curve fittings of the seven novae, we estimated their absolute magnitudes, distances, and WD masses. In PW Vul and V705 Cas, free-free emission still dominates the spectrum in the optical and NIR bands. In the very slow novae, RR Pic, V5558 Sgr, HR Del, and V723 Cas, photospheric emission dominates the spectrum rather than free-free emission, which makes a deviation from the universal decline law. We have confirmed that the absolute brightnesses of our model light curves are consistent with the distance moduli of four classical novae with known distances (GK Per, V603 Aql, RR Pic, and DQ Her). We also discussed the reason why the very slow novae are about 1 mag brighter than the proposed maximum magnitude vs. rate of decline relation.

A Light Curve Analysis of Classical Novae: Free-free Emission vs. Photospheric Emission

V1280 Sco is one of the slowest dust-forming nova ever historically observed. We performed multi-epoch high-spatial resolution observations of the circumstellar dusty environment of V1280 Sco to investigate the level of asymmetry of the ejecta We observed V1280 Sco in 2009, 2010 and 2011 using unprecedented high angular resolution techniques. We used the NACO/VLT adaptive optics system in the J, H and K bands, together with contemporaneous VISIR/VLT mid-IR imaging that resolved the dust envelope of V1280 Sco, and SINFONI/VLT observations secured in 2011. We report the discovery of a dusty hourglass-shaped bipolar nebula. The apparent size of the nebula increased from 0.30" x 0.17" in July 2009 to 0.64" x 0.42" in July 2011. The aspect ratio suggests that the source is seen at high inclination. The central source shines efficiently in the K band and represents more than 56+/-5% of the total flux in 2009, and 87+/-6% in 2011. A mean expansion rate of 0.39+/-0.03 mas per day is inferred from the VISIR observations in the direction of the major axis, which represents a projected upper limit. Assuming that the dust shell expands in that direction as fast as the low-excitation slow ejecta detected in spectroscopy, this yields a lower limit distance to V1280 Sco of 1kpc; however, the systematic errors remain large due to the complex shape and velocity field of the dusty ejecta. The dust seems to reside essentially in the polar caps and no infrared flux is detected in the equatorial regions in the latest dataset. This may imply that the mass-loss was dominantly polar.

/pdf/the-expanding-dusty-bipolar-nebula-around-the-nova-v1280-20ruwe3rhb.pdf

The expanding dusty bipolar nebula around the nova V1280 Scorpi

The spectral evolution of an extremely slow nova V723 Cas was monitored at Asiago Observatory for seven years. Observations in the long pre-maximum stage, which lasted more than four months, were reported in our previous paper. Here, we report the spectral evolution in the decline stage from January 1996 to December 2001. The spectra just after maximum luminosity showed prominent emission lines of H I, He I, Fe II, Ti II, Si II, Na I, etc. P Cygni type absorption components appeared on H I, He I, and Fe II lines about two months after maximum when the nova performed the second brightening. The radial velocities of the absorption components of H I and He I lines varied from -600 km s -1 in February to -1600 km s -1 in June 1996. Broad emission wings of H I and He I lines that were red-shifted by about 1000 km s -1 were detected in the same season. When the third brightening began in July 1996, a new absorption system of H I and He I appeared in which the blue-shift changed from -1000 km s -1 in July 1996 to -1600 km s -1 in February 1997. Prominent emission lines of highly ionized ions such as [Fe VI], [Fe VII], and [Ca V] emerged in the period between May 30 and July 1, 1997. This nova probably entered the nebular stage in this period. The interval from maximum luminosity to the beginning of nebular stage is about 18 months, which is still longer than those of the other extremely slow novae: 10 months of RR Pic or 8 months of HR Del. Some emission lines of [Fe IV], which were not found on the spectra of usual classical novae, were detected on the spectra in the nebular stage. The ionization state grew with time to have a coronal emission line [Fe X]  λ 6375 in November 1999 and later. The interstellar extinction is estimated at $E(B-V) = 0.57\pm 0.05$ and the distance to the nova at about $d = 2.8$ kpc, while the mass of the ejecta may be about $5\times 10^{-6}$ $M_{\odot}$. The abundance of helium is estimated at N (He)/ N (H) = $0.18\pm 0.01$. The abundance of oxygen is not so different from those of usual classical novae, while a rather low abundance of nitrogen is noticed. The abundance of neon is roughly comparable to that of a neon nova QU Vul.

/pdf/spectral-evolution-of-the-slowest-classical-nova-v723-2s6u3uw0bb.pdf

Spectral evolution of the slowest classical nova V723 Cassiopeiae in the decline stage

We identified a general course of classical nova outbursts in the B-V versus U-B color-color diagram. It is reported that novae show spectra similar to those of A--F supergiants near optical light maximum. However, they do not follow the supergiant sequence in the color-color diagram, neither the blackbody nor the main-sequence sequence. Instead, we found that novae evolve along a new sequence in the pre-maximum and near-maximum phases, which we call "the nova-giant sequence." This sequence is parallel to but \Delta (U-B) \approx -0.2 mag bluer than the supergiant sequence. This is because the mass of a nova envelope is much (\sim10^{-4} times) less than that of a normal supergiant. After optical maximum, its color quickly evolves back blueward along the same nova-giant sequence and reaches the point of free-free emission (B-V=-0.03, U-B=-0.97), which coincides with the intersection of the blackbody sequence and the nova-giant sequence, and remains there for a while. Then the color evolves leftward (blueward in B-V but almost constant in U-B), owing mainly to the development of strong emission lines. This is the general course of nova outbursts in the color-color diagram, which was deduced from eight well-observed novae in various speed classes. For a nova with unknown extinction, we can determine a reliable value of the color excess by matching the observed track of the target nova with this general course. This is a new and convenient method for obtaining the color excesses of classical novae. Using this method, we redetermined the color excesses of twenty well-observed novae. The obtained color excesses are in reasonable agreement with the previous results, which in turn supports the idea of our general track of nova outbursts.

The UBV Color Evolution of Classical Novae. I. Nova-Giant Sequence in the Color-Color Diagram

We present a unified model of optical and ultraviolet (UV) light curves for one of the fastest classical novae, V838 Herculis (Nova Herculis 1991), and estimate its white dwarf (WD) mass. Based on an optically thick wind theory of nova outbursts, we model the optical light curves with free-free emission and the UV 1455 A light curves with blackbody emission. Our models of 1.35 +- 0.02 M {sub sun} WD simultaneously reproduce the optical and UV 1455 A observations. The mass lost by the wind is DELTAM {sub wind} approx 2 x 10{sup -6} M {sub sun}. We provide new determinations of the reddening, E(B - V) = 0.53 +- 0.05, and of the distance, 2.7 +- 0.5 kpc.

http://iopscience.iop.org/article/10.1088/0004-637X/704/2/1676/pdf

A universal decline law of classical novae. iv. v838 her (1991): a very massive white dwarf

We present observations of the classical nova V723 Cassiopeiae (Nova Cas 1995), obtained both with the Infrared Space Observatory (ISO) and from the ground. The infrared spectrum was dominated in the first year by H and He recombination lines, and at later times by coronal lines. The H recombination lines imply a reddening of E(B-V) = 0.78, an electron temperature of 7000 K, and an electron density of 2 × 108 cm-3 on day 250. We argue that the high-ionization species in the infrared are most likely the result of collisional ionization rather than photoionization and are therefore truly "coronal"; we estimate a temperature of 3.2 × 105 K in the coronal region and abundance ratios of S/Si 2.1, Ca/Si 1.6, and Al/Si 1.5. The ejected mass as determined from the Brα line was 2.6 × 10-5 M⊙ for a distance of 4 kpc; however, the mass deduced from the free-free emission, which we conclude arises primarily in the coronal zone, is 4.3 × 10-4 M⊙. V723 Cas did not display the [O IV] 25.89 μm fine-structure line, which was typically seen in the spectra of novae observed with ISO. There was no evidence of dust emission in V723 Cas.

http://iopscience.iop.org/article/10.1086/377618/pdf

Infrared space observatory and ground-based infrared observations of the classical Nova V723 Cassiopeiae

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.

R. Antolin Sanchez

Author Tools

Chat about Author

Papers

Infrared space observatory and ground-based infrared observations of the classical Nova V723 Cassiopeiae