Observability of Scattered-Light Echoes around Variable Stars and Cataclysmic Events

Sugerman, Ben

doi:10.1086/378358

Cited by 64 publications

(101 citation statements)

References 85 publications

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“…The calculated dust masses (1−3 × 10 −4 M ) agree with the amount of SiO calculated by Kotak et al (2006) and with the results of Kotak (2008), and they are also similar to the values found in other SNe. Another explanation for the observed behavior of MIR SEDs may be the thermal radiation of pre-existing dust in the CSM re-heated by the SN, i.e., the IR-echo (Bode & Evans 1980;Dwek 1983Dwek , 1985Sugerman 2003). We have very little information on the properties of the CSM around this SN.…”

Section: Discussionmentioning

confidence: 93%

Twelve type II-P supernovae seen with the eyes ofSpitzer

Szalai

Vinkó

2012

A&A

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Context. Core-collapse supernovae (CC SNe), especially those of type II-plateau (II-P), are thought to be important contributors to cosmic dust production. The most obvious indicator of newly-formed and/or pre-existing dust is the time-dependent mid-infrared (MIR) excess coming from the environment of SNe. In the past few years several CC SNe were monitored by the Spitzer Space Telescope in the nebular phase, hundreds of days after explosion. On the other hand, only a few of these objects have been analyzed and published to date. Aims. Our goal was to collect publicly available, previously unpublished measurements on type II-P (or peculiar IIP) SNe from the Spitzer database. The most important aspect was to find SNe observed with the Infrared Array Camera (IRAC) on at least two epochs. The temporal changes of the observed fluxes may be indicative of the underlying supernova, while spectral energy distribution (SED) fitting to the fluxes in different IRAC channels may reveal the physical parameters of the mid-IR radiation, which is presumably caused by warm dust. Methods. The IRS spectra were extracted and calibrated with SPICE, while photometric SEDs were assembled using IRAF and MOPEX. Calculated SEDs from observed fluxes were fit with simple dust models to obtain basic information on the dust presumed as the source of MIR radiation. Results. We found twelve SNe that satisfied the criterion above, observed at late-time epochs (typically after +300 days). In three cases we could not identify any point source at the SN position on late-time IRAC images. We found two SNe, 2005ad and 2005af, which likely have newly formed dust in their environment, while in the other seven cases the observed MIR flux may originate from pre-existing circumstellar or interstellar dust. Our results support the previous observational conclusions that warm new dust in the environment of SNe contributes only marginally to the cosmic dust content.

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Section: Discussionmentioning

confidence: 93%

Twelve type II-P supernovae seen with the eyes ofSpitzer

Szalai

Vinkó

2012

A&A

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“…A very thin veil of dust will result in a perfect contrast of the echoes compared to the star's light curve. A thick dust layer will naturally decrease the echoes contrast, as a continuum of light-scattering particles with different phases are then present on the line of sight, resulting in a smeared light curve (Sugerman 2003;Bond & Sparks 2009). Qualitatively, the fact that we observe contrasted light echoes indicates that the dust is spread over a thin surface, compared to the spatial extent of a propagating echo c × P (with c the speed of light and P the period of the Cepheid), rather than within a thick layer.…”

Section: Thickness Of the Scattering Layermentioning

confidence: 99%

The long-period Galactic Cepheid RS Puppis

Kervella¹,

Mérand²,

Szabados³

et al. 2012

A&A

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Context. The southern long-period Cepheid RS Pup is surrounded by a large circumstellar dusty nebula reflecting the light from the central star. Due to the changing luminosity of the central source, light echoes propagate into the nebula. This remarkable phenomenon was the subject of Paper I. The origin and physical properties of the nebula are however uncertain: it may have been created through mass loss from the star itself, or it could be the remnant of a pre-existing interstellar cloud. Aims. Our goal is to determine the three-dimensional structure of the light-scattering nebula, and estimate its mass. This will bring us new clues on the origin of the nebula. Knowing the geometrical shape of the nebula will also allow us to retrieve the distance of RS Pup in an unambiguous manner using a model of its light echoes (in a forthcoming work). Methods. The scattering angle of the Cepheid light in the circumstellar nebula can be recovered from its degree of linear polarization. We thus observed the nebula surrounding RS Pup using the polarimetric imaging mode of the VLT/FORS instrument, and obtained a map of the degree and position angle of linear polarization. Results. From our FORS observations, we derive a three-dimensional map of the distribution of the dust around RS Pup, whose overall geometry is an irregular and geometrically thin layer. The nebula does not present a well-defined central symmetry. Using a simple scattering model, we derive a total dust mass of M dust = 2.9 ± 0.9 M for the light-scattering dust within 1.8 of the Cepheid. This translates into a total mass of M gas+dust = 290 ± 120 M , assuming a dust-to-gas ratio of M dust /M gas = 1.0 ± 0.3%. Conclusions. The high mass of the dusty nebula excludes that it was created by mass-loss from the star. However, the thinness of the dust distribution is an indication that the Cepheid participated to the shaping of the nebula, e.g. through its radiation pressure or stellar wind. RS Pup therefore appears as a regular long-period Cepheid located in an exceptionally dense interstellar environment.

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“…This offers a unique opportunity to determine the distance of the Cepheid by comparing the angular and linear radii of the denser rings in the reflection nebula. The positional coincidence of RS Pup with the reflection nebula can Article published by EDP Sciences indeed be used for determining the distance and luminosity of the Cepheid, based on the light echo phenomenon occurring around such a large amplitude variable (Havlen 1972a; see also Sugerman 2003). This distance is independent of the results obtained by other methods applicable for such variable stars.…”

Section: Introductionmentioning

confidence: 99%

The long-period Galactic Cepheid RS Puppis

Kervella¹,

Mérand

Szabados

et al. 2008

A&A

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Context. The bright southern Cepheid RS Pup is surrounded by a circumstellar nebula reflecting the light from the central star. The propagation of the light variations from the Cepheid inside the dusty nebula creates spectacular light echoes that can be observed up to large distances from the star itself. This phenomenon is currently unique in this class of stars. Aims. For this relatively distant star, the trigonometric parallax available from Hipparcos has a low accuracy. A careful observation of the light echoes has the potential to provide a very accurate, geometric distance to RS Pup. Methods. We obtained a series of CCD images of RS Pup with the NTT/EMMI instrument covering the variation period of the star (P = 41.4 d), allowing us to track the progression of the light wavefronts over the nebular features surrounding the star. We measured precisely the phase lag of the photometric variation in several regions of the circumstellar nebula. Results. From our phase lag measurements, we derive a geometric distance of 1992 ± 28 pc to RS Pup. This distance is affected by a total uncertainty of 1.4%, and corresponds to a parallax of π = 0.502 ± 0.007 mas and a distance modulus of µ = 11.50 ± 0.03. Conclusions. The geometric distance we derive is by far the most accurate to a Cepheid, and among the most accurate to any star. RS Pup appears both as somewhat neglected and particularly promising to investigate the mass-loss history of Cepheids. Thanks to its highly accurate distance, it is also bound to become an important luminosity fiducial for the long period part of the period-luminosity diagram.

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Observability of Scattered-Light Echoes around Variable Stars and Cataclysmic Events

Cited by 64 publications

References 85 publications

Twelve type II-P supernovae seen with the eyes ofSpitzer

Twelve type II-P supernovae seen with the eyes ofSpitzer

The long-period Galactic Cepheid RS Puppis

The long-period Galactic Cepheid RS Puppis

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