Nova V4444 Sagittarii 1999: Spectropolarimetric Evidence for a Preexisting Circumstellar Dust Cloud

Kawabata, Koji S.; Hirata, Ryuko; Ikeda, Yuji; Akitaya, Hiroshi; Seki, M.; Matsumura, Masatoshi; Okazaki, Akira

doi:10.1086/309339

Cited by 17 publications

(23 citation statements)

References 31 publications

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“…It is observed in a variety of objects, including Be stars (McLean & Clarke 1979), novae (Bjorkman et al 1994;Kawabata et al 2006), supernovae (SN 1987A, Cropper et al 1988, eruptive events such as V838 Mon (Wisniewski et al 2003), and the post-red supergiant IRC+10420 (Patel et al 2008). However, we note that there are exceptions, in which continuum polarization is observed but no line effect is detected, both in Be stars (McLean & Clarke 1979;Quirrenbach et al 1997) and in Nova Sagittarii 1999 (Kawabata et al 2000).…”

Section: Electron Scatteringmentioning

confidence: 55%

VLT spectropolarimetry of the optical transient in NGC 300

Patat¹,

Maund²,

Benetti³

et al. 2010

A&A

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Aims. We study possible signs of asymmetry in the bright optical transient in NGC 300, to obtain independent information about the explosion mechanism, the progenitor star and its circumstellar environment. Methods. Using VLT-FORS1, we obtained low-resolution optical linear spectropolarimetry of NGC 300 OT2008-1 on two epochs, 48 and 55 days after the discovery, covering the spectral range 3600-9330 Å. Results. The data exhibit a continuum polarization at a very significant level. At least two separate components are identified. The first is characterized by both a strong wavelength dependency and a constant position angle (68.6 ± 0.3 degrees), which is parallel to the local spiral arm of the host galaxy. The latter is aligned along a completely different position angle (151.3 ± 0.4). While the former is identified as arising in the interstellar dust associated with NGC 300, the latter is most likely caused by continuum polarization by dust scattering in the circumstellar environment. No line depolarization is detected in correspondence to the most intense emission lines, disfavoring electron scattering as the source of intrinsic polarization. This implies that there is a very small deviation from symmetry in the continuum-forming region. Given the observed level of intrinsic polarization, the transient must be surrounded by a significant amount of dust (≥4 × 10 −5 M ), asymmetrically distributed within a few thousand AU. This probably implies that one or more asymmetric outflow episodes took place during the past history of the progenitor.

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Section: Electron Scatteringmentioning

confidence: 55%

VLT spectropolarimetry of the optical transient in NGC 300

Patat¹,

Maund²,

Benetti³

et al. 2010

A&A

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“…It was observed during lunar occultations (Dunham 1974;Schmidtke et al 1989) and recorded as double in the University of Texas Special Double Star list (Schmidtke 1979). Previous prism observations (typically 39/91 Å mm −1 ) were obtained by several authors (see, e.g., Houk & Cowley 1975;Reed & Beatty 1995;Garrison et al 1977;Abt et al 1979;Kennedy 1983;Kawabata et al 2000). The composite spectrum is usually classified combining an early B to late A star component, plus an early F. In particular, Garrison et al (1977) classified V 4385 Sgr as a shell star having Mg, He, and Si like a B5 star but with very broad H and Ca ii and the rest of the spectrum like an F2 star.…”

Section: V4385 Sgr -Composite Spectrummentioning

confidence: 91%

VSOP: the variable star one-shot project

Dall¹,

Foellmi²,

Pritchard

et al. 2007

A&A

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Context. About 500 new variable stars enter the General Catalogue of Variable Stars (GCVS) every year. Most of them however lack spectroscopic observations, which remains critical for a correct assignement of the variability type and for the understanding of the object. Aims. The Variable Star One-shot Project (VSOP) is aimed at (1) providing the variability type and spectral type of all unstudied variable stars, (2) process, publish, and make the data available as automatically as possible, and (3) generate serendipitous discoveries. This first paper describes the project itself, the acquisition of the data, the dataflow, the spectroscopic analysis and the on-line availability of the fully calibrated and reduced data. We also present the results on the 221 stars observed during the first semester of the project. Methods. We used the high-resolution echelle spectrographs HARPS and FEROS in the ESO La Silla Observatory (Chile) to survey known variable stars. Once reduced by the dedicated pipelines, the radial velocities are determined from cross correlation with synthetic template spectra, and the spectral types are determined by an automatic minimum distance matching to synthetic spectra, with traditional manual spectral typing cross-checks. The variability types are determined by manually evaluating the available light curves and the spectroscopy. In the future, a new automatic classifier, currently being developed by members of the VSOP team, based on these spectroscopic data and on the photometric classifier developed for the COROT and Gaia space missions, will be used. Results. We confirm or revise spectral types of 221 variable stars from the GCVS. We identify 26 previously unknown multiple systems, among them several visual binaries with spectroscopic binary individual components. We present new individual results for the multiple systems V349 Vel and BC Gru, for the composite spectrum star V4385 Sgr, for the T Tauri star V1045 Sco, and for DM Boo which we re-classify as a BY Draconis variable. The complete data release can be accessed via the VSOP web site.

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“…To calculate the visual extinction, we used the color excess value of 1.07, thus A v = 3.32 AE 0.31 with a calculated distance of d = 4.48 AE 0.44 kpc. For comparison, Kawabata et al (2000) found the following results: t 2 = 3.2 days, M v = À9.0 AE 0.2, E(BÀV ) = 0.75 AE 0.04, A v = 2.8 AE 0.3, and d = 4.7 AE 0.7 kpc.…”

Section: Light Curve Reddening and Distancementioning

confidence: 91%

“…Alternatively, the thermal emission and lack of a dust formation signature may be because of preexisting dust that was warmed by the current outburst. Optical spectropolarimetry of V4444 Sgr by Kawabata et al (2000) showed evidence of preexisting small grains located around the WD. They concluded that the dust cloud was located less than 50 AU from the central star.…”

Section: Light Curve Reddening and Distancementioning

confidence: 99%

Near-Infrared Spectroscopy of Nova Sagittarius 1999 (V4444 Sagittarii)

Venturini¹,

Rudy²,

Lynch³

et al. 2002

The Astronomical Journal

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We present 0.8-2.5 lm near-IR spectrophotometry of the very fast nova Nova Sagittarius 1999 (V4444 Sgr) taken 125 days after outburst. The emission-line spectrum of V4444 Sgr, with features ranging from C i to [Si ix] and [Si viii], exhibited perhaps the greatest spread of excitation for any single-epoch observation of a nova. However, two other novae, Nova Sagittarius 1992 No. 2 and Nova Aquila 1993, had spectra similar to V4444 Sgr between 0.8 and 1.4 lm, so such manifestations may not be uncommon. The continuum of V4444 Sgr showed a significant rise longward of 1.5 lm indicative of thermal emission from dust. The absence of any dust features in the light curve of V4444 Sgr suggests that we may have a relatively unobscured line of sight, or that some or all of the circumstellar dust was preexisting. The latter would indicate that V4444 Sgr is possibly a recurrent nova.

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Nova V4444 Sagittarii 1999: Spectropolarimetric Evidence for a Preexisting Circumstellar Dust Cloud

Cited by 17 publications

References 31 publications

VLT spectropolarimetry of the optical transient in NGC 300

VLT spectropolarimetry of the optical transient in NGC 300

VSOP: the variable star one-shot project

Near-Infrared Spectroscopy of Nova Sagittarius 1999 (V4444 Sagittarii)

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