Optical spectropolarimetry of V4332 Sagittarii

Kamiński, T.; Tylenda, R.

doi:10.1051/0004-6361/201321852

Cited by 15 publications

(8 citation statements)

References 15 publications

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“…Although this interpretation is not firm, as our data lack the angular resolution to be definitive, such a structure is expected to exist around merged systems. Also, disks are observed in other red-nova remnants (Kamiński & Tylenda 2013;Tylenda et al 2011a). Such a disk or a toruslike structure is expected to carry most of the angular momentum of the former binary and consist of the common envelope material.…”

Section: Dusty Remnantmentioning

confidence: 90%

V838 Monocerotis as seen by ALMA: a remnant of a binary merger in a triple system

Kamiński,

Tylenda,

Kiljan

et al. 2021

Preprint

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Context. V838 Mon erupted in 2002 quickly becoming the prototype of a new type of stellar eruptions known today as (luminous) red novae. The red nova outbursts are thought to be caused by stellar mergers. The merger in V838 Mon took place in a triple or higher system involving two B-type stars. Aims. We wish to characterize the merger remnant ∼17 yr after the eruption to learn more about the remaining system, the progenitor, and merger physics. Methods. We mapped the merger site with ALMA at a resolution of ∼25 mas, or 148 au for a distance of 5.9 kpc, in continuum dust emission and in rotational lines of simple molecules, including CO, SiO, SO, SO 2 , AlOH, and H 2 S. We use radiative transfer calculations to reproduce the remnant's architecture at the epoch of the ALMA observations. Results. For the first time, we identify the position of the B-type companion relative to the outbursting component of V838 Mon. The stellar remnant is surrounded by a clumpy wind with characteristics similar to winds of red supergiants. The merger product is also associated with an elongated structure, 17.6 × 7.6 mas (104 × 45 au), seen in continuum emission, and which we interpret as a disk seen at a moderate inclination. Maps of continuum and molecular emission show also a complex region of interaction between the B-type star (its gravity, radiation, and wind) and the flow of matter ejected in 2002. The remnant's molecular mass is about 0.1 M and the dust mass is 8.3•10 −3 M . The mass of the atomic component remains unconstrained.Conclusions. The most interesting region for understanding the merger of V838 Mon remains unresolved but appears elongated. To study it further in more detail will require even higher angular resolutions. ALMA maps show us an extreme form of interaction between the merger ejecta with a distant (∼250 au) companion. This interaction is similar to that known from the Anteres AB system but at a much higher mass loss rate. The B-type star not only deflects the merger ejecta but also changes its chemical composition with an involvement of circumstellar shocks. The ALMA view on V838 Mon offers the best so far images of a merger site.

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Section: Dusty Remnantmentioning

confidence: 90%

V838 Monocerotis as seen by ALMA: a remnant of a binary merger in a triple system

Kamiński,

Tylenda,

Kiljan

et al. 2021

Preprint

View full text Add to dashboard Cite

show abstract

“…Although this interpretation is not firm, as our data lack the angular resolution needed for a definitive conclusion, such a structure is expected to exist around merged systems. Also, disks are observed in other rednova remnants (Kamiński & Tylenda 2013;Tylenda et al 2011a). Such a disk or a torus-like structure is expected to carry most of the angular momentum of the former binary and consist of the common envelope material.…”

Section: Dusty Remnantmentioning

confidence: 92%

V838 Monocerotis as seen by ALMA: A remnant of a binary merger in a triple system

Kamiński

Tylenda

Kiljan

et al. 2021

A&A

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Context. V838 Mon erupted in 2002, quickly becoming the prototype of a new type of stellar eruption known today as the (luminous) red nova. Red nova outbursts are thought to be caused by stellar mergers. The merger in V838 Mon took place in a triple or higher system involving two B-type stars. Aims. We wish to characterize the merger remnant ~17 yr after the eruption to learn more about the remaining system, the progenitor, and the merger physics. Methods. We mapped the merger site with ALMA at a resolution of ~25 mas, or 148 au for a distance of 5.9 kpc, in continuum dust emission and in rotational lines of simple molecules, including CO, SiO, SO, SO2, AlOH, and H2S. We use radiative transfer calculations to reproduce the architecture of the remnant at the epoch of the ALMA observations. We also make use of optical spectroscopy data obtained mainly with VLT/X-shooter and SALT/HRS. Results. For the first time, we identify the position of the B-type companion relative to the outbursting component of V838 Mon. The stellar remnant is surrounded by a clumpy wind with characteristics similar to those of the winds of red supergiants. The merger product is also associated with an elongated structure of 17.6 × 7.6 mas (104 × 45 au) seen in continuum emission, and which we interpret as a disk seen at a moderate inclination. Maps of continuum and molecular emission also show a complex region of interaction between the B-type star (its gravity, radiation, and wind) and the flow of matter ejected in 2002. The remnant’s molecular mass is about 0.1 M⊙ and the dust mass is 8.3 × 10−3 M⊙. The mass of the atomic component remains unconstrained. Conclusions. The most interesting region for understanding the merger of V838 Mon lies in its direct vicinity and appears elongated, but details of its substructure remain unknown. To study it further and in more detail will require even higher angular resolutions. ALMA maps show us an extreme form of interaction between the merger ejecta and the distant (~250 au) companion. This interaction is similar to that known from the Anteres AB system but at a much higher mass loss rate. The B-type star not only deflects the merger ejecta but also changes its molecular composition with an involvement of circumstellar shocks. The ALMA view of V838 Mon offers the best images of a merger site so far.

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“…The polarization properties of V854 Cen are similar (albeit weaker) to those of the intermediate-luminosity red transient (ILOT) V4332 Sgr (Kamiński & Tylenda 2013;Berger et al 2009) that suffered an outburst in 1994 and later developed the characteristics of a large giant. ILOTs are outbursts with energies intermediate between those of novae and supernovae (Kasliwal 2012) examples of which are V838 Mon (Bond et al 2003) or V1309 Sco (Tylenda et al 2011).…”

Section: Discussionmentioning

confidence: 78%

“…ILOTs are outbursts with energies intermediate between those of novae and supernovae (Kasliwal 2012) examples of which are V838 Mon (Bond et al 2003) or V1309 Sco (Tylenda et al 2011). Kamiński & Tylenda (2013) show that the polarized continuum of V4332 Sgr in 2011 disagrees with the unpolarised emission lines. This is interpreted as evidence for a disk seen at high inclination that completely obscures the central source.…”

Section: Discussionmentioning

confidence: 96%

The RCB star V854 Centauri is surrounded by a hot dusty shell

Chesneau

Millour

Marco

et al. 2014

A&A

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Aims. The hydrogen-deficient supergiants known as R Coronae Borealis (RCB) stars might be the result of a double-degenerate merger of two white dwarfs (WDs), or a final helium shell flash in a planetary nebula central star. In this context, any information on the geometry of their circumstellar environment and, in particular, the potential detection of elongated structures, is of great importance. Methods. We obtained near-IR observations of V854 Cen with the AMBER recombiner located at the Very Large Telescope Interferometer (VLTI) array with the compact array (B ≤ 35 m) in 2013 and the long array (B ≤ 140 m) in 2014. At each time, V854 Cen was at maximum light. The H-and K-band continua were investigated by means of spectrally dependant geometric models. These data were supplemented with mid-IR VISIR/VLT images. Results. A dusty slightly elongated overdensity is discovered both in the H-and K-band images. With the compact array, the central star is unresolved (Θ ≤ 2.5 mas), but a flattened dusty environment of 8 × 11 mas is discovered whose flux increases from about ∼20% in the H band to reach about ∼50% at 2.3μm, which indicates hot (T ∼ 1500 K) dust in the close vicinity of the star. The major axis is oriented at a position angle (PA) of 126 ± 29• . Adding the long-array configuration dataset provides tighter constraints on the star diameter (Θ ≤ 1.0 mas), a slight increase of the overdensity to 12 × 15 mas and a consistent PA of 133 ± 49• . The closure phases, sensitive to asymmetries, are null and compatible with a centro-symmetric, unperturbed environment excluding point sources at the level of 3% of the total flux in 2013 and 2014. The VISIR images exhibit a flattened aspect ratio at the 15−20% level at larger distances (∼1 ) with a position angle of 92 ± 19• , marginally consistent with the interferometric observations. Conclusions. This is the first time that a moderately elongated structure has been observed around an RCB star. These observations confirm the numerous suggestions for a bipolar structure proposed for this star in the literature, which were mainly based on polarimetric and spectroscopic observations.

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Optical spectropolarimetry of V4332 Sagittarii

Cited by 15 publications

References 15 publications

V838 Monocerotis as seen by ALMA: a remnant of a binary merger in a triple system

V838 Monocerotis as seen by ALMA: a remnant of a binary merger in a triple system

V838 Monocerotis as seen by ALMA: A remnant of a binary merger in a triple system

The RCB star V854 Centauri is surrounded by a hot dusty shell

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