Time evolution of the line emission from the inner circumstellar ring of SN 1987A and its hot spots

Gröningsson, Per; Fransson, Claes; Leibundgut, B.; Lundqvist, Peter; Challis, P.; Chevalier, Roger A.; Spyromilio, J.

doi:10.1051/0004-6361:200810551

Cited by 44 publications

(69 citation statements)

References 49 publications

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“…In addition, we compared emission line fluxes from different exposures (and hence with different atmospheric seeing conditions) within the same epochs. From these measurements and the results from HST photometry presented in Gröningsson et al (2008b) we conclude that the accuracy in relative fluxes should be within 10−15%. The estimate of the absolute systematic flux error was done from a comparison between the UVES fluxes and HST spectra and photometry (see Gröningsson et al (2008a,b).…”

Section: Uvesmentioning

confidence: 59%

The outer rings of SN 1987A

Tziamtzis

Lundqvist

Gröningsson

et al. 2011

A&A

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Aims. We investigate the physical properties and structure of the outer rings of SN 1987A to understand their formation and evolution. Methods. We used low resolution spectroscopy from VLT/FORS1 and high resolution spectra from VLT/UVES to estimate the physical conditions in the outer rings, using nebular analysis for emission lines such as [ . We also measured the velocity at two positions of the outer rings to test a geometrical model for the rings. Additionally, we used data from the HST science archives to check the evolution of the outer rings of SN 1987A for a period that covers almost 11 years. Results. We measured the flux in four different regions, two for each outer ring. We chose regions away from the two bright neighbouring stars and as far as possible from the inner ring and created light curves for the emission lines of [O III], Hα, and [N II]. The light curves display a declining behaviour, which is consistent with the initial supernova-flash powering of the outer rings. The electron density of the emitting gas in the outer rings, as estimated by nebular analysis from the [O II] and [S II] lines, is < ∼ 3 × 10 3 cm −3 , has not changed over the last ∼15 years, and the [N II] temperature remains also fairly constant at ∼1.2 × 10 4 K. We find no obvious difference in density and temperature for the two outer rings. The highest density, as estimated from the decay of Hα, could be ∼5 × 10 3 cm −3 however, and because the decay is somewhat faster in the southern outer ring than it is in the northern, the highest density in the outer rings may be found in the southern outer ring. For an assumed distance of 50 kpc to the supernova, the distance between the supernova and the closest parts of the outer rings could be as short as ∼1.7 × 10 18 cm. Interaction between the supernova ejecta and the outer rings could therefore start in less than ∼20 years. We do not expect the outer rings to show the same optical display as the equatorial ring when this happens. Instead soft X-rays should provide a better way of observing the ejecta -outer rings interaction.

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Section: Uvesmentioning

confidence: 59%

The outer rings of SN 1987A

Tziamtzis

Lundqvist

Gröningsson

et al. 2011

A&A

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“…Furthermore, we also note the stronger emission from the southern part in the red-shifted [500, 1500] km s −1 bin, while the northern part dominates the blue-shifted [−1500, 500] km s −1 bin. Although the lines from the shocked ring are of intermediate width (200-400 km s −1 ) (Gröningsson et al 2008a), we see that the ring is visible in all the velocity bins. This is caused by the continuum and other lines from the ring and/or a broadening of them due to the shock interaction in the ring.…”

Section: The Ejecta Geometrymentioning

confidence: 68%

The 3-D structure of SN 1987A's inner ejecta

Kjaer¹,

Leibundgut

Fransson

et al. 2010

A&A

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Context. Observing the inner ejecta of a supernova is possible only in a handful of nearby supernova remnants. The core-collapse explosion mechanism has been extensively explored in recent models and predict large asymmetries. SN 1987A is the first modern stellar explosion that has been continuously observed from its beginning to the supernova remnant phase. Twenty years after the explosion, we are now able to observe the three-dimensional spatially resolved inner ejecta of this supernova. Aims. Detailed mapping of newly synthesised material and its radioactive decay daughter products sheds light on the explosion mechanism. This may reveal the geometry of the explosion and its connection to the equatorial ring and the outer rings around SN 1987A. Methods. We have used integral field spectroscopy to image the supernova ejecta and the equatorial ring in the emission lines of [Si I] + [Fe II] (λ1.64 μm) and He I (λ2.058 μm). The spectral information can be mapped into a radial velocity image revealing the expansion of the ejecta both as projected onto the sky and perpendicular to the sky plane. Results. The inner ejecta are spatially resolved in a North-South direction and are clearly asymmetric. Like the ring emission, the northern parts of the ejecta are blueshifted, while the material projected to the South of the supernova centre is moving away from us. We argue that the bulk of the ejecta is situated in the same plane as defined by the equatorial ring and does not form a bipolar structure as has been suggested. The exact shape of the ejecta is modelled and we find that an elongated triaxial ellipsoid fits the observations best. The velocity measured in the [Si I] + [Fe II] line corresponds to ∼3000 km s −1 and is the same as the width of the IR [Fe II] line profiles during the first years. From our spectral analyses of the ejecta spectrum we find that most of the He I, [Si I] and [Fe I-II] emission originates in the core material which has undergone explosive nucleosynthesis. The He I emission may be the result of α-rich freeze-out if the positron energy is deposited locally. Conclusions. Our observations clearly indicate a non-symmetric explosion mechanism for SN 1987A. The elongation and velocity asymmetries point towards a large-scale spatial non-spherical distribution as predicted in recent explosion models. The orientation of the ejecta in the plane of the equatorial ring argues against a jet-induced explosion through the poles due to stellar rotation.

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“…However this spectral resolution is insufficient to distinguish between the ionized but unshocked component of the ring and the shocked component of the ring, which are clearly seen as narrow (FWHM∼10 km s −1 ) and intermediate (FWHM∼300 km s −1 ) width components in high resolution optical spectra (e.g., Gröningsson et al 2008a).…”

Section: Line Identificationmentioning

confidence: 99%

“…The dotted lines at constant wavelength indicate the rest wavelength of each line. The spectra are not adjusted for the systemic velocity of the ER, ∼287 kms −1 (Gröningsson et al 2008a epochs. The shorter wavelength feature may be a blend of the H I 6-5 and 8-6 transitions.…”

Section: Line Identificationmentioning

confidence: 99%

“…Spitzer observations commenced near day 6100 (Bouchet et al 2006) while the number and brightness of hotspots around the ER were increasing (Gröningsson et al 2008a;Fransson et al 2015). This epoch is also when the soft X-ray light curve turned up (Park et al 2005(Park et al , 2006, indicating that the shock started interacting with dense protrusions from the ER.…”

Section: Introductionmentioning

confidence: 99%

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Infrared Continuum and Line Evolution of the Equatorial Ring Around Sn 1987a

Arendt

Dwek

Bouchet

et al. 2016

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Spitzer observations of SN 1987A have now spanned more than a decade. Since day ∼4000, mid-infrared (mid-IR) emission has been dominated by that from shock-heated dust in the equatorial ring (ER). From 6000 to 8000 days after the explosion, Spitzer observations included broadband photometry at 3.6-24 μm, and low and moderate resolution spectroscopy at 5-35 μm. Here we present later Spitzer observations, through day 10,377, which include only the broadband measurements at 3.6 and 4.5 μm. These data show that the 3.6 and 4.5 μm brightness has clearly begun to fade after day ∼8500, and no longer tracks the X-ray emission as well as it did at earlier epochs. This can be explained by the destruction of the dust in the ER on timescales shorter than the cooling time for the shocked gas. We find that the evolution of the late time IR emission is also similar to the now fading optical emission. We provide the complete record of the IR emission lines, as seen by Spitzer prior to day 8000. The past evolution of the gas as seen by the IR emission lines seems largely consistent with the optical emission, although the IR [Fe II] and [Si II] lines show different, peculiar velocity structures.

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Time evolution of the line emission from the inner circumstellar ring of SN 1987A and its hot spots

Cited by 44 publications

References 49 publications

The outer rings of SN 1987A

The outer rings of SN 1987A

The 3-D structure of SN 1987A's inner ejecta

Infrared Continuum and Line Evolution of the Equatorial Ring Around Sn 1987a

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