| 151. |
- Kuncarayakti, Hanindyo, et al.
(författare)
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SN 2017dio : A Type-Ic Supernova Exploding in a Hydrogen-rich Circumstellar Medium
- 2018
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8205 .- 2041-8213. ; 854:1
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Tidskriftsartikel (refereegranskat)abstract
- SN 2017dio shows both spectral characteristics of a type-Ic supernova (SN) and signs of a hydrogen-rich circumstellar medium (CSM). Prominent, narrow emission lines of H and He are superposed on the continuum. Subsequent evolution revealed that the SN ejecta are interacting with the CSM. The initial SN Ic identification was confirmed by removing the CSM interaction component from the spectrum and comparing with known SNe Ic and, reversely, adding a CSM interaction component to the spectra of known SNe Ic and comparing them to SN 2017dio. Excellent agreement was obtained with both procedures, reinforcing the SN Ic classification. The light curve constrains the pre-interaction SN Ic peak absolute magnitude to be around M-g = -17.6 mag. No evidence of significant extinction is found, ruling out a brighter luminosity required by an SN Ia classification. These pieces of evidence support the view that SN 2017dio is an SN Ic, and therefore the first firm case of an SN Ic with signatures of hydrogen-rich CSM in the early spectrum. The CSM is unlikely to have been shaped by steady-state stellar winds. The mass loss of the progenitor star must have been intense, M similar to 0.02 (epsilon(H alpha)/0.01)(-1) (nu(wind)/500 km s(-1)) (nu(shock)/10,000 km s(-1))M--3(circle dot) yr(-1), peaking at a few decades before the SN. Such a high mass-loss rate might have been experienced by the progenitor through eruptions or binary stripping.
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| 152. |
- Kundu, Esha, et al.
(författare)
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Constraining Magnetic Field Amplification in SN Shocks Using Radio Observations of SNe 2011fe and 2014J
- 2017
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 842:1
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Tidskriftsartikel (refereegranskat)abstract
- We modeled the radio non-detection of two Type Ia supernovae (SNe), SN 2011fe and SN 2014J, considering synchrotron emission from the interaction between SN ejecta and the circumstellar medium. For ejecta whose outer parts have a power-law density structure, we compare synchrotron emission with radio observations. Assuming that 20% of the bulk shock energy is being shared equally between electrons and magnetic fields, we found a very low-density medium around both the SNe. A less tenuous medium with particle density similar to 1 cm(-3), which could be expected around both SNe, can be estimated when the magnetic field amplification is less than that presumed for energy equipartition. This conclusion also holds if the progenitor of SN. 2014J was a rigidly rotating white dwarf (WD) with a main-sequence (MS) or red giant companion. For a He star companion, or a MS for SN. 2014J, with 10% and 1% of bulk kinetic energy in magnetic fields, we obtain mass-loss rates of < 10(-9) and 99% onto the WD, but is less restricted for the latter case. However, if the tenuous medium is due to a recurrent nova, it is difficult from our model to predict synchrotron luminosities. Although the formation channels of SNe. 2011fe and 2014J are not clear, the null detection in radio wavelengths could point toward a low amplification efficiency for magnetic fields in SN shocks.
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| 153. |
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| 154. |
- Kundu, Esha, 1987-
(författare)
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Modeling of Radio Emission from Supernovae : Application to Type Ia
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The interaction of supernova (SN) ejecta with the circumstellar medium (CSM) drives a strong shock wave into the CSM. These shocks are ideal places where effective particle acceleration and magnetic field amplification can take place. The accelerated relativistic particles, in the presence of magnetic field, could emit a part of their energy via synchrotron radiation in radio wavelengths. The flux of this radiation, when compared with observations, gives an estimate of the CSM density. This could either be the particle density ($\rm n_{ISM}$) in case of the SN exploding in a constant density medium, characteristic of interstellar medium, or pre-SN mass loss rate ($\mdot$) of the progenitor system for a wind medium. In this work we have modeled the synchrotron luminosities and compared that with the radio upper limits measured for the Type Ia SNe 2011fe and 2014J. Assuming equipartition of energy between electric and magnetic fields, with 10$\%$ of the thermal shock energy in each field, we found a very low density medium, having $\rm n_{ISM} < \sim $ 0.35 $\ccc$,around both the SNe. In terms of $\mdot$ this implies an upper limit of $10^{-9}$ \msunyr for a wind velocity of 100 \kms. From the measurements of H I column density it could be expected that $\rm n_{ISM} \sim $ 1 $\ccc$ around both the SNe. If this is the true value close to the SNe, this would indicate that the energy density in magnetic field is less than that presumed for energy equipartition. The progenitors of both SNe 2011fe and 2014J are not clear. However previous studies have pointed toward a few potential channels. Here, we have compared the CSM densities estimated by our models with that predicted by those different plausible formation channels and have tried to constrain the amplification of magnetic fields in SN shocks.
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| 155. |
- Kundu, Esha, 1987-
(författare)
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Radio emission from supernovae
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents the modeling of radio and X-ray emissions from supernova (SN) shock fronts and hydrodynamical simulations of SN-circumstellar medium (CSM) interaction. The interaction of SN ejecta with the CSM drives a strong shock wave into the CSM. These shocks are ideal places where effective particle acceleration and magnetic field amplification can take place. The accelerated relativistic particles, in the presence of magnetic field, could emit part of their energy via synchrotron radiation in radio wavelengths. The flux of this radiation, when compared with observations, gives an estimate of the CSM density. This could either be the particle density (nISM) in case of the SN exploding in a constant density medium, characteristic of interstellar medium, or pre-SN mass loss rate (dM/dt) of the progenitor system for a wind medium. In Paper I we have modeled the synchrotron emission and compared that with the radio upper limits measured for the Type Ia SNe 2011fe and 2014J. Assuming equipartition of energy between electric and magnetic fields, with 10% of the thermal shock energy in each field, we obtain a very low density medium, having nISM <~ 0.35 cm-3, around both the SNe. In terms of dM/dt this implies an upper limit of 10-9 Msun yr-1 for a wind velocity, vw, of 100 km s-1. This study suggests that in SN shocks it is more likely that the amplification efficiency of magnetic fields is less than that for the electric fields. In Paper II, we carry out the hydrodynamical simulations of the interaction between SN ejecta and CSM for SN 1993J and SN 2011dh. Subsequently, the radio and X-ray emission have been calculated from the shocked gas encapsulated between the forward and reverse shocks. Considering the ejecta profile of these SNe from multi-group radiation hydrodynamics simulation (STELLA), it is found from our investigation that for a wind velocity of 10 km/s around 6500 years prior to the explosion of SN 1993J a change in mass loss rate occurred in the system. For a binary system this may imply that the change in dM/dt could be due to a change in the mass accretion efficiency of the companion star. In case of SN 2011dh the late time emission is turned up to be consistent with a wind medium with (dM/dt)/vw = 4 × 10-6 Msun yr-1/10 km s-1. Paper III focuses on the radio emission from four young SNe Type Ia, SN 2013dy, SN 2016coj, SN 2018pv and SN 2018gv. Using the same model for radio emission as in Paper I, the upper limits on dM/dt and nISM are estimated. We found tenuous media around these SNe, which put tight constrain on their progenitor systems.
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| 156. |
- Kundu, Esha, et al.
(författare)
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uEvolution of the Progenitors of SNe 1993J and 2011dh Revealed through Late-time Radio and X-Ray Studies
- 2019
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 875:1
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Tidskriftsartikel (refereegranskat)abstract
- We perform hydrodynamical simulations of the interaction between supernova (SN) ejecta and circumstellar medium (CSM) for SN 1993J and SN 2011dh, and calculate the radio and X-ray emissions expected from the shocked gas at late epochs (t). Considering the ejecta structure from multi-group radiation hydrodynamics simulation, we find that the observed rapid drop in radio and X-ray light curves of SN 1993J at t > 3000 days may be due to a change in the mass-loss rate ((M)over dot) similar to 6500 yr prior to the explosion of the SN. The exact epoch scales inversely with the assumed wind velocity of nu(w) = 10 km s(-1). The progenitor of this SN very likely belonged to a binary system, where, during its evolution, the primary had transferred material to the secondary. It is argued in this paper that the change in (M)over dot can happen because of a change in the mass accretion efficiency (eta) of the companion star. It is possible that before similar to 6500. (nu(w)/10 km s(-1))(-1) yr prior to the explosion, eta was high, and thus the CSM was tenuous, which causes the late-time downturn in fluxes. In the case of SN. 2011dh, the late-time evolution is found to be consistent with a wind medium with (M)over dot/nu(w) = 4 x 10(-6) M-circle dot yr(-1)/10 km s(-1). It is difficult from our analysis to predict whether the progenitor of this SN had a binary companion; however, if future observations show a similar decrease in radio and X-ray fluxes, then this would give strong support to a scenario where both SNe had undergone a similar kind of binary evolution before explosion.
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| 157. |
- Larsson, Josefin, et al.
(författare)
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Clumps and Rings of Ejecta in SNR 0540-69.3 as Seen in 3D
- 2021
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 922:2
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Tidskriftsartikel (refereegranskat)abstract
- The distribution of ejecta in young supernova remnants offers a powerful observational probe of their explosions and progenitors. Here we present a 3D reconstruction of the ejecta in SNR 0540-69.3, which is an O-rich remnant with a pulsar wind nebula located in the LMC. We use observations from the Very Large Telescope (VLT)/MUSE to study Hβ, [O iii] λλ4959, 5007, Hα, [S ii] λλ6717, 6731, [Ar iii] λ7136, and [S iii] λ9069. This is complemented by 2D spectra from VLT/X-shooter, which also cover [O ii] λλ3726, 3729, and [Fe ii] λ12567. We identify three main emission components: (i) clumpy rings in the inner nebula (≲1000 km s−1) with similar morphologies in all lines; (ii) faint extended [O iii] emission dominated by an irregular ring-like structure with radius ∼1600 km s−1 and inclination ∼40°, but with maximal velocities reaching ∼3000 km s−1; and (iii) a blob of Hα and Hβ located southeast of the pulsar at velocities ∼1500–3500 km s−1. We analyze the geometry using a clump-finding algorithm and use the clumps in the [O iii] ring to estimate an age of 1146 ± 116 yr. The observations favor an interpretation of the [O iii] ring as ejecta, while the origin of the H-blob is more uncertain. An alternative explanation is that it is the blown-off envelope of a binary companion. From the detection of Balmer lines in the innermost ejecta we confirm that SNR 0540 was a Type II supernova and that hydrogen was mixed down to low velocities in the explosion.
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| 158. |
- Larsson, Josefin, et al.
(författare)
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The Matter Beyond the Ring : The Recent Evolution of SN 1987A Observed by the Hubble Space Telescope
- 2019
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Ingår i: Astrophysical Journal. - : IOP PUBLISHING LTD. - 0004-637X .- 1538-4357. ; 886:2
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Tidskriftsartikel (refereegranskat)abstract
- The nearby SN 1987A offers a spatially resolved view of the evolution of a young supernova (SN) remnant. Here we present recent Hubble Space Telescope imaging observations of SN 1987A, which we use to study the evolution of the ejecta, the circumstellar equatorial ring (ER), and the increasing emission from material outside the ER. We find that the inner ejecta have been brightening at a gradually slower rate and that the western side has been brighter than the eastern side since similar to 7000 days. This is expected given that the X-rays from the ER are most likely powering the ejecta emission. At the same time, the optical emission from the ER continues to fade linearly with time. The ER is expanding at 680 50 km s(-1), which reflects the typical velocity of transmitted shocks in the dense hot spots. A dozen spots and a rim of diffuse H alpha emission have appeared outside the ER since 9500 days. The new spots are more than an order of magnitude fainter than the spots in the ER and also fade faster. We show that the spots and diffuse emission outside the ER may be explained by fast ejecta interacting with high-latitude material that extends from the ER toward the outer rings. Further observations of this emission will make it possible to determine the detailed geometry of the high-latitude material and provide insight into the formation of the rings and the mass-loss history of the progenitor.
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| 159. |
- Larsson, Josefin, et al.
(författare)
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The morphology of the ejecta in supernova 1987a : A study over time and wavelength
- 2013
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 768:1, s. 89-
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Tidskriftsartikel (refereegranskat)abstract
- We present a study of the morphology of the ejecta in Supernova 1987A based on images and spectra from the Hubble Space Telescope (HST) as well as integral field spectroscopy from VLT/SINFONI. The HST observations were obtained between 1994 and 2011 and primarily probe the outer H-rich zones of the ejecta. The SINFONI observations were obtained in 2005 and 2011 and instead probe the [Si I]+[Fe II] emission from the inner regions. We find a strong temporal evolution of the morphology in the HST images, from a roughly elliptical shape before similar to 5000 days, to a more irregular, edge-brightened morphology with a "hole" in the middle thereafter. This transition is a natural consequence of the change in the dominant energy source powering the ejecta, from radioactive decay before similar to 5000 days to X-ray input from the circumstellar interaction thereafter. The [Si I]+[Fe II] images display a more uniform morphology, which may be due to a remaining significant contribution from radioactivity in the inner ejecta and the higher abundance of these elements in the core. Both the Ha and the [Si I]+[Fe II] line profiles show that the ejecta are distributed fairly close to the plane of the inner circumstellar ring, which is assumed to define the rotational axis of the progenitor star. The Ha emission extends to higher velocities than [Si I]+[Fe II], as expected from theoretical models. There is no clear symmetry axis for all the emission. Instead, we find that the emission is concentrated to clumps and that the emission is distributed somewhat closer to the ring in the north than in the south. This north-south asymmetry may be partially explained by dust absorption. We compare our results with explosion models and find some qualitative agreement, but note that the observations show a higher degree of large-scale asymmetry.
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| 160. |
- Larsson, Josefin, et al.
(författare)
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THREE-DIMENSIONAL DISTRIBUTION OF EJECTA IN SUPERNOVA 1987A AT 10,000 DAYS
- 2016
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Ingår i: Astrophysical Journal. - : Institute of Physics Publishing (IOPP). - 0004-637X .- 1538-4357. ; 833:2
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Tidskriftsartikel (refereegranskat)abstract
- Due to its proximity, SN. 1987A offers a unique opportunity to directly observe the geometry of a stellar explosion as it unfolds. Here we present spectral and imaging observations of SN. 1987A obtained similar to 10,000 days after the explosion with HST/STIS and VLT/SINFONI at optical and near-infrared wavelengths. These observations allow us to produce the most detailed 3D map of Ha to date, the first 3D maps for [Ca II] lambda lambda 7292, 7324, [O I] lambda lambda 6300, 6364, and Mg. II lambda lambda 9218, 9244, as well as new maps for [Si I]+[Fe II] 1.644 mu m and He I 2.058 mu m. A comparison with previous observations shows that the [Si I]+[Fe II] flux and morphology have not changed significantly during the past ten years, providing evidence that this line is powered by Ti-44. The time evolution of Ha shows that it is predominantly powered by X-rays from the ring, in agreement with previous findings. All lines that have sufficient signal show a similar large-scale 3D structure, with a north-south asymmetry that resembles a broken dipole. This structure correlates with early observations of asymmetries, showing that there is a global asymmetry that extends from the inner core to the outer envelope. On smaller scales, the two brightest lines, Ha and [Si I]+[Fe II] 1.644 mu m, show substructures at the level of similar to 200-1000 km s(-1) and clear differences in their 3D geometries. We discuss these results in the context of explosion models and the properties of dust in the ejecta.
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