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| 2. |
- Deckers, M., et al.
(författare)
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Photometric study of the late-time near-infrared plateau in Type Ia supernovae
- 2023
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 521:3, s. 4414-4430
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Tidskriftsartikel (refereegranskat)abstract
- We present an in-depth study of the late-time near-infrared plateau in Type Ia supernovae (SNe Ia), which occurs between 70 and 500 d. We double the existing sample of SNe Ia observed during the late-time near-infrared plateau with new observations taken with the Hubble Space Telescope, Gemini, New Technology Telescope, the 3.5-m Calar Alto Telescope, and the Nordic Optical Telescope. Our sample consists of 24 nearby SNe Ia at redshift < 0.025. We are able to confirm that no plateau exists in the Ks band for most normal SNe Ia. SNe Ia with broader optical light curves at peak tend to have a higher average brightness on the plateau in J and H, most likely due to a shallower decline in the preceding 100 d. SNe Ia that are more luminous at peak also show a steeper decline during the plateau phase in H. We compare our data to state-of-the-art radiative transfer models of nebular SNe Ia in the near-infrared. We find good agreement with the sub-Mch model that has reduced non-thermal ionization rates, but no physical justification for reducing these rates has yet been proposed. An analysis of the spectral evolution during the plateau demonstrates that the ratio of [Fe II] to [Fe III] contribution in a near-infrared filter determines the light curve evolution in said filter. We find that overluminous SNe decline slower during the plateau than expected from the trend seen for normal SNe Ia.
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| 3. |
- Hosseinzadeh, Griffin, et al.
(författare)
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Weak Mass Loss from the Red Supergiant Progenitor of the Type II SN 2021yja
- 2022
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 935:1
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Tidskriftsartikel (refereegranskat)abstract
- We present high-cadence optical, ultraviolet (UV), and near-infrared data of the nearby (D approximate to 23 Mpc) Type II supernova (SN) 2021yja. Many Type II SNe show signs of interaction with circumstellar material (CSM) during the first few days after explosion, implying that their red supergiant (RSG) progenitors experience episodic or eruptive mass loss. However, because it is difficult to discover SNe early, the diversity of CSM configurations in RSGs has not been fully mapped. SN 2021yja, first detected within approximate to 5.4 hours of explosion, shows some signatures of CSM interaction (high UV luminosity and radio and x-ray emission) but without the narrow emission lines or early light-curve peak that can accompany CSM. Here we analyze the densely sampled early light curve and spectral series of this nearby SN to infer the properties of its progenitor and CSM. We find that the most likely progenitor was an RSG with an extended envelope, encompassed by low-density CSM. We also present archival Hubble Space Telescope imaging of the host galaxy of SN 2021yja, which allows us to place a stringent upper limit of less than or similar to 9 M-circle dot; on the progenitor mass. However, this is in tension with some aspects of the SN evolution, which point to a more massive progenitor. Our analysis highlights the need to consider progenitor structure when making inferences about CSM properties, and that a comprehensive view of CSM tracers should be made to give a fuller view of the last years of RSG evolution.
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| 5. |
- Medler, K., et al.
(författare)
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SN 2020acat : an energetic fast rising Type IIb supernova
- 2022
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 513:4, s. 5540-5558
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Tidskriftsartikel (refereegranskat)abstract
- The ultraviolet (UV) and near-infrared (NIR) photometric and optical spectroscopic observations of SN 2020acat covering ∼250 d after explosion are presented here. Using the fast rising photometric observations, spanning from the UV to NIR wavelengths, a pseudo-bolometric light curve was constructed and compared to several other well-observed Type IIb supernovae (SNe IIb). SN 2020acat displayed a very short rise time reaching a peak luminosity of Log10(L)=42.49±0.17ergs−1 in only ∼14.6 ± 0.3 d. From modelling of the pseudo-bolometric light curve, we estimated a total mass of 56Ni synthesized by SN 2020acat of MNi = 0.13 ± 0.03 M⊙, with an ejecta mass of Mej = 2.3 ± 0.4 M⊙ and a kinetic energy of Ek = 1.2 ± 0.3 × 1051 erg. The optical spectra of SN 2020acat display hydrogen signatures well into the transitional period (≳ 100 d), between the photospheric and the nebular phases. The spectra also display a strong feature around 4900 Å that cannot be solely accounted for by the presence of the Fe II 5018 line. We suggest that the Fe II feature was augmented by He I 5016 and possibly by the presence of N II 5005. From both photometric and spectroscopic analysis, we inferred that the progenitor of SN 2020acat was an intermediate-mass compact star with an MZAMS of 15–20 M⊙.
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| 6. |
- Gustavsson, B, et al.
(författare)
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First observations of X-mode suppression of O-mode HF enhancements at 6300 angstrom
- 2009
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 36, s. L20102-
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Tidskriftsartikel (refereegranskat)abstract
- We present observations of radio induced optical emissions from a HAARP experiment with simultaneous transmission in X and O-mode. The additional transmission of X-mode with a frequency 700 kHz higher than the O-mode, reduces the enhancement of the 6300 A emission. This suggests that the wave-plasma process that energizes the electrons, which excites oxygen to the O(D-1) state, is closely connected to the excitation of upper-hybrid waves, whose onset and initial growth are reduced by additional X-mode pumping. Citation: Gustavsson, B., R. Newsome, T. B. Leyser, M. J. Kosch, L. Norin, M. McCarrick, T. Pedersen, and B. J. Watkins (2009), First observations of X-mode suppression of O-mode HF enhancements at 6300 angstrom, Geophys. Res. Lett., 36, L20102, doi:10.1029/2009GL039421.
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| 8. |
- Nakazawa, K., et al.
(författare)
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Defective processing of keratan sulfate in Macular corneal dystrophy
- 1984
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Ingår i: Journal of Biological Chemistry. - 0021-9258. ; 259:22, s. 13751-13757
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Tidskriftsartikel (refereegranskat)abstract
- macular corneal dystrophy is a human genetic disorder characterized by corneal opacities that arise, in part, from a failure to synthesize mature keratan sulfate proteoglycans. The macromolecules in macular corneas and in keratoconus corneas, an abnormality not involving proteoglycans, were biosynthetically labeled with [3H]mannose and [14C]glucosamine in organ culture, and the keratan sulfate proteoglycans were immunoprecipitated with antibodies against the protein core of monkey keratan sulfate proteoglycan. The chondroitin sulfate proteoglycans, which did not react with the antibody, were oversulfated in corneas from patients with macular corneal dystrophy. Characterization of the immunoprecipitates showed that macular corneas did not make keratan sulfate proteoglycan but did synthesize an immunoreactive glycoprotein in nearly equal amounts as keratan sulfate proteoglycan was synthesized by the keratoconus cornea. The oligosaccharides on the immunoprecipitated macular glycoprotein appeared to be normal. However, the macromolecules contained an unsulfated glycoconjugate that was nearly as large as the normal keratan sulfate chains isolated from the keratoconus keratan sulfate-proteoglycan and contained the same relative proportions of labeled glucosamine, mannose, and fucose. This glycoconjugate was resistant to digestion with keratanase. These observations indicate that macular corneal dystropy is caused by an error in the synthesis of keratan sulfate, possibly involving the specific sulfotransferases involved in sulfation of the lactosaminoglycan backbone of the chains.
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| 9. |
- Wang, Qinan, et al.
(författare)
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Revealing the Progenitor of SN 2021zby through Analysis of the TESS Shock-cooling Light Curve
- 2023
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8205 .- 2041-8213. ; 943:2
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Tidskriftsartikel (refereegranskat)abstract
- We present early observations and analysis of the double-peaked Type IIb supernova (SN IIb) SN 2021zby. TESS captured the prominent early shock-cooling peak of SN 2021zby within the first ∼10 days after explosion with a 30 minute cadence. We present optical and near-infrared spectral series of SN 2021zby, including three spectra during the shock-cooling phase. Using a multiband model fit, we find that the inferred properties of its progenitor are consistent with a red supergiant or yellow supergiant, with an envelope mass of ∼0.30–0.65 M⊙ and an envelope radius of ∼120–300 R⊙. These inferred progenitor properties are similar to those of other SNe IIb with a double-peaked feature, such as SNe 1993J, 2011dh, 2016gkg, and 2017jgh. This study further validates the importance of the high cadence and early coverage in resolving the shape of the shock-cooling light curve, while the multiband observations, particularly UV, are also necessary to fully constrain the progenitor properties.
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| 10. |
- Wevers, T., et al.
(författare)
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An elliptical accretion disk following the tidal disruption event AT 2020zso
- 2022
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 666
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Tidskriftsartikel (refereegranskat)abstract
- Aims. The modelling of spectroscopic observations of tidal disruption events (TDEs) to date suggests that the newly formed accretion disks are mostly quasi-circular. In this work we study the transient event AT 2020zso, hosted by an active galactic nucleus (AGN; as inferred from narrow emission line diagnostics), with the aim of characterising the properties of its newly formed accretion flow.Methods. We classify AT 2020zso as a TDE based on the blackbody evolution inferred from UV/optical photometric observations and spectral line content and evolution. We identify transient, double-peaked Bowen (N III), He I, He II, and Hα emission lines. We model medium-resolution optical spectroscopy of the He II (after careful de-blending of the N III contribution) and Hα lines during the rise, peak, and early decline of the light curve using relativistic, elliptical accretion disk models.Results. We find that the spectral evolution before the peak can be explained by optical depth effects consistent with an outflowing, optically thick Eddington envelope. Around the peak, the envelope reaches its maximum extent (approximately 1015 cm, or ∼3000–6000 gravitational radii for an inferred black hole mass of 5−10 × 105 M⊙) and becomes optically thin. The Hα and He II emission lines at and after the peak can be reproduced with a highly inclined (i = 85 ± 5 degrees), highly elliptical (e = 0.97 ± 0.01), and relatively compact (Rin = several 100 Rg and Rout = several 1000 Rg) accretion disk.Conclusions. Overall, the line profiles suggest a highly elliptical geometry for the new accretion flow, consistent with theoretical expectations of newly formed TDE disks. We quantitatively confirm, for the first time, the high inclination nature of a Bowen (and X-ray dim) TDE, consistent with the unification picture of TDEs, where the inclination largely determines the observational appearance. Rapid line profile variations rule out the binary supermassive black hole hypothesis as the origin of the eccentricity; these results thus provide a direct link between a TDE in an AGN and the eccentric accretion disk. We illustrate for the first time how optical spectroscopy can be used to constrain the black hole spin, through (the lack of) disk precession signatures (changes in inferred inclination). We constrain the disk alignment timescale to > 15 days in AT2020zso, which rules out high black hole spin values (a < 0.8) for MBH ∼ 106 M⊙ and disk viscosity α ≳ 0.1.
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