We report on our study of the supernova (SN) 2022xxf based on observations obtained during the first four months of its evolution. The light curves (LCs) display two humps of similar maximum ...brightness separated by 75 days, unprecedented for a broad-lined (BL) Type Ic supernova (SN IcBL). SN 2022xxf is the most nearby SN IcBL to date (in NGC 3705,
z
= 0.0037, at a distance of about 20 Mpc). Optical and near-infrared photometry and spectroscopy were used to identify the energy source powering the LC. Nearly 50 epochs of high signal-to-noise ratio spectroscopy were obtained within 130 days, comprising an unparalleled dataset for a SN IcBL, and one of the best-sampled SN datasets to date. The global spectral appearance and evolution of SN 2022xxf points to typical SN Ic/IcBL, with broad features (up to ~14 000 km s
−1
) and a gradual transition from the photospheric to the nebular phase. However, narrow emission lines (corresponding to ~ 1000–2500 km s
−1
) are present in the spectra from the time of the second rise, suggesting slower-moving circumstellar material (CSM). These lines are subtle, in comparison to the typical strong narrow lines of CSM-interacting SNe, for example, Type IIn, Ibn, and Icn, but some are readily noticeable at late times, such as in Mg I
λ
5170 and O I
λ
5577. Unusually, the near-infrared spectra show narrow line peaks in a number of features formed by ions of O and Mg. We infer the presence of CSM that is free of H and He. We propose that the radiative energy from the ejecta-CSM interaction is a plausible explanation for the second LC hump. This interaction scenario is supported by the color evolution, which progresses to blue as the light curve evolves along the second hump, and by the slow second rise and subsequent rapid LC drop. SN 2022xxf may be related to an emerging number of CSM-interacting SNe Ic, which show slow, peculiar LCs, blue colors, and subtle CSM interaction lines. The progenitor stars of these SNe likely experienced an episode of mass loss consisting of H/He-free material shortly prior to explosion.
We present optical and near-infrared observations of Swift GRB 080325 classified as a 'dark gamma-ray burst (GRB)'. Near-infrared observations with Subaru/MOIRCS provided a clear detection of ...afterglow in the K{sub s} band, although no optical counterpart was reported. The flux ratio of rest-wavelength optical to X-ray bands of the afterglow indicates that the dust extinction along the line of sight to the afterglow is A{sub V} = 2.7-10 mag. This large extinction is probably the major reason for the optical faintness of GRB 080325. The J - K{sub s} color of the host galaxy, (J - K{sub s} = 1.3 in AB magnitude), is significantly redder than those for typical GRB hosts previously identified. In addition to J and K{sub s} bands, optical images in B, R{sub c} , i', and z' bands with Subaru/Suprime-Cam were obtained at about 1 year after the burst, and a photometric redshift of the host is estimated to be z {sub photo} = 1.9. The host luminosity is comparable to L* at z {approx} 2 in contrast to the sub-L* property of typical GRB hosts at lower redshifts. The best-fit stellar population synthesis model for the host shows that the red nature of the host is attributed to a large dust extinction (A{sub V} = 0.8 mag), and that the host galaxy is massive (M* = 7.0 x 10{sup 10} M {sub sun}), which makes it one of the most massive GRB hosts yet identified. By assuming that the mass-metallicity relation for star-forming galaxies at z {approx} 2 is applicable for the GRB host, this large stellar mass suggests the high-metallicity environment around GRB 080325, consistent with inferred large extinction.
ABSTRACT We report the results of a multiband observing campaign on the famous blazar 3C 279 conducted during a phase of increased activity from 2013 December to 2014 April, including first ...observations of it with NuSTAR. The γ-ray emission of the source measured by Fermi-LAT showed multiple distinct flares reaching the highest flux level measured in this object since the beginning of the Fermi mission, with of 10−5 photons cm−2 s−1, and with a flux-doubling time scale as short as 2 hr. The γ-ray spectrum during one of the flares was very hard, with an index of , which is rarely seen in flat-spectrum radio quasars. The lack of concurrent optical variability implies a very high Compton dominance parameter . Two 1 day NuSTAR observations with accompanying Swift pointings were separated by 2 weeks, probing different levels of source activity. While the 0.5−70 keV X-ray spectrum obtained during the first pointing, and fitted jointly with Swift-XRT is well-described by a simple power law, the second joint observation showed an unusual spectral structure: the spectrum softens by at ∼4 keV. Modeling the broadband spectral energy distribution during this flare with the standard synchrotron plus inverse-Compton model requires: (1) the location of the γ-ray emitting region is comparable with the broad-line region radius, (2) a very hard electron energy distribution index , (3) total jet power significantly exceeding the accretion-disk luminosity , and (4) extremely low jet magnetization with . We also find that single-zone models that match the observed γ-ray and optical spectra cannot satisfactorily explain the production of X-ray emission.
Type Ic supernovae, the explosions after the core collapse of massive stars that have previously lost their hydrogen and helium envelopes, are particularly interesting because of their link with ...long-duration gamma ray bursts. Although indications exist that these explosions are aspherical, direct evidence has been missing. Late-time observations of supernova SN 2003jd, a luminous type Ic supernova, provide such evidence. Recent Subaru and Keck spectra reveal double-peaked profiles in the nebular lines of neutral oxygen and magnesium. These profiles are different from those of known type Ic supernovae, with or without a gamma ray burst, and they can be understood if SN 2003jd was an aspherical axisymmetric explosion viewed from near the equatorial plane. If SN 2003jd was associated with a gamma ray burst, we missed the burst because it was pointing away from us.
We performed high-dispersion spectropolarimetry for the T Tauri star RY Tauri and measured linear polarization in seven forbidden lines of OI$\lambda\lambda$5577, 6300, 6364, NIIλ6583, ...SII$\lambda\lambda$6716, 6731, and FeIIλ7155. This is the first high-dispersion spectropolarimetry for forbidden lines in T Tauri stars. We successfully detected intrinsic polarization in the OIλ6300 line. The intrinsic OIλ6300 polarization corrected for the foreground polarization was derived as $p_\mathrm{OI}=1.17\pm 0.54\%$ and $\theta_\mathrm{OI} = 107\degr\pm 13\degr$, whereas the polarization of the nearby continuum was $p_\mathrm{cont}=2.4{-}3.1\%$ and $\theta_\mathrm{cont}=2\degr{-}11\degr$. The position angle of OIλ6300 polarization is compared with the circumstellar structures found by previous studies. It is nearly perpendicular to the disk long-axis and parallel to the optical H$\mathrm\alpha$ jet. Both the perpendicularity and parallelism potentially suggest relatively axisymmetric distribution of the OIλ6300 emitting region and surrounding scattering medium. We constructed a simplified scattering model composed of a point source on a jet axis as an OIλ6300 emitter and a flat disk with an inner hole as a scatterer. Applying the observed polarization to the model suggests that the OIλ6300 emission emerges close to the central star with a possible separation of less than a few $\times$0.1 AU.
Global DNA hypomethylation in CD4+ cells in systemic lupus erythematosus (SLE) was suggested to play a key role in the pathogenesis. To identify new methylation-sensitive genes, we integrated ...genome-wide DNA methylation and mRNA profiling data in CD4+ cells of MRL/lpr (MRL) and C57BL6/J (B6) mice. We identified Cathepsin E (Ctse), in which 13 methyl-CpGs within 583 bp region of intron 1 were hypomethylated, and Ctse mRNA upregulated in MRL compared with B6 mice. One of methyl-CpGs, mCGCG was 93.3 ± 2.05% methylated in B6 mice, while 80.0 ± 6.2% methylated and mutated to CGGG in MRL mice. Kaiso is known to bind to mCGCG and we hypothesized that it represses expression of Ctse in B6 mice. The binding of Kaiso to mCGCG site in B6 mice was reduced in MRL mice revealed by ChIP-PCR. EL4 cells treated with 5-azaC and/or Trichostatin A showed the suppression of binding of Kaiso to mCGCG motif by ChIP-PCR and the overexpression of Ctse was demonstrated by qPCR. Ctse gene silencing by siRNA in EL4 cells resulted in reduction of IL-10 secretion. The hypomethylation of mCGCG motif, reduced recruitment of Kaiso, and increased expression of Ctse and Il-10 in CD4+ cells may be involved in the pathogenesis of SLE.
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