Astrophysics and Space Science最新文献

Magnetic reconnection is a fundamental mechanism through which energy stored in magnetic fields is released explosively on a massive scale, they could be presented as eruptive or confined flares, depending on their association with coronal mass ejections (CMEs). Several previous works have concluded that there is no correlation between flare duration and flare class, however, their sample sizes are skewed towards B and C classes; they hardly represent the higher classes. Therefore, we studied a sample without extreme events in order to determine the correlation between flare duration and flare type (confined and eruptive). We examined 33 flares with classes between M5 to X5 within 45° of the disk centres, using data from the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI). We find that the linear correlation between flare class against flare duration by full width half maximum (FWHM) in general is weak ((r = 0.19)); however, confined flares have a significant correlation ((r = 0.58)) compared to eruptive types ((r = 0.08)). Also, the confined M class flares’ average duration is less than half of the eruptive flares. Similarly, confined flares have a higher correlation ((r = 0.89)) than eruptive flares ((r = 0.60)) between flare classes against magnetic reconnection flux. In this work, a balanced sample size between flare types is an important strategy for obtaining a reliable quantitative comparison.

Early-time radioactive signals from type Ia supernovae (SNeIa) can provide important constraints on the explosion mechanism and the progenitor system. We present observations and analysis of SN 2023mnc, a SN Ia, (sim 7) days following its discovery. Follow-up observations were conducted in optical bands, covering phases from (sim -4) days to (sim 15) days relative to its r-band peak luminosity. The early photometry allows us to estimate the physical properties of the ejecta and characterize the possible divergence from a normal SN Ia; we were able to characterize it as a Type Iax supernova instead. The estimated date of explosion is (t_{0}=60130) MJD and implies a short rise time of (t_{rise} approx 16) days. The apparent g-band peak magnitude and the post-peak decline rate are (m_{max}(g)=-19.52pm 0.47) mag and (Delta m_{15}(g)=0.825pm 1.635) mag, respectively. Based on the light curve fitting of standard SN Ia models, the distance modulus is predicted to be (37.98pm 0.207) mag for g-band measurements, and the SN is predicted to be (394.46pm 38) Mpc from Earth. Assuming a ⁵⁶Ni powered radiative diffusion, the estimated bolometric light-curve peaks at (3.8 times 10^{41}) erg s⁻¹ and indicates that only (0.017 M_{odot }) of ⁵⁶Ni was produced, making SN 2023mnc a moderate luminosity object in the Iax class with peak absolute magnitude of (M_{V}=-15.3) mag. Comparing the observed color evolution with the predicted by different models such as deflagration-to-detonation transition and pure-deflagration scenario, the latter one is favored. The photometry of SN 2023mnc offers a unique opportunity to examine the progenitor systems and ignition process of the SNe Iax, adding weight to the population study of such sub-class SNe.

Previous studies have identified the Fundamental Plane (FP) of Active Galactic Nuclei (AGNs) in recent years. However, these findings relied on total black hole mass, also known as dynamical mass, (Mdyn). Instead the fundamental plane may be governed by BH spin. In this study, we take the black hole spin-mass energy ((M_{mathrm{spin}})) as a new variable, which is closely related to the supermassive black hole (SMBH). We collected a sample of 62 flat-spectrum radio quasars (FSRQs) with gamma-ray luminosity ((L_{gamma })), X-ray luminosity ((L_{mathrm{X}})) and spin-mass energy ((M_{ mathrm{spin}})) to construct a new fundamental plane of blazars. Our analysis demonstrates that the fundamental plane ((log L_{gamma }={0.662}_{+0.193}^{-0.193}log L_{ mathrm{X}}+{0.495}_{+0.154}^{-0.154}log M_{mathrm{spin}} +{14.579}_{+7.140}^{-7.140}) with R-Square = 0.783) has a stronger correlation with spin-mass energy ((M_{mathrm{spin}})) compared to the black hole mass. Therefore, (M_{mathrm{spin}}) should be considered as an essential variable for the fundamental plane of blazars. Our findings may improve the understanding of the Blandford-Znajek process in FSRQs.

By means of the data sets of the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS), we investigate the relationship between the variability amplitude and luminosity at 5100 Å, black hole mass, Eddington ratio, (R_{mathrm{Fe}, mathrm{II}}) (the ratio of the flux of Fe II line within 4435–4685 Å to the broad proportion of (mathrm{H}beta ) line) as well as (R_{5007}) (the ratio of the flux [O III] line to the total (mathrm{H}beta ) line) of the broad line Seyfert 1 (BLS1) and narrow line Seyfert 1 (NLS1) galaxies sample in g, r, i, z and y bands, respectively. We also analyze the similarities and differences of the variability characteristics between the BLS1 galaxies and NLS1 galaxies. The results are listed as follows. (1). The cumulative probability distribution of the variability amplitude shows that NLS1 galaxies are lower than that in BLS1 galaxies. (2). We analyze the dependence of the variability amplitude with the luminosity at 5100 Å, black hole mass, Eddington ratio, (R_{mathrm{Fe} ,mathrm{II}}) and (R_{5007}), respectively. We find significantly negative correlations between the variability amplitude and Eddington ratio, insignificant correlations with the luminosity at 5100 Å. The results also show significantly positive correlations with the black hole mass and (R_{5007}), significantly negative correlations with (R_{mathrm{Fe}, mathrm{II}}) which are consistent with (Rakshit and Stalin in Astrophys. J. 842: 96, 2017) in low redshift bins (z < 0.4) and (Ai et al. in Astrophys. J. Lett. 716:L31, 2010). (3). The relationship between the variability amplitude and the radio loudness is investigated for 155 BLS1 galaxies and 188 NLS1 galaxies. No significant correlations are found in our results.

We investigate the impact of hyperon and dark matter on macroscopic properties of neutron stars, including mass, radius, gravitational redshift, and moment of inertia, within the framework of relativistic mean field theory. Our findings reveal that the absorbing of hyperon and dark matter components significantly softens the equation of state of neutron star. Dark matter Fermi momentum varies between 0 and 0.06 GeV, and all types of neutron stars yield to the current observational constraints with dark matter Fermi momentum being (k_{f}^{DM}=0.03text{ GeV}). In addition, both hyperons and dark matter increase the gravitational redshift while decreasing the moment of inertia. Lastly, we present the linear relationships between mass, gravitational redshift and moment of inertia that can further assist in identifying neutron star types.

We analyze here an energetic proton enhancement in a sheath ahead of a slow interplanetry coronal mass ejection (ICME) detected by Parker Solar Probe on June 30, 2021 at the heliospheric distance of 0.76 AU. The shock was likely quasi-parallel and had a high Mach number. However, the proton fluxes were not enhanced at the shock but about an hour later. The fluxes stayed elevated with a sporadic behaviour throughout the sheath. We suggest that some mechanism internal to the sheath was responsible for the energization. The observations show enhanced levels of magnetic field fluctuations in the sheath and frequent presence of highly reduced magnetic helicity structures ((sigma _{m})) at various time scales, representing either small-scale flux ropes or Alfvénic fluctuations that could have contributed to the energization. The correlation between the energetic proton fluxes and normalized fluctuation amplitudes/occurrence of high (sigma _{m}) structures was generally weak or negligible. The most striking feature of the sheath was a strong enhancement of density (up to 50 cm⁻³) that implies the importance of compressive acceleration in the sheath. A statistical analysis of ion enhancements of 73 sheaths detected by ACE at ({sim} 1) AU reveals that this sheath was peculiar as in ICME-driven sheaths preceded by strong shocks the ion fluxes typically peak at the shock and strongly decline through the sheath.

We investigate high-resolution observations with the spectropolarimeter (SP) aboard the Hinode satellite of the Solar Optical Telescope (SOT) of a positive polarity sunspot of an active region (AR) (NOAA 12546). We present a case study for the properties of the thermal, magnetic field, and plasma flows as a function of the optical depth from the inversion of the observed Stokes profiles, covering a wide field of view area. Particular attention is paid to the examination of the net circular polarization (NCP) and area asymmetry of spectral lines in sunspots. We detect a large red-shifted velocity of 10 km sec⁻¹ localized with the presence of a strong magnetic field corresponding to the NCP best fit of the inverted profiles. In addition, the comparison between the observed and calculated NCPs or Stokes V area asymmetries of spectral lines fitted well for most pixels in the field of view region, with a significant indication of a single-component inversion. We study the vertical gradients of temperature, magnetic strength, inclination field, and LOS velocity in the deeper and higher layers of the photosphere. The difference in the penumbral temperature between the two atmospheric layers is −130 K. The penumbral regions reveal a magnetic field gradient of (Delta B sim -0.5) to −0.9 G km⁻¹. The inclination gradient in the limb-side penumbra is between ((Delta gamma /Delta z) = -9 times 10^{-3}) deg km⁻¹ to (-3.5 times 10^{-2}) deg km⁻¹. In particular, we find a higher positive inclination gradient in the disk center-side penumbra ((Delta gamma /Delta z)= 0.2 - 1.5 deg text{ km}^{-1}). The velocity gradient is ((Delta V_{LOS}/Delta log tau )= -0.13) to −0.30 km sec⁻¹ in the limb-side penumbra, and the disk center-side penumbra is given by ((Delta V_{LOS}/Delta log tau )= 0.11) to 0.29 km sec⁻¹.

The distribution of stellar (mathrm{H}alpha ) chromospheric activity with respect to stellar atmospheric parameters (effective temperature (T_{mathrm{eff}}), surface gravity (log ,g), and metallicity (mathrm{[Fe/H]})) and main-sequence/giant categories is investigated for the F-, G-, and K-type stars observed by the LAMOST Medium-Resolution Spectroscopic Survey (MRS). A total of 329,294 MRS spectra from LAMOST DR8 are utilized in the analysis. The (mathrm{H}alpha ) activity index ((I_{mathrm{H}{alpha }})) and (mathrm{H}alpha ) (R)-index (({R_{mathrm{H}{alpha }}})) are evaluated for the MRS spectra. The (mathrm{H}alpha ) chromospheric activity distributions with individual stellar parameters, as well as in the (T_{mathrm{eff}}) – (log ,g) and (T_{mathrm{eff}}) – (mathrm{[Fe/H]}) parameter spaces, are analyzed based on the ({R_{mathrm{H}{alpha }}}) index data. It is found that: (1) for the main-sequence sample, the ({R_{mathrm{H}{alpha }}}) distribution with (T_{mathrm{eff}}) has a bowl-shaped lower envelope with a minimum at about 6200 K, a hill-shaped middle envelope with a maximum at about 5600 K, and an upper envelope continuing to increase from hotter to cooler stars; (2) for the giant sample, the middle and upper envelopes of the (R_{mathrm{H}{alpha }}) distribution first increase with a decrease of (T_{mathrm{eff}}) and then drop to a lower activity level at about 4300 K, revealing different activity characteristics at different stages of the stellar evolution; (3) for both the main-sequence and giant samples, the upper envelope of the (R_{mathrm{H}{alpha }}) distribution with metallicity is higher for stars with (mathrm{[Fe/H]}) greater than about −1.0, and the lowest-metallicity stars hardly exhibit high (mathrm{H}alpha ) indices. A dataset of (mathrm{H}alpha ) activity indices for the LAMOST MRS spectra analyzed is provided with this paper.