2021-W02

# 2101.02497
- https://arxiv.org/abs/2101.02497
- **Quasi-Periodic Oscillations in the long term radio light curves of the blazar AO 0235+164**
- A quasi-periodic oscillation ~ 965 days was detected (> 3.5 sigma) from long radio observations of the blazar AO 0235+164.
 The jets of blazars involves an internal helical structure or the jet precession could served as plausible explanations for the origins of such long and persistent periodicity.
- by：**鲍通**

# 2101.02290
- https://arxiv.org/abs/2101.02290
- **High-energy emission from tidal disruption events in active galactic nuclei**
- During a TDE happening in the AGN, the debris stream will drill through the pre-existing AGN accretion disk near the stream pericenter, destroying the inner disk in the process, and then intersects with the disk a second time at radii ranging from a few to hundreds of times the pericenter distance. The authors explore the dynamics of the debris streams with simulation and found that strong shocks may form as the debris stopped by the dense disk in the 'second impact', which may produce hard X-ray or soft gamma photons. The X-ray hardness and smoothness of the light curve can be used to distinguish TDEs in AGN from AGN flares.
- ![PV](https://leanote.com/api/file/getImage?fileId=60002abbab6441467f0005c0)

# 2101.02526 
- https://arxiv.org/abs/2101.02526
- **Review of the particle background of the Athena X-IFU instrument**
- by **华子乾**
- This paper mainly talks about the particle background estimation with a Monto-Carlo simulation. The background contains two parts —— soft protons (SP) and galactic cosmic rays (GCR). The situation in a L1 and L2 orbits are predicted with the up-to-date models. A simulated observation of a typical galaxy cluster has been carried out from its center to 1.2 R200 as well. 
As the future generation X-ray mission of ESA, Athena has attracted tremendous attention and it will be very fascinating to learn more details about this telescope.

# 2101.03059
- https://arxiv.org/abs/2101.03059
- **X-ray and ultraviolet observations of the eclipsing cataclysmic variables OV Bootis and SDSS J103533.02+055158.3 with degenerate donors**
- 鲍通说他看

# 2101.03910
- https://arxiv.org/abs/2101.03019
- **Virtual Data Cosmos -- Information Design in Modern Astronomy**
- 用ML算法对XMM-Newton中一些未被分类的点源做分类，然后用VR来做可视化，可以显示分类的相关性等等。作者做了个视频，见http://annok.de/vdc-2/（需要科学上网），虽然有点花里胡哨，但是感觉非常酷炫。

# 2101.03302
- https://arxiv.org/abs/2101.03302
- **Origin of Galactic Spurs: New Insight from Radio/X-ray All-sky Maps**
- They discuss two types of giant spurs:  one is the brightest diffuse emission near the map’s center, which is likely to be related to Fermi bubbles (NPSs/SPSs, north/south polar spurs, respectively)(In my view, the two spurs are just eROSITA bubbles),  and the other is weaker spurs that coincide positionally with local spiral arms in our Galaxy (LAS, local arm spur). They argue that the former was produced by shock-heated halo gas, and the later was produced by the weak condensation of halo gas in the arm potential or star formation activity without shock heating.
- ![1](https://leanote.com/api/file/getImage?fileId=60002abbab6441467f0005c1)
- by **张孟飞**

# 2101.04546
- https://arxiv.org/pdf/2101.04546.pdf
- **Spectro-Timing Analysis of a highly variable narrow-line Seyfert 1 galaxy NGC 4748 with AstroSat and XMM-Newton**
- The authors present a detailed timing and spectral study of an extremely variable narrow-line Seyfert 1 galaxy NGC 4748 using observations in the year 2017 and 2014 performed with AstroSat and XMM-Newton, respectively.
In the 2014 data set, the source retains its general behaviour of “softer when brighter” while the 2017 observation exhibits a “harder when brighter” nature. This suggests a possible change in the accretion mode from standard to the advection-dominated flow.
- by **黄健**

# 2101.04045
- https://arxiv.org/abs/2101.04045
- **A population of heavily reddened, optically missed classical novae from Palomar Gattini-IR: Constraints on the Galactic nova rate**
- Using the sample of 12 spectroscopically confirmed novae detected in the Palomar Gattini-IR survey, they derive an estimates of the Galactic nova rate about 46(+13,-13) yr-1, combining the quantification of the detection efficiency and simulations of the survey pointing schedule. The difference between this rate estimates and previous works via extrapolations from nearby galaxies could be explained by differences in assumptions regarding the relative contribution of bulge and disk novae.
- ![2](https://leanote.com/api/file/getImage?fileId=60002abbab6441467f0005bf)
- by: **鲍通**

# 2101.04278
- https://arxiv.org/abs/2101.04278
- **A HaloSat Analysis of the Cygnus Superbubble**
- The authors analyzed X-ray data of Cygnus Superbubble (CSB) obtained by HaloSat and found that the absorption and temperature of the CSB are consistent over ~13 deg, indicating a single origin -- a hypernova. The authors also found that the absorption of CSB is more consistent with Cygnus OB1 associations than previously believed OB2. The distance of the CSB would be at ~ 1.1-1.4 kpc.

# 2101.05146
- https://arxiv.org/abs/2101.05146
- **Rapid Spectral Variability of a Giant Flare from a Magnetar in NGC 253**
- This paper ((Nature format?) presents X- and gamma-ray observations of GRB 200415A, which exhibits a rapid onset, very fast time variability, flat spectra and significant sub-millisecond spectral evolution. These attributes match well with those expected for a giant flare from an extra-galactic magnetar.
- by **周平**

# 2101.04692
- https://arxiv.org/abs/2101.04692
- **Rapid accretion state transitions following the tidal disruption event AT2018fyk**
- The authors present a two-year multi-wavelengthmonitoring of TDE AT2018fyk and identify 3 accretion states (soft state/ hard state/ quiescent state) and 2 transistion states between them, similar to stellar mass black hole.

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