Evidence for Gamma-Ray Pulsations from the Classical Nova ASASSN-16ma

I report here a new result extracted from the Fermi Large Area Telescope observation of the classical nova ASASSN-16ma that exhibits coherent γ-ray pulsations at 544.84(7) s during its outburst in 2016. Considering the number of independent trials, the significance of the evidence is 4.0σ, equivalent to a false-alarm probability of 5.9 × 10−5. The periodicity was steady during the 4 days of its appearance, indicating its origin as the spinning signal of the white dwarf. Given that the optical and γ-ray light curves of some shock-powered γ-ray novae have been recently shown to be closely correlated to each other, the γ-ray pulsation phenomenon likely implies an existence of associated optical pulsations, which would provide detailed ephemerides for these extreme white dwarf binaries for further investigations in the near future.

Detection likelihood of cluster-induced CMB polarization

Nearby galaxy clusters can potentially induce sub-microkelvin polarization signals in the cosmic microwave background (CMB) at characteristic scales of a few arcminutes. We explore four such polarization signals induced in a rich nearby fiducial cluster and calculate the likelihood of their detection by a telescope project with capabilities such as those of the Simons Observatory (SO). In our feasibility analysis, we include instrumental noise, primordial CMB anisotropy, statistical thermal Sunyaev-Zeldovich (SZ) cluster signal, and point source confusion, assuming a few percent of the nominal telescope observation time of an SO-like project. Our analysis indicates that the thermal SZ intensity can be sensitively mapped in rich nearby clusters and that the kinematic SZ intensity can be measured with high statistical significance toward a fast moving nearby cluster. The detection of polarized SZ signals will be quite challenging but could still be feasible toward several very rich nearby clusters with very high SZ intensity. The polarized SZ signal from a sample of ∼20 clusters can be statistically detected at S/N ∼ 3, if observed for several months.

Spectral Line Registration Backend Based on USRP X300 Software Defined Radio

This paper presents implementation of spectrometer based on off-the-shelf software defined radio (SDR) Ettus Research USRP X300 equipped with TwinRX daughterboard. Parallelized software, employing Fast Fourier Transform (FFT), is developed which allows two channel spectrum processing in real time with bandwidths up to 50[Formula: see text]MHz per channel, sample resolution of 14 bits and FFT lengths up to 32k points. Measured Allan stability time of the spectrometer is at least 750 sin laboratory environment. Software has network server-type interface that allows to conveniently integrate the spectrometer in radio telescope observation control and monitoring system with versatility of SDR allowing to implement various observation modes, for example, total power detection functionality with high frequency selectivity, which allows to carry continuum amplitude calibration in presence of near-by radio frequency interference. Presented spectrometer has been successfully integrated and used at RT-32 and RT-16 radio telescopes of Ventspils International Radio Astronomy Centre.

Accurate and Rapid Auto-Focus Methods Based on Image Quality Assessment for Telescope Observation

Aiming at improving the speed and accuracy of auto-focus for telescope observation, algorithms for image estimation and auto-focus were investigated and are discussed in this article. Based on the image quality assessment, the auto-focusing process of the telescope system is realized by using the mountain-climb search method. Several evaluation functions were tested in different scenarios. It is demonstrated that the Tenengrad image estimation function (IEF) is suitable for an instant and accurate auto-focus process of the telescope. Furthermore, we implemented sampling and dynamic adaptive focusing window (ES-DAFW) methods with the Tenengrad IEF to enhance the sensitivity and accuracy of the auto-focus process. The experimental results showed that our ES-DATW method can provide more accurate results in less time for the auto-focus process compared to the conventional approaches, especially for a sparse image. These results promise significant applications to the auto-focusing of other telescopes with image quality assessment.

The evolution of the X-ray afterglow emission of GW 170817/ GRB 170817A in XMM-Newton observations

We report our observation of the short gamma-ray burst (GRB) GRB 170817A, associated to the binary neutron star merger gravitational wave (GW) event GW 170817, performed in the X-ray band with XMM-Newton 135 d after the event (on 29 December, 2017). We find evidence for a flattening of the X-ray light curve with respect to the previously observed brightening. This is also supported by a nearly simultaneous optical Hubble Space Telescope observation and successive X-ray Chandra and low-frequency radio observations recently reported in the literature. Since the optical-to-X-ray spectral slope did not change with respect to previous observations, we exclude that the change in the temporal evolution of the light curve is due to the passage of the cooling frequency: its origin must be geometric or dynamical. We interpret all the existing afterglow data with two models: i) a structured jet and ii) a jet-less isotropic fireball with some stratification in its radial velocity structure. Both models fit the data and predict that the radio flux must decrease simultaneously with the optical and X-ray emission, making it difficult to distinguish between them at the present stage. Polarimetric measurements and the rate of short GRB-GW associations in future LIGO/Virgo runs will be key to disentangle these two geometrically different scenarios.

A Proposed Astronomy Learning Progression For Remote Telescope Observation

Providing meaningful telescope observing experiences for students who are deeply urban or distantly rural place-boundor even daylight time-boundhas consistently presented a formidable challenge for astronomy educators. For nearly 2 decades, the Internet has promised unfettered access for large numbers of students to conduct remote telescope observing, but it has only been in recent years that the technology has become readily available. Now that this once fanciful possibility is becoming a reality, astronomy education researchers need a guiding theory on which to develop learning experiences. As one departure point, we propose a potential learning progression anchored on one end with recognizing that stars visible at night have describable locations and predictable motions, and anchored at the other with distant robotic telescopes can be programmed to record specific astronomical data for later analysis.

Modeling and Simulation of Chinese SONG Telescope

Telescope structure is used to support and position the optical mirrors in the right place during the period of telescope observation, so it will have such capability to withstand a certain load. In order to ensure SONG telescope has such capability, FEM analysis and calculation are finished in this paper. With the help of ANSYS, firstly the finite element model of SONG telescope is built. Then using this model, the analysis and calculation of static and dynamic are performed, including the deformation under the gravity load with the tube in different directions, eigenfrequency calculation of the whole system and the responses under the seismic acceleration spectra. The results show that the max. offsets and max. relative tilt angles between primary mirror and secondary mirror are very little under the gravity load. The first natural frequency is 20.083Hz, larger than the design requirement 8Hz. The results of seismic load analysis show that the deformation in the telescope structure is 0.42mm and the stress is 33.8MPa, less than the allowable stress of the structure material. The above analyses verified that the structure design of SONG telescope is reliable and acceptable.