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NGC 4117: A New Compton-thick AGN Revealed by Broadband X-Ray Spectral Analysis
Mohanadas, Pavithra; Annuar, Adlyka
In this paper, we present the broadband (0.5-195 keV) X-ray spectral analysis for one of the newly detected AGNs in the Swift-BAT 105 month Hard X-ray Survey Catalog, NGC 4117. According to our ongoing research on low luminosity AGNs from the Swift-BAT 105 month catalog, we examine whether they are indeed low luminosity or heavily obscured AGNs. O…
An astrometric approach to measuring the colour of an object
Lin, F. R.; Peng, Q. Y.; Guo, B. F. +1 more
The colour of a star is a critical feature to reflect its physical property such as the temperature. The colour index is usually obtained via absolute photometry, which is demanding for weather conditions and instruments. In this work, we present an astrometric method to measure the catalogue-matched colour index of an object based on the effect o…
Photometric calibration in u-band using blue halo stars
von der Linden, Anja; Liang, Shuang
We develop a method to calibrate u-band photometry based on the observed colour of blue Galactic halo stars. The Galactic halo stars belong to an old stellar population of the Milky Way and have relatively low metallicity. The 'blue tip' of the halo population - the main sequence turn-off (MSTO) stars - is known to have a relatively uniform intrin…
G 68-34: A Double-lined M-dwarf Eclipsing Binary in a Hierarchical Triple System
Charbonneau, David; Pass, Emily K.
Using high-resolution spectra from the Tillinghast Reflector Echelle Spectrograph and photometry from sector 56 of the Transiting Exoplanet Survey Satellite, we report that the nearby M dwarf G 68-34 is a double-lined eclipsing binary. The pair is spin-orbit synchronized with a period of 0.655 days. The light curve shows significant spot modulatio…
A Catalog of Collected Debris Disks: Properties, Classifications and Correlations between Disks and Stars/Planets
Liu, Qiong; Liao, Neng-Hui; Cao, Peng-Cheng +2 more
We have collected a catalog of 1095 debris disks with properties and classification (resolved, planet, gas) information. From the catalog, we defined a less biased sample with 612 objects and presented the distributions of their stellar and disk properties to search for correlations between disks and stars. We found debris disks were widely distri…
A possible mechanism for the formation of an eastward moving auroral spiral
Grigorenko, Elena E.; Kronberg, Elena A.; Partamies, Noora +1 more
The generation process of auroral spirals is described by different theories varying for their morphology and surrounding conditions. Here, a possible mechanism is proposed for an eastward moving auroral spiral, which was observed in Tromsø, Norway, during the expansion phase of a substorm on 18 September 2013. Measurements from the THEMIS-A and C…
Spectral Clustering of CRISM Datasets in Jezero Crater Using UMAP and k-Means
Thomas, Nicolas; Rossi, Angelo Pio; Fernandes, Michael +2 more
In this paper, we expand upon our previous research on unsupervised learning algorithms to map the spectral parameters of the Martian surface. Previously, we focused on the VIS-NIR range of hyperspectral data from the CRISM imaging spectrometer instrument onboard NASA's Mars Reconnaissance Orbiter to relate to other correspondent imager data sourc…
Astrometric Calibration of the Beijing-Arizona Sky Survey
Fan, Xiaohui; Jiang, Linhua; Dey, Arjun +13 more
We present the astrometric calibration of the Beijing-Arizona Sky Survey (BASS). The BASS astrometry was tied to the International Celestial Reference Frame via the Gaia Data Release 2 reference catalog. For effects that were stable throughout the BASS observations, including differential chromatic refraction and the low charge transfer efficiency…
Where is the base of the Transition Region? Evidence from TRACE, SDO, IRIS and ALMA observations
Alissandrakis, Costas E.
Classic solar atmospheric models put the Chromosphere-Corona Transition Region (CCTR) at ∼ 2 Mm above the τ5000 = 1 level, whereas radiative MHD (rMHD) models place the CCTR in a wider range of heights. However, observational verification is scarce. In this work we review and discuss recent results from various instruments and spectral …
Nonthermal X-Rays from Pulsation-driven Shocks in Cepheids
Drake, Jeremy J.; Evans, Nancy Remage; Fraschetti, Federico +1 more
Rapid X-ray phase-dependent flux enhancement in the archetype classical Cepheid star δ Cep was observed by XMM-Newton and Chandra. We jointly analyze thermal and nonthermal components of the time-resolved X-ray spectra prior to, during, and after the enhancement. A comparison of the timescales of shock particle acceleration and energy losses is co…