ﻻ يوجد ملخص باللغة العربية
We present optical and infrared characterization of the polluted DAZ white dwarf GALEX J193156.8+011745. Imaging and spectroscopy from the ultraviolet to the thermal infrared indicates that the white dwarf hosts excess infrared emission consistent with the presence of an orbiting dusty debris disk. In addition to the five elements previously identified, our optical echelle spectroscopy reveals chromium and manganese and enables restrictive upper limits on several other elements. Synthesis of all detections and upper limits suggests that the white dwarf has accreted a differentiated parent body. We compare the inferred bulk elemental composition of the accreted parent body to expectations for the bulk composition of an Earth-like planet stripped of its crust and mantle and find relatively good agreement. At least two processes could be important in shaping the final bulk elemental composition of rocky bodies during the late phases of stellar evolution: irradiation and interaction with the dense stellar wind.
White dwarfs are the end state of most stars, including the Sun, after they exhaust their nuclear fuel. Between 1/4 and 1/2 of white dwarfs have elements heavier than helium in their atmospheres, even though these elements should rapidly settle into
The detection of a dust disc around G29-38 and transits from debris orbiting WD1145+017 confirmed that the photospheric trace metals found in many white dwarfs arise from the accretion of tidally disrupted planetesimals. The composition of these plan
By using six new determined mid-eclipse times together with those collected from the literature, we found that the Observed-Calculated (O-C) curve of RR Cae shows a cyclic change with a period of 11.9 years and an amplitude of 14.3s, while it undergo
Astronomers have discovered thousands of planets outside the solar system, most of which orbit stars that will eventually evolve into red giants and then into white dwarfs. During the red giant phase, any close-orbiting planets will be engulfed by th
Monitoring the long-term radial velocity (RV) and acceleration of nearby stars has proven an effective method for directly detecting binary and substellar companions. Some fraction of nearby RV trend systems are expected to be comprised of compact ob