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For the First Time Hubble Directly Measures Mass of a Lone White Dwarf | NASA
noting
First semi-empirical test of the white dwarf mass–radius relationship using a single white dwarf via astrometric microlensing | Monthly Notices of the Royal Astronomical Society | Oxford Academic
The selection of a star to observe for lensing was made possible by the GAIA satellite, from its doing very high-precision astrometry on a very large number of stars.
They find a mass of 0.56 +- 0.08 solar masses, stating
Back to the NASA article.
Hubble Astronomers Develop a New Use for a Century-Old Relativity Experiment to Measure a White Dwarf's Mass
noting
First semi-empirical test of the white dwarf mass–radius relationship using a single white dwarf via astrometric microlensing | Monthly Notices of the Royal Astronomical Society | Oxford Academic
White dwarf LAWD 37 passed in front of another star, doing gravitational lensing on that star's light. That lensing was difficult to observe, because it was very close in line of sight to LAWD 37, close enough to be obscured by that WD's light.In November 2019, the nearby single, isolated DQ-type white dwarf LAWD 37 (WD 1142-645) aligned closely with a distant background source and caused an astrometric microlensing event. Leveraging astrometry from Gaia and followup data from the Hubble Space Telescope, we measure the astrometric deflection of the background source and obtain a gravitational mass for LAWD 37.
The selection of a star to observe for lensing was made possible by the GAIA satellite, from its doing very high-precision astrometry on a very large number of stars.
They find a mass of 0.56 +- 0.08 solar masses, stating
This mass is in agreement with the theoretical mass–radius relationship and cooling tracks expected for CO core white dwarfs. Furthermore, the mass is consistent with no or trace amounts of hydrogen that is expected for objects with helium-rich atmospheres like LAWD 37.
Back to the NASA article.
notingKailash Sahu of the Space Telescope Science Institute in Baltimore, Maryland, the principal Hubble investigator on this latest observation, first used microlensing in 2017 to measure the mass of another white dwarf, Stein 2051 B. But that dwarf is in a widely separated binary system. "Our latest observation provides a new benchmark because LAWD 37 is all by itself," Sahu said.
The collapsed remains of a star that burned out 1 billion years ago, LAWD 37 has been extensively studied because it is only 15 light-years away in the constellation Musca. "Because this white dwarf is relatively close to us, we’ve got lots of data on it – we've got information about its spectrum of light, but the missing piece of the puzzle has been a measurement of its mass," said McGill.
Hubble Astronomers Develop a New Use for a Century-Old Relativity Experiment to Measure a White Dwarf's Mass