J/ApJ/894/19 SOAR spectra of the WD EPIC 228939929 (Reding+, 2020)
An isolated white dwarf with 317s rotation and magnetic emission.
Reding J.S., Hermes J.J., Vanderbosch Z., Dennihy E., Kaiser B.C.,
Mace C.B., Dunlap B.H., Clemens J.C.
<Astrophys. J., 894, 19 (2020)>
=2020ApJ...894...19R 2020ApJ...894...19R
ADC_Keywords: Stars, white dwarf; Spectra, optical
Keywords: White dwarf stars; Magnetic variable stars; Extrasolar rocky planets;
Stellar mergers; Stellar rotation
Abstract:
We report the discovery of short-period photometric variability and
modulated Zeeman-split hydrogen emission in SDSSJ125230.93-023417.72
(EPIC 228939929), a variable white dwarf star observed at long cadence
in K2 Campaign 10. The behavior is associated with a magnetic
(B=5.0MG) spot on the stellar surface, making the 317.278s period a
direct measurement of the stellar rotation rate. This object is
therefore the fastest-rotating, apparently isolated (without a stellar
companion) white dwarf yet discovered and the second found to exhibit
chromospheric Balmer emission after GD 356, in which the emission has
been attributed to a unipolar inductor mechanism driven by a possible
rocky planet. We explore the properties and behavior of this object,
and consider whether its evolution may hold implications for white
dwarf mergers and their remnants.
Description:
The SDSS collected photometry of SDSSJ125230.93-023417.7 (J1252) in
DR7, and Kepler observed it in K2 Campaign 10, which ran from 2016
July 6 through September 20 (EPIC228939929).
Independently, the Galaxy Evolution Explorer (GALEX2414916899208956898)
and the Wide-Field Infrared Survey Explorer (AllWISEJ125230.98-023418.4)
collected ultraviolet and infrared photometry, respectively.
Gaia measured J1252 (DR2 3682469122383597056) to have a parallax of
plx=12.94±0.11mas (d=77.26±0.67pc).
We observed J1252 on the 4.1m Southern Astrophysical Research (SOAR)
Telescope on 2018 April 24. We collected a total of 2.9hr of
integration time with 20s exposures using an S8612 broad-bandpass
red-cutoff filter. See Section 2.2.
Owing to the poor quality of the SOAR data, we collected additional
photometric measurements of J1252 using the Otto Struve 2.1m Telescope
at McDonald Observatory, Fort Davis, TX, on 2018 May 18-19 and
on 2019 March 7. See Section 2.3.
We collected 2hr of time-series spectroscopy of J1252 in 2 minute
exposures with SOAR and the Goodman HTS on 2019 June 1 using a
400line/mm grating and 3.2" slit, corresponding to a slit width of
21Å. Our spectral resolution was therefore seeing-limited by the
sky conditions at an FWHM of 7Å (1").
Objects:
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RA (ICRS) DE Designation(s)
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12 52 30.93 -02 34 17.7 SDSS J125230.93-023417.7 = EPIC 228939929
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig3.dat 63 1691 Flux-calibrated and phase-binned SOAR spectra
of SDSS J125230.93-023417.7
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See also:
II/328 : AllWISE Data Release (Cutri+ 2013)
V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)
II/335 : Revised catalog of GALEX UV sources (GUVcat_AIS GR6+7) (Bianchi+ 2017)
IV/34 : K2 Ecliptic Plane Input Catalog (EPIC) (Huber+, 2017)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/ApJS/133/413 : BVRIJHK photometry of cool white dwarfs (Bergeron+, 2001)
J/AJ/132/1221 : VJHK and SDSS photometry of DA white dwarfs (Holberg+, 2006)
J/MNRAS/417/1210 : DA-white dwarfs from SDSS and UKIDSS (Girven+, 2011)
J/ApJ/730/128 : Spectroscopy of DA WD from the SDSS-DR4 (Tremblay+, 2011)
J/ApJS/201/19 : Hawaii Infrared Parallax Program. I. (Dupuy+, 2012)
J/ApJ/833/96 : Hawaii infrared plx prog. II. Ultracool dwarfs (Liu+, 2016)
J/ApJS/232/23 : 27 pulsating DA WDs follow-up observations (Hermes+, 2017)
J/MNRAS/482/4570 : Gaia DR2 white dwarf candidates (Gentile Fusillo+, 2019)
Byte-by-byte Description of file: fig3.dat
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Bytes Format Units Label Explanations
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1- 8 F8.3 0.1nm lambda [3725.9/7079.5] Wavelength; in Angstrom units
10- 19 E10.3 cW/m2/nm Flux15 [1.6e-16/9.1e-16] Flux at 15 degree phase (1)
21- 30 E10.3 cW/m2/nm Flux87 [1.5e-16/8.8e-16] Flux at 87 degree phase (1)
32- 41 E10.3 cW/m2/nm Flux159 [1.5e-16/8.1e-16] Flux at 159 degree phase (1)
43- 52 E10.3 cW/m2/nm Flux231 [1.5e-16/8.7e-16] Flux at 231 degree phase (1)
54- 63 E10.3 cW/m2/nm Flux303 [1.6e-16/8.8e-16] Flux at 303 degree phase (1)
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Note (1): In units of erg/s/cm2/Angstrom.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 10-Sep-2021