J/ApJ/823/49 HST/COS observations of 7 white dwarfs (Sandhaus+, 2016)
A search for short-period rocky planets around WDs with the
Cosmic Origins Spectrograph (COS).
Sandhaus P.H., Debes J.H., Ely J., Hines D.C., Bourque M.
<Astrophys. J., 823, 49-49 (2016)>
=2016ApJ...823...49S 2016ApJ...823...49S (SIMBAD/NED BibCode)
ADC_Keywords: Stars, white dwarf ; Spectra, ultraviolet ; Stars, masses
Keywords: binaries: eclipsing; eclipses; planetary systems;
planets and satellites: detection; ultraviolet: general; white dwarfs
Abstract:
The search for transiting habitable exoplanets has broadened to
include several types of stars that are smaller than the Sun in an
attempt to increase the observed transit depth and hence the
atmospheric signal of the planet. Of all spectral types, white dwarfs
(WDs) are the most favorable for this type of investigation. The
fraction of WDs that possess close-in rocky planets is unknown, but
several large angle stellar surveys have the photometric precision and
cadence to discover at least one if they are common. Ultraviolet
observations of WDs may allow for detection of molecular oxygen or
ozone in the atmosphere of a terrestrial planet. We use archival
Hubble Space Telescope data from the Cosmic Origins Spectrograph to
search for transiting rocky planets around UV-bright WDs. In the
process, we discovered unusual variability in the pulsating WD GD 133,
which shows slow sinusoidal variations in the UV. While we detect no
planets around our small sample of targets, we do place stringent
limits on the possibility of transiting planets, down to sub-lunar
radii. We also point out that non-transiting small planets in thermal
equilibrium are detectable around hotter WDs through infrared
excesses, and identify two candidates.
Description:
We chose seven non-variable WDs with publicly available HST/COS data
and with total exposure times that exceeded 7200s.
In Table 3 we list a sample of the COS observations of WDs used to
create Figure 1 to look into the potential systematic uncertainties of
COS time-series photometry with roughly 90 different targets.
In Table 4 we list sample tables of COS observations for the 7 WDs
surveyed for transits in Section 3.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 68 7 Properties of transit search targets
table3.dat 110 174 Short exposure COS observations (79 targets)
table4.dat 111 1225 COS observations of the seven transit search targets
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See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
I/329 : URAT1 Catalog (Zacharias+, 2015)
I/322 : UCAC4 Catalog (Zacharias+, 2012)
V/139 : The SDSS Photometric Catalog, Release 9 (Adelman-McCarthy+, 2012)
J/A+A/560/A106 : NLTE spectral analysis of white dwarf G191-B2B (Rauch+, 2013)
J/ApJS/204/5 : SDSS DR7 white dwarf catalog (Kleinman+, 2013)
J/AJ/143/135 : Ages of A-K type stars in DEBRIS survey (Vican, 2012)
J/ApJ/743/138 : Spectroscopic survey of bright white dwarfs (Gianninas+, 2011)
J/ApJ/730/128 : Spectroscopy of DA WD from the SDSS-DR4 (Tremblay+, 2011)
J/ApJ/712/585 : Apparent velocity measurements of DA WDs (Falcon+, 2010)
J/ApJS/187/149 : StarCAT: STIS UV echelle spectra of stars (Ayres, 2010)
J/A+A/505/441 : UVES/VLT spectra of white dwarfs (Koester+, 2009)
J/AJ/135/1239 : Spectral distances to DA white dwarfs (Holberg+, 2008)
J/AJ/135/1225 : Parameters of the local white dwarfs (Holberg+, 2008)
J/A+A/470/1079 : UVES/VLT spectroscopy of white dwarfs (Voss+, 2007)
J/ApJ/652/1554 : Iron in hot DA white dwarfs (Vennes+, 2006)
J/ApJS/161/394 : Low-luminosity companions to white dwarfs (Farihi+, 2005)
J/ApJS/147/145 : IUE low-dispersion spectra of white dwarfs (Holberg+, 2003)
J/A+A/373/730 : The IUE Absolute Flux Scale (Gonzalez-Riestra+, 2001)
J/ApJS/119/207 : IUE echelle spectra of hot white dwarfs (Holberg+, 1998)
J/ApJS/61/569 : KPD UV-excess objects (Downes+, 1986)
http://www.stsci.edu/hst/cos : COS website
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 23 A23 --- ID WD name (as in table 4)
26- 30 I5 K Teff [20900/60920] Effective temperature
33- 36 F4.2 [cm/s2] logg [7.5/8.3] Surface gravity
39- 43 F5.2 [Lsun] logL [-1.7/0.8] Log of WD luminosity
46- 49 F4.2 Msun Mass [0.5/0.9] WD mass
52- 56 F5.3 Rsun Rad [0.01/0.02] WD radius
59- 62 F4.2 AU Ri [0.1/0.7] RPHZ,i value (1)
65- 68 F4.2 AU Ro [0.2/3.4] RPHZ,o value (1)
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Note (1): PHZ = potentially habitable zone. See section 3.1.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 23 A23 --- Name Target identifier
25- 34 A10 "Y/M/D" Obs.date Date of observation start
36- 47 A12 "h:m:s" Obs.time Time of the observation start
49- 52 I4 s Exp [150/2475] Exposure time
54- 68 F15.8 s-1 CR [4952/339310] Median count rate
70- 74 A5 --- Grating Grating identifier
76- 79 I4 0.1nm lambda [1291/1623] Central wavelength of Grating;
in Angstroms
81- 85 I5 --- PID Proposal identifier
87-110 A24 --- File File identifier
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 23 A23 --- ID WD name
25- 34 A10 "Y/M/D" Obs.date Date of the Observation start
36- 47 A12 "h:m:s" Obs.time Time of the Observation start
49- 52 I4 s Exp [45/2985] Exposure time
54- 69 F16.9 ct/s CR [-30054/319872] Count rate
71- 75 A5 --- Grating Grating identifier
77- 80 I4 0.1nm lambda [1055/3360] Grating central wavelength
82- 86 I5 --- PID Proposal identifier
88-111 A24 --- File File name
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 08-Aug-2016