J/A+A/623/A57 WASP-121 b Swift UVOT near-UV transit observations (Salz+, 2019)
Swift UVOT near-UV transit observations of WASP-121 b.
Salz M., Schneider P.C., Fossati L., Czesla S., France K., Schmitt J.H.M.M.
<Astron. Astrophys. 623, A57 (2019)>
=2019A&A...623A..57S 2019A&A...623A..57S (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets ; Photometry, ultraviolet
Keywords: planets and satellites: atmospheres - techniques: photometric -
planets and satellites: physical evolution -
planet-star interactions -
planets and satellites: individual: WASP-121 b -
planets and satellites: individual: WASP-12 b
Abstract:
Close-in gas planets are subject to continuous photoevaporation that
can erode their volatile envelopes. Today, ongoing mass loss has been
confirmed in a few individual systems via transit observations in the
ultraviolet spectral range. We demonstrate that the
Ultraviolet/Optical Telescope (UVOT) onboard the Neil Gehrels Swift
Observatory enables photometry to a relative accuracy of about 0.5%
and present the first near-UV (200-270nm, NUV) transit observations
of WASP-121 b, a hot Jupiter with one of the highest predicted
mass-loss rates. The data cover the orbital phases 0.85 to 1.15 with
three visits. We measure a broad-band NUV transit depth of
2.10±0.29%. While still consistent with the optical value of 1.55%,
the NUV data indicate excess absorption of 0.55% at a 1.9-sigma level.
Such excess absorption is known from the WASP-12 system, and both of
these hot Jupiters are expected to undergo mass loss at extremely high
rates. With a CLOUDY simulation, we show that absorption lines of Fe
II in a dense extended atmosphere can cause broad-band NUV absorption
at the 0.5% level. Given the numerous lines of low-ionization metals,
the NUV range is a promising tracer of photoevaporation in the hottest
gas planets.
Description:
Three transit light curves of WASP-121 b observed with the
Ultraviolet/Optical Telescope (UVOT) onboard the Neil Gehrels Swift
Observatory in the UVM2 filter observed on Aug 4, Sept 3, and Sept 5,
2017. The raw data was reduced and corrected as described in Sect. 3
of the publication. Fig. A.1 shows this data binned to 200 sec per
bin. Exposures during which the source was placed on low-sensitivity
patches are not contained.
Objects:
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RA (2000) DE Designation(s)
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07 10 24.06 -39 05 50.6 WASP-121 b = WASP-121b
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
w121b-lc.dat 44 1003 UV transit light curve of WASP-121b
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Byte-by-byte Description of file: w121b-lc.dat
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Bytes Format Units Label Explanations
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1- 14 E14.8 d Time Barycentric Julian date (TDB) (BJD-2450000)
16- 29 E14.8 ct/s CRate Count rate
31- 44 E14.8 ct/s e_CRate Mean error on count rate
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Acknowledgements:
Michael Salz, msalz(at)hs.uni-hamburg.de
(End) Michael Salz [Hamburg], Patricia Vannier [CDS] 29-Jan-2019