J/AJ/166/171 HST/WFC3 light curve in LTT 144 system (Pass+, 2023)
HST/WFC3 Light Curve Supports a Terrestrial Composition for the Closest
Exoplanet to Transit an M-Dwarf.
Pass E.K., Winters J.G., Charbonneau D., Balkanski A., Lewis N., Lally M.,
Bean J.L., Cloutier R., Eastman J.D.
<Astron. J., 166, 171 (2023)>
=2023AJ....166..171P 2023AJ....166..171P
ADC_Keywords: Exoplanets; Stars, double and multiple; Photometry, HST
Keywords: Exoplanet astronomy ; Transit photometry ; Exoplanets ; M dwarf
stars ; Transits ; HST photometry ; Hubble Space Telescope ;
Multiple stars
Abstract:
Previous studies of the exoplanet LTT1445Ac concluded that the light
curve from the Transiting Exoplanet Survey Satellite (TESS) was
consistent with both grazing and nongrazing geometries. As a result,
the radius and hence density of the planet remained unknown. To
resolve this ambiguity, we observed the LTT1445 system for six
spacecraft orbits of the Hubble Space Telescope (HST) using WFC3/UVIS
imaging in spatial scan mode, including one partial transit of
LTT1445Ac. This imaging produces resolved light curves of each of the
three stars in the LTT1445 system. We confirm that the planet transits
LTT1445A and that LTT 1445C is the source of the rotational modulation
seen in the TESS light curve, and we refine the estimate of the
dilution factor for the TESS data. We perform a joint fit to the TESS
and HST observations, finding that the transit of LTT1445Ac is not
grazing with 97% confidence. We measure a planetary radius of
1.07-0.07+0.10R⊕. Combined with previous radial velocity
observations, our analysis yields a planetary mass of
1.37±0.19M⊕ and a planetary density of
5.9-1.5+1.8g/cm3. LTT1445Ac is likely an Earth analog with
respect to its mass and radius, albeit with a higher instellation, and
is therefore an exciting target for future atmospheric studies.
Description:
We gathered the HST photometry under program 16503 (PI: Winters),
using WFC3/UVIS in spatial scanning mode with the F814W filter and the
512x52 subarray. Our data set comprises six HST orbits, divided
between two visits and consisting of sequences of 22s exposures taken
at a 76s cadence. The first visit occurred on 2021 September 26 from
11:27:24 to 15:35:39 UT and the second on 2021 September 29 from
14:07:57 to 18:14:44 UT.
Objects:
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RA (2000) DE Designation(s)
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03 01 51.39 -16 35 36.0 LTT 1445A = ** RST 2292A
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 76 188 Raw and systematics-corrected light curves of the
LTT 1445 System
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See also:
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
J/ApJ/757/112 : Stellar diameters. II. K and M-stars (Boyajian+, 2012)
J/AJ/152/141 : Solar neighborhood. XXXVII. RVs for M dwarfs (Benedict+, 2016)
J/ApJ/834/17 : Mass & radius of planets, moons, low mass stars (Chen+, 2017)
J/AJ/154/109 : California-Kepler Survey. III. Planet radii (Fulton+, 2017)
J/AJ/157/143 : Kepler GK dwarf planet candidate samples (Burke+, 2019)
J/AJ/161/269 : HST WFC3/UVIS normalized light curve of WASP-43 (Fraine+, 2021)
J/A+A/648/A15 : beta Pictoris photometry (Kenworthy+, 2021)
J/other/Sci/377.1211 : RV and LC of 8 M dwarf stars with planets (Luque+, 2022)
J/AJ/163/168 : Photometry and radial velocity of LTT 1445A (Winters+, 2022)
J/A+A/673/A69 : LTT 1445A ESPRESSO observations (Lavie+, 2023)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 10 F10.5 d BJD [2483/2488] TESS Barycentric Julian Date
12- 19 I8 ct FluxA [52862829/53097082] Raw flux of LTT 1445A
21- 28 I8 ct FluxB [38455361/38581187] Raw flux of LTT 1445B
30- 37 I8 ct FluxC [19841068/20089003] Raw flux of LTT 1445C
39- 44 F6.3 --- CFluxA [-1.4/0.69] Corrected flux of LTT 1445A; parts
per thousand (1)
46- 50 F5.3 --- e_CFluxA [0.2/0.3] Uncertainty on CFluxA; parts
per thousand
52- 57 F6.3 --- CFluxB [-0.47/0.77] Corrected flux of LTT 1445B; parts
per thousand (1)
59- 63 F5.3 --- e_CFluxB [0.2/0.3] Uncertainty on CFluxB; parts
per thousand
65- 70 F6.3 --- CFluxC [-0.58/0.76] Corrected flux of LTT 1445C; parts
per thousand (1)
72- 76 F5.3 --- e_CFluxC [0.2/0.3] Uncertainty on CFluxC; parts
per thousand
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Note (1): The corrected flux columns use the maximum a posteriori systematics
correction, as plotted in Figure 4
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 08-Apr-2024