J/AJ/169/104 Light curve & excess absorption of TOI-1259 A b (Saidel+, 2025)
Atmospheric mass loss from TOI-1259 A b, a gas giant planet with a white dwarf
companion.
Saidel M., Vissapragada S., Spake J., Knutson H.A., Linssen D., Zhang M.,
Greklek-McKeon M., Perez-Gonzalez J., Oklopcic A.
<Astron. J., 169, 104 (2025)>
=2025AJ....169..104S 2025AJ....169..104S
ADC_Keywords: Exoplanets; Stars, white dwarf; Photometry; Spectra, infrared
Keywords: Exoplanet evolution ; Exoplanets ; Exoplanet atmospheres ;
Exoplanet astronomy ; Planetary atmospheres ;
Extrasolar gaseous planets ; Extrasolar gaseous giant planets
Abstract:
The lack of close-in Neptune-mass exoplanets evident in transit
surveys has largely been attributed to either photoevaporative mass
loss or high-eccentricity migration. To distinguish between these two
possibilities, we investigate the origins of TOI-1259 A b,
a Saturn-mass (0.4MJ, 1.0RJ) exoplanet lying along the upper edge
of the Neptune desert. TOI-1259 A b's close-in (P=3.48d) orbit and low
bulk density make the planet particularly vulnerable to
photoevaporation. We studied the upper atmosphere of TOI-1259 A b
using metastable helium 1083nm transits observed with Palomar/WIRC and
Keck/NIRSPEC. We report a band-integrated excess absorption of
0.395%±0.072% with Palomar/WIRC and a spectroscopically resolved
5.5±0.94km/s blueshifted absorption of 2.4%±0.52% (T1-T4) and
3.5%±0.72% (T2-T3) with Keck/NIRSPEC. These measurements indicate
the presence of an extended escaping atmosphere. Fitting these signals
with a Parker wind model, we determine a corresponding atmospheric
mass-loss rate of log({dot}M)=10.2-10.65g/s for thermosphere
temperatures between 7900 and 8600K. This relatively low rate suggests
that this planet would not have been significantly altered by mass
loss even if it formed in situ. However, the presence of a white dwarf
companion, TOI-1259 B, hints that this planet may not have formed
close-in, but rather migrated inward relatively late. Given the
estimated parameters of the proto-white dwarf companion, we find that
high-eccentricity migration is possible for the system.
Description:
We observed two transits of TOI-1259 A b on UT 2022 April 15 and UT
2022 June 20 with Palomar/WIRC. The Wide-field Infrared Camera (WIRC)
is a prime focus instrument at the Palomar Observatory 200-inch
telescope in California, US. All transits were observed in an
ultra-narrow-band helium filter centered on the helium 1083.3nm line
with an FWHM of 0.635nm as discussed in Vissapragada+2020b (J/AJ/159/278).
We observed a full transit of TOI-1259 A b with Keck/NIRSPEC on UT
2022 June 27, using the Y-band filter (0.947-1.121um) in the
high-resolution mode. The Near Infrared Spectrometer (NIRSPEC) is an
all-reflective, near-infrared, high-resolution spectrograph on the
Keck II telescope in Hawaii, US. Observations were obtained using the
0.288"x12" slit, which has a slit resolution of 37,500. We used 300s
exposures with an ABBA nodding pattern to subtract the background.
Objects:
------------------------------------------------------------------------
RA (2000) DE Designation(s) (Period)
------------------------------------------------------------------------
18 48 24.07 +79 15 21.7 TOI-1259 A b = TOI-1259b (Period=3.48d)
------------------------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
fig3b.dat 104 407 Excess absorption spectra in the planetary rest frame
as a function of wavelength (data behind Figure 3b)
fig4.dat 61 53 Band-integrated light curve of TOI-1259 A b
(data behind Figure 4)
fig5.dat 113 407 Average excess absorption during the first and second
halfs of transit (data behind Figure 5)
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See also:
J/ApJ/757/18 : RVs for 16 hot Jupiter host stars (Albrecht+, 2012)
J/MNRAS/422/2024 : X-ray-age relation & exoplanet evaporation (Jackson+, 2012)
J/ApJ/843/31 : MUSCLES Treasury Surv. IV. M dwarf UV fluxes (Youngblood+, 2017)
J/AJ/159/278 : He-filter obs. of WASP-69b & WASP-52b (Vissapragada+, 2020)
J/ApJ/940/L35 : HAT-P-18b JWST NIRISS transmission spectrum (Fu+, 2022)
J/AJ/163/67 : 5-55000Å spectrum of TOI 560 (Zhang+, 2022)
J/A+A/361/641 : Investigation of mass loss mechanism of LPVs (Winters+, 2000)
Byte-by-byte Description of file: fig3b.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 F18.16 um lambda [1.081/1.085] Wavelength
20- 42 F23.20 % ExAbsT1T4 [-1.6/2.5]? Excess Absorption T1-T4
(all in-transit)
44- 61 F18.16 % e_ExAbsT1T4 Uncertainty in ExAbsT1T4
63- 85 F23.20 % ExAbsT2T3 [-2.6/3.5]? Excess Absorption T2-T3
(occlusion only)
87- 104 F18.16 % e_ExAbsT2T3 Uncertainty in ExAbsT2T3
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Byte-by-byte Description of file: fig4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 20 F20.17 h dT [-4.1/1.4] Time since mid-transit
22- 39 F18.16 --- Flux [0.9/1.01] Band Integrated Relative Flux (1)
41- 61 F21.19 --- e_Flux [0.002/0.015] Uncertainty in Flux
--------------------------------------------------------------------------------
Note (1): Integrated within 0.75Å of the main peak in the helium
triplet (10833.0Å).
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Byte-by-byte Description of file: fig5.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 F18.16 um lambda [1.081/1.085] Wavelength
20- 41 F22.19 % ExAbs1 [-2.8/2.8] Excess Absorption First Half
Transit
43- 65 A23 % BestFit1 Best Fit First Half Transit (1)
67- 89 F23.20 % ExAbs2 [-1.9/2.9] Excess Absorption Second Half
Transit
91- 113 A23 % BestFit2 Best Fit Second Half Transit (1)
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Note (1): Gaussian fit functions evaluated at lambda.
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File description: fig3a.p
Pickled Python Dictionary for Panel A, Figure 3
[md5 = 16a3b0014fd284bea494488b9c54fc4d]
History:
From electronic version of the journal
(End) Prepared by [AAS], Robin Leichtnam [CDS] 03-Dec-2025