J/ApJ/931/L15 Obs. of two transits of GJ 3470b with NEID (Stefansson+, 2022)
The warm Neptune GJ 3470b has a polar orbit.
Stefansson G., Mahadevan S., Petrovich C., Winn J.N., Kanodia S.,
Millholland S.C., Maney M., Canas C.I., Wisniewski J., Robertson P.,
Ninan J.P., Ford E.B., Bender C.F., Blake C.H., Cegla H., Cochran W.D.,
Diddams S.A., Dong J., Endl M., Fredrick C., Halverson S., Hearty F.,
Hebb L., Hirano T., Lin A.S.J., Logsdon S.E., Lubar E., McElwain M.W.,
Metcalf A.J., Monson A., Rajagopal J., Ramsey L.W., Roy A., Schwab C.,
Schweiker H., Terrien R.C., Wright J.T.
<Astrophys. J., 931, L15 (2022)>
=2022ApJ...931L..15S 2022ApJ...931L..15S
ADC_Keywords: Exoplanets; Spectra, optical; Radial velocities; Photometry
Keywords: Exoplanet astronomy ; Exoplanet dynamics ; Exoplanet systems ;
Radial velocity ; Transit photometry ; Exoplanets ;
Extrasolar gaseous planets ; Hot Neptunes
Abstract:
The warm Neptune GJ 3470b transits a nearby (d=29 pc) bright slowly
rotating M1.5-dwarf star. Using spectroscopic observations during two
transits with the newly commissioned NEID spectrometer on the WIYN
3.5m Telescope at Kitt Peak Observatory, we model the classical
Rossiter-McLaughlin effect, yielding a sky-projected obliquity of
λ=98-12+15° and a vsini=0.85-0.33+0.27km/s.
Leveraging information about the rotation period and size of the host
star, our analysis yields a true obliquity of ψ=95-8+9°,
revealing that GJ 3470b is on a polar orbit. Using radial velocities
from HIRES, HARPS, and the Habitable-zone Planet Finder, we show that
the data are compatible with a long-term radial velocity (RV) slope of
{dot}gamma=-0.0022±0.0011m/s/d over a baseline of 12.9yr. If the RV
slope is due to acceleration from another companion in the system, we
show that such a companion is capable of explaining the polar and
mildly eccentric orbit of GJ 3470b using two different secular
excitation models. The existence of an outer companion can be further
constrained with additional RV observations, Gaia astrometry, and
future high-contrast imaging observations. Lastly, we show that tidal
heating from GJ 3470b's mild eccentricity has most likely inflated the
radius of GJ 3470b by a factor of ∼1.5-1.7, which could help account
for its evaporating atmosphere.
Description:
We observed two transits of the low-density warm Neptune GJ 3470b with
the NEID spectrograph (wavelength range from 380 to 930nm at a
resolving power of R∼110000) on the WIYN 3.5m Telescope at Kitt Peak
Observatory, on the nights of 2021 January 1 (January 2 UT) and
2021 January 11 (12 January UT).
We obtained 25 and 24 spectra for the two transits, respectively,
using an exposure time of 600s.
See Section 3.1.
To refine the transit ephemeris, we observed two photometric transits
of GJ 3470b using the Astrophysical Research Council Telescope Imaging
Camera (ARCTIC) on the ARC 3.5m Telescope at Apache Point Observatory
in New Mexico. The two nights were 2019 December 2 and 22 UT. We used
the Engineered Diffuser available on the ARCTIC imager because it
enables high-precision photometry by molding the point-spread function
into a broad and stabilized top-hat shape. To minimize atmospheric
systematics, we used a narrowband (30nm wide) filter from Semrock
Optics, which is centered in a region with minimal telluric absorption
at 857nm. The mean cadence was 19.1 and 18.2s for the two transits,
respectively.
See Section 3.2.
In addition to the in-transit spectroscopy with NEID, we analyzed
out-of-transit radial velocities (RVs) to constrain the possibility of
an outer companion. For this analysis, we used RVs from the High
Resolution Echelle Spectrometer (HIRES) on the Keck I telescope on
Maunakea, the HARPS spectrograph on the 3.6m Telescope at La Silla
Observatory in Chile, and the HPF spectrograph on the 10m Hobby-Eberly
Telescope in Texas.
Together, the available RV data from HIRES, HARPS, and HPF span a
baseline of 4709d, or about 12.9yr from 2008-Dec-07 to 2021-Oct-29.
See Section 3.3.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
07 59 05.83 +15 23 29.2 GJ 3470b = NAME Phailinsiam
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig1ab.dat 52 1718 Diffuser assisted transits taken with the 3.5m
Telescope at Apache Point Observatory
fig1cd.dat 27 48 In transit WIYN/NEID radial velocities
fig23.dat 62 187 Table including out-of-transit RVs obtained with
HARPS, HIRES and HPF as shown in Figure 2 and
activity indicators as shown in Figure 3
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See also:
I/347 : Distances to 1.33 billion stars in Gaia DR2 (Bailer-Jones+, 2018)
J/ApJ/723/L223 : Radial velocities of HAT-P-11 (Winn+, 2010)
J/ApJ/757/18 : RVel for 16 hot Jupiter host stars (Albrecht+, 2012)
J/A+A/546/A27 : Radial velocity and photometry for GJ3470 (Bonfils+, 2012)
J/A+A/559/A32 : Light curves of GJ3470b (Nascimbeni+, 2013)
J/AJ/155/255 : RVel and activity measurements of HAT-P-11 (Yee+, 2018)
J/AJ/157/97 : RVel measurements of K2-3 & GJ3470 (Kosiarek+, 2019)
J/AJ/159/18 : Jovian-type planets around M dwarfs with MIRI (Brande+, 2020)
J/AJ/159/100 : Flux & RVs of G9-40 with K2 & HPF (Stefansson+, 2020)
J/AJ/160/192 : Photometry and RVs of K2-25b with HPF (Stefansson+, 2020)
J/AJ/159/19 : SOAR TESS survey. I. (Ziegler+, 2020)
J/AJ/161/70 : RVel for WASP-107 with HIRES & CORALIE (Piaulet+, 2021)
J/AJ/161/119 : The TESS-Keck survey. IV. Rvel for WASP-107 (Rubenzahl+, 2021)
Byte-by-byte Description of file: fig1ab.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 F14.6 d BJD Barycentric Julian Date at TDB
16- 23 F8.6 --- Flux [0.99/1.01] Normalized flux
25- 32 F8.6 --- e_Flux [0.00078/0.0011] Uncertainty in Flux
34- 41 F8.6 --- Model [0.993/1.007] Transit and Gaussian Process Red
Noise Model
43- 50 F8.6 --- Gp [0.999/1.007] GP Red Noise Model
52 I1 --- Transit [1/2] Transit number
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Byte-by-byte Description of file: fig1cd.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 F14.6 d BJD Barycentric Julian Date at TDB
16- 20 F5.2 m/s RV [-9/5] Radial velocity
22- 25 F4.2 m/s e_RV [1.4/6] Error on RV
27 I1 --- Transit [0/1] Transit - transit number
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Byte-by-byte Description of file: fig23.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 F14.6 d BJD Barycentric Julian Date at TDB
16- 21 F6.2 m/s RV [-16/17] Radial velocity (Figure 2)
23- 27 F5.2 m/s e_RV [1.4/17.4] Error on RV (Figure 2)
29- 34 F6.4 --- Ha [0.84/1]? H-alpha index as calculated by
SERVAL (Figure 3)
36- 41 F6.4 --- e_Ha [0.003/0.008]? Error on Ha
43- 48 F6.4 --- SHK [0.24/2.4]? Ca II H & K index (Figure 3)
50- 55 F6.4 --- e_SHK [0.0098/0.06]? Error on SHK
57- 62 A6 --- Inst Instrument name (1)
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Note (1): Instrument as follows:
HARPS1 = HARPS spectrograph data on the 3.6m Telescope at La Silla
Observatory in Chile, obtained before the HARPS fiber intervention
(95 occurrences)
HARPS2 = HARPS data obtained after the HARPS fiber intervention
(27 occurrences)
HIRES = the High Resolution Echelle Spectrometer on the Keck I telescope
on Maunakea; RVs derived with the iodine technique as published
by Kosiarek+ (2019AJ....157...97K 2019AJ....157...97K) (56 occurrences)
HPF = the Habitable-zone Planet Finder NIR spectrograph on the 10m
Hobby-Eberly Telescope at McDonald Observatory in Texas. A subset
of the HPF spectra was originally discussed by
Ninan+ (2020ApJ...894...97N 2020ApJ...894...97N) (9 occurrences)
See Section 3.3. for further explanations.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 11-Feb-2025