63 research outputs found
Design and performance of a F/#-conversion microlens for Prime Focus Spectrograph at Subaru Telescope
The PFS is a multi-object spectrograph fed by 2394 fibers at the prime focus
of Subaru telescope. Since the F/# at the prime focus is too fast for the
spectrograph, we designed a small concave-plano negative lens to be attached to
the tip of each fiber that converts the telescope beam (F/2.2) to F/2.8. We
optimized the lens to maximize the number of rays that can be confined inside
F/2.8 while maintaining a 1.28 magnification. The microlenses are manufactured
by glass molding, and an ultra-broadband AR coating (<1.5% for lambda=0.38-1.26
um) will be applied to the front surface.Comment: 7 pages, 8 figures, SPIE201
Evidence for Spin–Orbit Alignment in the TRAPPIST-1 System
In an effort to measure the Rossiter–McLaughlin effect for the TRAPPIST-1 system, we performed high-resolution spectroscopy during transits of planets e, f, and b. The spectra were obtained with the InfraRed Doppler spectrograph on the Subaru 8.2 m telescope, and were supplemented with simultaneous photometry obtained with a 1 m telescope of the Las Cumbres Observatory Global Telescope. By analyzing the anomalous radial velocities, we found the projected stellar obliquity to be λ = 1 ± 28° under the assumption that the three planets have coplanar orbits, although we caution that the radial-velocity data show correlated noise of unknown origin. We also sought evidence for the expected deformations of the stellar absorption lines, and thereby detected the "Doppler shadow" of planet b with a false-alarm probability of 1.7%. The joint analysis of the observed residual cross-correlation map including the three transits gave λ = 19_(-15)^(+13)°. These results indicate that the the TRAPPIST-1 star is not strongly misaligned with the common orbital plane of the planets, although further observations are encouraged to verify this conclusion
Detectors and cryostat design for the SuMIRe Prime Focus Spectrograph (PFS)
We describe the conceptual design of the camera cryostats, detectors, and
detector readout electronics for the SuMIRe Prime Focus Spectrograph (PFS)
being developed for the Subaru telescope. The SuMIRe PFS will consist of four
identical spectrographs, each receiving 600 fibers from a 2400 fiber robotic
positioner at the prime focus. Each spectrograph will have three channels
covering wavelength ranges 3800 {\AA} - 6700 {\AA}, 6500 {\AA} - 10000 {\AA},
and 9700 {\AA} - 13000 {\AA}, with the dispersed light being imaged in each
channel by a f/1.10 vacuum Schmidt camera. In the blue and red channels a pair
of Hamamatsu 2K x 4K edge-buttable CCDs with 15 um pixels are used to form a 4K
x 4K array. For the IR channel, the new Teledyne 4K x 4K, 15 um pixel,
mercury-cadmium-telluride sensor with substrate removed for short-wavelength
response and a 1.7 um cutoff will be used. Identical detector geometry and a
nearly identical optical design allow for a common cryostat design with the
only notable difference being the need for a cold radiation shield in the IR
camera to mitigate thermal background. This paper describes the details of the
cryostat design and cooling scheme, relevant thermal considerations and
analysis, and discusses the detectors and detector readout electronics
Planet(esimal)s Around Stars with TESS (PAST) III: A Search for Triplet He I in the Atmospheres of Two 200 Myr-old Planets
We report a search for excess absorption in the 1083.2 nm line of ortho
(triplet) helium during transits of TOI-1807b and TOI-2076b, 1.25 and
2.5R planets on 0.55- and 10.4-day orbits around nearby
200~Myr-old K dwarf stars. We limit the equivalent width of any
transit-associated absorption to 4 and 8 mA, respectively. We limit the
escape of solar-composition atmospheres from TOI-1807b and TOI-2076b to
1 and 0.1M Gyr, respectively,
depending on wind temperature. The absence of a H/He signature for TOI-1807b is
consistent with a measurement of mass indicating a rocky body and the
prediction by a hydrodynamic model that any H-dominated atmosphere would be
unstable and already have been lost. Differential spectra obtained during the
transit of TOI-2076b contain a He I-like feature, but this closely resembles
the stellar line and extends beyond the transit interval. Until additional
transits are observed, we suspect this to be the result of variation in the
stellar He I line produced by rotation of active regions and/or flaring on the
young, active host star. Non-detection of escape could mean that TOI-2076b is
more massive than expected, the star is less EUV-luminous, the models
overestimate escape, or the planet has a H/He-poor atmosphere that is primarily
molecules such as HO. Photochemical models of planetary winds predict a
semi-major axis at which triplet He I observations are most sensitive to mass
loss: TOI-2076b orbits near this optimum. Future surveys could use a distance
criterion to increase the yield of detections.Comment: Accepted to MNRA
Cerium features in kilonova near-infrared spectra: implication from a chemically peculiar star
Observations of the kilonova from a neutron star merger event GW170817 opened
a way to directly study r-process nucleosynthesis by neutron star mergers. It
is, however, challenging to identify the individual elements in the kilonova
spectra due to lack of complete atomic data, in particular, at near-infrared
wavelengths. In this paper, we demonstrate that spectra of chemically peculiar
stars with enhanced heavy element abundances can provide us with an excellent
astrophysical laboratory for kilonova spectra. We show that the photosphere of
a late B-type chemically peculiar star HR 465 has similar lanthanide abundances
and ionization degrees with those in the line forming region in a kilonova at
days after the merger. The near-infrared spectrum of HR 465 taken
with Subaru/IRD indicates that Ce III lines give the strongest absorption
features around 16,000 A and there are no other comparably strong transitions
around these lines. The Ce III lines nicely match with the broad absorption
features at 14,500 A observed in GW170817 with a blueshift of v=0.1c, which
supports recent identification of this feature as Ce III by Domoto et al.
(2022).Comment: 12 pages, 6 figures, accepted for publication in Ap
Limits on the Spin-Orbit Angle and Atmospheric Escape for the 22 Myr-old Planet AU Mic b
We obtained spectra of the pre-main sequence star AU Microscopii during a
transit of its Neptune-sized planet to investigate its orbit and atmosphere. We
used the high-dispersion near-infrared spectrograph IRD on the Subaru telescope
to detect the Doppler "shadow" from the planet and constrain the projected
stellar obliquity. Modeling of the observed planetary Doppler shadow suggests a
spin-orbit alignment of the system ( degrees), but
additional observations are needed to confirm this finding. We use both the IRD
data and spectra obtained with NIRSPEC on Keck-II to search for absorption in
the 1083 nm line of metastable triplet He I by the planet's atmosphere and
place an upper limit for the equivalent width of 3.7 m\AA at 99
confidence. With this limit and a Parker wind model we constrain the escape
rate from the atmosphere to Gyr, comparable to
the rates predicted by an XUV energy-limited escape calculation and
hydrodynamic models, but refinement of the planet mass is needed for rigorous
tests.Comment: 10 pages, 5 figures, accepted for publication in ApJ Letter
Absence of extended atmospheres in low-mass star radius-gap planets GJ 9827 b, GJ 9827 d and TOI-1235 b
\textit{Kepler} showed a paucity of planets with radii of 1.5 - 2 around solar mass stars but this radius-gap has not been well
studied for low-mass star planets. Energy-driven escape models like
photoevaporation and core-powered mass-loss predict opposing transition regimes
between rocky and non-rocky planets when compared to models depicting planets
forming in gas-poor environments. Here we present transit observations of three
super-Earth sized planets in the radius-gap around low-mass stars using
high-dispersion InfraRed Doppler (IRD) spectrograph on the Subaru 8.2m
telescope. The planets GJ 9827 b and d orbit around a K6V star and TOI-1235 b
orbits a M0.5 star. We limit any planet-related absorption in the 1083.3 nm
lines of triplet He I by placing an upper-limit on the equivalent width of
14.71 m{\AA}, 18.39 m{\AA}, and 1.44 m{\AA}, for GJ 9827 b (99% confidence), GJ
9827 d (99% confidence) and TOI-1235 b (95% confidence) respectively. Using a
Parker wind model, we cap the mass-loss at 0.25
Gyr and 0.2 Gyr for GJ 9827 b and d,
respectively (99% confidence), and 0.05 Gyr for
TOI-1235 b (95\% confidence) for a representative wind temperature of 5000 K.
Our observed results for the three planets are more consistent with the
predictions from photoevaporation and/or core-powered mass-loss models than the
gas-poor formation models. However, more planets in the radius-gap regime
around the low-mass stars are needed to robustly predict the atmospheric
evolution in planets around low-mass stars.Comment: Accepted for MNRAS. 12 pages, 15 figure
Prime Focus Instrument of Prime Focus Spectrograph for Subaru Telescope
The Prime Focus Spectrograph (PFS) is a new optical/near-infrared multi-fiber
spectrograph design for the prime focus of the 8.2m Subaru telescope. PFS will
cover 1.3 degree diameter field with 2394 fibers to complement the imaging
capability of Hyper SuprimeCam (HSC). The prime focus unit of PFS called Prime
Focus Instrument (PFI) provides the interface with the top structure of Subaru
telescope and also accommodates the optical bench in which Cobra fiber
positioners are located. In addition, the acquisition and guiding (A&G)
cameras, the optical fiber positioner system, the cable wrapper, the fiducial
fibers, illuminator, and viewer, the field element, and the telemetry system
are located inside the PFI. The mechanical structure of the PFI was designed
with special care such that its deflections sufficiently match those of the HSC
Wide Field Corrector (WFC) so the fibers will stay on targets over the course
of the observations within the required accuracy.Comment: 9 pages, 7 figures, SPIE Astronomical Telescopes and Instrumentation
201
Prime Focus Spectrograph - Subaru's future -
The Prime Focus Spectrograph (PFS) of the Subaru Measurement of Images and
Redshifts (SuMIRe) project has been endorsed by Japanese community as one of
the main future instruments of the Subaru 8.2-meter telescope at Mauna Kea,
Hawaii. This optical/near-infrared multi-fiber spectrograph targets cosmology
with galaxy surveys, Galactic archaeology, and studies of galaxy/AGN evolution.
Taking advantage of Subaru's wide field of view, which is further extended with
the recently completed Wide Field Corrector, PFS will enable us to carry out
multi-fiber spectroscopy of 2400 targets within 1.3 degree diameter. A
microlens is attached at each fiber entrance for F-ratio transformation into a
larger one so that difficulties of spectrograph design are eased. Fibers are
accurately placed onto target positions by positioners, each of which consists
of two stages of piezo-electric rotary motors, through iterations by using
back-illuminated fiber position measurements with a wide-field metrology
camera. Fibers then carry light to a set of four identical fast-Schmidt
spectrographs with three color arms each: the wavelength ranges from 0.38
{\mu}m to 1.3 {\mu}m will be simultaneously observed with an average resolving
power of 3000. Before and during the era of extremely large telescopes, PFS
will provide the unique capability of obtaining spectra of 2400
cosmological/astrophysical targets simultaneously with an 8-10 meter class
telescope. The PFS collaboration, led by IPMU, consists of USP/LNA in Brazil,
Caltech/JPL, Princeton, & JHU in USA, LAM in France, ASIAA in Taiwan, and
NAOJ/Subaru.Comment: 13 pages, 11 figures, submitted to "Ground-based and Airborne
Instrumentation for Astronomy IV, Ian S. McLean, Suzanne K. Ramsay, Hideki
Takami, Editors, Proc. SPIE 8446 (2012)
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