3 research outputs found
HST/WFC3 Light Curve Confirms the Closest Exoplanet to Transit an M Dwarf is Terrestrial
Previous studies of the exoplanet LTT 1445Ac concluded that the light curve
from the Transiting Exoplanet Survey Satellite (TESS) was consistent with both
grazing and non-grazing geometries. As a result, the radius and hence density
of the planet remained unknown. To resolve this ambiguity, we observed the LTT
1445 system for six spacecraft orbits of the Hubble Space Telescope (HST) using
WFC3/UVIS imaging in spatial scan mode, including one partial transit of LTT
1445Ac. This imaging produces resolved light curves of each of the three stars
in the LTT 1445 system. We confirm that the planet transits LTT 1445A 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 LTT 1445Ac is not grazing with 97% confidence. We measure a planetary radius
of 1.10 R. Combined with previous radial velocity
observations, our analysis yields a planetary mass of M
and a planetary density of 5.6 g cm. LTT 1445Ac is 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.Comment: Submitted to AJ. 9 pages, 7 figures, 3 table
Laminate polyethylene window development for large aperture millimeter receivers
New experiments that target the B-mode polarization signals in the Cosmic
Microwave Background require more sensitivity, more detectors, and thus
larger-aperture millimeter-wavelength telescopes, than previous experiments.
These larger apertures require ever larger vacuum windows to house cryogenic
optics. Scaling up conventional vacuum windows, such as those made of High
Density Polyethylene (HDPE), require a corresponding increase in the thickness
of the window material to handle the extra force from the atmospheric pressure.
Thicker windows cause more transmission loss at ambient temperatures,
increasing optical loading and decreasing sensitivity. We have developed the
use of woven High Modulus Polyethylene (HMPE), a material 100 times stronger
than HDPE, to manufacture stronger, thinner windows using a pressurized hot
lamination process. We discuss the development of a specialty autoclave for
generating thin laminate vacuum windows and the optical and mechanical
characterization of full scale science grade windows, with the goal of
developing a new window suitable for BICEP Array cryostats and for future CMB
applications
HST/WFC3 Light Curve Supports a Terrestrial Composition for the Closest Exoplanet to Transit an M Dwarf
Previous studies of the exoplanet LTT 1445Ac 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 LTT 1445 system for six spacecraft orbits of the Hubble Space Telescope (HST) using WFC3/UVIS imaging in spatial scan mode, including one partial transit of LTT 1445Ac. This imaging produces resolved light curves of each of the three stars in the LTT 1445 system. We confirm that the planet transits LTT 1445A 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 LTT 1445Ac is not grazing with 97% confidence. We measure a planetary radius of . Combined with previous radial velocity observations, our analysis yields a planetary mass of 1.37 Β± 0.19 M _β and a planetary density of g cm ^β3 . LTT 1445Ac 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