arXiv subjects

BJ Fulton

Publications and source records attributed to BJ Fulton.

3 recordsLinked to original sources

arXiv2022

Report on Community Cadence Observing to Maximize the Scientific Output of the Keck Planet Finder

The arrival of the Keck Planet Finder (KPF) in 2022 represents a major advance in the precision radial velocity (PRV) capabilities of the W. M. Keck Observatory. In preparation for KPF science, our committee of PRV experts and WMKO staff studied the current implementation of cadence observing at Keck and other PRV facilities. We find that many of KPF's major science cases are not feasible through Keck's standard allocations of full or half nights to individual PIs. Pooling time among several PIs as is currently done by the California Planet Search (CPS) collaboration with HIRES results in lower quality science results than is possible when KPF is available at higher observational cadence. This strategy also creates barriers to entry, particularly for researchers wishing to lead small proposals. This report makes recommendations for optimizing PRV cadence at Keck subject to the following constraints: preservation of clear boundaries between cadence observations and classically scheduled time; and ensuring fairness and scientific independence of different Keck TACs and different KPF PIs. We recommend establishing a new category of Keck time allocation, "KPF Community Cadence" (KPF-CC). In many ways, KPF-CC will formalize observing strategies provided by CPS, but with higher observational cadence appropriate for KPF science and with universal access to the program for all Keck users. We recommend that KPF-CC time be scheduled classically into blocks as small as a quarter night subject to considerations of bright/dark time, variations in proposal pressure with the seasons, and the needs of non-KPF observing programs. Within KPF-CC time, the Keck Observing Assistants would execute observations generated by a dynamic scheduler. We recommend that Keck staff and a board of PRV experts design and maintain the scheduling software.

astro-ph.IM↗

arXiv2018

An Excess of Jupiter Analogs in Super-Earth Systems

We use radial velocity observations to search for long-period gas giant companions in systems hosting inner super-Earth (1-4 R_Earth, 1-10 M_Earth) planets to constrain formation and migration scenarios for this population. We consistently re-fit published RV datasets for 65 stars and find 9 systems with statistically significant trends indicating the presence of an outer companion. We combine these RV data with AO images to constrain the masses and semi-major axes of these companions. We quantify our sensitivity to the presence of long-period companions by fitting the sample with a power law distribution and find an occurrence rate of 39+/-7% for companions 0.5-20 M_Jup and 1-20 AU. Half of our systems were discovered by the transit method and half were discovered by the RV method. While differences in RV baselines and number of data points between the two samples lead to different sensitivities to distant companions, we find that occurrence rates of gas giant companions in each sample are consistent at the 0.5$\sigma$ level. We compare the frequency of Jupiter analogs in these systems to the equivalent rate from field star surveys and find that Jupiter analogs are more common around stars hosting super-Earths. We conclude that the presence of outer gas giants does not suppress the formation of inner super-Earths, and that these two populations of planets instead appear to be correlated. We also find that the stellar metallicities of systems with gas giant companions are higher than those without companions, in agreement with the well-established metallicity correlation from RV surveys of field stars.

astro-ph.EP↗

arXiv2016

Dynamical Constraints on the Core Mass of Hot Jupiter HAT-P-13b

HAT-P-13b is a Jupiter-mass transiting exoplanet that has settled onto a stable, short-period, and mildly eccentric orbit as a consequence of the action of tidal dissipation and perturbations from a second, highly eccentric, outer companion. Due to the special orbital configuration of the HAT-P-13 system, the magnitude of HAT-P-13b's eccentricity ($e_b$) is in part dictated by its Love number ($k_{2_b}$), which is in turn a proxy for the degree of central mass concentration in its interior. Thus, the measurement of $e_b$ constrains $k_{2_b}$ and allows us to place otherwise elusive constraints on the mass of HAT-P-13b's core ($M_{\rm{core,b}}$). In this study we derive new constraints on the value of $e_b$ by observing two secondary eclipses of HAT-P-13b with the Infrared Array Camera on board the $\textit{Spitzer Space Telescope}$. We fit the measured secondary eclipse times simultaneously with radial velocity measurements and find that $e_b = 0.00700 \pm 0.00100$. We then use octupole-order secular perturbation theory to find the corresponding $k_{2_b} = 0.31^{+0.08}_{-0.05}$. Applying structural evolution models, we then find, with 68\% confidence, that $M_{\rm{core,b}}$ is less than 25 Earth masses ($M_{\oplus}$). The most likely value of $M_{\rm{core,b}} = 11 M_{\oplus}$, which is similar to the core mass theoretically required for runaway gas accretion. This is the tightest constraint to date on the core mass of a hot Jupiter. Additionally, we find that the measured secondary eclipse depths, which are in the 3.6 $\mu$m and 4.5 $\mu$m bands, best match atmospheric model predictions with a dayside temperature inversion and relatively efficient day-night circulation.

astro-ph.EP↗