XO-2b: A Hot Jupiter With A Variable Host Star That Potentially Affects ...

Astrophysics > Earth and Planetary Astrophysics arXiv:1505.01063 (astro-ph) [Submitted on 5 May 2015 (v1), last revised 26 Aug 2015 (this version, v2)] Title:XO-2b: a hot Jupiter with a variable host star that potentially affects its measured transit depth Authors:Robert T. Zellem, Caitlin A. Griffith, Kyle A. Pearson, Jake D. Turner, Gregory W. Henry, Michael W. Williamson, M. Ryleigh Fitzpatrick, Johanna K. Teske, Lauren I. Biddle View a PDF of the paper titled XO-2b: a hot Jupiter with a variable host star that potentially affects its measured transit depth, by Robert T. Zellem and 8 other authors View PDF

Abstract:The transiting hot Jupiter XO-2b is an ideal target for multi-object photometry and spectroscopy as it has a relatively bright ($V$-mag = 11.25) K0V host star (XO-2N) and a large planet-to-star contrast ratio (R$_{p}$/R$_{s}\approx0.015$). It also has a nearby (31.21") binary stellar companion (XO-2S) of nearly the same brightness ($V$-mag = 11.20) and spectral type (G9V), allowing for the characterization and removal of shared systematic errors (e.g., airmass brightness variations). We have therefore conducted a multiyear (2012--2015) study of XO-2b with the University of Arizona's 61" (1.55~m) Kuiper Telescope and Mont4k CCD in the Bessel U and Harris B photometric passbands to measure its Rayleigh scattering slope to place upper limits on the pressure-dependent radius at, e.g., 10~bar. Such measurements are needed to constrain its derived molecular abundances from primary transit observations. We have also been monitoring XO-2N since the 2013--2014 winter season with Tennessee State University's Celestron-14 (0.36~m) automated imaging telescope to investigate stellar variability, which could affect XO-2b's transit depth. Our observations indicate that XO-2N is variable, potentially due to {cool star} spots, {with a peak-to-peak amplitude of $0.0049 \pm 0.0007$~R-mag and a period of $29.89 \pm 0.16$~days for the 2013--2014 observing season and a peak-to-peak amplitude of $0.0035 \pm 0.0007$~R-mag and $27.34 \pm 0.21$~day period for the 2014--2015 observing season. Because of} the likely influence of XO-2N's variability on the derivation of XO-2b's transit depth, we cannot bin multiple nights of data to decrease our uncertainties, preventing us from constraining its gas abundances. This study demonstrates that long-term monitoring programs of exoplanet host stars are crucial for understanding host star variability.

Comments:	published in ApJ, 9 pages, 11 figures, 3 tables; updated figures with more ground-based monitoring, added more citations to previous works
Subjects:	Earth and Planetary Astrophysics (astro-ph.EP)
Cite as:	arXiv:1505.01063 [astro-ph.EP]
(or arXiv:1505.01063v2 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.1505.01063 Focus to learn more arXiv-issued DOI via DataCite
Journal reference:	2015, ApJ, 810, 11
Related DOI:	https://doi.org/10.1088/0004-637X/810/1/11 Focus to learn more DOI(s) linking to related resources

Submission history

From: Robert Zellem [view email] [v1] Tue, 5 May 2015 16:14:49 UTC (458 KB) [v2] Wed, 26 Aug 2015 16:39:07 UTC (530 KB) Full-text links:

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