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We analyse Chandra X-ray data of HD179949, a Sun-like star with a close Jupiter-mass planet. We study short-term spectral variability as well as phase-dependent Star-Planet Interaction (SPI) effects. We model the observed spectra with a two-component thermal model and obtain robust estimates for abundances. We find consistent estimates for change points across multiple passbands and evidence for short-term variability in spectral hardness. We also find evidence for X-ray variability related to the planetary orbit of the close Jupiter-mass planet., {"references":["Fares et al. (2012), MNRAS 2, 423, 1006","Lomb N. R. (1976) Ap&SS 39, 447","Scandariato G. et al. (2013), A&A 552, A7","Scargle J. D. (1982), ApJ 263, 835","Scargle J. D. et al. (2013), ApJ 764, 167","Shkolnik E. et al. (2007), ApJ 676, 628","Shkolnik E. et al. (2003), ApJ 597, 1092","van Dyk D. et al. (2001), ApJ 548, 224","Vanderplas J. T. (2018), ApJS 236, 16"]}

We carry out detailed spectral and timing analyses of the $Chandra$ X-ray data of HD 179949, a prototypical example of a star with a close-in giant planet with possible star-planet interaction (SPI) effects. We find a low coronal abundance $A({\rm Fe})/A({\rm H}){\approx}0.2$ relative to the solar photospheric baseline of Anders & Grevesse (1989), and significantly lower than the stellar photosphere as well. We further find low abundances of high First Ionization Potential (FIP) elements $A({\rm O})/A({\rm Fe}){\lesssim}1$, $A({\rm Ne})/A({\rm Fe}){\lesssim}0.1$, but with indications of higher abundances of $A({\rm N})/A({\rm Fe}){\gg}1, A({\rm Al})/A({\rm Fe}){\lesssim}10$. We estimate a FIP bias for this star in the range $\approx{-0.3}$ to ${-0.1}$, larger than the ${\lesssim}-$0.5 expected for stars of this type, but similar to stars hosting close-in hot Jupiters. We detect significant intensity variability over time scales ranging from 100 s - 10 ks, and also evidence for spectral variability over time scales of 1-10 ks. We combine the $Chandra$ flux measurements with $Swift$ and XMM-$Newton$ measurements to detect periodicities and determine that the dominant signal is tied to the stellar polar rotational period, consistent with expectations that the corona is rotational-pole dominated. We also find evidence for periodicity at both the planetary orbital frequency and at its beat frequency with the stellar polar rotational period, suggesting the presence of a magnetic connection between the planet and the stellar pole. If these periodicities represent an SPI signal, it is likely driven by a quasi-continuous form of heating (e.g., magnetic field stretching) rather than sporadic, hot, impulsive flare-like reconnections., 26 pages, 12 figures, 11 tables. Accepted for publication in the Astrophysical Journal