CHROMOSPHERIC ACTIVITY AND JITTER MEASUREMENTS FOR 2630 STARS ON THE CALIFORNIA PLANET SEARCH

By H. Isaacson, Debra A. Fischer. 2010

320 citations recorded by the source corpus.

We present time series measurements of chromospheric activity for more than 2600 main-sequence and subgiant stars on the California Planet Search (CPS) program with spectral types ranging from about F5V to M4V for main-sequence stars and from G0IV to about K5IV for subgiants. The large data set of more than 44,000 spectra allows us to identify an empirical baseline floor for chromospheric activity as a function of color and height above the main sequence. We define ΔS as an excess in emission in the Ca ii H and K lines above the baseline activity floor and define radial velocity jitter as a function of ΔS and B − V for main-sequence and subgiant stars. Although the jitter for any individual star can always exceed the baseline level, we find that K dwarfs have the lowest level of jitter. The lack of correlation between observed jitter and chromospheric activity in K dwarfs suggests that the observed jitter is dominated by instrumental or analysis errors and not astrophysical noise sources. Thus, given the long-term precision for the CPS program, radial velocities are not correlated with astrophysical noise for chromospherically quiet K dwarf stars, making these stars particularly well suited for the highest precision Doppler surveys. Chromospherically quiet F and G dwarfs and subgiants exhibit higher baseline levels of astrophysical jitter than K dwarfs. Despite the fact that the rms in Doppler velocities is correlated with the mean chromospheric activity, it is rare to see one-to-one correlations between the individual time series activity and Doppler measurements, diminishing the prospects for correcting activity-induced velocity variations in F and G dwarfs.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/0c87b573e64d6c210239e9f71ad7dcadfd2a66d9

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In Astronomy and Astrophysics

1. D. Charbonneau
2. Timothy Morton
3. J. Johnson
4. Jon Fortney
5. J. Winn
6. Andrew W. Howard
7. G. Marcy
8. E. Gaidos

In Instrumentation

1. D. Charbonneau
2. Timothy Morton
3. E. Gaidos
4. J. Johnson
5. J. Winn
6. G. Marcy
7. Jon Fortney
8. Andrew W. Howard

Citations in the corpus

• The planet search programme at the ESO CES and HARPS - IV. The search for Jupiter analogues around solar-like stars (2012, methodology): “Both are K dwarfs with 1.0 B − V 1.3 and, according to Isaacson & Fischer (2010), those stars have the lowest level of velocity jitter decoupled from their chromospheric activity.”
• THE TWENTY-FIVE YEAR LICK PLANET SEARCH (2013, background): “These earlier spectral types contributed to the Doppler errors since the late F and early G dwarfs have more intrinsic stellar variability (Isaacson & Fischer 2010) and tend to be more rapidly rotating.”
• FRIENDS OF HOT JUPITERS. I. A RADIAL VELOCITY SEARCH FOR MASSIVE, LONG-PERIOD COMPANIONS TO CLOSE-IN GAS GIANT PLANETS (2013, background): “RV “jitter” may be dominated by instrumental effects as opposed to astrophysical noise and thus should not be expected to converge to the same value for different instruments (Isaacson & Fischer 2010).”
• Limits on Planetary Companions from Doppler Surveys of Nearby Stars (2016, background): “Long-term magnetic cycles analogous to our Sunʼs activity cycle pose perhaps the greatest challenge in the search for longperiod planets (Isaacson & Fischer 2010; Lovis et al. 2011).”
• State of the Field: Extreme Precision Radial Velocities (2016, methodology): “The radial velocity rms is typically greater than 2 m s−1 because of instrumental errors, limitations of the iodine technique (Isaacson & Fischer 2010; Spronck et al. 2015), and the impact of stellar photospheric velocities, or stellar “jitter.””
• A SPECTROSCOPIC CATALOG OF THE BRIGHTEST (J < 9) M DWARFS IN THE NORTHERN SKY, (2012, background): “Some M dwarfs have significant photometric variability (flares, spots) which are affecting transit searches (Hartman et al. 2011); some display chromospheric emission affecting Doppler searches (Isaacson & Fischer 2010).”
• The California-Kepler Survey. I. High-resolution Spectroscopy of 1305 Stars Hosting Kepler Transiting Planets (2017, methodology): “The Ca II H & K measurements for this sample, in conjunction with stellar photometry, will be valuable when determining age-activity-rotation correlations (Isaacson & Fischer 2010).”
• Chromospheric activity catalogue of 4454 cool stars (2018, background): “Additionally, 1798 stars were also observed as part of the California planet survey (Isaacson & Fischer 2010); they have only S med values.”
• The LCES HIRES/Keck Precision Radial Velocity Exoplanet Survey (2017, methodology): “We then used the (B V- ) color of each star along with the median of its calibrated S-values to calculate its expected jitter (blue histogram in Figure 5) following the steps outlined in Isaacson & Fischer (2010).”
• A Gaussian process framework for modelling stellar activity signals in radial velocity data (2015, methodology): “For example, the S HK chromospheric activity index can be related to spot coverage in the same way as the log R (cid:48) HK index (Isaacson & Fischer 2010).”
• SPECTRAL PROPERTIES OF COOL STARS: EXTENDED ABUNDANCE ANALYSIS OF 1,617 PLANET-SEARCH STARS (2016, methodology): “We calculated both the logR ′ HK and SHK values for all stars where we also had broadband colors following the procedure outlined in Isaacson & Fischer (2010).”
• Speckle Interferometry at SOAR in 2016 and 2017 (2014, background): “The star is on the California program of planet search (Isaacson & Fischer 2010).”