No planet for HD 166435

“…we began a campaign of highprecision photometric observations with an automatic photoelectric telescope (APT) at Fairborn Observatory in Arizona to search for planetary transits and made tentative plans to announce the new planet at the Protostars and Planets IV conference (Mannings et al. 2000).”

“This phenomena is observed on the Sun to a lesser degree where leader spots tend to be larger and to live longer than follower spots, resulting in a displacement up to 5 0 between the photocenters of the spot and the associated plages (Dobson-Hockey & Radick 1986).”

“From 1998 June to 1998 August, 141 Ca II H and K measurements were made on 20 nights with the 100-inch telescope at Mount Wilson Observatory as part of the HK Project (Baliunas et al. 1998).”

“In addition to the stellar radial velocity, the cross-correlation function (CCF) provides additional information about features in the averaged spectral lines (see Queloz 1994 for a review).”

“SD97 quantify the predicted amplitude of this phenomenon, and it has been observationally confirmed by several groups (e.g. Queloz et al. 2001; Henry et al. 2002; Paulson et al. 2004; Saar & Fischer 2000; Saar et al. 1998).”

“Understanding stellar magnetic activity is also relevant to studies of exoplanets because starspots and flares can mimic or obscure the signatures of planets (Queloz et al. 2001) and may affect those planets’ habitability.”

“The long-term variations were detected in the S MW, Hα, and He i indices and in the BIS, full-width-at-half-maximum (FWHM), and contrast of the crosscorrelation function (CCF) but only two stars were found to have correlations with RV stronger than ρ > |0.75|: one positive correlation and one anti-correlation.”

“We have computed the bisectors of our observed CCFs (for detail, see Queloz et al. 2001) for GJ 3021.”

“For example, Queloz et al. (2001) and Paulson et al. (2004) have demonstrated how rotational modulation in the visibility of starspots on active stars can result in periodic radial velocity variations and, therefore, the potential for erroneous planetary detections.”

“This level of jitter has already proven sufficient to mimic a planetary companion (e.g., Queloz et al. 2001; Henry et al. 2002).”

“Contamination from a background eclipsing binary Following our earlier work (Bakos et al. 2010; Hartman et al. 2009) we make use of the high proper motion of HAT-P-26 to rule out the possibility that the observed transits and RV variation may be due to a background eclipsing binary that is aligned, by chance, with the…”

“That apparent Doppler shift can easily happen to mimic a Keplerian orbit (e.g. Queloz et al. 2001; Bonfils et al. 2007).”

“Moreover, analysis of the bisector shape of the crosscorrelation function (see details on the method in Queloz et al. 2001) shows no variations in the CCF profile down to the photon noise level (Fig.”

“This asymmetry is quantified as the difference in the line-bisector velocity in the upper and lower parts of the CCF, commonly referred to as the Bisector Inverse Slope (BIS; Queloz et al. 2001).”

“…in red giants may also be related to a combination of effects including stellar rotation, activity, and nonradial pulsations (e.g., Hatzes et al. 2006), we have analyzed the photometric data and the behavior of line bisectors of the star, following the established practice (Queloz et al. 2001).”

“3), we could expect a negative correlation between thebisector span and the RV residuals (e.g. Queloz et al. 2001; Boisse et al. 2010b).”

“We analyse the bisector velocity span (Vspan), a measurement of the shape of the CCF as defined in Queloz et al. (2001).”

“To test this, one can analyse theR′HK-index and the shape of the cross-correlation function (CCF) function in particular its full width at half maximum (FWHM) and bisector span (BIS, Queloz et al. 2001) which are measures for the averaged stellar line width and asymmetry, respectively.”

“The rotational period and the phase of each sinusoid are common to all datasets, but we must take into account a possible delay on the effect of activity on the stellar line shape and the brightness of the star (Queloz et al. 2001).”

“To confirm that the RV signal originates from a planet-mass object orbiting the star, we analyzed the CORALIE cross-correlation functions (CCF) using the line-bisector technique described in Queloz et al (2001).”

“Queloz et al. (2001) and Paulson et al. (2004) have demonstrated how rotational modulation in the visibility of star spots on active stars can result in periodic radial velocity variations that mimic the presence of a planetary companion.”

“Recognising and characterising them is key to disentangling true planet-induced signals (Queloz et al. 2001; Dumusque et al. 2012; Santos et al. 2014; Robertson et al. 2014; Faria et al. 2020).”

“Starspots can give rise to RV variations by modifying the spectral line profile as the starspot moves across the stellar disk (e.g. Queloz et al. 2001).”

“5 of Queloz et al. (2001) for a helpful schematic representation.”

“Others are demonstrably variable from starspots (e.g., Hall 1976; Queloz et al. 2001).”

“Second, we have verified the bisector of the crosscorrelation function with the method described in Queloz et al. (2001a).”

“This technique was used by Queloz et al. (2001) to establish the spotted nature of the observed RV variation for HD 164335.”

“The individual spectra were also used to derive both the Bisector Inverse Slope (BIS) of the HARPS Cross-Correlation Function (CCF), as defined by Queloz et al. (2001), as well as a measurement of the chromospheric activity index logR′HK, following the same recipe used by Santos et al. (2000) for…”

“They are followed by BIS and Vspan.”

“In that case, the “bisector span” of the average spectral line should vary periodically with amplitude and phase similar to the measured velocities themselves (Queloz et al. 2001; Mandushev et al. 2005).”

“…profiles arising from contamination of the spectrum by the presence of a binary with a period of 2.79 days, we would expect the bisector spans (which measure line asymmetry) to vary with this period and with an amplitude similar to the velocities (see, e.g., Queloz et al. 2001; Torres et al. 2005).”

“For each system we tested the hypothesis that the RV variations are due to spectral-line distortions caused by a blended eclipsing binary or star spots by performing a line-bisector analysis (Queloz et al. 2001) of the CORALIE cross-correlation functions.”

“…Paulson et al. 2002) can prevent us from finding planets (if the perturbation is stronger than the orbital radial-velocity variation); but perhaps more important, they might give us false candidates if they produce a periodic signal (Queloz et al. 2001; Bonfils et al. 2007; Huélamo et al. 2008).”

“In that case the “bisector span” of the average spectral line should vary periodically with amplitude and phase similar to the measured velocities themselves (Queloz et al. 2001; Mandushev et al. 2005).”

“It has been well established that periodic RV signals can be caused by stellar chromospheric variability, as traced by photometry or activity indicators such as Ca H and K (Queloz et al. 2001; Forveille et al. 2009; Robertson et al. 2012a).”

“We then calculated the velocity difference in the bisector at two different correlation levels, which we refer to as the “bisector span”.11 This is analogous to the definition employed by Queloz et al. (2001) and Santos et al. (2002).”

“This would also rule out the possibility that a quasi-periodic RV signal is due to rotating spots on the stellar surface instead of a planetary companion as, e.g., in the case of HD 166435 (Queloz et al. 2001).”

“Other methods, based for example on variable line bisector changes (Saar et al. 2001; Saar et al. 2002; Queloz et al. 2001) may be useful in diagnosing (and possibly correcting) for short term vrad jitter from spots and plages.”

“E P] 1 3 Fe b 20 17 (e.g. Queloz et al. 2001; Santos et al. 2014; Rajpaul et al. 2015).”

“Our analysis of the available photometric data and the behavior of line bisectors in the three stars, following the established practices (Queloz et al. 2001), has shown no significant correlations between the time variability of these stellar activity indicators and the RV variations.”

“In addition, we measured the bisector velocity span (e.g. Queloz et al. 2001) and found no dependence between the asymmetry of the spectral line profile and the measured radial velocities (Fig.”

“These asymmetries can be quantified by measuring the ‘‘bisector spans,’’ usually defined as the velocity difference between the top and bottom of the line bisectors (see, e.g., Queloz et al. 2001; Torres et al. 2004a) or between any other two reference levels.”

“It can even mimic the RV signature of a short-period planet like in the case of HD 166435 (Queloz et al. 2001).”

“A first comparison between simulated 12 As estimate from SOAP 2.0. and real data shows that the simulation of stellar signals presented in this paper manages to reproduce the correlation between the different observables given in the data set of the RV fitting challenge fairly well, that is, RV, BIS SPAN, FWHM, and lo…”

“For each case we verified that the RVs did not correlate with the bisector spanof the CCF (calculated following Queloz et al. (2001)) or with the FWHM of the CCF.”

“2 indicates that it is highly improbable that the RV variations are due to an unresolved eclipsing binary or chromospheric activity (Queloz et al. 2001).”

“Using the highest resolution spectra in our data-set (i.e., the HARPS measurements) and following the line-bisector technique described in Queloz et al. (2001), we derived the difference in velocity space between the lower and upper part of the HARPS CCFs (i.e., bisector span).”

“Queloz et al. (2001) find that the phase of the RV variation is confined to a ±0.1 interval (their Fig.”

“Finally, observations were also obtained with the FEROS spectrograph (Kaufer & Pasquini 1998) mounted on the ESO/MPG 2.2m telescope and with the CORALIE spectrograph (Queloz et al. 2001a) mounted on the Euler 1.2m telescope in La Silla.”

“…stars have shown that their presence can induce low amplitude, periodic RV shifts, and thus mimic the effect of one or more orbiting planets (Queloz et al. 2001; Paulson & Yelda 2006; Huerta et al. 2008; Prato et al. 2008; Reiners et al. 2010; Crockett et al. 2011; Mahmud et al. 2011);…”

“…that can mask, and sometimes even mimic, the presence of orbital reflex motion due to planetary mass companions (Saar et al. 1998; Santos et al. 2000; Queloz et al. 2001; Paulson et al. 2004), particularly in the case of young (e.g., Setiawan et al. 2008; Huélamo et al. 2008) and evolved (e.g.,…”

“Queloz et al. (2001) found HD 166435 to have a large velocity amplitude, but it turned out also to show sinusoidal photometric amplitude in Strömgren y with the same period.”

“As demonstrated in several studies (e.g. Queloz et al. 2001), BIS often anti-correlates with spurious RV offsets if a cool spot is responsible for the apparent RV shifts.”

“We also investigated the correlation between the TERRA RVs and the BIS (Queloz et al. 2001) obtained with the HARPSN DRS in order to understand the variability of the line profile due to stellar activity.”

“Several cases of apparent periodic RV variations in solar-type stars induced by the presence of photospheric starspots have been discussed in the literature (e.g., Queloz et al. 2001; Paulson et al. 2004; Bonfils et al. 2007b; Forveille et al. 2009).”

“This is consistent with the lack of detection of the photometric signal in the radial velocities of Bonfils et al. (2012) and confirms that RV variations in GJ 3470 are indeed due to planetary reflex motion and not line-profile variations due to spots (e.g. Queloz et al. 2001; Paulson et al. 2004).”

“An additional advantage of the SYSTEMIC console is that it computes a stellar “jitter” term–a measure of random fluctuations in the stellar photosphere–(e.g. Queloz et al. 2001) for each star, which we include in Table 6.”

“Several cases of apparent periodic RV variations in solar-type stars induced by the presence of photospheric starspots have been discussed by Queloz et al. (2001) and Paulson et al. (2004).”

“For example, Queloz et al. (2001) found radial velocity variations with an amplitudeK p 83 m s 1 in the young G0 dwarf HD 166435 that were, at first, interpreted as the signature of a planet in a 3.8 day0.”

“The bisectors of the cross-correlation function likewise show no variability (Queloz et al. 2001).”

“The BIS values for HARPS were taken from the HARPS-DRS and measured following the method explained in Queloz et al. (2001).”

“This definition accounts for the inverse slope of the bisector (BIS), as introduced by Queloz et al. (2001), and it is the most commonly used in recent studies based on HARPS data (Baştürk et al. 2011; Figueira et al. 2013).”

“Stellar spots and plages, combined with the rotation of the star, can mimic periodic Radial Velocity (hereafter RV) signals which may lead to false positives in the detection of a planet (Queloz et al. 2001; Bonfils et al. 2007; Huélamo et al. 2008; Boisse et al. 2009, 2011).”

“To confirm that the RV signal originates well from planetmass objects orbiting the stars, we analyzed the CORALIE crosscorrelation functions (CCF) using the line-bisector technique described in Queloz et al. (2001).”

“Bisector analysis We carried out a bisector span analysis (Queloz et al. 2001; Torres et al. 2007) of the FIES spectra to explore the possibility that the transit like events are due to an eclipsing binary blended with light from a third star.”

“…(FWHM), contrast or bisector-span of the CrossCorrelation functions that correlate with the radial velocity variations denotes that those originate in stellar phenomena such as spots, visible granulation density or oscillations (Queloz et al. 2001; Boisse et al. 2011; Dumusque et al. 2011).”

“This high precision is by virtue of using the CORALIE instrument with planet-finding precision to observe much larger amplitude binaries.”

“No changes to the spectroscopic profile were detected, ruling out a blended eclipsing binary or starspots as the cause of the radialvelocity variation (Queloz et al. 2001) (see bottom diagram in Fig 2).”

“It is well known that these tests are sensitive to distortions caused by hidden background (or physically related) unresolved eclipsing binaries or stellar activity (Queloz et al. 2001; Torres et al. 2007).”

“In the case of the main sequence star HD 166435, it has been concluded that the observed periodic variations of RV (about 200 m/s total amplitude) could be completely explained by magnetic spots (Queloz et al. 2001; Martinez Fiorenzano et al. 2005).”

“…in red giants may also be related to a combination of effects including stellar rotation, activity, and nonradial pulsations (e.g., Hatzes et al. 2006), we have analyzed the photometric data and the behavior of line bisectors of the star, following the established practices (Queloz et al. 2001).”

“The variation of the line bisector with orbital phase is often used as a tool to detect blended stellar companions or chromospheric activity (Queloz et al. 2001).”

“…reported above are crucial for establishing whether a star with a transit-like light curve is orbited by a planetary companion, but they are generally not sufficient because of the variety of and frequency with which false positives occur (e.g., Queloz et al. 2001; Yee et al. 2002; Latham 2003).”

“We inspected the line bisector and searched for asymmetry in the stellar line profiles that may have arisen through stellar activity or a blended binary system (Queloz et al. 2001).”

“False positive signals of this type tend to occur around chromospherically active stars (Queloz et al. 2001; Paulson et al. 2005).”

“In addition, we observed for HD 78647 a correlation between the RV measurements and the bisector velocity span (see Queloz et al. 2001), shown in Fig.”

“No bisector effect (Queloz et al. 2001) or mask effect were detected in the SOPHIE data, supporting the sub-stellar companion hypothesis.”

“One of these sources is the activity in the star’s chromosphere, otherwise called “photospheric jitter” (Queloz et al. 2001; Henry et al. 2002; Santos et al. 2003).”

“These stars have been already extensively studied for more activity indicators to ensure robust planet detection (e.g., Queloz et al. 2001; Boisse et al. 2011; Robertson et al. 2014; Suárez Mascareño et al. 2015; Hatzes 2016; Suárez Mascareño et al. 2017c).”

“The BIS is a measure of the asymmetry of the average spectral line and should correlate with the RV if the observed offsets are caused by spots or plages rotating with the star (Queloz et al. 2001).”

“3 is due to spectral line distortions cause by a blended eclipsing binary, the CORALIE and HARPS cross-correlation functions were analyzed using the line-bisector technique described in Queloz et al. (2001).”

“Queloz et al. (2001) and Paulson et al. (2004) have found several examples of periodic radial velocity variations in solar-type stars caused by photospheric spots and plages.”

“Since Queloz et al. (2001), variations in BIS are the paradigm for the signature of activity-induced RV variations.”

“These asymmetries have become the standard criterion for rejecting starspots as the cause of false RV signals (e.g., Queloz et al. 2001; Bouvier et al. 2007; Huerta et al. 2008; Setiawan et al. 2008).”

“4 where we plot the radial velocities, bisector “span” (in this case the Bisector Invese Slope, BIS, as defined in Queloz et al. 2001), and the ratio of the BIS-to-radial-velocity amplitudes, as a function of v sin i.”

“R’HK), the bisector span (BIS SPAN), and the full-width half maximum (FWHM) of the cross-correlation function (Queloz 2009, Bonfils 2007, Queloz 2001) are observables sensitive to stellar activity.”

“This quantity, called “bisector velocity span” (Toner & Gray 1988; Queloz et al. 2001; Dall et al. 2006), is a good measure of the changes in bisector orientation, and hence of the asymmetry of the peak.”

“The bisector analysis is one of the best tools to discriminate between radial-velocity variations due to changes in the spectral-line shapes and variations due to the real orbital motion of the star (see Queloz et al. 2001, for a description of this method).”

“These data are given in Table 1 and shown phase-folded in Figure 3: the low-amplitude radial velocity variations and the lack of correlation between the bisector spans and radial velocity (Queloz et al. 2001), shown in Figure 4, are consistent with a planet-mass object orbiting the host star.”

“We also calculated the bisector velocity span of the cross-correlation function, following the procedure described in Queloz et al. (2001).”

“In addition to each RV calculation, the bisector inverse slope was computed from the CCF function following the procedure described in Queloz et al. (2001).”