Spectrally resolved detection of sodium in the atmosphere of HD 189733b with the HARPS spectrograph

Wyttenbach, A.; Ehrenreich, D.; Lovis, C.; Udry, S.; Pepe, F.

doi:10.1051/0004-6361/201525729

Cited by 290 publications

(527 citation statements)

References 59 publications

(136 reference statements)

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“…The archive ID for each data set is given in Table 1. We note that the HARPS data is the same used by Wyttenbach et al (2015) and Louden & Wheatley (2015) to study Na I absorption in HD 189733 b's atmosphere. The Keck data from 2006 August 21 is the same data used to measure the Rossiter-McLaughlin effect for HD 189733 b by Winn et al (2006).…”

Section: Observations and Data Reductionmentioning

confidence: 99%

A Decade of Hα Transits for HD 189733 b: Stellar Activity versus Absorption in the Extended Atmosphere

Cauley

Redfield

Jensen

2017

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HD 189733 b is one of the most well-studied exoplanets due to its large transit depth and host star brightness. The focus on this object has produced a number of high-cadence transit observations using high-resolution optical spectrographs. Here we present an analysis of seven full Hα transits of HD 189733 b using HARPS on the 3.6 meter La Silla telescope and HIRES on Keck I, taken over the course of nine years from 2006 to 2015. Hα transmission signals are analyzed as a function of the stellar activity level, as measured using the normalized core flux of the Ca II H and K lines. We find strong variations in the strength of the Hα transmission spectrum from epoch to epoch. However, there is no clear trend between the Ca II core emission and the strength of the in-transit Hα signal, although the transit showing the largest absorption value also occurs when the star is the most active. We present simulations of the in-transit contrast effect and find that the planet must consistently transit active latitudes with very strong facular and plage emission regions in order to reproduce the observed line strengths. We also investigate the measured velocity centroids with models of planetary rotation and show that the small line profile velocities could be due to large velocities in the upper atmosphere of the planet. Overall, we find it more likely that the measured Hα signals arise in the extended planetary atmosphere, although a better understanding of active region emission for active stars such as HD 189733 are needed.

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Section: Observations and Data Reductionmentioning

confidence: 99%

A Decade of Hα Transits for HD 189733 b: Stellar Activity versus Absorption in the Extended Atmosphere

Cauley

Redfield

Jensen

2017

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“…Its atmosphere has been observed both in trasmission and during secondary eclipses (e.g. Deming et al 2006;Huitson et al 2012;Wyttenbach et al 2015).…”

Section: Harps Data and Radial Velocity Extractionmentioning

confidence: 99%

“…We note that the data reduction as used by the ESO archive used different masks for different nights, that is, a K5 mask for the first night and a G2 mask for the others. We used the data for the first night reduced with the G2 mask with the HARPS Data Reduction Software by Wyttenbach et al (2015).…”

Section: Harps Data and Radial Velocity Extractionmentioning

confidence: 99%

“…One way to mitigate these issues is by using ground-based highdispersion spectroscopy. For example, detections of sodium and potassium have been presented in the optical (Redfield et al 2008;Snellen et al 2008;Sing et al 2011a;Wood et al 2011;Jensen et al 2011;Zhou & Bayliss 2012;Wyttenbach et al 2015), and detections of carbon monoxide and water in the infrared (Brogi et al 2012(Brogi et al , 2014Rodler et al 2012;de Kok et al 2013;Birkby et al 2013;Lockwood et al 2014).…”

Section: Introductionmentioning

confidence: 99%

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Using the chromatic Rossiter-McLaughlin effect to probe the broadband signature in the optical transmission spectrum of HD 189733b

Gloria

Snellen

Albrecht

2015

A&A

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Context. Transmission spectroscopy is a powerful technique for probing exoplanetary atmospheres. A successful ground-based observational method uses a differential technique that uses high-dispersion spectroscopy, but it only preserves narrow features in transmission spectra. Broadband features, such as the remarkable Rayleigh-scattering slope from possible hazes in the atmosphere of HD 189733b as observed by the Hubble Space Telescope, cannot be probed in this way. Aims. Here we use the chromatic Rossiter-McLaughlin (RM) effect to measure the Rayleigh-scattering slope in the transmission spectrum of HD 189733b with the aim to show that it can be effectively used to measure broadband transmission features. The amplitude of the RM effects depends on the effective size of the planet, and in the case of an atmospheric contribution therefore depends on the observed wavelength. Methods. We analysed archival HARPS data of three transits of HD 189733b, covering a wavelength range of 400 to 700 nm. The radial velocity (RV) time-series were determined for white light and for six wavelength bins each 50 nm wide, using the crosscorrelation profiles as provided by the HARPS data reduction pipeline. The RM effect was first fitted to the white-light RV time series using the publicly available code AROME. The residuals to this best fit were subsequently subtracted from the RV time series of each wavelength bin, after which they were also fitted using the same code, leaving only the effective planet radius to vary. Results. We measured the slope in the transmission spectrum of HD 189733b at a 2.5σ significance. Assuming it is due to Rayleigh scattering and not caused by stellar activity, it would correspond to an atmospheric temperature, as set by the scale height, of T = 2300 ± 900 K, well in line with previously obtained results. Conclusions. Ground-based high-dispersion spectral observations can be used to probe broad-band features in the transmission spectra of extrasolar planets, such as the optical Rayleigh-scattering slope of HD 189733b, by using the chromatic Rossiter-McLaughlin effect. The precision achieved with HARPS per transit is about an order of magnitude lower than that with STIS on the Hubble Space Telescope. This method will be particularly interesting in conjunction with the new echelle spectrograph ESPRESSO, which currently is under construction for ESO's Very Large Telescope, which will provide a gain in signal-to-noise ratio of about a factor 4 compared to HARPS. This will be of great value because of the limited and uncertain future of the Hubble Space Telescope and because the future James Webb Space Telescope will not cover this wavelength regime.

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“…Although it cannot be proved, they may well be triggered by the primary flare. As our observations remain so far the only in-transit flare observations in HD 189733, although many observations during a transit have already been carried out (e.g., Redfield et al 2008;Wyttenbach et al 2015;Triaud et al 2009), we consider a star-planet-interaction scenario as proposed by Pillitteri et al (2014) to be unlikely in this case and we rather consider the flare timing a chance coincidence.…”

Section: Discussionmentioning

confidence: 98%

Time-resolved UVES observations of a stellar flare on the planet host HD 189733 during primary transit

Klocová

Czesla

Khalafinejad

et al. 2017

A&A

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Context. HD 189733 is an exoplanetary system consisting of a transiting hot Jupiter and an active K2V-type main sequence star. Rich manifestations of a stellar activity, like photometric spots or chromospheric flares were repeatedly observed in this system in optical, UV and X-rays. Aims. We aim to use VLT/UVES high resolution (R = 60 000) echelle spectra to study a stellar flare. Methods. We have performed simultaneous analyses of the temporal evolution in several chromospheric stellar lines, namely, the, H (3970 Å), the Ca ii infrared triplet line (8498, 8542 and 8662 Å), and He i D3 (5875.6 Å). Observations were carried out with a time resolution of approximately 1 min for a duration of four hours, including a complete planetary transit. Results. We determine the energy released during the flare in all studied chromospheric lines combined to be about 8.7 × 10 31 erg, which puts this event at the upper end of flare energies observed on the Sun. Our analysis does not reveal any significant delay of the flare peak observed in the Balmer and Ca ii H & K lines, although we find a clear difference in the temporal evolution of these lines. The He i D3 shows additional absorption possibly related to the flare event. Based on the flux released in Ca ii H & K lines during the flare, we estimate the soft X-ray flux emission to be 7 × 10 30 erg. Conclusions. The observed flare can be ranked as a moderate flare on a K-type star and confirms a rather high activity level of HD 189733 host star. The cores of the studied chromospheric lines demonstrate the same behavior and let us study the flare evolution. We demonstrate that the activity of an exoplanet host star can play an important role in the detection of exoplanet atmospheres, since these are frequently discovered as an additional absorption in the line cores. A possible star-planet interaction responsible for a flare occurrence during a transit can neither be confirmed nor ruled out.

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Spectrally resolved detection of sodium in the atmosphere of HD 189733b with the HARPS spectrograph

Cited by 290 publications

References 59 publications

A Decade of Hα Transits for HD 189733 b: Stellar Activity versus Absorption in the Extended Atmosphere

A Decade of Hα Transits for HD 189733 b: Stellar Activity versus Absorption in the Extended Atmosphere

Using the chromatic Rossiter-McLaughlin effect to probe the broadband signature in the optical transmission spectrum of HD 189733b

Time-resolved UVES observations of a stellar flare on the planet host HD 189733 during primary transit

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