Stellar activity consequence on the retrieved transmission spectra through chromatic Rossiter-McLaughlin observations

Boldt, S.; Oshagh, M.; Mallonn, M.; Santos, N. C.; Claret, A.; Reiners, A.; Sedaghati, E.

doi:10.1051/0004-6361/201937419

Cited by 10 publications

(13 citation statements)

References 53 publications

(69 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The overestimation of vsin(i) could have variety of reasons. For instance, the RM signal can be affected by second-order effects such as the convective blueshift and granulation (Shporer & Brown 2011;Cegla et al 2016b), stellar differential rotation (Hirano et al 2011;Hirano 2014;Albrecht et al 2012;Cegla et al 2016b;Serrano et al 2020), microlensing effect due to the transiting planet's mass (Oshagh et al 2013), impact of ringed exoplanet on RM signal (Akinsanmi et al 2018;de Mooij et al 2017), occulted stellar active regions (Oshagh et al 2016(Oshagh et al , 2018, nonocculted stellar active regions (Boldt et al 2020), and also inaccurate estimations of stellar limb darkening (Csizmadia et al 2013;Yan et al 2015). Some of these effects will have minor impact on the RM shape and amplitude (such as microlensing and ring around the planet), however, some like the stellar active region occulation and stellar differential rotation could cause significant deformation of the RM shape and also alter its amplitude.…”

Section: Modeling Rm With Additional Gaussian Processmentioning

confidence: 99%

Transmission spectroscopy and Rossiter-McLaughlin measurements of the young Neptune orbiting AU Mic

Πάλλη

Oshagh

Casasayas-Barris

et al. 2020

A&A

Self Cite

View full text Add to dashboard Cite

AU Mic b is a Neptune-sized planet on an 8.47-day orbit around the nearest pre-main sequence (~20 Myr) star to the Sun, the bright (V = 8.81) M dwarf AU Mic. The planet was preliminary detected in Doppler radial velocity time series and recently confirmed to be transiting with data from the TESS mission. AU Mic b is likely to be cooling and contracting and might be accompanied by a second, more massive planet, in an outer orbit. Here, we present the observations of the transit of AU Mic b using ESPRESSO on the Very Large Telescope. We obtained a high-resolution time series of spectra to measure the Rossiter-McLaughlin effect, to constrain the spin-orbit alignment of the star and planet, and to simultaneously attempt to retrieve the planet’s atmospheric transmission spectrum. These observations allowed us to study, for the first time, the early phases of the dynamical evolution of young systems. We applied different methodologies to derive the spin-orbit angle of AU Mic b, and all of them retrieve values consistent with the planet being aligned with the rotation plane of the star. We determined a conservative spin-orbit angle λ value of −2.96−10.30+10.44 degrees, indicative that the formation and migration of the planets of the AU Mic system occurred within the disc. Unfortunately, and despite the large signal-to-noise ratio of our measurements, the degree of stellar activity prevented us from detecting any features from the planetary atmosphere. In fact, our results suggest that transmission spectroscopy for recently formed planets around active young stars is going to remain very challenging, if at all possible, for the near future.

show abstract

Section: Modeling Rm With Additional Gaussian Processmentioning

confidence: 99%

Transmission spectroscopy and Rossiter-McLaughlin measurements of the young Neptune orbiting AU Mic

Πάλλη

Oshagh

Casasayas-Barris

et al. 2020

A&A

Self Cite

View full text Add to dashboard Cite

show abstract

“…The second reason for this steeper slope could be related to the stellar activity. Boldt et al (2020) demonstrated that stellar activity can easily mimic broadband features in transmission spectra retrieved from chromatic RM. We assess this possibility and also what can be learned from our observation about the stellar active region in Sect.…”

Section: Resultsmentioning

confidence: 97%

“…In the RM observations, the active regions induce an offset and an additional underlying slope in the out-of-transit RV measurements (in addition to the gravitationally induced RV variation caused by the orbiting planet). The activity-induced out-of-transit RV slope can significantly differ from transit to transit because of variations in the configuration of stellar active regions over different nights, as shown by Di Gloria et al ( 2015), Oshagh et al (2018), andBoldt et al (2020). A conventional practical approach to eliminate this effect is to remove a linear trend from the out-of-transit RVs.…”

Section: Models For the Rossiter-mclaughlin Effectmentioning

confidence: 99%

“…SOAP3.0 does not only take the flux contrast effect of the stellar active regions into consideration, but also includes the RV shift caused by the inhibition of the convective blueshift within those regions. Because the latest version of SOAP3.0 performs the simulations at one single wavelength, we modified the code to be able to adjust the wavelength as one of the input parameters (Boldt et al 2020). After adjusting SOAP3.0, the code automatically takes care of wavelength-dependent parameters, such as the active region contrast (based on Planck's law) and coefficients of the quadratic stellar limb-darkening law (u 1 and u 2 ), which are adopted from the LDTk model (Parviainen & Aigrain 2015).…”

Section: Stellar Activity Contaminationmentioning

confidence: 99%

See 1 more Smart Citation

The widest broadband transmission spectrum (0.38-1.71 $μ$m) of HD 189733b from ground-based chromatic Rossiter-McLaughlin observations

Oshagh,

Bauer,

Lafarga

et al. 2020

Preprint

Self Cite

View full text Add to dashboard Cite

Multiband photometric transit observations (spectro-photometric) have been used mostly so far to retrieve broadband transmission spectra of transiting exoplanets in order to study their atmospheres. An alternative method was proposed, and has only been used once, to recover broadband transmission spectra using chromatic Rossiter-McLaughlin observations. We use the chromatic Rossiter-McLaughlin technique on archival and new observational data obtained with the HARPS and CARMENES instruments to retrieve transmission spectra of HD 189733b. The combined results cover the widest retrieved broadband transmission spectrum of an exoplanet obtained from ground-based observation. Our retrieved spectrum in the visible wavelength range shows the signature of a hazy atmosphere, and also includes an indicateion for the presence of sodium and potassium. These findings all agree with previous studies. The combined visible and near-infrared transmission spectrum exhibits a strong steep slope that may have several origins, such as a super-Rayleigh slope in the atmosphere of HD 189733b, an unknown systematic instrumental offset between the visible and near-infrared, or a strong stellar activity contamination. The host star is indeed known to be very active and might easily generate spurious features in the retrieved transmission spectra. Using our CARMENES observations, we assessed this scenario and place an informative constraint on some properties of the active regions of HD 18973. We demonstrate that the presence of starspots on HD 189733 can easily explain our observed strong slope in the broadband transmission spectrum.

show abstract

“…In the same paper, the hypothesis is raised that the standard templates from the HARPS DRS can contain blended lines that contribute to changes in the retrieved RVs, contaminating the transmission spectrum. Alternatively, Oshagh et al (2014) and Boldt et al (2020) show that stellar activity, such as spots of faculae, can mimic broadband features such as the slopes from Rayleigh scattering mechanisms. In particular, the activity seems to affect the RVs' observations producing variable slopes.…”

Section: Parameter Priormentioning

confidence: 99%

CaRM: Exploring the chromatic Rossiter-McLaughlin effect

Cristo¹,

Santos²,

Martins³

et al. 2022

A&A

Self Cite

View full text Add to dashboard Cite

Aims. In this paper we introduce CaRM, a semi-automatic code for the retrieval of broadband transmission spectra of transiting planets through the chromatic Rossiter-McLaughlin method. We applied it to HARPS and ESPRESSO observations of two exoplanets to retrieve the transmission spectrum and we analyze its fitting transmission models. Methods. We used the strong radius dependence of the Rossiter-McLaughlin (RM) effect amplitude, caused by planetary companions, to measure the apparent radius change caused by the exoplanet atmosphere. In order to retrieve the transmission spectrum, the radial velocities, which were computed over wavelength bins that encompass several spectral orders, were used to simultaneously fit the Keplerian motion and the RM effect. From this, the radius ratio was computed as a function of the wavelength, which allows one to retrieve the low-resolution broadband transmission spectrum of a given exoplanet. CaRM offers the possibility to use two Rossiter-McLaughlin models taken from ARoME and PyAstronomy, associated with a Keplerian function to fit radial velocities during transit observations automatically. Furthermore it offers the possibility to use some methods that could, in theory, mitigate the effect of perturbation in the radial velocities during transits. Results. We applied CaRM to recover the transmission spectrum of HD 189733b and WASP-127b, with HARPS and ESPRESSO data, respectively. Our results for HD 189733b suggest that the blue part of the spectrum is dominated by Rayleigh scattering, which is compatible with former studies. The analysis of WASP-127b shows a flat transmission spectrum. Conclusions. The CaRM code allows one to retrieve the transmission spectrum of a given exoplanet using minimal user interaction. We demonstrate that it allows one to compute the low-resolution broadband transmission spectra of exoplanets observed using high-resolution spectrographs such as HARPS and ESPRESSO.

show abstract

Stellar activity consequence on the retrieved transmission spectra through chromatic Rossiter-McLaughlin observations

Cited by 10 publications

References 53 publications

Transmission spectroscopy and Rossiter-McLaughlin measurements of the young Neptune orbiting AU Mic

Transmission spectroscopy and Rossiter-McLaughlin measurements of the young Neptune orbiting AU Mic

The widest broadband transmission spectrum (0.38-1.71 $μ$m) of HD 189733b from ground-based chromatic Rossiter-McLaughlin observations

CaRM: Exploring the chromatic Rossiter-McLaughlin effect

Contact Info

Product

Resources

About