Multi-band high resolution spectroscopy rules out the hot Jupiter BD+20 1790b

First data from the GIARPS Commissioning

¹ Dipartimento di Fisica e Astronomia, “Galilei”– Universtà degli Studi di Padova, Vicolo dell’Osservatorio 3, 35122 Padova, Italy
e-mail: ilaria.carleo@oapd.inaf.it
² INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
³ INAF – Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania, Italy
⁴ Department of Astronomy and McDonald Observatory – The University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, TX 78712-1205, USA
⁵ INAF – Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy
⁶ Fundación Galileo Galilei – INAF, Rambla José Ana Fernandez Pérez 7, 38712 Breña Baja, TF, Spain
⁷ INAF – Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
⁸ INAF – Osservatorio Astronomico di Trieste, via Tiepolo 11, 34143 Trieste, Italy
⁹ Département d’Astronomie – Université de Genève, Chemin des Maillettes, 51 1290 Versoix, Switzerland
¹⁰ INAF – Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807 Merate (LC), Italy
¹¹ Dipartimento di Fisica e Chimica – Università degli Studi di Palermo, Via Archirafi 36, 90123 Palermo, Italy
¹² Officina Stellare S.r.l., Via Della Tecnica, 87/89, 36030 Sarcedo (VI), Italy
¹³ INAF – Osservatorio Astronomico di Bologna, Via Gobetti 93/3, 40129, Bologna, Italy
¹⁴ Institut für Astrophysik – Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
¹⁵ INAF – Osservatorio Astrofisico di Torino, Via Osservatorio 20, 10025, Pino Torinese (TO), Italy
¹⁶ INAF – Osservatorio Astronomico di Cagliari, Via della Scienza 5, 09047, Selargius (CA), Italy

Received: 23 November 2017
Accepted: 16 April 2018

Abstract

Context. Stellar activity is currently challenging the detection of young planets via the radial velocity (RV) technique.

Aims. We attempt to definitively discriminate the nature of the RV variations for the young active K5 star BD+20 1790, for which visible (VIS) RV measurements show divergent results on the existence of a substellar companion.

Methods. We compare VIS data with high precision RVs in the near-infrared (NIR) range by using the GIANO–B and IGRINS spectrographs. In addition, we present for the first time simultaneous VIS-NIR observations obtained with GIARPS (GIANO–B and HARPS–N) at Telescopio Nazionale Galileo (TNG). Orbital RVs are achromatic, so the RV amplitude does not change at different wavelengths, while stellar activity induces wavelength-dependent RV variations, which are significantly reduced in the NIR range with respect to the VIS.

Results. The NIR radial velocity measurements from GIANO–B and IGRINS show an average amplitude of about one quarter with respect to previously published VIS data, as expected when the RV jitter is due to stellar activity. Coeval multi-band photometry surprisingly shows larger amplitudes in the NIR range, explainable with a mixture of cool and hot spots in the same active region.

Conclusions. In this work, the claimed massive planet around BD+20 1790 is ruled out by our data. We exploited the crucial role of multi-wavelength spectroscopy when observing young active stars: thanks to facilities like GIARPS that provide simultaneous observations, this method can reach its maximum potential.