Hint of an exocomet transit in the CHEOPS light curve of HD 172555

F. Kiefer; V. Van Grootel; A. Lecavelier Des Etangs; G.M. Szabó; A. Brandeker; C. Broeg; A. Collier Cameron; A. Deline; G. Olofsson; T.G. Wilson; S.G. Sousa; D. Gandolfi; G. Hébrard; Y. Alibert; R. Alonso; G. Anglada; T. Bárczy; D. Barrado; S.C.C. Barros; W. Baumjohann; M. Beck; T. Beck; W. Benz; N. Billot; X. Bonfils; J. Cabrera; S. Charnoz; S. Csizmadia; M.B. Davies; M. Deleuil; L. Delrez; O.D.S. Demangeon; B.-O. Demory; D. Ehrenreich; A. Erikson; A. Fortier; L. Fossati; M. Fridlund; M. Gillon; M. Güdel; K. Heng; S. Hoyer; K.G. Isaak; L.L. Kiss; J. Laskar; M. Lendl; C. Lovis; D. Magrin; P.F.L. Maxted; M. Munari; V. Nascimbeni; R. Ottensamer; I. Pagano; E. Pallé; G. Peter; D. Piazza; G. Piotto; D. Pollacco; D. Queloz; R. Ragazzoni; N. Rando; F. Ratti; H. Rauer; C. Reimers; I. Ribas; N.C. Santos; G. Scandariato; D. Ségransan; A.E. Simon; A.M.S. Smith; M. Steller; N. Thomas; S. Udry; I. Walter; N.A. Walton

doi:10.1051/0004-6361/202245104

Hint of an exocomet transit in the CHEOPS light curve of HD 172555

F. Kiefer^*, V. Van Grootel, A. Lecavelier Des Etangs, G.M. Szabó, A. Brandeker, C. Broeg, A. Collier Cameron, A. Deline, G. Olofsson, T.G. Wilson, S.G. Sousa, D. Gandolfi, G. Hébrard, Y. Alibert, R. Alonso, G. Anglada, T. Bárczy, D. Barrado, S.C.C. Barros, W. BaumjohannM. Beck, T. Beck, W. Benz, N. Billot, X. Bonfils, J. Cabrera, S. Charnoz, S. Csizmadia, M.B. Davies, M. Deleuil, L. Delrez, O.D.S. Demangeon, B.-O. Demory, D. Ehrenreich, A. Erikson, A. Fortier, L. Fossati, M. Fridlund, M. Gillon, M. Güdel, K. Heng, S. Hoyer, K.G. Isaak, L.L. Kiss, J. Laskar, M. Lendl, C. Lovis, D. Magrin, P.F.L. Maxted, M. Munari, V. Nascimbeni, R. Ottensamer, I. Pagano, E. Pallé, G. Peter, D. Piazza, G. Piotto, D. Pollacco, D. Queloz, R. Ragazzoni, N. Rando, F. Ratti, H. Rauer, C. Reimers, I. Ribas, N.C. Santos, G. Scandariato, D. Ségransan, A.E. Simon, A.M.S. Smith, M. Steller, N. Thomas, S. Udry, I. Walter, N.A. Walton

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

Abstract

HD 172555 is a young (∼20 Myr) A7V star surrounded by a 10 au wide debris disk suspected to be replenished partly by collisions between large planetesimals. Small evaporating transiting bodies, that is exocomets, have also been detected in this system by spectroscopy. After β Pictoris, this is another example of a system possibly witnessing a phase of the heavy bombardment of planetesimals. In such a system, small bodies trace dynamical evolution processes. We aim to constrain their dust content by using transit photometry. We performed a 2-day-long photometric monitoring of HD 172555 with the CHEOPS space telescope in order to detect shallow transits of exocomets with a typical expected duration of a few hours. The large oscillations in the light curve indicate that HD 172555 is a δ Scuti pulsating star. After removing those dominating oscillations, we found a hint of a transient absorption. If fitted with an exocomet transit model, it would correspond to an evaporating body passing near the star at a distance of 6.8±1.4R∗ (or 0.05±0.01 au) with a radius of 2.5 km. These properties are comparable to those of the exocomets already found in this system using spectroscopy, as well as those found in the β Pic system. The nuclei of the Solar System's Jupiter family comets, with radii of 2-6 km, are also comparable in size. This is the first piece of evidence of an exocomet photometric transit detection in the young system of HD 172555.

Original language	English
Article number	A25
Number of pages	12
Journal	Astronomy and Astrophysics
Volume	671
Early online date	1 Mar 2023
DOIs	https://doi.org/10.1051/0004-6361/202245104
Publication status	Published - 1 Mar 2023

Keywords

Circumstellar matter
Comets: general
Stars: individual: HD 172555
Stars: variables: δ Scuti
Techniques: photometric

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Kiefer_2023_AA_Exocomet-transit_CC
Copyright © The Authors 2023. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Final published version, 2.67 MBLicence: CC BY

Astronomy at St Andrews 2018-2021: Astronomy at St Andrews 2018-2021
Jardine, M. M. (PI), Bonnell, I. A. (CoI), Cameron, A. C. (CoI), Cyganowski, C. J. (CoI), Dominik, M. (CoI), Helling, C. (CoI), Horne, K. D. (CoI), Scholz, A. (CoI), Tojeiro, R. (CoI), Weijmans, A.-M. (CoI), Wild, V. (CoI), Woitke, P. (CoI), Wood, K. (CoI) & Zhao, H. (CoI)
1/04/18 → 31/03/22
Project: Standard

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Kiefer, F., Van Grootel, V., Lecavelier Des Etangs, A., Szabó, G. M., Brandeker, A., Broeg, C., Collier Cameron, A., Deline, A., Olofsson, G., Wilson, T. G., Sousa, S. G., Gandolfi, D., Hébrard, G., Alibert, Y., Alonso, R., Anglada, G., Bárczy, T., Barrado, D., Barros, S. C. C., ... Walton, N. A. (2023). Hint of an exocomet transit in the CHEOPS light curve of HD 172555. Astronomy and Astrophysics, 671, Article A25. https://doi.org/10.1051/0004-6361/202245104

@article{2b30380806884bc8904fba64f9b8f38c,

title = "Hint of an exocomet transit in the CHEOPS light curve of HD 172555",

abstract = "HD 172555 is a young (∼20 Myr) A7V star surrounded by a 10 au wide debris disk suspected to be replenished partly by collisions between large planetesimals. Small evaporating transiting bodies, that is exocomets, have also been detected in this system by spectroscopy. After β Pictoris, this is another example of a system possibly witnessing a phase of the heavy bombardment of planetesimals. In such a system, small bodies trace dynamical evolution processes. We aim to constrain their dust content by using transit photometry. We performed a 2-day-long photometric monitoring of HD 172555 with the CHEOPS space telescope in order to detect shallow transits of exocomets with a typical expected duration of a few hours. The large oscillations in the light curve indicate that HD 172555 is a δ Scuti pulsating star. After removing those dominating oscillations, we found a hint of a transient absorption. If fitted with an exocomet transit model, it would correspond to an evaporating body passing near the star at a distance of 6.8±1.4R∗ (or 0.05±0.01 au) with a radius of 2.5 km. These properties are comparable to those of the exocomets already found in this system using spectroscopy, as well as those found in the β Pic system. The nuclei of the Solar System's Jupiter family comets, with radii of 2-6 km, are also comparable in size. This is the first piece of evidence of an exocomet photometric transit detection in the young system of HD 172555.",

keywords = "Circumstellar matter, Comets: general, Stars: individual: HD 172555, Stars: variables: δ Scuti, Techniques: photometric",

author = "F. Kiefer and {Van Grootel}, V. and {Lecavelier Des Etangs}, A. and G.M. Szab{\'o} and A. Brandeker and C. Broeg and {Collier Cameron}, A. and A. Deline and G. Olofsson and T.G. Wilson and S.G. Sousa and D. Gandolfi and G. H{\'e}brard and Y. Alibert and R. Alonso and G. Anglada and T. B{\'a}rczy and D. Barrado and S.C.C. Barros and W. Baumjohann and M. Beck and T. Beck and W. Benz and N. Billot and X. Bonfils and J. Cabrera and S. Charnoz and S. Csizmadia and M.B. Davies and M. Deleuil and L. Delrez and O.D.S. Demangeon and B.-O. Demory and D. Ehrenreich and A. Erikson and A. Fortier and L. Fossati and M. Fridlund and M. Gillon and M. G{\"u}del and K. Heng and S. Hoyer and K.G. Isaak and L.L. Kiss and J. Laskar and M. Lendl and C. Lovis and D. Magrin and P.F.L. Maxted and M. Munari and V. Nascimbeni and R. Ottensamer and I. Pagano and E. Pall{\'e} and G. Peter and D. Piazza and G. Piotto and D. Pollacco and D. Queloz and R. Ragazzoni and N. Rando and F. Ratti and H. Rauer and C. Reimers and I. Ribas and N.C. Santos and G. Scandariato and D. S{\'e}gransan and A.E. Simon and A.M.S. Smith and M. Steller and N. Thomas and S. Udry and I. Walter and N.A. Walton",

note = "Funding: F.K., A.L. and G.H. acknowledge funding from the Centre National d{\textquoteright}Etudes Spatiales and from the French National Research Agency (ANR) under contract number ANR-18-CE31-0019 (SPlaSH). F.K. also acknowledges support from the Universit{\'e} Paris Sciences et Lettres under the DIM-ACAV program Origines et conditions d{\textquoteright}apparition de la vie. V.V.G. is an F.R.S-FNRS Research Associate. G.M.S. acknowledges the support of the Hungarian National Research, Development and Innovation Office (NKFIH) grant K-125015, a PRODEX Experiment Agreement No. 4000137122, the Lend{\"u}let LP2018-7/2021 grant of the Hungarian Academy of Science and the support of the city of Szombathely. A.B. was supported by the SNSA. A.C.C. acknowledges support from STFC consolidated grant numbers ST/R000824/1 and ST/V000861/1, and UKSA grant number ST/R003203/1. A.C.C. and T.W. acknowledge support from STFC consolidated grant numbers ST/R000824/1 and ST/V000861/1, and UKSA grant number ST/R003203/1. S.G.S. acknowledges support from FCT through FCT contract nr. CEECIND/00826/2018 and POPH/FSE (EC). D.G. gratefully acknowledges financial support from the CRT foundation under Grant No. 2018.2323 “Gaseousor rocky? Unveiling the nature of small worlds”. Y.A. and M.J.H. acknowledge the support of the Swiss National Fund under grant 200020_172746. We acknowledge support from the Spanish Ministry of Science and Innovation and the European Regional Development Fund through grants ESP2016-80435-C2-1-R, ESP2016-80435-C2-2-R, PGC2018-098153-B-C33, PGC2018-098153-B-C31, ESP2017-87676-C5-1-R, MDM-2017-0737 Unidad de Excelencia Maria de Maeztu-Centro de Astrobiologia (INTA-CSIC), as well as the support of the Generalitat de Catalunya/CERCA programme. The MOC activities have been supported by the ESA contract No. 4000124370. S.C.C.B. acknowledges support from FCT through FCT contracts nr. IF/01312/2014/CP1215/CT0004. X.B., S.C., D.G., M.F. and J.L. acknowledge their role as ESA-appointed CHEOPS science team members. This project was supported by the CNES. The Belgian participation to CHEOPS has been supported by the Belgian Federal Science Policy Office (BELSPO) in the framework of the PRODEX Program, and by the University of Li{\`e}ge through an ARC grant for Concerted Research Actions financed by the Wallonia-Brussels Federation. L.D. is an F.R.S.-FNRS Postdoctoral Researcher. This work was supported by FCT - Funda{\c c}{\^a}o para a Ci{\^e}ncia e a Tecnologia through national funds and by FEDER through COMPETE2020 - Programa Operacional Competitividade e Internacionalizac{\^a}o by these grants: UID/FIS/04434/2019, UIDB/04434/2020, UIDP/04434/2020, PTDC/FIS-AST/32113/2017 & POCI-01-0145-FEDER-032113, PTDC/FIS-AST/28953/2017 & POCI-01-0145-FEDER-028953, PTDC/FIS-AST/28987/2017 & POCI-01-0145-FEDER-028987, O.D.S.D. is supported in the form of work contract (DL 57/2016/CP1364/CT0004) funded by national funds through FCT. B.-O.D. acknowledges support from the Swiss National Science Foundation (PP00P2-190080). This project has received funding from the European Research Council (ERC) under the European Union{\textquoteright}s Horizon 2020 research and innovation programme (project F OUR A CES . grant agreement No 724427). It has also been carried out in the frame of the National Centre for Competence in Research PlanetS supported by the Swiss National Science Foundation (SNSF). D.E. acknowledges financial support from the Swiss National Science Foundation for project 200021_200726. M.F. and C.M.P. gratefully acknowledge the support of the Swedish National Space Agency (DNR 65/19, 174/18). M.G. is an F.R.S.-FNRS Senior Research Associate. S.H. gratefully acknowledges CNES funding through the grant 837319. K.G.I. is the ESA CHEOPS Project Scientist and is responsible for the ESA CHEOPS Guest Observers Programme. This work was granted access to the HPC resources of MesoPSL financed by the Region Ile de France and the project Equip@Meso (reference ANR-10-EQPX-29-01) of the programme Investissements d{\textquoteright}Avenir supervised by the Agence Nationale pour la Recherche. M.L. acknowledges support of the Swiss National Science Foundation under grant number PCEFP2_194576. P.M. acknowledges support from STFC research grant number ST/M001040/1. L.B., G.B., V.N., I.P., G.P., R.R., G.S., V.S., and T.Z. acknowledge support from CHEOPS ASI-INAF agreement n. 2019-29-HH.0. This work was also partially supported by a grant from the Simons Foundation (PI Queloz, grant number 327127). I.R.I. acknowledges support from the Spanish Ministry of Science and Innovation and the European Regional Development Fund through grant PGC2018-098153-B-C33, as well as the support of the Generalitat de Catalunya/CERCA programme. N.A.W. acknowledges UKSA grant ST/R004838/1.",

year = "2023",

month = mar,

day = "1",

doi = "10.1051/0004-6361/202245104",

language = "English",

volume = "671",

journal = "Astronomy and Astrophysics",

issn = "0004-6361",

publisher = "EDP SCIENCES S A",

}

Kiefer, F, Van Grootel, V, Lecavelier Des Etangs, A, Szabó, GM, Brandeker, A, Broeg, C, Collier Cameron, A, Deline, A, Olofsson, G, Wilson, TG, Sousa, SG, Gandolfi, D, Hébrard, G, Alibert, Y, Alonso, R, Anglada, G, Bárczy, T, Barrado, D, Barros, SCC, Baumjohann, W, Beck, M, Beck, T, Benz, W, Billot, N, Bonfils, X, Cabrera, J, Charnoz, S, Csizmadia, S, Davies, MB, Deleuil, M, Delrez, L, Demangeon, ODS, Demory, B-O, Ehrenreich, D, Erikson, A, Fortier, A, Fossati, L, Fridlund, M, Gillon, M, Güdel, M, Heng, K, Hoyer, S, Isaak, KG, Kiss, LL, Laskar, J, Lendl, M, Lovis, C, Magrin, D, Maxted, PFL, Munari, M, Nascimbeni, V, Ottensamer, R, Pagano, I, Pallé, E, Peter, G, Piazza, D, Piotto, G, Pollacco, D, Queloz, D, Ragazzoni, R, Rando, N, Ratti, F, Rauer, H, Reimers, C, Ribas, I, Santos, NC, Scandariato, G, Ségransan, D, Simon, AE, Smith, AMS, Steller, M, Thomas, N, Udry, S, Walter, I & Walton, NA 2023, 'Hint of an exocomet transit in the CHEOPS light curve of HD 172555', Astronomy and Astrophysics, vol. 671, A25. https://doi.org/10.1051/0004-6361/202245104

TY - JOUR

T1 - Hint of an exocomet transit in the CHEOPS light curve of HD 172555

AU - Kiefer, F.

AU - Van Grootel, V.

AU - Lecavelier Des Etangs, A.

AU - Szabó, G.M.

AU - Brandeker, A.

AU - Broeg, C.

AU - Collier Cameron, A.

AU - Deline, A.

AU - Olofsson, G.

AU - Wilson, T.G.

AU - Sousa, S.G.

AU - Gandolfi, D.

AU - Hébrard, G.

AU - Alibert, Y.

AU - Alonso, R.

AU - Anglada, G.

AU - Bárczy, T.

AU - Barrado, D.

AU - Barros, S.C.C.

AU - Baumjohann, W.

AU - Beck, M.

AU - Beck, T.

AU - Benz, W.

AU - Billot, N.

AU - Bonfils, X.

AU - Cabrera, J.

AU - Charnoz, S.

AU - Csizmadia, S.

AU - Davies, M.B.

AU - Deleuil, M.

AU - Delrez, L.

AU - Demangeon, O.D.S.

AU - Demory, B.-O.

AU - Ehrenreich, D.

AU - Erikson, A.

AU - Fortier, A.

AU - Fossati, L.

AU - Fridlund, M.

AU - Gillon, M.

AU - Güdel, M.

AU - Heng, K.

AU - Hoyer, S.

AU - Isaak, K.G.

AU - Kiss, L.L.

AU - Laskar, J.

AU - Lendl, M.

AU - Lovis, C.

AU - Magrin, D.

AU - Maxted, P.F.L.

AU - Munari, M.

AU - Nascimbeni, V.

AU - Ottensamer, R.

AU - Pagano, I.

AU - Pallé, E.

AU - Peter, G.

AU - Piazza, D.

AU - Piotto, G.

AU - Pollacco, D.

AU - Queloz, D.

AU - Ragazzoni, R.

AU - Rando, N.

AU - Ratti, F.

AU - Rauer, H.

AU - Reimers, C.

AU - Ribas, I.

AU - Santos, N.C.

AU - Scandariato, G.

AU - Ségransan, D.

AU - Simon, A.E.

AU - Smith, A.M.S.

AU - Steller, M.

AU - Thomas, N.

AU - Udry, S.

AU - Walter, I.

AU - Walton, N.A.

N1 - Funding: F.K., A.L. and G.H. acknowledge funding from the Centre National d’Etudes Spatiales and from the French National Research Agency (ANR) under contract number ANR-18-CE31-0019 (SPlaSH). F.K. also acknowledges support from the Université Paris Sciences et Lettres under the DIM-ACAV program Origines et conditions d’apparition de la vie. V.V.G. is an F.R.S-FNRS Research Associate. G.M.S. acknowledges the support of the Hungarian National Research, Development and Innovation Office (NKFIH) grant K-125015, a PRODEX Experiment Agreement No. 4000137122, the Lendület LP2018-7/2021 grant of the Hungarian Academy of Science and the support of the city of Szombathely. A.B. was supported by the SNSA. A.C.C. acknowledges support from STFC consolidated grant numbers ST/R000824/1 and ST/V000861/1, and UKSA grant number ST/R003203/1. A.C.C. and T.W. acknowledge support from STFC consolidated grant numbers ST/R000824/1 and ST/V000861/1, and UKSA grant number ST/R003203/1. S.G.S. acknowledges support from FCT through FCT contract nr. CEECIND/00826/2018 and POPH/FSE (EC). D.G. gratefully acknowledges financial support from the CRT foundation under Grant No. 2018.2323 “Gaseousor rocky? Unveiling the nature of small worlds”. Y.A. and M.J.H. acknowledge the support of the Swiss National Fund under grant 200020_172746. We acknowledge support from the Spanish Ministry of Science and Innovation and the European Regional Development Fund through grants ESP2016-80435-C2-1-R, ESP2016-80435-C2-2-R, PGC2018-098153-B-C33, PGC2018-098153-B-C31, ESP2017-87676-C5-1-R, MDM-2017-0737 Unidad de Excelencia Maria de Maeztu-Centro de Astrobiologia (INTA-CSIC), as well as the support of the Generalitat de Catalunya/CERCA programme. The MOC activities have been supported by the ESA contract No. 4000124370. S.C.C.B. acknowledges support from FCT through FCT contracts nr. IF/01312/2014/CP1215/CT0004. X.B., S.C., D.G., M.F. and J.L. acknowledge their role as ESA-appointed CHEOPS science team members. This project was supported by the CNES. The Belgian participation to CHEOPS has been supported by the Belgian Federal Science Policy Office (BELSPO) in the framework of the PRODEX Program, and by the University of Liège through an ARC grant for Concerted Research Actions financed by the Wallonia-Brussels Federation. L.D. is an F.R.S.-FNRS Postdoctoral Researcher. This work was supported by FCT - Fundaçâo para a Ciência e a Tecnologia through national funds and by FEDER through COMPETE2020 - Programa Operacional Competitividade e Internacionalizacâo by these grants: UID/FIS/04434/2019, UIDB/04434/2020, UIDP/04434/2020, PTDC/FIS-AST/32113/2017 & POCI-01-0145-FEDER-032113, PTDC/FIS-AST/28953/2017 & POCI-01-0145-FEDER-028953, PTDC/FIS-AST/28987/2017 & POCI-01-0145-FEDER-028987, O.D.S.D. is supported in the form of work contract (DL 57/2016/CP1364/CT0004) funded by national funds through FCT. B.-O.D. acknowledges support from the Swiss National Science Foundation (PP00P2-190080). This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (project F OUR A CES . grant agreement No 724427). It has also been carried out in the frame of the National Centre for Competence in Research PlanetS supported by the Swiss National Science Foundation (SNSF). D.E. acknowledges financial support from the Swiss National Science Foundation for project 200021_200726. M.F. and C.M.P. gratefully acknowledge the support of the Swedish National Space Agency (DNR 65/19, 174/18). M.G. is an F.R.S.-FNRS Senior Research Associate. S.H. gratefully acknowledges CNES funding through the grant 837319. K.G.I. is the ESA CHEOPS Project Scientist and is responsible for the ESA CHEOPS Guest Observers Programme. This work was granted access to the HPC resources of MesoPSL financed by the Region Ile de France and the project Equip@Meso (reference ANR-10-EQPX-29-01) of the programme Investissements d’Avenir supervised by the Agence Nationale pour la Recherche. M.L. acknowledges support of the Swiss National Science Foundation under grant number PCEFP2_194576. P.M. acknowledges support from STFC research grant number ST/M001040/1. L.B., G.B., V.N., I.P., G.P., R.R., G.S., V.S., and T.Z. acknowledge support from CHEOPS ASI-INAF agreement n. 2019-29-HH.0. This work was also partially supported by a grant from the Simons Foundation (PI Queloz, grant number 327127). I.R.I. acknowledges support from the Spanish Ministry of Science and Innovation and the European Regional Development Fund through grant PGC2018-098153-B-C33, as well as the support of the Generalitat de Catalunya/CERCA programme. N.A.W. acknowledges UKSA grant ST/R004838/1.

PY - 2023/3/1

Y1 - 2023/3/1

N2 - HD 172555 is a young (∼20 Myr) A7V star surrounded by a 10 au wide debris disk suspected to be replenished partly by collisions between large planetesimals. Small evaporating transiting bodies, that is exocomets, have also been detected in this system by spectroscopy. After β Pictoris, this is another example of a system possibly witnessing a phase of the heavy bombardment of planetesimals. In such a system, small bodies trace dynamical evolution processes. We aim to constrain their dust content by using transit photometry. We performed a 2-day-long photometric monitoring of HD 172555 with the CHEOPS space telescope in order to detect shallow transits of exocomets with a typical expected duration of a few hours. The large oscillations in the light curve indicate that HD 172555 is a δ Scuti pulsating star. After removing those dominating oscillations, we found a hint of a transient absorption. If fitted with an exocomet transit model, it would correspond to an evaporating body passing near the star at a distance of 6.8±1.4R∗ (or 0.05±0.01 au) with a radius of 2.5 km. These properties are comparable to those of the exocomets already found in this system using spectroscopy, as well as those found in the β Pic system. The nuclei of the Solar System's Jupiter family comets, with radii of 2-6 km, are also comparable in size. This is the first piece of evidence of an exocomet photometric transit detection in the young system of HD 172555.

AB - HD 172555 is a young (∼20 Myr) A7V star surrounded by a 10 au wide debris disk suspected to be replenished partly by collisions between large planetesimals. Small evaporating transiting bodies, that is exocomets, have also been detected in this system by spectroscopy. After β Pictoris, this is another example of a system possibly witnessing a phase of the heavy bombardment of planetesimals. In such a system, small bodies trace dynamical evolution processes. We aim to constrain their dust content by using transit photometry. We performed a 2-day-long photometric monitoring of HD 172555 with the CHEOPS space telescope in order to detect shallow transits of exocomets with a typical expected duration of a few hours. The large oscillations in the light curve indicate that HD 172555 is a δ Scuti pulsating star. After removing those dominating oscillations, we found a hint of a transient absorption. If fitted with an exocomet transit model, it would correspond to an evaporating body passing near the star at a distance of 6.8±1.4R∗ (or 0.05±0.01 au) with a radius of 2.5 km. These properties are comparable to those of the exocomets already found in this system using spectroscopy, as well as those found in the β Pic system. The nuclei of the Solar System's Jupiter family comets, with radii of 2-6 km, are also comparable in size. This is the first piece of evidence of an exocomet photometric transit detection in the young system of HD 172555.

KW - Circumstellar matter

KW - Comets: general

KW - Stars: individual: HD 172555

KW - Stars: variables: δ Scuti

KW - Techniques: photometric

U2 - 10.1051/0004-6361/202245104

DO - 10.1051/0004-6361/202245104

M3 - Article

SN - 0004-6361

VL - 671

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

M1 - A25

ER -

Hint of an exocomet transit in the CHEOPS light curve of HD 172555

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Astronomy at St Andrews 2018-2021: Astronomy at St Andrews 2018-2021

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