Key Publications
Morrell, Samuel A. F.
Solving the Ubiquitous Problem of Stellar Radii PhD Thesis
2020, (Publication Title: Ph.D. Thesis ADS Bibcode: 2020PhDT........17M).
@phdthesis{morrell_solving_2020,
title = {Solving the Ubiquitous Problem of Stellar Radii},
author = {Samuel A. F. Morrell},
url = {https://ui.adsabs.harvard.edu/abs/2020PhDT........17M},
year = {2020},
date = {2020-03-01},
urldate = {2022-01-25},
abstract = {This thesis will address the problem of measuring stellar radii, which is ubiquitous across many fields of modern astrophysics. A technique is introduced which integrates the area beneath the stellar spectral energy distribution (SED) of a star to measure its luminosity, and the shape of the SED to measure its temperature - from which follows its radius. This method addresses many of the problems facing of existing methods, which are reviewed, as it provides accurate measurements of stellar radius using only multiband photometry and precision parallaxes. It is well known that the radii and temperatures of M-dwarf prescribed by models are in disagreement with observations, both on the pre-main-sequence (pre-MS) and the main-sequence (MS). This methodology is applied to pre-MS M-dwarfs in the Pleiades and Praesepe clusters to perform a direct comparison to the radii predicted by stellar interiors. Assessment of the physicality and accuracy of the stellar atmosphere models is also performed by comparing synthetic spectra generated from them to flux--calibrated spectroscopic observations. The parameters for the synthetic spectra are provided by the SED fitting, allowing verification of the methodology itself to be performed. The advent of Gaia DR2 means that reliable distances are now available for field M-dwarfs, permitting the extension of this investigation to MS stars. Through this investigation, the nature of radius inflation in MS M-dwarfs is studied as a function of mass. This crucially allows insight into the physics behind the observed radius inflation, allowing current theories underpinning radius inflation to be critically assessed. The conclusion of this investigation is that magnetic models are currently unable to explain radius inflation in M-dwarfs. Given the successful application of the SED fitting methodology in measuring the stellar radii of miscellaneous field stars, this work is built upon to address the problem of determining the stellar parameters of exoplanet host radii. In doing so, it is demonstrated that the SED fitting technique extends well to the mass range of stars currently being scrutinised to discover and characterise exoplanets. Given its wide applicability for exoplanet host characterisation, the potential systematic errors that may prove problematic are reviewed and methods for their mitigation are suggested.},
note = {Publication Title: Ph.D. Thesis
ADS Bibcode: 2020PhDT........17M},
keywords = {},
pubstate = {published},
tppubtype = {phdthesis}
}
This thesis will address the problem of measuring stellar radii, which is ubiquitous across many fields of modern astrophysics. A technique is introduced which integrates the area beneath the stellar spectral energy distribution (SED) of a star to measure its luminosity, and the shape of the SED to measure its temperature - from which follows its radius. This method addresses many of the problems facing of existing methods, which are reviewed, as it provides accurate measurements of stellar radius using only multiband photometry and precision parallaxes. It is well known that the radii and temperatures of M-dwarf prescribed by models are in disagreement with observations, both on the pre-main-sequence (pre-MS) and the main-sequence (MS). This methodology is applied to pre-MS M-dwarfs in the Pleiades and Praesepe clusters to perform a direct comparison to the radii predicted by stellar interiors. Assessment of the physicality and accuracy of the stellar atmosphere models is also performed by comparing synthetic spectra generated from them to flux--calibrated spectroscopic observations. The parameters for the synthetic spectra are provided by the SED fitting, allowing verification of the methodology itself to be performed. The advent of Gaia DR2 means that reliable distances are now available for field M-dwarfs, permitting the extension of this investigation to MS stars. Through this investigation, the nature of radius inflation in MS M-dwarfs is studied as a function of mass. This crucially allows insight into the physics behind the observed radius inflation, allowing current theories underpinning radius inflation to be critically assessed. The conclusion of this investigation is that magnetic models are currently unable to explain radius inflation in M-dwarfs. Given the successful application of the SED fitting methodology in measuring the stellar radii of miscellaneous field stars, this work is built upon to address the problem of determining the stellar parameters of exoplanet host radii. In doing so, it is demonstrated that the SED fitting technique extends well to the mass range of stars currently being scrutinised to discover and characterise exoplanets. Given its wide applicability for exoplanet host characterisation, the potential systematic errors that may prove problematic are reviewed and methods for their mitigation are suggested.
Morrell, Sam; Naylor, Tim
Exploring the M-dwarf Luminosity-Temperature-Radius relationships using Gaia DR2 Journal Article
In: Monthly Notices of the Royal Astronomical Society, vol. 489, pp. 2615–2633, 2019, ISSN: 0035-8711.
@article{morrell_exploring_2019,
title = {Exploring the M-dwarf Luminosity-Temperature-Radius relationships using Gaia DR2},
author = {Sam Morrell and Tim Naylor},
url = {http://adsabs.harvard.edu/abs/2019MNRAS.489.2615M},
doi = {10.1093/mnras/stz2242},
issn = {0035-8711},
year = {2019},
date = {2019-10-01},
urldate = {2020-06-15},
journal = {Monthly Notices of the Royal Astronomical Society},
volume = {489},
pages = {2615--2633},
abstract = {There is growing evidence that M-dwarf stars suffer radius inflation
when compared to theoretical models, suggesting that models are missing
some key physics required to completely describe stars at effective
temperatures less than about 4000 K. The advent of Gaia DR2 distances
finally makes available large data sets to determine the nature and
extent of this effect. We employ an all-sky sample, comprising of textgreater15
000 stars, to determine empirical relationships between luminosity,
temperature, and radius. This is accomplished using only geometric
distances and multiwave-band photometry, by utilizing a modified
spectral energy distribution fitting method. The radii we measure show
an inflation of 3 - 7 per cent compared to models, but no more than
a 1 - 2 per cent intrinsic spread in the inflated sequence. We show
that we are currently able to determine M-dwarf radii to an accuracy of
2.4 per cent using our method. However, we determine that this is
limited by the precision of metallicity measurements, which contribute
1.7 per cent to the measured radius scatter. We also present
evidence that stellar magnetism is currently unable to explain radius
inflation in M-dwarfs.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
There is growing evidence that M-dwarf stars suffer radius inflation
when compared to theoretical models, suggesting that models are missing
some key physics required to completely describe stars at effective
temperatures less than about 4000 K. The advent of Gaia DR2 distances
finally makes available large data sets to determine the nature and
extent of this effect. We employ an all-sky sample, comprising of textgreater15
000 stars, to determine empirical relationships between luminosity,
temperature, and radius. This is accomplished using only geometric
distances and multiwave-band photometry, by utilizing a modified
spectral energy distribution fitting method. The radii we measure show
an inflation of 3 - 7 per cent compared to models, but no more than
a 1 - 2 per cent intrinsic spread in the inflated sequence. We show
that we are currently able to determine M-dwarf radii to an accuracy of
2.4 per cent using our method. However, we determine that this is
limited by the precision of metallicity measurements, which contribute
1.7 per cent to the measured radius scatter. We also present
evidence that stellar magnetism is currently unable to explain radius
inflation in M-dwarfs.
when compared to theoretical models, suggesting that models are missing
some key physics required to completely describe stars at effective
temperatures less than about 4000 K. The advent of Gaia DR2 distances
finally makes available large data sets to determine the nature and
extent of this effect. We employ an all-sky sample, comprising of textgreater15
000 stars, to determine empirical relationships between luminosity,
temperature, and radius. This is accomplished using only geometric
distances and multiwave-band photometry, by utilizing a modified
spectral energy distribution fitting method. The radii we measure show
an inflation of 3 - 7 per cent compared to models, but no more than
a 1 - 2 per cent intrinsic spread in the inflated sequence. We show
that we are currently able to determine M-dwarf radii to an accuracy of
2.4 per cent using our method. However, we determine that this is
limited by the precision of metallicity measurements, which contribute
1.7 per cent to the measured radius scatter. We also present
evidence that stellar magnetism is currently unable to explain radius
inflation in M-dwarfs.
All Publications
2024
1.
Morrell, Sam; Hatchell, Jennifer; Wordingham, Freddy; Bennie, Jonathan; Inston, Maisy J.; Gaston, Kevin J.
Changing streetlighting schemes and the ecological availability of darkness Journal Article
In: J. R. Soc. Interface., vol. 21, no. 211, 2024, ISSN: 1742-5662.
@article{Morrell2024,
title = {Changing streetlighting schemes and the ecological availability of darkness},
author = {Sam Morrell and Jennifer Hatchell and Freddy Wordingham and Jonathan Bennie and Maisy J. Inston and Kevin J. Gaston},
url = {https://royalsocietypublishing.org/doi/10.1098/rsif.2023.0555},
doi = {10.1098/rsif.2023.0555},
issn = {1742-5662},
year = {2024},
date = {2024-02-00},
urldate = {2024-02-00},
journal = {J. R. Soc. Interface.},
volume = {21},
number = {211},
publisher = {The Royal Society},
abstract = {<jats:p>Artificial light at night (ALAN), from streetlights and other sources, has a wide variety of impacts on the natural environment. A significant challenge remains, however, to predict at intermediate spatial extents (e.g. across a city) the ALAN that organisms experience under different lighting regimes. Here we use Monte Carlo radiative Transfer to model the three-dimensional lighting environment at, and just above, ground level, on the spatial scales at which animals and humans experience it. We show how this technique can be used to model a suite of both real and hypothetical lighting environments, mimicking the transition of public infrastructure between different lighting technologies. We then demonstrate how the behaviour of animals experiencing these simulated lighting environments can be emulated to probe the availability of darkness, and dark corridors, within them. Our simulations show that no single lighting technology provides an unmitigated alleviation of negative impacts within urban environments, and that holistic treatments of entire lighting environments should be employed when understanding how animals use and traverse them.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:p>Artificial light at night (ALAN), from streetlights and other sources, has a wide variety of impacts on the natural environment. A significant challenge remains, however, to predict at intermediate spatial extents (e.g. across a city) the ALAN that organisms experience under different lighting regimes. Here we use Monte Carlo radiative Transfer to model the three-dimensional lighting environment at, and just above, ground level, on the spatial scales at which animals and humans experience it. We show how this technique can be used to model a suite of both real and hypothetical lighting environments, mimicking the transition of public infrastructure between different lighting technologies. We then demonstrate how the behaviour of animals experiencing these simulated lighting environments can be emulated to probe the availability of darkness, and dark corridors, within them. Our simulations show that no single lighting technology provides an unmitigated alleviation of negative impacts within urban environments, and that holistic treatments of entire lighting environments should be employed when understanding how animals use and traverse them.</jats:p>
2023
2.
Rescigno, F.; Hébrard, G.; Vanderburg, A.; Mann, A. W.; Mortier, A.; Morrell, S.; Buchhave, L. A.; Collins, K. A.; Mann, C. R.; Hellier, C.; Haywood, R. D.; West, R.; Stalport, M.; Heidari, N.; Anderson, D.; Huang, C. X.; López-Morales, M.; Cortés-Zuleta, P.; Lewis, H. M.; Dumusque, X.; Boisse, I.; Rowden, P.; Cameron, A. Collier; Deleuil, M.; Vezie, M.; Pepe, F. A.; Delfosse, X.; Charbonneau, D.; Rice, K.; Demangeon, O.; Quinn, S. N.; Udry, S.; Forveille, T.; Winn, J. N.; Sozzetti, A.; Hoyer, S.; Seager, S.; Wilson, T. G.; Dalal, S.; Martioli, E.; Striegel, S.; Boschin, W.; Dragomir, D.; Fiorenzano, A. F. Martínez; Cosentino, R.; Ghedina, A.; Malavolta, L.; Affer, L.; Lakeland, B. S.; Nicholson, B. A.; Foschino, S.; Wünsche, A.; Barkaoui, K.; Srdoc, G.; Randolph, J.; Guillet, B.; Conti, D. M.; Ghachoui, M.; Gillon, M.; Benkhaldoun, Z.; Pozuelos, F. J.; Timmermans, M.; Girardin, E.; Matutano, S.; Bosch-Cabot, P.; Muñoz, J. A.; Forés-Toribio, R.
A hot mini-Neptune and a temperate, highly eccentric sub-Saturn around the bright K-dwarf TOI-2134 Journal Article
In: Monthly Notices of the Royal Astronomical Society, 2023.
@article{Rescigno2023,
title = {A hot mini-Neptune and a temperate, highly eccentric sub-Saturn around the bright K-dwarf TOI-2134},
author = {F. Rescigno and G. Hébrard and A. Vanderburg and A. W. Mann and A. Mortier and S. Morrell and L. A. Buchhave and K. A. Collins and C. R. Mann and C. Hellier and R. D. Haywood and R. West and M. Stalport and N. Heidari and D. Anderson and C. X. Huang and M. López-Morales and P. Cortés-Zuleta and H. M. Lewis and X. Dumusque and I. Boisse and P. Rowden and A. Collier Cameron and M. Deleuil and M. Vezie and F. A. Pepe and X. Delfosse and D. Charbonneau and K. Rice and O. Demangeon and S. N. Quinn and S. Udry and T. Forveille and J. N. Winn and A. Sozzetti and S. Hoyer and S. Seager and T. G. Wilson and S. Dalal and E. Martioli and S. Striegel and W. Boschin and D. Dragomir and A. F. Martínez Fiorenzano and R. Cosentino and A. Ghedina and L. Malavolta and L. Affer and B. S. Lakeland and B. A. Nicholson and S. Foschino and A. Wünsche and K. Barkaoui and G. Srdoc and J. Randolph and B. Guillet and D. M. Conti and M. Ghachoui and M. Gillon and Z. Benkhaldoun and F. J. Pozuelos and M. Timmermans and E. Girardin and S. Matutano and P. Bosch-Cabot and J. A. Muñoz and R. Forés-Toribio},
url = {https://academic.oup.com/mnras/article/527/3/5385/7330172},
doi = {10.1093/mnras/stad3255},
year = {2023},
date = {2023-10-25},
urldate = {2023-10-25},
journal = {Monthly Notices of the Royal Astronomical Society},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
2022
3.
Zarrilli, Sebastian A.; Kraus, Stefan; Kreplin, Alexander; Monnier, John D.; Gardner, Tyler; Mérand, Antoine; textbfSam Morrell,; Davies, Claire L.; Labdon, Aaron; Ennis, Jacob; Setterholm, Benjamin; Le Bouquin, Jean-Baptiste; Anugu, Narsireddy; Lanthermann, Cyprien; Schaefer, Gail; ten Brummelaar, Theo
Characterising the orbit and circumstellar environment of the high-mass binary MWC 166 A Journal Article
In: Astronomy & Astrophysics, vol. 665, pp. A146, 2022.
@article{{Zarrilli}2022,
title = {Characterising the orbit and circumstellar environment of the high-mass binary MWC 166 A},
author = {{Zarrilli}, Sebastian A. and {Kraus}, Stefan and {Kreplin}, Alexander and {Monnier}, John D. and {Gardner}, Tyler and {Mérand}, Antoine and textbf{Sam Morrell} and {Davies}, Claire L. and {Labdon}, Aaron and {Ennis}, Jacob and {Setterholm}, Benjamin and {Le Bouquin}, Jean-Baptiste and {Anugu}, Narsireddy and {Lanthermann}, Cyprien and {Schaefer}, Gail and {ten Brummelaar}, Theo},
doi = {10.1051/0004-6361/202243957},
year = {2022},
date = {2022-07-01},
urldate = {2022-07-01},
journal = {Astronomy & Astrophysics},
volume = {665},
pages = {A146},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
4.
Morrell, Sam; Davies, Claire L.; Bate, Matthew R.; Mills, Alice; Whitehead, Natalie J.; Rieder, Steven; Hatchell, Jennifer; Krijt, Sebastiaan; Mayne, Nathan J.; Thomson, Stephen I.; Rescigno, Federica; Houge, Adrien; Brunt, Christopher M.
Sharing the 2020 Great Conjunction with the World Proceedings
Proceedings of the Communicating Astronomy with the Public Conference 2021, 2022, ISBN: 978-4-908895-03-6.
@proceedings{cap2021-great-conjunction,
title = {Sharing the 2020 Great Conjunction with the World},
author = {Sam Morrell and Claire L. Davies and Matthew R. Bate and Alice Mills and Natalie J. Whitehead and Steven
Rieder and Jennifer Hatchell and Sebastiaan Krijt and Nathan J. Mayne and Stephen I. Thomson and Federica
Rescigno and Adrien Houge and Christopher M. Brunt},
url = {https://www.communicatingastronomy.org/cap2021-proceedings/
https://sammorrell.co.uk/pubs/2022/cap2021-great-conjunction.pdf},
isbn = {978-4-908895-03-6},
year = {2022},
date = {2022-06-21},
urldate = {2022-06-22},
abstract = {On 21st December 2020, Jupiter and Saturn came closer together in the sky than they have been since
1623, appearing less than one-fifth the apparent diameter of the full Moon apart—an event known as a Great
Conjunction. With a second lockdown looking imminent in the UK, and with it the impossibility of organising
in-person events, the team from the University of Exeter and Exeter Science Centre in the UK innovated to
communicate this event to the world. We designed and organised an online campaign, including a website for
the event (http://jupitersaturn2020.org/), pre-event educational video content, and a live stream interleaving
segments from team members and live views of the conjunction through a telescope to engage with the world. In
parallel, we collaborated with Exeter-based community placemakers, Interwoven Productions CIC, to engage
thousands of residents in Exeter through community-run COVID-safe star parties, an immersive play themed on
Jupiter and Saturn which toured local schools, and a week-long shop front installation in the city centre featuring
bespoke print and digital media themed around the event. In this proceeding, we describe how our work engaged
over a million people around the world in the Great Conjunction},
howpublished = {Proceedings of the Communicating Astronomy with the Public Conference 2021},
keywords = {},
pubstate = {published},
tppubtype = {proceedings}
}
On 21st December 2020, Jupiter and Saturn came closer together in the sky than they have been since
1623, appearing less than one-fifth the apparent diameter of the full Moon apart—an event known as a Great
Conjunction. With a second lockdown looking imminent in the UK, and with it the impossibility of organising
in-person events, the team from the University of Exeter and Exeter Science Centre in the UK innovated to
communicate this event to the world. We designed and organised an online campaign, including a website for
the event (http://jupitersaturn2020.org/), pre-event educational video content, and a live stream interleaving
segments from team members and live views of the conjunction through a telescope to engage with the world. In
parallel, we collaborated with Exeter-based community placemakers, Interwoven Productions CIC, to engage
thousands of residents in Exeter through community-run COVID-safe star parties, an immersive play themed on
Jupiter and Saturn which toured local schools, and a week-long shop front installation in the city centre featuring
bespoke print and digital media themed around the event. In this proceeding, we describe how our work engaged
over a million people around the world in the Great Conjunction
1623, appearing less than one-fifth the apparent diameter of the full Moon apart—an event known as a Great
Conjunction. With a second lockdown looking imminent in the UK, and with it the impossibility of organising
in-person events, the team from the University of Exeter and Exeter Science Centre in the UK innovated to
communicate this event to the world. We designed and organised an online campaign, including a website for
the event (http://jupitersaturn2020.org/), pre-event educational video content, and a live stream interleaving
segments from team members and live views of the conjunction through a telescope to engage with the world. In
parallel, we collaborated with Exeter-based community placemakers, Interwoven Productions CIC, to engage
thousands of residents in Exeter through community-run COVID-safe star parties, an immersive play themed on
Jupiter and Saturn which toured local schools, and a week-long shop front installation in the city centre featuring
bespoke print and digital media themed around the event. In this proceeding, we describe how our work engaged
over a million people around the world in the Great Conjunction
2021
5.
Morrell, Sam; Naylor, Tim
Exploring the M-dwarf Luminosity--Temperature-- Radius Relationships using Gaia DR2 Miscellaneous
2021.
@misc{morrell_sam_2021_4565843,
title = {Exploring the M-dwarf Luminosity--Temperature--
Radius Relationships using Gaia DR2},
author = {Sam Morrell and Tim Naylor},
url = {https://doi.org/10.5281/zenodo.4565843},
doi = {10.5281/zenodo.4565843},
year = {2021},
date = {2021-02-01},
publisher = {Zenodo},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
6.
Morrell, Sam; Naylor, Tim
Exploring the M-dwarf Luminosity-Temperature-Radius Relationships using Gaia DR2 Proceedings Article
In: The 20.5th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun (CS20.5), pp. 186, 2021.
@inproceedings{2021csss.confE.186M,
title = {Exploring the M-dwarf Luminosity-Temperature-Radius Relationships using Gaia DR2},
author = {Sam Morrell and Tim Naylor},
doi = {10.5281/zenodo.4565843},
year = {2021},
date = {2021-03-01},
booktitle = {The 20.5th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun (CS20.5)},
pages = {186},
series = {Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
2020
7.
Morrell, Samuel A. F.
Solving the Ubiquitous Problem of Stellar Radii PhD Thesis
2020, (Publication Title: Ph.D. Thesis ADS Bibcode: 2020PhDT........17M).
@phdthesis{morrell_solving_2020,
title = {Solving the Ubiquitous Problem of Stellar Radii},
author = {Samuel A. F. Morrell},
url = {https://ui.adsabs.harvard.edu/abs/2020PhDT........17M},
year = {2020},
date = {2020-03-01},
urldate = {2022-01-25},
abstract = {This thesis will address the problem of measuring stellar radii, which is ubiquitous across many fields of modern astrophysics. A technique is introduced which integrates the area beneath the stellar spectral energy distribution (SED) of a star to measure its luminosity, and the shape of the SED to measure its temperature - from which follows its radius. This method addresses many of the problems facing of existing methods, which are reviewed, as it provides accurate measurements of stellar radius using only multiband photometry and precision parallaxes. It is well known that the radii and temperatures of M-dwarf prescribed by models are in disagreement with observations, both on the pre-main-sequence (pre-MS) and the main-sequence (MS). This methodology is applied to pre-MS M-dwarfs in the Pleiades and Praesepe clusters to perform a direct comparison to the radii predicted by stellar interiors. Assessment of the physicality and accuracy of the stellar atmosphere models is also performed by comparing synthetic spectra generated from them to flux--calibrated spectroscopic observations. The parameters for the synthetic spectra are provided by the SED fitting, allowing verification of the methodology itself to be performed. The advent of Gaia DR2 means that reliable distances are now available for field M-dwarfs, permitting the extension of this investigation to MS stars. Through this investigation, the nature of radius inflation in MS M-dwarfs is studied as a function of mass. This crucially allows insight into the physics behind the observed radius inflation, allowing current theories underpinning radius inflation to be critically assessed. The conclusion of this investigation is that magnetic models are currently unable to explain radius inflation in M-dwarfs. Given the successful application of the SED fitting methodology in measuring the stellar radii of miscellaneous field stars, this work is built upon to address the problem of determining the stellar parameters of exoplanet host radii. In doing so, it is demonstrated that the SED fitting technique extends well to the mass range of stars currently being scrutinised to discover and characterise exoplanets. Given its wide applicability for exoplanet host characterisation, the potential systematic errors that may prove problematic are reviewed and methods for their mitigation are suggested.},
note = {Publication Title: Ph.D. Thesis
ADS Bibcode: 2020PhDT........17M},
keywords = {},
pubstate = {published},
tppubtype = {phdthesis}
}
This thesis will address the problem of measuring stellar radii, which is ubiquitous across many fields of modern astrophysics. A technique is introduced which integrates the area beneath the stellar spectral energy distribution (SED) of a star to measure its luminosity, and the shape of the SED to measure its temperature - from which follows its radius. This method addresses many of the problems facing of existing methods, which are reviewed, as it provides accurate measurements of stellar radius using only multiband photometry and precision parallaxes. It is well known that the radii and temperatures of M-dwarf prescribed by models are in disagreement with observations, both on the pre-main-sequence (pre-MS) and the main-sequence (MS). This methodology is applied to pre-MS M-dwarfs in the Pleiades and Praesepe clusters to perform a direct comparison to the radii predicted by stellar interiors. Assessment of the physicality and accuracy of the stellar atmosphere models is also performed by comparing synthetic spectra generated from them to flux--calibrated spectroscopic observations. The parameters for the synthetic spectra are provided by the SED fitting, allowing verification of the methodology itself to be performed. The advent of Gaia DR2 means that reliable distances are now available for field M-dwarfs, permitting the extension of this investigation to MS stars. Through this investigation, the nature of radius inflation in MS M-dwarfs is studied as a function of mass. This crucially allows insight into the physics behind the observed radius inflation, allowing current theories underpinning radius inflation to be critically assessed. The conclusion of this investigation is that magnetic models are currently unable to explain radius inflation in M-dwarfs. Given the successful application of the SED fitting methodology in measuring the stellar radii of miscellaneous field stars, this work is built upon to address the problem of determining the stellar parameters of exoplanet host radii. In doing so, it is demonstrated that the SED fitting technique extends well to the mass range of stars currently being scrutinised to discover and characterise exoplanets. Given its wide applicability for exoplanet host characterisation, the potential systematic errors that may prove problematic are reviewed and methods for their mitigation are suggested.
8.
Morrell, Sam; Naylor, Tim
Erratum: Exploring the M-dwarf Luminosity-Temperature-Radius relationships using Gaia DR2 Journal Article
In: Monthly Notices of the RAS, vol. 498, no. 4, pp. 5048-5050, 2020.
@article{2020MNRAS.498.5048M,
title = {Erratum: Exploring the M-dwarf Luminosity-Temperature-Radius relationships using Gaia DR2},
author = {Sam Morrell and Tim Naylor},
doi = {10.1093/mnras/staa926},
year = {2020},
date = {2020-11-01},
journal = {Monthly Notices of the RAS},
volume = {498},
number = {4},
pages = {5048-5050},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
9.
Carter, Aarynn L.; Nikolov, Nikolay; Sing, David K.; Alam, Munazza K.; Goyal, Jayesh M.; Mikal-Evans, Thomas; Wakeford, Hannah R.; Henry, Gregory W.; Morrell, Sam; L'opez-Morales, Mercedes; Smalley, Barry; Lavvas, Panayotis; Barstow, Joanna K.; Garc'ia Mu noz, Antonio; Gibson, Neale P.; Wilson, Paul A.
Detection of Na, K, and H2O in the hazy atmosphere of WASP-6b Journal Article
In: Detection of Na, K, and H$_2$O in the hazy atmosphere of WASP-6b, vol. jun, iss. 494, no. 4, pp. 5449-5472, 2020.
@article{2020MNRAS.494.5449C,
title = {Detection of Na, K, and H2O in the hazy atmosphere of WASP-6b},
author = {{Carter}, Aarynn L. and {Nikolov}, Nikolay and {Sing}, David K. and {Alam}, Munazza K. and {Goyal}, Jayesh M. and {Mikal-Evans}, Thomas and {Wakeford}, Hannah R. and {Henry}, Gregory W. and {Morrell}, Sam and {L{'o}pez-Morales}, Mercedes and {Smalley}, Barry and {Lavvas}, Panayotis and {Barstow}, Joanna K. and {Garc{'i}a Mu{~n}oz}, Antonio and {Gibson}, Neale P. and {Wilson}, Paul A.},
url = {https://ui.adsabs.harvard.edu/abs/2020MNRAS.494.5449C/abstract},
doi = {10.1093/mnras/staa1078},
year = {2020},
date = {2020-06-01},
urldate = {2020-06-01},
journal = {Detection of Na, K, and H$_2$O in the hazy atmosphere of WASP-6b},
volume = {jun},
number = {4},
issue = {494},
pages = {5449-5472},
abstract = {We present new observations of the transmission spectrum of the hot Jupiter WASP-6b both from the ground with the Very Large Telescope FOcal Reducer and Spectrograph (FORS2) from 0.45 to 0.83 μm, and space with the Transiting Exoplanet Survey Satellite from 0.6 to 1.0 μm and the Hubble Space Telescope (HST) Wide Field Camera 3 from 1.12 to 1.65 μm. Archival data from the HST Space Telescope Imaging Spectrograph (STIS) and Spitzer are also re-analysed on a common Gaussian process framework, of which the STIS data show a good overall agreement with the overlapping FORS2 data. We also explore the effects of stellar heterogeneity on our observations and its resulting implications towards determining the atmospheric characteristics of WASP-6b. Independent of our assumptions for the level of stellar heterogeneity we detect Na I, K I, and H2O absorption features and constrain the elemental oxygen abundance to a value of [O/H] ≃ -0.9 ± 0.3 relative to solar. In contrast, we find that the stellar heterogeneity correction can have significant effects on the retrieved distributions of the [Na/H] and [K/H] abundances, primarily through its degeneracy with the sloping optical opacity of scattering haze species within the atmosphere. Our results also show that despite this presence of haze, WASP-6b remains a favourable object for future atmospheric characterization with upcoming missions such as the James Webb Space Telescope. },
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We present new observations of the transmission spectrum of the hot Jupiter WASP-6b both from the ground with the Very Large Telescope FOcal Reducer and Spectrograph (FORS2) from 0.45 to 0.83 μm, and space with the Transiting Exoplanet Survey Satellite from 0.6 to 1.0 μm and the Hubble Space Telescope (HST) Wide Field Camera 3 from 1.12 to 1.65 μm. Archival data from the HST Space Telescope Imaging Spectrograph (STIS) and Spitzer are also re-analysed on a common Gaussian process framework, of which the STIS data show a good overall agreement with the overlapping FORS2 data. We also explore the effects of stellar heterogeneity on our observations and its resulting implications towards determining the atmospheric characteristics of WASP-6b. Independent of our assumptions for the level of stellar heterogeneity we detect Na I, K I, and H2O absorption features and constrain the elemental oxygen abundance to a value of [O/H] ≃ -0.9 ± 0.3 relative to solar. In contrast, we find that the stellar heterogeneity correction can have significant effects on the retrieved distributions of the [Na/H] and [K/H] abundances, primarily through its degeneracy with the sloping optical opacity of scattering haze species within the atmosphere. Our results also show that despite this presence of haze, WASP-6b remains a favourable object for future atmospheric characterization with upcoming missions such as the James Webb Space Telescope.
2019
10.
Morrell, Sam; Naylor, Tim
Exploring the M-dwarf Luminosity-Temperature-Radius relationships using Gaia DR2 Journal Article
In: Monthly Notices of the Royal Astronomical Society, vol. 489, pp. 2615–2633, 2019, ISSN: 0035-8711.
@article{morrell_exploring_2019,
title = {Exploring the M-dwarf Luminosity-Temperature-Radius relationships using Gaia DR2},
author = {Sam Morrell and Tim Naylor},
url = {http://adsabs.harvard.edu/abs/2019MNRAS.489.2615M},
doi = {10.1093/mnras/stz2242},
issn = {0035-8711},
year = {2019},
date = {2019-10-01},
urldate = {2020-06-15},
journal = {Monthly Notices of the Royal Astronomical Society},
volume = {489},
pages = {2615--2633},
abstract = {There is growing evidence that M-dwarf stars suffer radius inflation
when compared to theoretical models, suggesting that models are missing
some key physics required to completely describe stars at effective
temperatures less than about 4000 K. The advent of Gaia DR2 distances
finally makes available large data sets to determine the nature and
extent of this effect. We employ an all-sky sample, comprising of textgreater15
000 stars, to determine empirical relationships between luminosity,
temperature, and radius. This is accomplished using only geometric
distances and multiwave-band photometry, by utilizing a modified
spectral energy distribution fitting method. The radii we measure show
an inflation of 3 - 7 per cent compared to models, but no more than
a 1 - 2 per cent intrinsic spread in the inflated sequence. We show
that we are currently able to determine M-dwarf radii to an accuracy of
2.4 per cent using our method. However, we determine that this is
limited by the precision of metallicity measurements, which contribute
1.7 per cent to the measured radius scatter. We also present
evidence that stellar magnetism is currently unable to explain radius
inflation in M-dwarfs.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
There is growing evidence that M-dwarf stars suffer radius inflation
when compared to theoretical models, suggesting that models are missing
some key physics required to completely describe stars at effective
temperatures less than about 4000 K. The advent of Gaia DR2 distances
finally makes available large data sets to determine the nature and
extent of this effect. We employ an all-sky sample, comprising of textgreater15
000 stars, to determine empirical relationships between luminosity,
temperature, and radius. This is accomplished using only geometric
distances and multiwave-band photometry, by utilizing a modified
spectral energy distribution fitting method. The radii we measure show
an inflation of 3 - 7 per cent compared to models, but no more than
a 1 - 2 per cent intrinsic spread in the inflated sequence. We show
that we are currently able to determine M-dwarf radii to an accuracy of
2.4 per cent using our method. However, we determine that this is
limited by the precision of metallicity measurements, which contribute
1.7 per cent to the measured radius scatter. We also present
evidence that stellar magnetism is currently unable to explain radius
inflation in M-dwarfs.
when compared to theoretical models, suggesting that models are missing
some key physics required to completely describe stars at effective
temperatures less than about 4000 K. The advent of Gaia DR2 distances
finally makes available large data sets to determine the nature and
extent of this effect. We employ an all-sky sample, comprising of textgreater15
000 stars, to determine empirical relationships between luminosity,
temperature, and radius. This is accomplished using only geometric
distances and multiwave-band photometry, by utilizing a modified
spectral energy distribution fitting method. The radii we measure show
an inflation of 3 - 7 per cent compared to models, but no more than
a 1 - 2 per cent intrinsic spread in the inflated sequence. We show
that we are currently able to determine M-dwarf radii to an accuracy of
2.4 per cent using our method. However, we determine that this is
limited by the precision of metallicity measurements, which contribute
1.7 per cent to the measured radius scatter. We also present
evidence that stellar magnetism is currently unable to explain radius
inflation in M-dwarfs.
11.
na, Carlos Contreras Pe; Naylor, Tim; Morrell, Sam
Determining the recurrence time-scale of long-lasting YSO outbursts Journal Article
In: Monthly Notices of the RAS, vol. 486, no. 4, pp. 4590-4611, 2019.
@article{2019MNRAS.486.4590C,
title = {Determining the recurrence time-scale of long-lasting YSO outbursts},
author = {Carlos Contreras Pe na and Tim Naylor and Sam Morrell},
doi = {10.1093/mnras/stz1019},
year = {2019},
date = {2019-07-01},
journal = {Monthly Notices of the RAS},
volume = {486},
number = {4},
pages = {4590-4611},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
12.
Cooper, Sam; Morrell, Sam; Jones, Aaron; Smetana, George; Buscicchio, Riccardo; Freise, Andreas
Chirp Gravitational Wave Alerts software
2019.
@software{sam_cooper_2019_3525064,
title = {Chirp Gravitational Wave Alerts},
author = {Sam Cooper and Sam Morrell and Aaron Jones and George Smetana and Riccardo Buscicchio and Andreas Freise},
url = {https://doi.org/10.5281/zenodo.3525064},
doi = {10.5281/zenodo.3525064},
year = {2019},
date = {2019-11-01},
publisher = {Zenodo},
keywords = {},
pubstate = {published},
tppubtype = {software}
}
2018
13.
Morrell, Sam; Barnes, William; Naylor, Tim
Solving the M Dwarf Luminosity Problem Journal Article
In: pp. 39, 2018, (Conference Name: 20th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun).
@article{morrell_solving_2018,
title = {Solving the M Dwarf Luminosity Problem},
author = {Sam Morrell and William Barnes and Tim Naylor},
url = {http://adsabs.harvard.edu/abs/2018csss.confE..39M},
doi = {10.5281/zenodo.1463024},
year = {2018},
date = {2018-07-01},
urldate = {2018-07-01},
pages = {39},
abstract = {There are troubling disagreements between model and observed parameters for M dwarf stars. These disagreements are evident in two of the most well understood open clusters in the sky; the Pleiades and Praesepe. Below about 4200K, the lower stellar sequence of both clusters diverges from theoretical isochrones (e.g. Bell et al. 2012). Using robust fitting methods, we have utilised optical to mid-infrared photometry to accurately measure the luminosity and effective temperature of a sample of M stars from these clusters, and hence determine their radii. We find that the radii are systematically inflated by at least 5 percent for a given age and luminosity when compared to the corresponding stellar model. We performed an independent check of the temperature using robust optical spectrophotometry of a sample from both clusters that spans the temperature range of the radius discrepancy. The cooler effective temperatures that result from fitting the optical/IR photometry alone match molecular and atomic features in optical spectra much more closely than the temperature provided by the isochrone. Despite this marked improvement, many molecular species still show considerable
discrepancies.Although there have been claims in the literature that M dwarfs are over radius, we show that our results, and those in the literature, could also be consistent with stars that are under luminous. This finding has important implications for stellar evolution and the radii of exoplanets.},
note = {Conference Name: 20th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
There are troubling disagreements between model and observed parameters for M dwarf stars. These disagreements are evident in two of the most well understood open clusters in the sky; the Pleiades and Praesepe. Below about 4200K, the lower stellar sequence of both clusters diverges from theoretical isochrones (e.g. Bell et al. 2012). Using robust fitting methods, we have utilised optical to mid-infrared photometry to accurately measure the luminosity and effective temperature of a sample of M stars from these clusters, and hence determine their radii. We find that the radii are systematically inflated by at least 5 percent for a given age and luminosity when compared to the corresponding stellar model. We performed an independent check of the temperature using robust optical spectrophotometry of a sample from both clusters that spans the temperature range of the radius discrepancy. The cooler effective temperatures that result from fitting the optical/IR photometry alone match molecular and atomic features in optical spectra much more closely than the temperature provided by the isochrone. Despite this marked improvement, many molecular species still show considerable
discrepancies.Although there have been claims in the literature that M dwarfs are over radius, we show that our results, and those in the literature, could also be consistent with stars that are under luminous. This finding has important implications for stellar evolution and the radii of exoplanets.
discrepancies.Although there have been claims in the literature that M dwarfs are over radius, we show that our results, and those in the literature, could also be consistent with stars that are under luminous. This finding has important implications for stellar evolution and the radii of exoplanets.
14.
Hillenbrand, Lynne A.; na, Carlos Contreras Pe; Morrell, Sam; Naylor, Tim; Kuhn, Michael A.; Cutri, Roc M.; Rebull, Luisa M.; Hodgkin, Simon; Froebrich, Dirk; Mainzer, Amy K.
Gaia 17bpi: An FU Ori-type Outburst Journal Article
In: Astrophysical Journal, vol. 869, no. 2, pp. 146, 2018.
@article{2018ApJ...869..146H,
title = {Gaia 17bpi: An FU Ori-type Outburst},
author = {Lynne A. Hillenbrand and Carlos Contreras Pe na and Sam Morrell and Tim Naylor and Michael A. Kuhn and Roc M. Cutri and Luisa M. Rebull and Simon Hodgkin and Dirk Froebrich and Amy K. Mainzer},
doi = {10.3847/1538-4357/aaf414},
year = {2018},
date = {2018-12-01},
journal = {Astrophysical Journal},
volume = {869},
number = {2},
pages = {146},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
15.
Morrell, Sam; Barnes, William; Naylor, Tim
Solving the M Dwarf Luminosity Problem Miscellaneous
2018.
@misc{morrell_sam_2018_1463024,
title = {Solving the M Dwarf Luminosity Problem},
author = {Sam Morrell and William Barnes and Tim Naylor},
url = {https://doi.org/10.5281/zenodo.1463024},
doi = {10.5281/zenodo.1463024},
year = {2018},
date = {2018-10-01},
publisher = {Zenodo},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
