arXiv subjects

Peter P. Pedersen

Publications and source records attributed to Peter P. Pedersen.

At least 19 recordsLinked to original sources

arXiv2026

DUET: Design of a simultaneous InGaAs--CCD split-beam imager for ultra-cool dwarf exoplanet transit survey

We present the design of DUET, a dual-channel imager being built for the SPECULOOS-Southern Observatory (SSO) to detect and characterise transiting terrestrial exoplanets orbiting ultra-cool dwarfs. A dichroic beamsplitter at 955\,nm directs visible light to a deeply-depleted silicon CCD and near-infrared light to a CMOS-based InGaAs detector, enabling fully simultaneous photometry with bandpasses from 0.4 to 1.7\,\textmu m. The near-infrared filters have been chosen to suppress sensitivity to atmospheric precipitable water vapour (PWV) variability, a dominant source of correlated noise in ground-based infrared photometry of cool stars. We describe the optical and mechanical architecture, the dichroic and filter selection, the choice of detectors, and the control system.

astro-ph.IM↗

arXiv2026

MIRA: a data management and education platform connecting students to robotic telescopes

Hands-on telescope experience is often used to drive student engagement in astronomy education, but scaling access to larger groups of students is operationally challenging. Consequently, students encounter only a fraction of the professional workflow, rarely engaging with the rigorous peer-review, time-allocation processes, or automated data reduction pipelines that govern modern research facilities. We present the design of MIRA (Mentored Investigations using Robotic Astronomy), a data management and educational platform that connects Swiss secondary school and undergraduate students with operational robotic observatories. MIRA structures the entire observation lifecycle: proposal, review, acceptance/rejection, scheduling, and observation. Following execution, the platform automatically reduces raw FITS frames (including astrometric calibration and photometry) and serves them via a web-accessible archive accompanied by Python-based analysis tutorials. By separating educational front-ends from low-level telescope controls through Astra and ASCOM Alpaca, MIRA delivers an authentic scientific research workflow that bridges classroom learning with professional observatory operations.

astro-ph.IM↗

arXiv2026

Astra: an open-source fully autonomous robotic observatory control software

Robotic and autonomous observatories are critical for modern time-domain and high-cadence astronomical surveys. The operation of these facilities requires complex software coordination to manage hardware, schedule observations, and ensure safety. However, existing observatory control software are often proprietary and platform-locked or require complex message-brokering infrastructure. Here we present Astra (Automated Survey observaTory Robotised with Alpaca): an open-source, cross-platform Python system for the sustained, fully autonomous operation of astronomical observatories, requiring no external message-broker infrastructure. Astra controls observatory hardware via the ASCOM Alpaca protocol, and executes prescheduled observatory actions under continuous safety supervision. Its multi-device actions include plate-solve-based pointing correction with a local Gaia--2MASS catalogue fallback, PID-controlled autoguiding, and autofocus. A FastAPI web service provides a browser UI, REST and WebSocket APIs for real-time status, image previews, and SQLite-backed telemetry and logs. Astra has run in fully unattended production since January 2024, scaling to six telescopes across three facilities: the SPECULOOS-South network (4 $\times$ 1\,m class, Chile), SAINT-EX (1\,m class, Mexico), and the ETH Observatory (0.5\,m class, Switzerland), with no schedule aborts attributable to Astra software. Across the SPECULOOS-South network, it achieves sub-arcsecond autoguiding (0.11\unit{\arcsecond} median pointing scatter) and plate-solve failure rates below 1\% on three of the four telescopes (3\% on the narrowest-field unit), demonstrating that an open, standards-based software stack can meet the reliability demands of production survey astronomy.

astro-ph.IM↗

arXiv2026

A Previously Underexplored Regime in TESS: Minute-Scale Eclipses Reveal Ten White Dwarf-Cool M-Dwarf Binaries

Short-period white-dwarf (WD) binaries are post-common-envelope systems that constrain orbital shrinkage, envelope evolution, and the survival of low-mass companions. We report the discovery and confirmation of ten fully eclipsing short-period WD + cool M-dwarf binaries identified through a tailored search for minute-scale eclipses in Transiting Exoplanet Survey Satellite (TESS) high-cadence data and validated with SPECULOOS multi-band photometry. The systems have orbital periods of a few hours and companions with effective temperatures of 2700-3400 K. These discoveries demonstrate that TESS contains a previously underexplored population of compact WD binaries whose short-duration, high-frequency, and often diluted eclipse signals are not efficiently recovered by standard transit-search pipelines. Whereas the literature contained only one eclipsing WD+M binary reported as a TESS-based discovery, our pilot search of $\sim3.7\times10^4$ Gaia-selected WDs yields ten new confirmed systems, increasing the TESS-discovered sample by an order of magnitude. SPECULOOS follow-up confirms the eclipses occur on target and uses chromatic eclipse dilution to distinguish stellar from substellar companions. We combine multi-band eclipse photometry with Bayesian spectral energy distribution modeling to derive self-consistent WD and companion parameters. The resulting systems expand the known population of fully eclipsing WD+M binaries and notably double the number of systems in temperature regimes corresponding to M4 and M7 companions. This work establishes a scalable framework for identifying compact WD binaries in time-domain photometric surveys. Applied to TESS archival data across the full Gaia WD-candidate catalog ($\sim1.3\times10^6$ sources), this approach opens the prospect of assembling a population large enough to constrain post-common-envelope evolution and the stellar-substellar transition.

astro-ph.SR↗

arXiv2026

Two temperate Earth- and Neptune-sized planets orbiting fully convective M dwarfs

As the diversity of exoplanets continues to grow, it is important to revisit assumptions about habitability and classical HZ definitions. In this work, we introduce an expanded 'temperate' zone, defined by instellation fluxes between $0.1<S/\mathrm{S}_\oplus<5$, thus encompassing a broader range of potentially habitable worlds. We also introduce the TEMPOS survey, which aims to produce a catalogue of precise radii for temperate planets orbiting M dwarfs with $T_\mathrm{eff}\leq3400\,$ K. This work reports the discovery and characterisation of two planets in this temperate regime orbiting mid-type M dwarfs: TOI-6716\,b, a $0.98\pm0.07\,\mathrm{R}_\oplus$ planet orbiting its M4 host star ($R_\star=0.231\,\pm0.015\mathrm{R}_\odot$, $M_\star=0.223\pm0.011\,\mathrm{M}_\odot$, $T_\mathrm{eff}=3110\pm80\,\mathrm{K}$) with a period $P=4.7185898^{+0.0000054}_{-0.0000041}\,\mathrm{d}$, and TOI-7384 b, a $3.56\pm0.21\,\mathrm{R}_\oplus$ planet orbiting an M4 ($R_\star=0.319\,\pm0.018\mathrm{R}_\odot$, $M_\star=0.318\pm0.016\,\mathrm{M}_\odot$, $T_\mathrm{eff}=3185\pm75\,\mathrm{K}$) star every $P=6.2340258^{+0.0000034}_{-0.0000036}\,\mathrm{d}$. The radii of TOI-6716 b and TOI-7384 b have precisions of $6.8\%$ and $5.9\%$ respectively. We validate these planets with multi-band ground-based photometric observations, high-resolution imaging and statistical analyses. We find these planets to have instellation fluxes close to the inner (hotter) edge of the temperate zone, with $4.4\pm1.1\,\mathrm{S}_\oplus$ and $4.9\pm1.1\,\mathrm{S}_\oplus$ for TOI-6716 b and TOI-7384 b respectively. Also, with a predicted TSM similar to the TRAPPIST-1 planets, TOI-6716 b is likely to be a good rocky-world JWST target, should it have retained its atmosphere.

astro-ph.EP↗

arXiv2025

TOI-7166 b: A Habitable Zone mini-Neptune planet around a nearby low-mass star

We present the discovery and validation of TOI-7166b, a 2.01+/-0.05R_Earth planet orbiting a nearby low-mass star. We validated the planet by combining TESS and multi-color high-precision photometric observations from ground-based telescopes, together with spectroscopic data, high-contrast imaging, archival images, and statistical arguments. The host star is an M4-type dwarf at a distance of ~35 pc from the Sun. It has a mass and a radius of Ms=0.190+/-0.004M_Sun and Rs=0.222+/-0.005R_Sun, respectively. TOI-7166b has an orbital period of 12.9 days, which places it close to the inner edge of the Habitable Zone of its host star, receiving an insolation flux of Sp=1.07+/-0.08S_Earth and an equilibrium temperature of Teq=249+/-5K (assuming a null Bond albedo). The brightness of the host star makes TOI-7166 a suitable target for radial velocity follow-up to measure the planetary mass and bulk density. Moreover, the physical parameters of the system including the infrared brightness (Kmag = 10.6) of the star and the planet-to-star radius ratio (0.0823+/-0.0012) make TOI-7166b an exquisite target for transmission spectroscopic observations with the JWST, to constrain the exoplanet atmospheric compositions.

astro-ph.EP↗

arXiv2025

Resolving star spots on WASP-85 A using high-resolution transit spectroscopy

Stellar surface inhomogeneities such as spots and faculae introduce Doppler variations that challenge exoplanet detection via the radial velocity method. While their impact on disc-integrated spectra is well established, detailed studies of the underlying local line profiles have so far been limited to the Sun. We present an observational campaign targeting the active star WASP-85 A during transits of its hot Jupiter companion. The transits span two stellar rotation periods, allowing us to probe the evolution of active regions. From ground-based photometry we identify seven active regions, six containing dark spots. Using simultaneous ESPRESSO transit spectroscopy, we spatially resolve these regions on the stellar surface by using the planet as a probe. We detect significant bisector shape changes, line broadening, and net redshifts during spot occultations, with velocity shifts of 108-333 m/s (mean uncertainty 50 m/s). The observed broadening is consistent with the Zeeman effect, implying magnetic field strengths (Stokes $I$) $B$ = 2.7-4.4 kG (mean uncertainty 0.6 kG), comparable to solar umbrae. Combined with our photometric spot model, this yields lower limits to the disc-integrated field $Bf = 16 \pm 3$ G and $61 \pm 9$ G for the two hemispheres probed -- at least three times higher than Sun-as-a-star values. We also measure centre-to-limb variations in FWHM, line depth, equivalent width, and convective blueshift, which broadly agree with solar observations and 3D MHD models. This work demonstrates a new way to characterise the surfaces of exoplanet host stars, paving the way for future analyses incorporating synthetic line profiles from 3D MHD simulations.

astro-ph.EP↗

arXiv2025

Detecting Urban PM$_{2.5}$ Hotspots with Mobile Sensing and Gaussian Process Regression

Low-cost mobile sensors can be used to collect PM$_{2.5}$ concentration data throughout an entire city. However, identifying air pollution hotspots from the data is challenging due to the uneven spatial sampling, temporal variations in the background air quality, and the dynamism of urban air pollution sources. This study proposes a method to identify urban PM$_{2.5}$ hotspots that addresses these challenges, involving four steps: (1) equip citizen scientists with mobile PM$_{2.5}$ sensors while they travel; (2) normalise the raw data to remove the influence of background ambient pollution levels; (3) fit a Gaussian process regression model to the normalised data and (4) calculate a grid of spatially explicit 'hotspot scores' using the probabilistic framework of Gaussian processes, which conveniently summarise the relative pollution levels throughout the city. We apply our method to create the first ever map of PM$_{2.5}$ pollution in Kigali, Rwanda, at a 200m resolution. Our results suggest that the level of ambient PM$_{2.5}$ pollution in Kigali is dangerously high, and we identify the hotspots in Kigali where pollution consistently exceeds the city-wide average. We also evaluate our method using simulated mobile sensing data for Beijing, China, where we find that the hotspot scores are probabilistically well calibrated and accurately reflect the 'ground truth' spatial profile of PM$_{2.5}$ pollution. Thanks to the use of open-source software, our method can be re-applied in cities throughout the world with a handful of low-cost sensors. The method can help fill the gap in urban air quality information and empower public health officials.

cs.LG↗

arXiv2024

Infrared photometry with InGaAs detectors: First light with SPECULOOS

We present the photometric performance of SPIRIT, a ground-based near-infrared InGaAs CMOS-based instrument (1280 by 1024 pixels, 12 micron pitch), using on-sky results from the SPECULOOS-Southern Observatory during 2022 - 2023. SPIRIT was specifically designed to optimise time-series photometric precision for observing late M and L type stars. To achieve this, a custom wide-pass filter (0.81 - 1.33 microns, zYJ ) was used, which was also designed to minimise the effects of atmospheric precipitable water vapour (PWV) variability on differential photometry. Additionally, SPIRIT was designed to be maintenance-free by eliminating the need for liquid nitrogen for cooling. We compared SPIRIT's performance with a deeply-depleted (2048 by 2048 pixels, 13.5 micron pitch) CCD-based instrument (using an I+z' filter, 0.7 - 1.1 microns) through simultaneous observations. For L type stars and cooler, SPIRIT exhibited better photometric noise performance compared to the CCD-based instrument. The custom filter also significantly minimised red noise in the observed light curves typically introduced by atmospheric PWV variability. In SPIRIT observations, the detector's read noise was the dominant limitation, although in some cases, we were limited by the lack of comparison stars.

astro-ph.IM↗

arXiv2024

Detection of an Earth-sized exoplanet orbiting the nearby ultracool dwarf star SPECULOOS-3

Located at the bottom of the main sequence, ultracool dwarf stars are widespread in the solar neighbourhood. Nevertheless, their extremely low luminosity has left their planetary population largely unexplored, and only one of them, TRAPPIST-1, has so far been found to host a transiting planetary system. In this context, we present the SPECULOOS project's detection of an Earth-sized planet in a 17 h orbit around an ultracool dwarf of M6.5 spectral type located 16.8 pc away. The planet's high irradiation (16 times that of Earth) combined with the infrared luminosity and Jupiter-like size of its host star make it one of the most promising rocky exoplanet targets for detailed emission spectroscopy characterization with JWST. Indeed, our sensitivity study shows that just ten secondary eclipse observations with the Mid-InfraRed Instrument/Low-Resolution Spectrometer on board JWST should provide strong constraints on its atmospheric composition and/or surface mineralogy.

astro-ph.EP↗

arXiv2023

An M dwarf accompanied by a close-in giant orbiter with SPECULOOS

In the last decade, a dozen close-in giant planets have been discovered orbiting stars with spectral types ranging from M0 to M4, a mystery since known formation pathways do not predict the existence of such systems. Here, we confirm TOI-4860 b, a Jupiter-sized planet orbiting an M4.5 host, a star at the transition between fully and partially convective interiors. First identified with TESS data, we validate the transiting companion's planetary nature through multicolour photometry from the TRAPPIST-South/North, SPECULOOS, and MuSCAT3 facilities. Our analysis yields a radius of $0.76 \pm 0.02~ \rm R_{Jup}$ for the planet, a mass of $0.34~\rm M_\odot$ for the star, and an orbital period of 1.52 d. Using the newly commissioned SPIRIT InGaAs camera at the SPECULOOS-South Observatory, we collect infrared photometry in zYJ that spans the time of secondary eclipse. These observations do not detect a secondary eclipse, placing an upper limit on the brightness of the companion. The planetary nature of the companion is further confirmed through high-resolution spectroscopy obtained with the IRD spectrograph at Subaru Telescope, from which we measure a mass of $0.67 \pm 0.14~\rm M_{Jup}$ . Based on its overall density, TOI-4860 b appears to be rich in heavy elements, like its host star.

astro-ph.EP↗

arXiv2023

A 1.55 R$_{\oplus}$ habitable-zone planet hosted by TOI-715, an M4 star near the ecliptic South Pole

A new generation of observatories is enabling detailed study of exoplanetary atmospheres and the diversity of alien climates, allowing us to seek evidence for extraterrestrial biological and geological processes. Now is therefore the time to identify the most unique planets to be characterised with these instruments. In this context, we report on the discovery and validation of TOI-715 b, a $R_{\rm b}=1.55\pm 0.06\rm R_{\oplus}$ planet orbiting its nearby ($42$ pc) M4 host (TOI-715/TIC 271971130) with a period $P_{\rm b} = 19.288004_{-0.000024}^{+0.000027}$ days. TOI-715 b was first identified by TESS and validated using ground-based photometry, high-resolution imaging and statistical validation. The planet's orbital period combined with the stellar effective temperature $T_{\rm eff}=3075\pm75~\rm K$ give this planet an instellation $S_{\rm b} = 0.67_{-0.20}^{+0.15}~\rm S_\oplus$, placing it within the most conservative definitions of the habitable zone for rocky planets. TOI-715 b's radius falls exactly between two measured locations of the M-dwarf radius valley; characterising its mass and composition will help understand the true nature of the radius valley for low-mass stars. We demonstrate TOI-715 b is amenable for characterisation using precise radial velocities and transmission spectroscopy. Additionally, we reveal a second candidate planet in the system, TIC 271971130.02, with a potential orbital period of $P_{02} = 25.60712_{-0.00036}^{+0.00031}$ days and a radius of $R_{02} = 1.066\pm0.092\,\rm R_{\oplus}$, just inside the outer boundary of the habitable zone, and near a 4:3 orbital period commensurability. Should this second planet be confirmed, it would represent the smallest habitable zone planet discovered by TESS to date.

astro-ph.EP↗

arXiv2022

Precise near-infrared photometry, accounting for precipitable water vapour at SPECULOOS Southern Observatory

The variability induced by precipitable water vapour (PWV) can heavily affect the accuracy of time-series photometric measurements gathered from the ground, especially in the near-infrared. We present here a novel method of modelling and mitigating this variability, as well as open-sourcing the developed tool -- Umbrella. In this study, we evaluate the extent to which the photometry in three common bandpasses (r', i', z'), and SPECULOOS' primary bandpass (I+z'), are photometrically affected by PWV variability. In this selection of bandpasses, the I+z' bandpass was found to be most sensitive to PWV variability, followed by z', i', and r'. The correction was evaluated on global light curves of nearby late M- and L-type stars observed by SPECULOOS' Southern Observatory (SSO) with the I+z' bandpass, using PWV measurements from the LHATPRO and local temperature/humidity sensors. A median reduction in RMS of 1.1% was observed for variability shorter than the expected transit duration for SSO's targets. On timescales longer than the expected transit duration, where long-term variability may be induced, a median reduction in RMS of 53.8% was observed for the same method of correction.

astro-ph.IM↗

arXiv2022

SPECULOOS Northern Observatory: searching for red worlds in the northern skies

SPECULOOS is a ground-based transit survey consisting of six identical 1-m robotic telescopes. The immediate goal of the project is to detect temperate terrestrial planets transiting nearby ultracool dwarfs (late M-dwarf stars and brown dwarfs), which could be amenable for atmospheric research with the next generation of telescopes. Here, we report the developments of the northern counterpart of the project - SPECULOOS Northern Observatory, and present its performance during the first three years of operations from mid-2019 to mid-2022. Currently, the observatory consists of one telescope, which is named Artemis. The Artemis telescope demonstrates remarkable photometric precision, allowing it to be ready to detect new transiting terrestrial exoplanets around ultracool dwarfs. Over the period of the first three years after the installation, we observed 96 objects from the SPECULOOS target list for 6000 hours with a typical photometric precision of $0.5\%$, and reaching a precision of $0.2\%$ for relatively bright non-variable targets with a typical exposure time of 25 sec. Our weather downtime (clouds, high wind speed, high humidity, precipitation and/or high concentration of dust particles in the air) over the period of three years was 30% of overall night time. Our actual downtime is 40% because of additional time loss associated with technical problems.

astro-ph.IM↗

arXiv2022

TESS discovery of a sub-Neptune orbiting a mid-M dwarf TOI-2136

We present the discovery of TOI-2136b, a sub-Neptune planet transiting every 7.85 days a nearby M4.5V-type star, identified through photometric measurements from the TESS mission. The host star is located $33$ pc away with a radius of $R_{\ast} = 0.34\pm0.02\ R_{\odot}$, a mass of $0.34\pm0.02\ M_{\odot}$ and an effective temperature of $\rm 3342\pm100\ K$. We estimate its stellar rotation period to be $75\pm5$ days based on archival long-term photometry. We confirm and characterize the planet based on a series of ground-based multi-wavelength photometry, high-angular-resolution imaging observations, and precise radial velocities from CFHT/SPIRou. Our joint analysis reveals that the planet has a radius of $2.19\pm0.17\ R_{\oplus}$, and a mass measurement of $6.4\pm2.4\ M_{\oplus}$. The mass and radius of TOI2136b is consistent with a broad range of compositions, from water-ice to gas-dominated worlds. TOI-2136b falls close to the radius valley for low-mass stars predicted by the thermally driven atmospheric mass loss models, making it an interesting target for future studies of its interior structure and atmospheric properties.

astro-ph.EP↗

arXiv2021

NGTS clusters survey -- III: A low-mass eclipsing binary in the Blanco 1 open cluster spanning the fully convective boundary

We present the discovery and characterisation of an eclipsing binary identified by the Next Generation Transit Survey in the $\sim$115 Myr old Blanco 1 open cluster. NGTS J0002-29 comprises three M dwarfs: a short-period binary and a companion in a wider orbit. This system is the first well-characterised, low-mass eclipsing binary in Blanco 1. With a low mass ratio, a tertiary companion and binary components that straddle the fully convective boundary, it is an important benchmark system, and one of only two well-characterised, low-mass eclipsing binaries at this age. We simultaneously model light curves from NGTS, TESS, SPECULOOS and SAAO, radial velocities from VLT/UVES and Keck/HIRES, and the system's spectral energy distribution. We find that the binary components travel on circular orbits around their common centre of mass in $P_{\rm orb} = 1.09800524 \pm 0.00000038$ days, and have masses $M_{\rm pri}=0.3978\pm 0.0033$ M$_{\odot}$ and $M_{\rm sec}=0.2245\pm 0.0018$ M$_{\odot}$, radii $R_{\rm pri}=0.4037\pm 0.0048$ R$_{\odot}$ and $R_{\rm sec}=0.2759\pm 0.0055$ R$_{\odot}$, and effective temperatures $T_{\rm pri}=3372\,^{+44}_{-37}$ K and $T_{\rm sec}=3231\,^{+38}_{-31}$ K. We compare these properties to the predictions of seven stellar evolution models, which typically imply an inflated primary. The system joins a list of 19 well-characterised, low-mass, sub-Gyr, stellar-mass eclipsing binaries, which constitute some of the strongest observational tests of stellar evolution theory at low masses and young ages.

astro-ph.SR↗

arXiv2021

A transit timing variation observed for the long-period extremely low density exoplanet HIP 41378f

HIP 41378 f is a temperate $9.2\pm0.1 R_{\oplus}$ planet with period of 542.08 days and an extremely low density of $0.09\pm0.02$ g cm$^{-3}$. It transits the bright star HIP 41378 (V=8.93), making it an exciting target for atmospheric characterization including transmission spectroscopy. HIP 41378 was monitored photometrically between the dates of 2019 November 19 and November 28. We detected a transit of HIP 41378 f with NGTS, just the third transit ever detected for this planet, which confirms the orbital period. This is also the first ground-based detection of a transit of HIP 41378 f. Additional ground-based photometry was also obtained and used to constrain the time of the transit. The transit was measured to occur 1.50 hours earlier than predicted. We use an analytic transit timing variation (TTV) model to show the observed TTV can be explained by interactions between HIP 41378 e and HIP 41378 f. Using our TTV model, we predict the epochs of future transits of HIP 41378 f, with derived transit centres of T$_{C,4} = 2459355.087^{+0.031}_{-0.022}$ (May 2021) and T$_{C,5} = 2459897.078^{+0.114}_{-0.060}$ (Nov 2022).

astro-ph.EP↗

arXiv2020

$π$ Earth: a 3.14-day Earth-sized Planet from $\textit{K2}$'s Kitchen Served Warm by the SPECULOOS Team

We report on the discovery of a transiting Earth-sized (0.95$R_\oplus$) planet around an M3.5 dwarf star at 57$\,$pc, K2-315b. The planet has a period of $\sim$3.14 days, i.e. ${\sim}π$, with an instellation of 7.45$\,$S$_{\oplus}$. The detection was made using publicly available data from $\textit{K2}$'s Campaign 15. We observed three additional transits with SPECULOOS Southern and Northern Observatories, and a stellar spectrum from Keck/HIRES, which allowed us to validate the planetary nature of the signal. The confirmed planet is well suited for comparative terrestrial exoplanetology. While exoplanets transiting ultracool dwarfs present the best opportunity for atmospheric studies of terrestrial exoplanets with the $\textit{James Webb Space Telescope}$, those orbiting mid-M dwarfs within 100$\,$pc such as K2-315b will become increasingly accessible with the next generation of observatories.

astro-ph.EP↗