26 research outputs found
Eclipse, transit and occultation geometry of planetary systems at exo-syzygy
Although conjunctions and oppositions frequently occur in planetary systems, eclipserelated phenomena are usually described from an Earth-centric perspective. Space missions to different parts of the Solar system, as well as the mounting number of known exo-planets in habitable zones and the possibility of sending featherweight robot
spacecraft to them, prompt broader considerations. Here, we derive the geometry of eclipses, transits and occultations from a primarily exo-Earth viewpoint, and apply the formulation to the Solar system and three types of three-body extrasolar planetary systems: with 1 star and 2 planets (Case I), with 2 stars and 1 planet (Case II), and
with 1 planet, 1 star and 1 moon (Case III). We derive the general conditions for total, partial and annular eclipses to occur at exo-syzygy, and implement them in each case in concert with stability criteria. We then apply the formalism to the TRAPPIST-1, Kepler-444 and Kepler-77 systems – the first of which contains multiple potentially
habitable planets – and provide reference tables of both Solar system and TRAPPIST- 1 syzygy properties. We conclude by detailing a basic algebraic algorithm which can be used to quickly characterize eclipse properties in any three-body system
Periodicities in the K2 light curve of HP Librae
We analyse Kepler/K2 light-curve data of the AM CVn system HP Librae (HP Lib). We detect with confidence four photometric periodicities in the system: the orbital frequency, both positive and negative superhumps, and the positive apsidal precession frequency of the accretion disc. This is only the second time that the apsidal precession frequency has ever been directly detected in the photometry of a helium accreting system, after SDSS J135154.46-064309.0. We present phase-folded light curves and sliding power spectra of each of the four periodicities. We measure rates of change of the positive superhump period of ∼10−7 d. We also redetect a quasi-periodic oscillation (QPO) at ∼300 cyc d–1, a feature that has been stable over decades, and show that it is harmonically related to two other QPOs, the lowest of which is centred on the superhump/orbital frequency. The continuum power spectrum is consistent with a single power law with no evidence of any breaks within our observed frequency range
The frequency of gaseous debris discs around white dwarfs
1-3 per cent of white dwarfs are orbited by planetary dusty debris detectable
as infrared emission in excess above the white dwarf flux. In a rare subset of
these systems, a gaseous disc component is also detected via emission lines of
the Ca II 8600\r{A} triplet, broadened by the Keplerian velocity of the disc.
We present the first statistical study of the fraction of debris discs
containing detectable amounts of gas in emission at white dwarfs within a
magnitude and signal-to-noise limited sample. We select 7705 single white
dwarfs spectroscopically observed by the Sloan Digital Sky Survey (SDSS) and
with magnitudes 19. We identify five gaseous disc hosts, all
of which have been previously discovered. We calculate the occurrence rate of a
white dwarf hosting a debris disc detectable via Ca II emission lines as
0.067 per cent. This corresponds to an occurrence rate
for a dusty debris disc to have an observable gaseous component in emission as
4 per cent. Given that variability is a common feature of the
emission profiles of gaseous debris discs, and the recent detection of a
planetesimal orbiting within the disc of SDSSJ122859.93+104032.9, we propose
that gaseous components are tracers for the presence of planetesimals embedded
in the discs and outline a qualitative model. We also present spectroscopy of
the Ca II triplet 8600\r{A} region for 20 white dwarfs hosting dusty debris
discs in an attempt to identify gaseous emission. We do not detect any gaseous
components in these 20 systems, consistent with the occurrence rate that we
calculated.Comment: 13 pages, 6 Figures, accepted for publication in MNRA
A catalogue of cataclysmic variables from 20 years of the Sloan Digital Sky Survey with new classifications, periods, trends and oddities
We present a catalogue of 507 cataclysmic variables (CVs) observed in SDSS I
to IV including 70 new classifications collated from multiple archival data
sets. This represents the largest sample of CVs with high-quality and
homogeneous optical spectroscopy. We have used this sample to derive unbiased
space densities and period distributions for the major sub-types of CVs. We
also report on some peculiar CVs, period bouncers and also CVs exhibiting large
changes in accretion rates. We report 70 new CVs, 59 new periods, 178
unpublished spectra and 262 new or updated classifications. From the SDSS
spectroscopy, we also identified 18 systems incorrectly identified as CVs in
the literature. We discuss the observed properties of 13 peculiar CVS, and we
identify a small set of eight CVs that defy the standard classification scheme.
We use this sample to investigate the distribution of different CV sub-types,
and we estimate their individual space densities, as well as that of the entire
CV population. The SDSS I to IV sample includes 14 period bounce CVs or
candidates. We discuss the variability of CVs across the Hertzsprung-Russell
diagram, highlighting selection biases of variability-based CV detection.
Finally, we searched for, and found eight tertiary companions to the SDSS CVs.
We anticipate that this catalogue and the extensive material included in the
Supplementary Data will be useful for a range of observational population
studies of CVs.Comment: Submitted to MNRAS. Supplementary information available at
https://warwick.ac.uk/fac/sci/physics/research/astro/people/keithinight/sdss_paper_supplementary_informatio
The frequency of gaseous debris discs around white dwarfs
A total of 1–3 per cent of white dwarfs are orbited by planetary dusty debris detectable as infrared emission in excess above the white dwarf flux. In a rare subset of these systems, a gaseous disc component is also detected via emission lines of the Ca ii 8600 Å triplet, broadened by the Keplerian velocity of the disc. We present the first statistical study of the fraction of debris discs containing detectable amounts of gas in emission at white dwarfs within a magnitude and signal-to-noise ratio limited sample. We select 7705 single white dwarfs spectroscopically observed by the Sloan Digital Sky Survey (SDSS) and Gaia with magnitudes g ≤ 19. We identify five gaseous disc hosts, all of which have been previously discovered. We calculate the occurrence rate of a white dwarf hosting a debris disc detectable via Ca ii emission lines as 0.067±0.0420.025 per cent. This corresponds to an occurrence rate for a dusty debris disc to have an observable gaseous component in emission as 4 ± 42 per cent. Given that variability is a common feature of the emission profiles of gaseous debris discs, and the recent detection of a planetesimal orbiting within the disc of SDSS J122859.93+104032.9, we propose that gaseous components are tracers for the presence of planetesimals embedded in the discs and outline a qualitative model. We also present spectroscopy of the Ca ii triplet 8600 Å region for 20 white dwarfs hosting dusty debris discs in an attempt to identify gaseous emission. We do not detect any gaseous components in these 20 systems, consistent with the occurrence rate that we calculated
An irradiated-Jupiter analogue hotter than the Sun
Planets orbiting close to hot stars experience intense extreme-ultraviolet
radiation, potentially leading to atmosphere evaporation and to thermal
dissociation of molecules. However, this extreme regime remains mainly
unexplored due to observational challenges. Only a single known ultra-hot giant
planet, KELT-9b, receives enough ultraviolet radiation for molecular
dissociation, with a day-side temperature of ~4,600K. An alternative approach
uses irradiated brown dwarfs as hot-Jupiter analogues. With atmospheres and
radii similar to those of giant planets, brown dwarfs orbiting close to hot
Earth-sized white-dwarf stars can be directly detected above the glare of the
star. Here we report observations revealing an extremely irradiated low-mass
companion to the hot white dwarf WD0032-317. Our analysis indicates a day-side
temperature of ~8,000K, and a day-to-night temperature difference of ~6,000K.
The amount of extreme-ultraviolet radiation (with wavelengths 100-912\r{A})
received by WD0032-317B is equivalent to that received by planets orbiting
close to stars as hot as a late B-type stars, and about 5,600 times higher than
that of KELT-9b. With a mass of ~75-88 Jupiter masses, this
near-hydrogen-burning-limit object is potentially one of the most massive brown
dwarfs known.Comment: Authors' version of the article published in Nature Astronomy (DOI
https://doi.org/10.1038/s41550-023-02048-z
The 2003 Shell Event in eta Carinae
Near-infrared, JHKL, photometry of eta Car is reported covering the period
2000 to 2004. This includes the 2003 shell event which was the subject of an
international multi-wavelength campaign. The fading that accompanied this event
was similar to, although slightly deeper than, that which accompanied the
previous one. The period between these events is 2023+/-3 days and they are
strictly periodic. Their cause, as well as that of the quasi-periodic
variations and secular brightening are discussed. It seems possible that all
three types of variability are consequences of the binary nature of the star.Comment: 11 pages, 5 figures, to appear in MNRA
Properties of an Eclipsing Double White Dwarf Binary NLTT 11748
We present high-quality ULTRACAM photometry of the eclipsing detached double white dwarf binary NLTT 11748. This system consists of a carbon/oxygen white dwarf and an extremely low mass (1.5 yr, we constrain the masses and radii of both objects in the NLTT 11748 system to a statistical uncertainty of a few percent. However, we find that overall uncertainty in the thickness of the envelope of the secondary carbon/oxygen white dwarf leads to a larger (≈13%) systematic uncertainty in the primary He WD's mass. Over the full range of possible envelope thicknesses, we find that our primary mass (0.136-0.162 M_☉) and surface gravity (log (g) = 6.32-6.38; radii are 0.0423-0.0433 R_☉) constraints do not agree with previous spectroscopic determinations. We use precise eclipse timing to detect the Rømer delay at 7σ significance, providing an additional weak constraint on the masses and limiting the eccentricity to ecos ω = (– 4 ± 5) × 10^(–5). Finally, we use multicolor data to constrain the secondary's effective temperature (7600 ± 120 K) and cooling age (1.6-1.7 Gyr)
An Eclipsing 47 minute Double White Dwarf Binary at 400 pc
We present the discovery of the eclipsing double white dwarf (WD) binary WDJ
022558.21-692025.38 that has an orbital period of 47.19 min. Following
identification with the Transiting Exoplanet Survey Satellite, we obtained
time-series ground based spectroscopy and high-speed multi-band ULTRACAM
photometry which indicate a primary DA WD of mass 0.40 +- 0.04 Msol and a 0.28
+- 0.02 Msol mass secondary WD, which is likely of type DA as well. The system
becomes the third-closest eclipsing double WD binary discovered with a distance
of approximately 400 pc and will be a detectable source for upcoming
gravitational wave detectors in the mHz frequency range. Its orbital decay will
be measurable photometrically within 10 yrs to a precision of better than 1%.
The fate of the binary is to merge in approximately 41 Myr, likely forming a
single, more massive WD.Comment: Accepted for publication in MNRAS, 8 pages + 2 appendix pages, 6
figure
TIC 378898110: A Bright, Short-Period AM CVn Binary in TESS
AM CVn-type systems are ultracompact, helium-accreting binary systems which
are evolutionarily linked to the progenitors of thermonuclear supernovae and
are expected to be strong Galactic sources of gravitational waves detectable to
upcoming space-based interferometers. AM CVn binaries with orbital periods
20--23 min exist in a constant high state with a permanently ionised
accretion disc. We present the discovery of TIC 378898110, a bright (
mag), nearby ( pc), high-state AM CVn binary discovered in TESS
two-minute-cadence photometry. At optical wavelengths this is the
third-brightest AM CVn binary known. The photometry of the system shows a
23.07172(6) min periodicity, which is likely to be the `superhump' period and
implies an orbital period in the range 22--23 min. There is no detectable
spectroscopic variability. The system underwent an unusual, year-long
brightening event during which the dominant photometric period changed to a
shorter period (constrained to min), which we suggest may be
evidence for the onset of disc-edge eclipses. The estimated mass transfer rate,
, is
unusually high and may suggest a high-mass or thermally inflated donor. The
binary is detected as an X-ray source, with a flux of erg cm s in the 0.3--10 keV range. TIC 378898110
is the shortest-period binary system discovered with TESS, and its large
predicted gravitational-wave amplitude makes it a compelling verification
binary for future space-based gravitational wave detectors.Comment: 15 pages, 14 figures. Accepted to MNRA