Abstract
We present the results of a multisite photometric observing campaign on the rapidly oscillating Ap (roAp) star 2MASS 16400299-0737293 (J1640; V = 12.7). We analyse photometric B data to show ...the star pulsates at a frequency of 151.93 d−1 (1758.45 μHz; P = 9.5 min) with a peak-to-peak amplitude of 20.68 mmag, making it one of the highest amplitude roAp stars. No further pulsation modes are detected. The stellar rotation period is measured at 3.674 7 ± 0.000 5 d, and we show that rotational modulation due to spots is in antiphase between broad-band and B observations. Analysis and modelling of the pulsation reveals this star to be pulsating in a distorted quadrupole mode, but with a strong spherically symmetric component. The pulsational phase variation in this star is suppressed, leading to the conclusion that the contribution of ℓ > 2 components dictate the shape of phase variations in roAp stars that pulsate in quadrupole modes. This is only the fourth time such a strong pulsation phase suppression has been observed, leading us to question the mechanisms at work in these stars. We classify J1640 as an A7 Vp SrEu(Cr) star through analysis of classification resolution spectra.
Abstract
We present a new analysis of the rapidly oscillating Ap (roAp) star, 2MASS J19400781 − 4420093 (J1940; V = 13.1). The star was discovered using SuperWASP broad-band photometry to have a ...frequency of 176.39 d−1 (2041.55 μHz; P = 8.2 min; Holdsworth et al. 2014a) and is shown here to have a peak-to-peak amplitude of 34 mmag. J1940 has been observed during three seasons at the South African Astronomical Observatory, and has been the target of a Whole Earth Telescope campaign. The observations reveal that J1940 pulsates in a distorted quadrupole mode with unusual pulsational phase variations. A higher signal-to-noise ratio spectrum has been obtained since J1940's first announcement, which allows us to classify the star as A7 Vp Eu(Cr). The observing campaigns presented here reveal no pulsations other than the initially detected frequency. We model the pulsation in J1940 and conclude that the pulsation is distorted by a magnetic field of strength 1.5 kG. A difference in the times of rotational maximum light and pulsation maximum suggests a significant offset between the spots and pulsation axis, as can be seen in roAp stars.
Abstract
Using six years of spectroscopic monitoring of the luminous quasar HE 0435-4312 (
z
= 1.2231) with the Southern African Large Telescope, in combination with photometric data (CATALINA, OGLE, ...SALTICAM, and BMT), we determined a rest-frame time delay of
days between the Mg
ii
broad-line emission and the ionizing continuum using seven different time-delay inference methods. Time-delay artifact peaks and aliases were mitigated using the bootstrap method and prior weighting probability function, as well as by analyzing unevenly sampled mock light curves. The Mg
ii
emission is considerably variable with a fractional variability of ∼5.4%, which is comparable to the continuum variability (∼4.8%). Because of its high luminosity (
L
3000
= 10
46.4
erg s
−1
), the source is beneficial for a further reduction of the scatter along the Mg
ii
-based radius–luminosity relation and its extended versions, especially when the highly accreting subsample that has an rms scatter of ∼0.2 dex is considered. This opens up the possibility of using the high-accretor Mg
ii
-based radius–luminosity relation for constraining cosmological parameters. With the current sample of 27 reverberation-mapped sources, the best-fit cosmological parameters (Ω
m
, Ω
Λ
) = (0.19; 0.62) are consistent with the standard cosmological model within the 1
σ
confidence level.
We present multiwavelength photometric monitoring of WD 1145+017, a white dwarf exhibiting periodic dimming events interpreted to be the transits of orbiting, disintegrating planetesimals. Our ...observations include the first set of near-infrared light curves for the object, obtained on multiple nights over the span of 1 month, and recorded multiple transit events with depths varying between ~20 and 50 per cent. Simultaneous near-infrared and optical observations of the deepest and longest duration transit event were obtained on two epochs with the Anglo-Australian Telescope and three optical facilities, over the wavelength range of 0.5-1.2 ...m. These observations revealed no measurable difference in transit depths for multiple photometric pass bands, allowing us to place a 2... lower limit of 0.8 ...m on the grain size in the putative transiting debris cloud. This conclusion is consistent with the spectral energy distribution of the system, which can be fit with an optically thin debris disc with minimum particle sizes of 10... ...m. (ProQuest: ... denotes formulae/symbols omitted.)
We use US Naval Observatory CCD Astrograph Catalogue (UCAC4) proper motions and Wide-Field Infrared Survey Explorer (WISE) W1-band apparent magnitudes and intensity means for almost 400 field RR ...Lyrae variables to determine the parameters of the velocity distribution of the Galactic RR Lyrae population and constrain the zero-points of the metallicity-〈M
V
〉, period-metallicity-〈 MKs
〉-band and period-metallicity-〈M
W1〉-band luminosity relations via statistical parallax. We find the mean velocities of the halo- and thick-disc RR Lyrae populations in the solar neighbourhood to be U
0(Halo), V
0(Halo), W
0(Halo) = (−7 ± 9, −214 ± 10, −10 ± 6) km s−1 and U
0(Disc), V
0(Disc), W
0(Disc) = (−13 ± 7, −37 ± 6, −17 ± 4) km s−1, respectively, while the corresponding components of the velocity-dispersion ellipsoids are σV
R
(Halo), σV
φ(Halo), σV
θ(Halo) = (153 ± 9, 101 ± 6, 96 ± 5) km s−1 and σV
R
(Disc), σV
φ(Disc), σV
θ(Disc) = (46 ± 7, 37 ± 5, 27 ± 4) km s−1, respectively. The fraction of thick-disc stars is estimated at 0.22 ± 0.03. The corrected infrared period-metallicity-luminosity relations are
and
and the optical metallicity-luminosity relation Fe/H-〈M
V
〉 is 〈M
V
〉 = +1.094 + 0.232Fe/H with a standard error of ±0.089, implying a Large Magellanic Cloud distance modulus of 18.32 ± 0.09, a solar Galactocentric distance of 7.73 ± 0.36 kpc and M31 and M33 distance moduli of DM
M31 = 24.24 ± 0.09 (D = 705 ± 30 kpc) and DM
M33 = 24.36 ± 0.09 (D = 745 ± 31 kpc), respectively. Extragalactic distances calibrated with our RR Lyrae star luminosity scale imply a Hubble constant of ∼80 km s−1 Mpc−1. Our results suggest marginal prograde rotation for the population of halo RR Lyraes in the Milky Way.
Abstract We present the results from the first two years of the Planet Hunters Next Generation Transit Survey (NGTS) citizen science project, which searches for transiting planet candidates in data ...from the NGTS by enlisting the help of members of the general public. Over 8000 registered volunteers reviewed 138,198 light curves from the NGTS Public Data Releases 1 and 2. We utilize a user weighting scheme to combine the classifications of multiple users to identify the most promising planet candidates not initially discovered by the NGTS team. We highlight the five most interesting planet candidates detected through this search, which are all candidate short-period giant planets. This includes the TIC-165227846 system that, if confirmed, would be the lowest-mass star to host a close-in giant planet. We assess the detection efficiency of the project by determining the number of confirmed planets from the NASA Exoplanet Archive and TESS Objects of Interest (TOIs) successfully recovered by this search and find that 74% of confirmed planets and 63% of TOIs detected by NGTS are recovered by the Planet Hunters NGTS project. The identification of new planet candidates shows that the citizen science approach can provide a complementary method to the detection of exoplanets with ground-based surveys such as NGTS.
ABSTRACT We report the discovery of EPIC 201702477b, a transiting brown dwarf in a long period (40.73691 0.00037 day) and eccentric (e = 0.2281 0.0026) orbit. This system was initially reported as a ...planetary candidate based on two transit events seen in K2 Campaign 1 photometry and later validated as an exoplanet candidate. We confirm the transit and refine the ephemeris with two subsequent ground-based detections of the transit using the Las Cumbres Observatory Global Telescope 1 m telescope network. We rule out any transit timing variations above the level of ∼30 s. Using high precision radial velocity measurements from HARPS and SOPHIE we identify the transiting companion as a brown dwarf with a mass, radius, and bulk density of 66.9 1.7 MJ, 0.757 0.065 RJ, and 191 51 g cm−3 respectively. EPIC 201702477b is the smallest radius brown dwarf yet discovered, with a mass just below the H-burning limit. It has the highest density of any planet, substellar mass object, or main-sequence star discovered so far. We find evidence in the set of known transiting brown dwarfs for two populations of objects-high mass brown dwarfs and low mass brown dwarfs. The higher-mass population have radii in very close agreement to theoretical models, and show a lower-mass limit around 60 MJ. This may be the signature of mass-dependent ejection of systems during the formation process.
We use data on space distribution of the currently most complete sample of Cepheids with reliable distances (565 stars), located within ~5 kpc from the Sun, to study the spiral pattern of the Milky ...Way galaxy. We estimate the pitch angle as 9°−10°; the most accurate estimate,
i
= 9.5° ± 0.1°, was obtained assuming the existence of a global four-armed spiral pattern; the solar phase angle in the spiral pattern is χ
⊙
= −121° ± 3°. Comparing positions of the spiral arms delineated by classical Cepheids and galactic masers, with the age difference of these objects in mind, we estimate the rotation angular speed of the spiral pattern to be Ω
P
= 25.2 ± 0.5 km s
−1
kpc
−1
.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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