ABSTRACT We develop a new photometry algorithm that is optimized for the Infrared Array Camera (IRAC) Spitzer time series in crowded fields and that is particularly adapted to faint or heavily ...blended targets. We apply this to the 170 targets from the 2015 Spitzer microlensing campaign and present the results of three variants of this algorithm in an online catalog. We present detailed accounts of the application of this algorithm to two difficult cases, one very faint and the other very crowded. Several of Spitzer's instrumental characteristics that drive the specific features of this algorithm are shared by Kepler and WFIRST, implying that these features may prove to be a useful starting point for algorithms designed for microlensing campaigns by these other missions.
ABSTRACT The co-planarity of solar system planets led Kant to suggest that they formed from an accretion disk, and the discovery of hundreds of such disks around young stars as well as hundreds of ...co-planar planetary systems by the Kepler satellite demonstrate that this formation mechanism is extremely widespread. Many moons in the solar system, such as the Galilean moons of Jupiter, also formed out of the accretion disks that coalesced into the giant planets. Here we report the discovery of an intermediate system, OGLE-2013-BLG-0723LB/Bb, composed of a Venus-mass planet orbiting a brown dwarf, which may be viewed either as a scaled-down version of a planet plus a star or as a scaled-up version of a moon plus a planet orbiting a star. The latter analogy can be further extended since they orbit in the potential of a larger, stellar body. For ice-rock companions formed in the outer parts of accretion disks, like Uranus and Callisto, the scaled masses and separations of the three types of systems are similar, leading us to suggest that the formation processes of companions within accretion disks around stars, brown dwarfs, and planets are similar.
ABSTRACT We report the detection and mass measurement of a binary lens OGLE-2015-BLG-1285La,b, with the more massive component having M1 > 1.35 M (80% probability). A main-sequence star in this mass ...range is ruled out by limits on blue light, meaning that a primary in this mass range must be a neutron star (NS) or black hole (BH). The system has a projected separation r = 6.1 0.4 AU and lies in the Galactic bulge. These measurements are based on the "microlens parallax" effect, i.e., comparing the microlensing light curve as seen from Spitzer, which lay at 1.25 AU projected from Earth, to the light curves from four ground-based surveys, three in the optical and one in the near-infrared. Future adaptive optics imaging of the companion by 30 m class telescopes will yield a much more accurate measurement of the primary mass. This discovery both opens the path and defines the challenges to detecting and characterizing BHs and NSs in wide binaries, with either dark or luminous companions. In particular, we discuss lessons that can be applied to future Spitzer and Kepler K2 microlensing parallax observations.
We report the detection of an extrasolar planet of mass ratio image in microlensing event MOA-2007-BLG-192. The best-fit microlensing model shows both the microlensing parallax and finite source ...effects, and these can be combined to obtain the lens masses of image for the primary and image for the planet. However, the observational coverage of the planetary deviation is sparse and incomplete, and the radius of the source was estimated without the benefit of a source star color measurement. As a result, the 2 capital sigma limits on the mass ratio and finite source measurements are weak. Nevertheless, the microlensing parallax signal clearly favors a substellar mass planetary host, and the measurement of finite source effects in the light curve supports this conclusion. Adaptive optics images taken with the Very Large Telescope (VLT) NACO instrument are consistent with a lens star that is either a brown dwarf or a star at the bottom of the main sequence. Follow-up VLT and/or Hubble Space Telescope (HST) observations will either confirm that the primary is a brown dwarf or detect the low-mass lens star and enable a precise determination of its mass. In either case, the lens star, MOA-2007-BLG-192L, is the lowest mass primary known to have a companion with a planetary mass ratio, and the planet, MOA-2007-BLG-192Lb, is probably the lowest mass exoplanet found to date, aside from the lowest mass pulsar planet.
In this first paper of a series, we describe our project to calibrate the distance determination method based on early-type binary systems. The final objective is to measure accurate, geometrical ...distances to galaxies beyond the Magellanic Clouds with a precision of 2%. We start with the analysis of two early-type systems for which we have collected all the required spectroscopic and photometric data. Apart from catalog publications, these systems have not been studied yet, and this is the first time the modeling of light and radial velocity curves is performed for them. From the analysis we obtained precise physical parameters of the components, including the masses measured with a precision of 0.6%-1% and radii measured with a precision of 0.4%-3%. For one system we determined the color and estimated the distance using the bolometric flux scaling method (DM = 18.47 0.15 mag), which agrees well with our accurate determination of the distance to the Large Magellanic Cloud from late-type giants. For the same system we determined the surface brightness of individual stars using our model, and checked that it is consistent with a recent surface-brightness-color relation. We compared our results with evolution theory models of massive stars and found they agree in general; however, models with higher overshooting values give more consistent results. The age of the system was estimated to range from 11.7 to 13.8 Myr, depending on the model.
The dusty aftermath of the V1309 Sco binary merger Nicholls, C. P; Melis, C; Soszy ski, I ...
Monthly notices of the Royal Astronomical Society. Letters,
05/2013, Letnik:
431, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We present mid-IR photometry and spectra of the merged binary V1309 Sco taken between 18 and 23 months after outburst. Strong mid-IR emission and a solid-state absorption feature indicate the ...presence of a significant amount of dust in the circumstellar environment. The absence of detectable mid-IR emission before the outburst suggests that this dust was produced in the eruptive merger event.
Model fits to the solid-state absorption feature constrain the constituent species and column density of the dust around V1309 Sco. We find that the absorption feature can be reproduced by large (3 μm) amorphous pyroxene grains at a temperature of 800 K. This grain size, if confirmed with longer wavelength spectroscopy and modelling, would be suggestive of dust processing in the circumstellar environment. The data in hand do not allow us to discriminate between disc or shell configurations for the dusty material.
We present non-linear hydrodynamic pulsation models for OGLE-BLG-RRLYR-02792 - a 0.26 M pulsator, component of the eclipsing binary system, analysed recently by Pietrzy ski et al. The star's light ...and radial velocity curves mimic that of classical RR Lyrae stars, except for the bump in the middle of the ascending branch of the radial velocity curve. We show that the bump is caused by the 2:1 resonance between the fundamental mode and the second overtone - the same mechanism that causes the Hertzsprung bump progression in classical Cepheids. The models allow us to constrain the parameters of the star, in particular to estimate its absolute luminosity ( 33 L) and effective temperature ( 6970 K, close to the blue edge of the instability strip).
We conduct a model survey for the new class of low-mass pulsators similar to OGLE-BLG-RRLYR-02792 - products of evolution in the binary systems. We compute a grid of models with masses corresponding to half (or less) of the typical mass of RR Lyrae variable, 0.20 ≤ M ≤ 0.30 M, and discuss the properties of the resulting light and radial velocity curves. Resonant bump progression is clear and may be used to distinguish such stars from classical RR Lyrae stars. We present the Fourier decomposition parameters for the modelled light and radial velocity curves. The expected values of the 31 Fourier phase for the light curves differ significantly from that observed in RR Lyrae stars, which is another discriminant of the new class.
ABSTRACT We present an analysis of a new detached eclipsing binary, OGLE-LMC-ECL-25658, in the Large Magellanic Cloud (LMC). The system consists of two late G-type giant stars on an eccentric orbit ...with an orbital period of ∼200 days. The system shows total eclipses and the components have similar temperatures, making it ideal for a precise distance determination. Using multi-color photometric and high resolution spectroscopic data, we have performed an analysis of light and radial velocity curves simultaneously using the Wilson-Devinney code. We derived orbital and physical parameters of the binary with a high precision of %. The masses and surface metallicities of the components are virtually the same and equal to and dex. However, their radii and rates of rotation show a distinct trace of differential stellar evolution. The distance to the system was calculated using an infrared calibration between V-band surface brightness and (V-K) color, leading to a distance modulus of (statistical) 0.046 (systematic). Because OGLE-LMC-ECL-25658 is located relatively far from the LMC barycenter, we applied a geometrical correction for its position in the LMC disk using the van der Marel et al. model of the LMC. The resulting barycenter distance to the galaxy is (stat.) kpc, and is in perfect agreement with the earlier result of Pietrzy ski et al.
Global 'second-generation' microlensing surveys aim to discover and characterize extrasolar planets and their frequency, by means of round-the-clock high-cadence monitoring of a large area of the ...Galactic bulge, in a controlled experiment. We report the discovery of a giant planet in microlensing event MOA-2011-BLG-322. This moderate-magnification event, which displays a clear anomaly induced by a second lensing mass, was inside the footprint of our second-generation microlensing survey, involving MOA, OGLE and the Wise Observatory. The event was observed by the survey groups, without prompting alerts that could have led to dedicated follow-up observations. Fitting a microlensing model to the data, we find that the time-scale of the event was t
E = 23.2 ± 0.8 d, and the mass ratio between the lens star and its companion is q = 0.028 ± 0.001. Finite-source effects are marginally detected, and upper limits on them help break some of the degeneracy in the system parameters. Using a Bayesian analysis that incorporates a Galactic structure model, we estimate the mass of the lens at
, at a distance of 7.56 ± 0.91 kpc. Thus, the companion is likely a planet of mass
, at a projected separation of
au, rather far beyond the snow line. This is the first pure-survey planet reported from a second-generation microlensing survey, and shows that survey data alone can be sufficient to characterize a planetary model. With the detection of additional survey-only planets, we will be able to constrain the frequency of extrasolar planets near their systems' snow lines.
ABSTRACT Determining the physical parameters of binary microlenses is hampered by the lack of information about the angular Einstein radius due to the difficulty involved in resolving caustic ...crossings. In this paper, we present an analysis of the binary microlensing event OGLE-2013-BLG-0578, for which the caustic exit was precisely predicted in advance from real-time analysis, enabling us to densely resolve the caustic crossing and to measure the Einstein radius. From the mass measurement of the lens system based on the Einstein radius, combined with additional information about the lens parallax, we determine that the lens is a binary composed of a late-type M dwarf primary and a substellar brown dwarf companion. This event demonstrates the capability of current real-time microlensing modeling and the usefulness of microlensing for detecting and characterizing faint or dark objects in the Galaxy.
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