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1681. I-band LC of the microlensing event KMT-2017-BLG-2820
ID:
ivo://CDS.VizieR/J/AJ/161/126
Title:
I-band LC of the microlensing event KMT-2017-BLG-2820
Short Name:
J/AJ/161/126
Date:
10 Dec 2021
Publisher:
CDS
Description:
We report a new free-floating planet (FFP) candidate, KMT-2017-BLG-2820, with Einstein radius {theta}E~6{mu}as, lens-source relative proper motion {mu}rel~8mas/yr, and Einstein timescale t_E_=6.5hr. It is the third FFP candidate found in an ongoing study of giant-source finite-source point-lens (FSPL) events in the KMTNet database and the sixth FSPL FFP candidate overall. We find no significant evidence for a host. Based on their timescale distributions and detection rates, we argue that five of these six FSPL FFP candidates are drawn from the same population as the six point-source point-lens (PSPL) FFP candidates found by Mroz et al. in the OGLE-IV database. The {theta}E distribution of the FSPL FFPs implies that they are either sub- Jovian planets in the bulge or super-Earths in the disk. However, the apparent "Einstein desert" (10<~{theta}E/{mu}as<~30) would argue for the latter. Whether each of the 12 (six FSPL and six PSPL) FFP candidates is truly an FFP or simply a very wide-separation planet can be determined at first adaptive optics (AO) light on 30m telescopes, and earlier for some. If the latter, a second epoch of AO observations could measure the projected planet- host separation with a precision of O(10au). At the present time, the balance of evidence favors the unbound-planet hypothesis.
1682. I-band LC of the microlensing event KMT-2016-BLG-1836
ID:
ivo://CDS.VizieR/J/AJ/159/98
Title:
I-band LC of the microlensing event KMT-2016-BLG-1836
Short Name:
J/AJ/159/98
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the discovery of a super-Jovian planet in the microlensing event KMT-2016-BLG-1836, which was found by the Korea Microlensing Telescope Network (KMTNet) high-cadence observations ({Gamma}~4/hr). The planet-host mass ratio q~0.004. A Bayesian analysis indicates that the planetary system is composed of a super-Jovian M_planet_=2.2_-1.1_^+1.9^M_J_ planet orbiting an M or K dwarf, M_host_=0.49_-0.25_^+0.38^M_{sun}_, at a distance of D_L_=7.1_-2.4_^+0.8^kpc. The projected planet-host separation is 3.5_-0.9_^+1.1^au, implying that the planet is located beyond the snow line of the host star. Future high-resolution images can potentially strongly constrain the lens brightness and thus the mass and distance of the planetary system. Without considering detailed detection efficiency, selection, or publication biases, we find a potential mass-ratio desert at -3.7<~logq<~-3.0 for the 31 published KMTNet planets.
1683. I-band light curve of KMT-2016-BLG-2605 with KMTNet
ID:
ivo://CDS.VizieR/J/AJ/162/96
Title:
I-band light curve of KMT-2016-BLG-2605 with KMTNet
Short Name:
J/AJ/162/96
Date:
11 Mar 2022 14:37:06
Publisher:
CDS
Description:
With a planet-host mass ratio q=0.012{+/-}0.001, KMT-2016-BLG-2605 has the shortest Einstein timescale, tE=3.41{+/-}0.13days, of any planetary microlensing event to date. This prompts us to examine the full sample of seven short (tE<7days) planetary events with good q measurements. We find that six have clustered Einstein radii {theta}E=115{+/-}20{mu}as and lens-source relative proper motions {mu}rel~9.5{+/-}2.5mas/yr. For the seventh, these two quantities could not be measured. These distributions are consistent with a Galactic bulge population of very low mass (VLM) hosts near the hydrogen-burning limit. This conjecture could be verified by imaging at first adaptive optics light on next-generation (30m) telescopes. Based on a preliminary assessment of the sample, "planetary" companions (i.e., below the deuterium-burning limit) are divided into "genuine planets," formed in their disks by core accretion, and VLM brown dwarfs, which form like stars. We discuss techniques for expanding the sample, which include taking account of the peculiar "anomaly-dominated" morphology of the KMT-2016-BLG-2605 light curve.
1684. I-band light curve of OGLE-2019-BLG-1058 with KMTNet
ID:
ivo://CDS.VizieR/J/AJ/162/267
Title:
I-band light curve of OGLE-2019-BLG-1058 with KMTNet
Short Name:
J/AJ/162/267
Date:
25 Mar 2022 06:06:33
Publisher:
CDS
Description:
We show that because the conditions for producing terrestrial microlens parallax (TPRX; i.e., a nearby disk lens) will also tend to produce a large lens-source relative proper motion ({mu}rel), source proper motion ({mu}S) measurements in general provide a strong test of TPRX signals, which Gould & Yee (2013) showed were an important probe of free-floating planet (FFP) candidates. As a case study, we report a single-lens/single-source microlensing event designated as OGLE-2019-BLG-1058. For this event, the short timescale (~2.5days) and very fast {mu}rel (~17.6mas/yr) suggest that this isolated lens is an FFP candidate located in the disk of our Galaxy. For this event, we find a TPRX signal consistent with a disk FFP, but at low significance. A direct measurement of the {mu}S shows that the large {mu}rel is due to an extreme {mu}S, and thus, the lens is consistent with being a very-low-mass star in the bulge and the TPRX measurement is likely spurious. By contrast, we show how a precise measurement of {mu}S with the mean properties of the bulge proper motion distribution would have given the opposite result; i.e., provided supporting evidence for an FFP in the disk and the TPRX measurement.
1685. I-band light curves of OGLE-2015-BLG-1771Lb
ID:
ivo://CDS.VizieR/J/AJ/159/116
Title:
I-band light curves of OGLE-2015-BLG-1771Lb
Short Name:
J/AJ/159/116
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the discovery and the analysis of the short (t_E_<5days) planetary microlensing event, OGLE-2015-BLG-1771. The event was discovered by the Optical Gravitational Lensing Experiment, and the planetary anomaly (at I~19) was captured by The Korea Microlensing Telescope Network. The event has three surviving planetary models that explain the observed light curves, with planet-host mass ratio q~5.4x10^-3^, 4.5x10^-3^ and 4.5x10^-2^, respectively. The first model is the best-fit model, while the second model is disfavored by {Delta}_{chi}^2^_~3. The last model is strongly disfavored by {Delta}_{chi}^2^_~15 but not ruled out. A Bayesian analysis using a Galactic model indicates that the first two models are probably composed of a Saturn-mass planet orbiting a late M dwarf, while the third one could consist of a super-Jovian planet and a mid-mass brown dwarf. The source-lens relative proper motion is {mu}_rel_~9mas/yr, so the source and lens could be resolved by current adaptive-optics instruments in 2020 if the lens is luminous.
1686. I-band light curves of OGLE LMC Miras
ID:
ivo://CDS.VizieR/J/AJ/152/164
Title:
I-band light curves of OGLE LMC Miras
Short Name:
J/AJ/152/164
Date:
21 Oct 2021
Publisher:
CDS
Description:
We develop a nonlinear semi-parametric Gaussian process model to estimate periods of Miras with sparsely sampled light curves. The model uses a sinusoidal basis for the periodic variation and a Gaussian process for the stochastic changes. We use maximum likelihood to estimate the period and the parameters of the Gaussian process, while integrating out the effects of other nuisance parameters in the model with respect to a suitable prior distribution obtained from earlier studies. Since the likelihood is highly multimodal for period, we implement a hybrid method that applies the quasi-Newton algorithm for Gaussian process parameters and search the period/frequency parameter space over a dense grid. A large-scale, high-fidelity simulation is conducted to mimic the sampling quality of Mira light curves obtained by the M33 Synoptic Stellar Survey. The simulated data set is publicly available and can serve as a testbed for future evaluation of different period estimation methods. The semi-parametric model outperforms an existing algorithm on this simulated test data set as measured by period recovery rate and quality of the resulting period-luminosity relations.
1687. I-band light curves of SNe II from OGLE-IV
ID:
ivo://CDS.VizieR/J/MNRAS/449/1753
Title:
I-band light curves of SNe II from OGLE-IV
Short Name:
J/MNRAS/449/1753
Date:
21 Oct 2021
Publisher:
CDS
Description:
We study a sample of 11 Type II supernovae (SNe) discovered by the OGLE-IV survey. All objects have well-sampled I-band light curves, and at least one spectrum. We find that two or three of the 11 SNe have a declining light curve, and spectra consistent with other SNe II-L, while the rest have plateaus that can be as short as 70 d, unlike the 100 d typically found in nearby galaxies. The OGLE SNe are also brighter, and show that magnitude-limited surveys find SNe that are different than usually found in nearby galaxies. We discuss this sample in the context of understanding Type II SNe as a class and their suggested use as standard candles.
1688. i-band variability of YSOs
ID:
ivo://CDS.VizieR/II/362
Title:
i-band variability of YSOs
Short Name:
II/362
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an i-band photometric study of over 800 young stellar objects in the OB association Cep OB3b, which samples timescales from 1 minute to ten years. Using structure functions we show that on all timescales (tau) there is a monotonic decrease in variability from Class I to Class II through the transition disc (TD) systems to Class III, i.e. the more evolved systems are less variable. The Class Is show an approximately power-law increase (tau^0.8^) in variability from timescales of a few minutes to ten years. The Class II, TDs and Class III systems show a qualitatively different behaviour with most showing a power-law increase in variability to a timescale corresponding to the rotational period of the star, with little additional variability beyond that timescale. However, about a third of the Class IIs show lower overall variability, but their variability is still increasing at 10 years. This behaviour can be explained if all Class IIs have two primary components to their variability. The first is an underlying roughly power-law variability spectrum, which evidence from the infrared suggests is driven by accretion rate changes. The second component is an approximately sinusoidal and results from the rotation of the star. We suggest that the systems with dominant longer-timescale variability have a smaller rotational modulation either because they are seen at low inclinations or have more complex magnetic field geometries. We derive a new way of calculating structure functions for large simulated datasets (the "fast structure function"), based on fast Fourier transforms.
1689. IC 4665
ID:
ivo://CDS.VizieR/J/AJ/105/1441
Title:
IC 4665
Short Name:
J/AJ/105/1441
Date:
21 Oct 2021
Publisher:
CDS
Description:
The results of a combined astrometric, photometric, and spectroscopic program to identify members of the open cluster IC 4665 are presented. Numerous new proper motion/photometric candidate members and at least 23 M dwarfs with H-alpha emission have been identified. A reanalysis of IC 4665's age using different methods yields conflicting results ranging from approx. 3x10^7^ yr to the age of the Pleiades. This study provides a list of candidate cluster members in the intermediate and low-mass regime of this cluster. Future spectroscopic observations of these candidates should eventually identify true cluster members. The results of new echelle observations of some candidates and the photometric monitoring of one apparent cluster member are given in an appendix.
1690. IC 4996 CCD photometry
ID:
ivo://CDS.VizieR/J/AJ/116/1801
Title:
IC 4996 CCD photometry
Short Name:
J/AJ/116/1801
Date:
21 Oct 2021
Publisher:
CDS
Description:
The results of a UBV CCD photometric study of the cluster IC 4996 are presented. We obtain new values for the cluster parameters: E(B-V)=0.71+/-0.08, V_0_-M_V_=11.9+/-0.1, and age=(7.5+/-3)x10^6^yr. The combined evidence from the photometric diagrams suggests the presence of a number of premain-sequence (PMS) cluster members with spectral types ~A0 to F5. The interpretation of these objects as PMS candidates is further supported by independent results from CCD uvbyH{beta} observations. If confirmed, these stars would bridge the existing gap in the sample of PMS stars, between the coolest Herbig AeBe stars (HAeBe), and the hottest T Tauri stars. These PMS candidates are located some 0.5 and 1 mag above the main sequence in the V-(B-V) diagram, around the location of spectral types AF. This feature, together with their locations in the (U-B)-(B-V) diagram and the interpretation that they are PMS members, suggest an additional reddening law with a slope {alpha}=E(U-B)/E(B-V)~0.55, probably caused by circumstellar material.