The Kilodegree Extremely Little Telescope (KELT) project is a survey for planetary transits of bright stars. It consists of a small‐aperture, wide‐field automated telescope located at Winer ...Observatory near Sonoita, Arizona. The telescope surveys a set of 26° × 26° fields that together cover about 25% of the northern sky, and targets stars in the range of
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mag, searching for transits by close‐in Jupiters. This paper describes the system hardware and software and discusses the quality of the observations. We show that KELT is able to achieve the necessary photometric precision to detect planetary transits around solar‐type main‐sequence stars.
We calibrate reverberation-based black hole (BH) masses in active galactic nuclei (AGNs) by using the correlation between BH mass, M sub(BH), and bulge/spheroid stellar velocity dispersion, sigma *. ...We use new measurements of sigma * for six AGNs and published velocity dispersions for 10 others, in conjunction with improved reverberation-mapping results, to determine the scaling factor required to bring reverberation-based BH masses into agreement with the quiescent galaxy M sub(BH)- sigma * relationship. The scatter in the AGN BH masses is found to be less than a factor of 3. The current observational uncertainties preclude the use of the scaling factor to discriminate between broad-line region models.
We present a revised measurement of the mass of the central black hole (M sub(BH)) in the Seyfert 1 galaxy NGC 4151. When our models attempt to fit both the NIFS kinematics and additional low spatial ...resolution kinematics, our results depend sensitively on how chi super(2) is computed-probably a consequence of complex bar kinematics that manifest immediately outside the nuclear region. The most robust results are obtained when only the high spatial resolution kinematic constraints in the nuclear region are included in the fit. The NIFS kinematics give a central bulge velocity dispersion sigma sub(c) = 116 + or - 3 km s super(-1), bringing this object slightly closer to the M sub(BH-)sigma relation for quiescent galaxies. Although NGC 4151 is one of only a few Seyfert 1 galaxies in which it is possible to obtain a direct dynamical black hole mass measurement-and thus, an independent calibration of the reverberation mapping mass scale-the complex bar kinematics makes it less than ideally suited for this purpose.
Abstract
We report a new free-floating planet (FFP) candidate, KMT-2017-BLG-2820, with Einstein radius
θ
E
≃ 6
μ
as, lens-source relative proper motion
μ
rel
≃ 8 mas yr
−1
, and Einstein timescale
t
...E
= 6.5 hr. 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 Mróz et al. in the OGLE-IV database. The
θ
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 ≲
θ
E
/
μ
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 30 m 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
. At the present time, the balance of evidence favors the unbound-planet hypothesis.
Abstract
We inaugurate a program of “mass production” of microlensing planets discovered in 2021 KMTNet data, with the aim of laying the basis for future statistical studies. While we ultimately plan ...to quickly publish all 2021 planets meeting some minimal criteria, the current sample of four was chosen simply on the basis of having low initial estimates of the planet–host mass ratio,
q
. It is therefore notable that two members of this sample suffer from a degeneracy in the normalized source radius
ρ
that arises from different morphologies of closely spaced caustics. All four planets (KMT-2021-BLG-1391, KMT-2021-BLG-1253, KMT-2021-BLG-1372, KMT-2021-BLG-0748) have well-characterized mass ratios,
q
, and therefore are suitable for mass-ratio frequency studies. Both of the
ρ
degeneracies can be resolved by future adaptive optics (AO) observations on 30 m class telescopes. We provide general guidance for such AO observations for all events in anticipation of the prospect that they will revolutionize the field of microlensing planets.
Aims.
We announce the discovery of a microlensing planetary system, in which a sub-Saturn planet is orbiting an ultracool dwarf host.
Methods.
We detected the planetary system by analyzing the ...short-timescale (
t
E
~ 4.4 days) lensing event KMT-2018-BLG-0748. The central part of the light curve exhibits asymmetry due to negative deviations in the rising side and positive deviations in the falling side.
Results.
We find that the deviations are explained by a binary-lens model with a mass ratio between the lens components of
q
~ 2 × 10
−3
. The short event timescale, together with the small angular Einstein radius,
θ
E
~ 0.11 mas, indicate that the mass of the planet host is very small. The Bayesian analysis conducted under the assumption that the planet frequency is independent of the host mass indicates that the mass of the planet is
M
p
= 0.18
−0.10
+0.29
M
J
, and the mass of the host,
M
h
= 0.087
−0.047
+0.138
M
⊙
, is near the star–brown dwarf boundary, but the estimated host mass is sensitive to this assumption about the planet hosting probability. High-resolution follow-up observations would lead to revealing the nature of the planet host.
Abstract
We measure the Einstein radius of the single-lens microlensing event KMT-2022-BLG-2397 to be
θ
E
= 24.8 ± 3.6
μ
as, placing it at the upper shore of the Einstein Desert, 9 ≲
θ
E
/
μ
as ≲ 25, ...between free-floating planets (FFPs) and bulge brown dwarfs (BDs). In contrast to the six BD (25 ≲
θ
E
≲ 50) events presented by Gould et al. (2022), which all had giant-star source stars, KMT-2022-BLG-2397 has a dwarf-star source, with angular radius
θ
ast
∼ 0.9
μ
as. This prompts us to study the relative utility of dwarf and giant sources for characterizing FFPs and BDs from finite-source point-lens (FSPL) microlensing events. We find “dwarfs” (including main-sequence stars and subgiants) are likely to yield twice as many
θ
E
measurements for BDs and a comparable (but more difficult to quantify) improvement for FFPs. We show that neither current nor planned experiments will yield complete mass measurements of isolated bulge BDs, nor will any other planned experiment yield as many
θ
E
measurements for these objects as the Korea Microlensing Telescope (KMT). Thus, the currently anticipated 10 yr KMT survey will remain the best way to study bulge BDs for several decades to come.
Abstract
We continue our program of publishing all planets (and possible planets) found by eye in 2021 Korea Microlensing Telescope Network (KMTNet) online data. We present four planets ...(KMT-2021-BLG-0712Lb, KMT-2021-BLG-0909Lb, KMT-2021-BLG-2478Lb, and KMT-2021-BLG-1105Lb), with planet-to-host mass ratios in the range
−
3.3
≲
log
q
≲
−
2.2
. This brings the total of secure, by-eye, 2021 KMTNet planets to 16, including 8 in this series. The by-eye sample is an important check of the completeness of semiautomated detections, which are the basis for statistical analyses. One of the planets, KMT-2021-BLG-1105Lb, is blended with a relatively bright (
I
,
V
) ∼ (18.9, 21.6) star that may be the host. This could be verified immediately by high-resolution imaging. If so, the host is an early G dwarf, and the planet could be characterized by radial velocity observations on 30 m class telescopes.
Abstract
We report on the discovery and analysis of the planetary microlensing event OGLE-2019-BLG-1180 with a planet-to-star mass ratio
q
∼ 0.003. The event OGLE-2019-BLG-1180 has unambiguous ...cusp-passing and caustic-crossing anomalies, which were caused by a wide planetary caustic with
s
≃ 2, where
s
is the star–planet separation in units of the angular Einstein radius
θ
E
. Thanks to well-covered anomalies by the Korea Micorolensing Telescope Network (KMTNet), we measure both the angular Einstein radius and the microlens parallax in spite of a relatively short event timescale of
t
E
= 28 days. However, because of a weak constraint on the parallax, we conduct a Bayesian analysis to estimate the physical lens parameters. We find that the lens system is a super-Jupiter-mass planet of
M
p
=
1.75
−
0.51
+
0.53
M
J
orbiting a late-type star of
M
h
=
0.55
−
0.26
+
0.27
M
⊙
at a distance
D
L
=
6.1
−
1.3
+
0.9
kpc
. The projected star–planet separation is
a
⊥
=
5.19
−
1.23
+
0.90
au
, which means that the planet orbits at about four times the snow line of the host star. Considering the relative lens–source proper motion of
μ
rel
= 6 mas yr
−1
, the lens will be separated from the source by 60 mas in 2029. At that time one can measure the lens flux from adaptive optics imaging of Keck or a next-generation 30 m class telescope. OGLE-2019-BLG-1180Lb represents a growing population of wide-orbit planets detected by KMTNet, so we also present a general investigation into prospects for further expanding the sample of such planets.
A reverberation-mapping program on NGC 4395, the least luminous known Seyfert 1 galaxy, undertaken with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope yields a measurement of ...the mass of the central black hole M sub(BH) = (3.6 c 1.1) x 10 super(5) M sub( ). The observations consist of two visits of five orbits each, in 2004 April and July. During each of these visits, the UV continuum varied by at least 10% (rms), and only C IV l1549 showed corresponding variations large enough to reliably determine the emission-line lag, which was measured to be of order 1 hr for both visits. The size of the C IV-emitting region is about a factor of 3 smaller than expected if the slope of the broad-line region radius-luminosity relationship is identical to that for the Hb emission line. NGC 4395 is underluminous even for its small black hole mass; the Eddington ratio of 61.2 x 10 super(-3) is lower than that of any other active galactic nucleus for which a black hole mass measurement has been made by emission-line reverberation.
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