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We report the discovery of a unique object of uncertain nature -- but quite possibly a disintegrating asteroid or minor planet -- orbiting one star of the widely separated binary TIC 400799224. We initially identified the system in data from TESS Sector 10 via an abnormally-shaped fading event in the light curve (hereafter 'dips'). Follow-up speckle imaging determined that TIC 400799224 is actually two stars of similar brightness at 0.62" separation, forming a likely bound binary with projected separation of ~300 au. We cannot yet determine which star in the binary is host to the dips in flux. ASAS-SN and Evryscope archival data show that there is a strong periodicity of the dips at ~19.77 days, leading us to believe that an occulting object is orbiting the host star, though the duration, depth, and shape of the dips vary substantially. Statistical analysis of the ASAS-SN data shows that the dips only occur sporadically at a detectable threshold in approximately one out of every three to five transits, lending credence to the possibility that the occulter is a sporadically-emitted dust cloud. The cloud is also fairly optically thick, blocking up to 37% or 75% of the light from the host star, depending on the true host. Further observations may allow for greater detail to be gleaned as to the origin and composition of the occulter, as well as to a determination of which of the two stars comprising TIC 400799224 is the true host star of the dips., Comment: Accepted for publication by The Astronomical Journal, 1 October 2021

This paper presents V- and g'-band observations of the F2V star KIC 8462852, which exhibited enigmatic fade patterns in Kepler mission data. We introduce a transit simulation model for interpretation of these fades, and use it to interpret an August 2017 dip as a repeat of the Kepler day 1540 dip (D1540). We suggest the August 2017 and D1540 dips may be caused by a brown dwarf and an associated ring system in a 1601-day elliptical orbit. Transiting icy moons of the proposed brown dwarf, sublimating near periapsis like comets, could provide an explanation for the significant dips observed by Kepler, as well as the recent May to October 2017 dips and the long term variation in flux detected by Simon et al. (2017). Whereas the presence of such a ring structure is attractive for its ability to explain short term fade events, we do not address how such a ring system can be created and maintained. If our speculation is correct, a brightening of about 1-2 percent should occur during October to November 2017. In addition, this scenario predicts that a set of dimming events, similar to those in 2013 (Kepler) and in 2017 (reported here), can be expected to repeat during October 2021 to January 2022 and a repeat of D1540 should occur on 27 December 2021., Comment: MNRAS approved, 10 figures, 9 pages

WD 1145+017 was observed from 2016 November through 2017 June for the purpose of further characterizing the transit behavior of the dusty debris clouds orbiting this white dwarf. The optical observations were carried out with a small ground-based telescope run by an amateur astronomer, and covered 53 different nights over the 8-month interval. We have found that the optical activity has increased to the highest level observed since its discovery with Kepler K2, with approximately 17% of the optical flux extinguished per orbit. The source exhibits some transits with depths of up to 55% and durations as long as two hours. The dominant period of the orbiting dust clouds during 2016-2017 is 4.49126 hours. We present 'waterfall' images for the entire 2016-2017 and 2015-2016 observing seasons. In addition, the white dwarf was observed with the Chandra X-ray Observatory for 10-ksec on each of four different occasions, separated by about a month each. The upper limit on the average X-ray flux from WD 1145+017 is ~5 x 10^{-15} ergs/cm^2/s (unabsorbed over the range 0.1-100 keV), which translates to an upper limit on the X-ray luminosity, Lx, of ~2 x 10^{28} ergs/s. If Lx = G Mwd Mdot/Rwd, where Mwd and Rwd are the mass and radius of the white dwarf, and Mdot is the accretion rate, then Mdot < 2 x 10^{11} g/s. This is just consistent with the value of Mdot that is inferred from the level of dust activity., 14 pages, 8 figures, submitted to MNRAS

WD 1145+017 was observed from 2015 November to 2016 July for the purpose of characterizing transit behavior of the white dwarf by dust clouds thought to be produced by fragments of an asteroid in close orbit with the star. Fortuitously, most of these observations were carried out during a time when the overall `dip' activity was dramatically enhanced over that during its discovery with Kepler K2. By the end of our reported observations the dip activity had declined to a level close to its K2 discovery state. Three notable events were observed. In 2016 January a large number of dust clouds appeared that had an orbital period of 4.4912 hours, and this event also marked the end of a 3-month interval dominated by the K2 `A' period. The second event was a 2016 April 21 appearance of four dip features with drift lines in a waterfall diagram (date vs. phase) that diverged from their origin date, at a location away from the `A' asteroid, and which lasted for two weeks. The third event was the sudden appearance of a dip feature with a period of 4.6064 hours, which is essentially the same as the K2 `B' period. The evolution of dip shape, depth, and total fade amount provide constraints on dust production and loss mechanisms. Collisions can account for the sudden appearance of dust clouds, and the sudden increase in dust amount, but another mechanism for continual dust production is also required.

We have discovered a doubly eclipsing, bound, quadruple star system in the field of K2 Campaign 7. EPIC 219217635 is a stellar image with $Kp = 12.7$ that contains an eclipsing binary (`EB') with $P_A = 3.59470$ d and a second EB with $P_B = 0.61825$ d. We have obtained followup radial-velocity (`RV') spectroscopy observations, adaptive optics imaging, as well as ground-based photometric observations. From our analysis of all the observations, we derive good estimates for a number of the system parameters. We conclude that (1) both binaries are bound in a quadruple star system; (2) a linear trend to the RV curve of binary A is found over a 2-year interval, corresponding to an acceleration, $\dot \gamma = 0.0024 \pm 0.0007$ cm s$^{-2}$; (3) small irregular variations are seen in the eclipse-timing variations (`ETVs') detected over the same interval; (4) the orbital separation of the quadruple system is probably in the range of 8-25 AU; and (5) the orbital planes of the two binaries must be inclined with respect to each other by at least 25$^\circ$. In addition, we find that binary B is evolved, and the cooler and currently less massive star has transferred much of its envelope to the currently more massive star. We have also demonstrated that the system is sufficiently bright that the eclipses can be followed using small ground-based telescopes, and that this system may be profitably studied over the next decade when the outer orbit of the quadruple is expected to manifest itself in the ETV and/or RV curves., Comment: Accepted for publication in MNRAS

WD 1145+017 is a unique white dwarf system that has a heavily polluted atmosphere, an infrared excess from a dust disk, numerous broad absorption lines from circumstellar gas, and changing transit features, likely from fragments of an actively disintegrating asteroid. Here, we present results from a large photometric and spectroscopic campaign with Hubble, Keck , VLT, Spitzer, and many other smaller telescopes from 2015 to 2018. Somewhat surprisingly, but consistent with previous observations in the u' band, the UV transit depths are always shallower than those in the optical. We develop a model that can quantitatively explain the observed "bluing" and the main findings are: I. the transiting objects, circumstellar gas, and white dwarf are all aligned along our line of sight; II. the transiting object is blocking a larger fraction of the circumstellar gas than of the white dwarf itself. Because most circumstellar lines are concentrated in the UV, the UV flux appears to be less blocked compared to the optical during a transit, leading to a shallower UV transit. This scenario is further supported by the strong anti-correlation between optical transit depth and circumstellar line strength. We have yet to detect any wavelength-dependent transits caused by the transiting material around WD 1145+017., Comment: 16 pages, 11 figures, 6 tables, ApJ, in press

The star XO-5 (GSC 02959-00729, V=12.1, G8V) hosts a Jupiter-sized, Rp=1.15+/-0.12 Rjup, transiting extrasolar planet, XO-5b, with an orbital period of P=4.187732+/-0.00002 days. The planet mass (Mp=1.15+/-0.08 Mjup) and surface gravity (gp=22+/-5 m/s^2) are significantly larger than expected by empirical Mp-P and Mp-P-[Fe/H] relationships. However, the deviation from the Mp-P relationship for XO-5b is not large enough to suggest a distinct type of planet as is suggested for GJ 436b, HAT-P-2b, and XO-3b. By coincidence XO-5 overlies the extreme H I plume that emanates from the interacting galaxy pair NGC 2444/NGC 2445 (Arp 143).

We report null results on a 2 year photometric search for outburst predictors in SS Cyg. Observa- tions in Johnson Vand Cousins I were obtained almost daily for multiple hours per night for two observing seasons. The accumulated data are put through various statistical and visual analysis techniques, but we fail to detect any outburst predictors. However, analysis of 102 years of AAVSO archival visual data has led to the detection of a correlation between a long term quasi-periodic feature at around 1000-2000 days in length and an increase in outburst rate.

We explored the statistical and compositional link between Chelyabinsk meteoroid and potentially hazardous asteroid (86039) 1999 NC43 to investigate their proposed relation proposed by Borovi\v{c}ka et al. (2013). Using detailed computation we confirm that the orbit of the Chelyabinsk impactor is anomalously close to 1999 NC43. We find about (1-3) x 10-4 likelihood of that to happen by chance. Taking the standpoint that the Chelyabinsk impactor indeed separated from 1999 NC43 by a cratering or rotational fission event, we run a forward probability calculation, which is an independent statistical test. However, we find this scenario is unlikely at the about (10-3 -10-2) level. We also verified compositional link between Chelyabinska and 1999NC43. Mineralogical analysis of Chelyabinsk (LL chondrite) and (8) Flora (the largest member of the presumed LL chondrite parent family) shows that their olivine and pyroxene chemistries are similar to LL chondrites. Similar analysis of 1999 NC43 shows that its olivine and pyroxene chemistries are more similar to L chondrites than LL chondrites (like Chelyabinsk). We also took photometric observations of 1999 NC43 over 54 nights during two apparitions (2000, 2014). The lightcurve of 1999 NC43 resembles simulated lightcurves of tumblers in Short-Axis Mode with the mean wobbling angle 20-30 deg. While, a mechanism of the non-principal axis rotation excitation is unclear, we can rule out the formation of asteroid in disruption of its parent body as a plausible cause, as it is unlikely that the rotation of an asteroid fragment from catastrophic disruption would be nearly completely halted. Considering all these facts, we find the proposed link between the Chelyabinsk meteoroid and the asteroid 1999 NC43 to be unlikely., Comment: 52 pages, 13 figures, 3 tables

The dwarf planet Ceres is likely differentiated similar to the terrestrial planets but with a water/ice dominated mantle and an aqueously altered crust. Detailed modeling of Ceres' phase function has never been performed to understand its surface properties. The Dawn spacecraft began orbital science operations at the dwarf planet in April 2015. We observed Ceres with flight spares of the seven Dawn Framing Camera color filters mounted on ground-based telescopes over the course of three years to model its phase function versus wavelength. Our analysis shows that the modeled geometric albedos derived from both the IAU HG model and the Hapke model are consistent with a flat and featureless spectrum of Ceres, although the values are ~10% higher than previous measurements. Our models also suggest a wavelength dependence of Ceres' phase function. The IAU G-parameter and the Hapke single-particle phase function parameter, g, are both consistent with decreasing (shallower) phase slope with increasing wavelength. Such a wavelength dependence of phase function is consistent with reddening of spectral slope with increasing phase angle, or phase-reddening. This phase reddening is consistent with previous spectra of Ceres obtained at various phase angles archived in the literature, and consistent with the fact that the modeled geometric albedo spectrum of Ceres is the bluest of all spectra because it represents the spectrum at 0 degree phase angle. Ground-based FC color filter lightcurve data are consistent with HST albedo maps confirming that Ceres' lightcurve is dominated by albedo and not shape. We detected a positive correlation between 1.1-micron absorption band depth and geometric albedo suggesting brighter areas on Ceres have absorption bands that are deeper., Comment: 40 pages, 9 figures, 5 tables. Accepted for publication in Icarus

We present time-series observations, spectra and archival outburst data of a newly-discovered variable star in Hercules, Var Her 04. Its orbital period, mass ratio, and outburst amplitude resemble those of the UGWZ-type subclass of UGSU dwarf novae. However, its supercycle and outburst light curve defy classification as a clear UGWZ. Var Her 04 is most similar to the small group of possible hydrogen-burning ``period bouncers'', dwarf novae that have passed beyond the period minimum and returned., Comment: 20 pages, 7 figures. Data in paper available at http://www.aavso.org/data/download/ Accepted for publication in PASP Dec 2004

Observations of KIC 8462852 (aka Boyajian's Star) reveal a yearlong fade pattern that is remarkably similar to the fade pattern derived from Kepler mission observations. The ground-based observations reported here can be described as a gradual fade that ended in late 2016 with the beginning of a yearlong U-shaped fade of 1.1 percent. Near the end of this U-shaped fade a series of very brief dips occurred. The Kepler data exhibit a similar pattern 1600 days earlier, except with an abrupt end of observations before the U-shape recovery. Observations lasting many years are needed, especially during our predicted repeat of the U-shape and short dip pattern in 2021.

We report the discovery of a massive (Mpsini = 13.02 +/- 0.64 Mjup; total mass 13.25 +/- 0.64 Mjup), large (1.95 +/- 0.16 Rjup) planet in a transiting, eccentric orbit (e = 0.260 +/- 0.017) around a 10th magnitude F5V star in the constellation Camelopardalis. We designate the planet XO-3b, and the star XO-3, also known as GSC 03727-01064. The orbital period of XO-3b is 3.1915426 +/- 0.00014 days. XO-3 lacks a trigonometric distance; we estimate its distance to be 260 +/- 23 pc. The radius of XO-3 is 2.13 +/- 0.21 Rsun, its mass is 1.41 +/- 0.08 Msun, its vsini = 18.54 +/- 0.17 km/s, and its metallicity is [Fe/H] = -0.177 +/- 0.027. This system is unusual for a number of reasons. XO-3b is one of the most massive planets discovered around any star for which the orbital period is less than 10 days. The mass is near the deuterium burning limit of 13 Mjup, which is a proposed boundary between planets and brown dwarfs. Although Burrows et al. (2001) propose that formation in a disk or formation in the interstellar medium in a manner similar to stars is a more logical way to differentiate planets and brown dwarfs, our current observations are not adequate to address this distinction. XO-3b is also unusual in that its eccentricity is large given its relatively short orbital period. Both the planetary radius and the inclination are functions of the spectroscopically determined stellar radius. Analysis of the transit light curve of XO-3b suggests that the spectroscopically derived parameters may be over estimated. Though relatively noisy, the light curves favor a smaller radius in order to better match the steepness of the ingress and egress. The light curve fits imply a planetary radius of 1.25 +/- 0.15 Rjup, which would correspond to a mass of 12.03 +/- 0.46 Mjup., Comment: 26 pages, 10 figures. Accepted by ApJ. Current version has several small corrections as a result of a bug in the fitting software

We report the results of a globally coordinated photometric campaign to search for transits by the P ~ 30 d and P ~ 60 d outer planets of the 3-planet system orbiting the nearby M-dwarf Gl 876. These two planets experience strong mutual perturbations, which necessitate use of a dynamical (four-body) model to compute transit ephemerides for the system. Our photometric data have been collected from published archival sources, as well as from our photometric campaigns that were targeted to specific transit predictions. Our analysis indicates that transits by planet "c" (P ~ 30 d) do not currently occur, in concordance with the best-fit i = 50 degree co-planar configuration obtained by dynamical fits to the most recent radial velocity data for the system. Transits by planet "b" (P ~ 60 d) are not entirely ruled out by our observations, but our data indicate that it is very unlikely that they occur. Our experience with the Gl 876 system suggests that a distributed ground-based network of small telescopes can be used to search for transits of very low mass M-stars by terrestrial-sized planets., Comment: currently 17pp w/Figs, 10 figures; to appear in Astrophysical Journal article December 2006 v653n1

Exoplanet transit and Doppler surveys discover many binary stars during their operation that can be used to conduct a variety of ancillary science. Specifically, eclipsing binary stars can be used to study the stellar mass-radius relationship and to test predictions of theoretical stellar evolution models. By cross-referencing 24 binary stars found in the MARVELS Pilot Project with SuperWASP photometry, we find two new eclipsing binaries, TYC 0272-00458-1 and TYC 1422-01328-1, which we use as case studies to develop a general approach to eclipsing binaries in survey data. TYC 0272-00458-1 is a single-lined spectroscopic binary for which we calculate a mass of the secondary and radii for both components using reasonable constraints on the primary mass through several different techniques. For a primary mass of M_1 = 0.92 +/- 0.1 M_solar, we find M_2 = 0.610 +/- 0.036 M_solar, R_1 = 0.932 +/- 0.076 R_solar and R_2 = 0.559 +/- 0.102 R_solar, and find that both stars have masses and radii consistent with model predictions. TYC 1422-01328-1 is a triple-component system for which we can directly measure the masses and radii of the eclipsing pair. We find that the eclipsing pair consists of an evolved primary star (M_1 = 1.163 +/- 0.034 M_solar, R_1 = 2.063 +/- 0.058 R_solar) and a G-type dwarf secondary (M_2 = 0.905 +/- 0.067 M_solar, R_2 = 0.887 +/- 0.037 R_solar). We provide the framework necessary to apply this analysis to much larger datasets., Comment: Accepted for publication in AJ

A recent work of Spencer and Christy (1990) on precise monitoring of global temperature trends from satellites is critically examined. It is tentatively concluded in the present comment that remote sensing using satellite microwave radiometers can in fact provide a means for the monitoring of troposphere-averaged air temperature. However, for this to be successful more than one decade of data will be required to overcome the apparent inherent variability of global average air temperature. It is argued that the data set reported by Spencer and Christy should be subjected to careful review before it is interpreted as evidence of the presence or absence of global warming. In a reply, Christy provides specific responses to the commenters' objections.

Computer simulations have been used to study the accuracy with which excess radio-propagation path delay due to atmospheric water vapor can be determined using a microwave remote-sensing technique. A number of strategies were investigated for the remote sensing of path delay with the objective of providing a broad foundation for the development and use of water-vapor radiometers (WVR's) for geodetic applications. A data base of nearly 10 000 radiosondes from a variety of climatological regions was used for the study. Strategies were judged by their "retrieval performance" on this data base; i.e., by the rms difference between simulations of "retrieved" path delay and "true" path delay, at the zenith, averaged over a radiosonde data base. An observing approach using the frequency set 20.7/22.2/31.4 GHz was found to be close to optimum. A statistical retrieval approach using retrieval coefficients stratified for clear and cloudy weather and for individual location was found to offer a substantial improvement over the use of a single all-weather set of retrieval coefficients. It was found that a reasonably well optimized WVR, with an estimated calibration uncertainty of 0.5 K, can achieve an overall retrieval performance of: 0.27 cm, clear; 0.51 cm, cloudy; and 0.38 cm, all weather average. The weather-averaged retrieval performance for individual locations was found to vary by no more than 14 percent from the average for all locations, in spite of the fact that the mean path delay for these locations ranged from 5 to 26 cm.

Radio observations of Jupiter have been carried out at Goldstone, CA at a wavelength of 13 cm during the oppositions of 1969 and 1971. In 1969, circular-polarization and total-flux measurements were made with a 64-m radio telescope. From May through October 1971, Jupiter's flux density was measured at weekly intervals with a 26-m antenna. The upper limit to the degree of circular polarization over the longitude ranges 10-100 deg and 160-250 deg System III (1957.0) is 1%; the flux data have been used to derive a magnetospheric rotation period which is approximately 0.37 sec longer than the IAU System III (1957.0). The flux-density data define beaming curves which are apparently different from 11-cm beaming curves measured in 1964. Jupiter's peak flux density decreased by 20% between 1964 and 1971, and 8% between 1969 and 1971.