This paper reports an update to the QUEST1 (QUasar Equatorial Survey Team, Phase 1) Variability Survey (QVS) light curve catalog, which links QVS instrumental magnitude light curves to Sloan Digital ...Sky Survey (SDSS) objects and photometry. In the time since the original QVS catalog release, the overlap between publicly available SDSS data and QVS data has increased by 8% in sky coverage and 16,728 in number of matched objects. The astrometric matching and the treatment of SDSS masks have been refined for the updated catalog. We report on these improvements and present multiple bandpass light curves, global variability information, and matched SDSS photometry for 214,941 QUEST1 objects.
We present orbit‐sampled photometry of the binary system WD 2154+408. The photometric study reveals a period of
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day, which is taken to be the orbital period of the binary. No evidence is seen for either an accretion disk or mass transfer, leading to the conclusion that WD 2154+408 is not a contact or semidetached system but has detached components with a visible irradiation effect. The short orbital period also leads to the conclusion that the system passed through a common‐envelope phase at some time in the past. A single spectrum is shown exhibiting both narrow emission and broad absorption components of the Hβ line. This and the photometric variations are consistent with the system being a post–common‐envelope binary consisting of a hot white dwarf primary and a cool irradiated companion.
This work aims at constraining the size, shape, and geometric albedo of the dwarf planet candidate 2002 MS4 through the analysis of nine stellar occultation events. Using multichord detection, we ...also studied the object's topography by analyzing the obtained limb and the residuals between observed chords and the best-fitted ellipse. We predicted and organized the observational campaigns of nine stellar occultations by 2002 MS4 between 2019 and 2022, resulting in two single-chord events, four double-chord detections, and three events with three to up to sixty-one positive chords. Using 13 selected chords from the 8 August 2020 event, we determined the global elliptical limb of 2002 MS4. The best-fitted ellipse, combined with the object's rotational information from the literature, constrains the object's size, shape, and albedo. Additionally, we developed a new method to characterize topography features on the object's limb. The global limb has a semi-major axis of 412 \(\pm\) 10 km, a semi-minor axis of 385 \(\pm\) 17 km, and the position angle of the minor axis is 121 \(^\circ\) \(\pm\) 16\(^\circ\). From this instantaneous limb, we obtained 2002 MS4's geometric albedo and the projected area-equivalent diameter. Significant deviations from the fitted ellipse in the northernmost limb are detected from multiple sites highlighting three distinct topographic features: one 11 km depth depression followed by a 25\(^{+4}_{-5}\) km height elevation next to a crater-like depression with an extension of 322 \(\pm\) 39 km and 45.1 \(\pm\) 1.5 km deep. Our results present an object that is \(\approx\)138 km smaller in diameter than derived from thermal data, possibly indicating the presence of a so-far unknown satellite. However, within the error bars, the geometric albedo in the V-band agrees with the results published in the literature, even with the radiometric-derived albedo.
As part of the QUEST (QUasar Equatorial Survey Team) collaboration, I have been studying the intrinsic variability of quasars as a means of quasar detection. I first give a brief review of the quasar ...central engine that suggests the mechanism driving quasar variability, then report on the current status of the QUEST project as a whole. I discuss the data collection, reduction and analysis program, and the findings over the course of three observing seasons (February 1999–April 2001) at the 1-m Schmidt telescope at the Venezuelan National Observatory. The method of incomplete ensemble photometry was used to compile a list of variable objects from these data. I then describe the subsequent spectroscopic confirmation work carried out at the WIYN 3.5-m telescope in April 2001 and February 2002. (The WIYN Observatory is a joint facility of the University of Wisconsin-Madison, Indiana University, Yale University, and the National Optical Astronomy Observatory.) Between the two spectroscopic observing campaigns, 30 of a selected subset of variable objects were identified as quasars by means of their distinctive spectral emission lines, 50% of which are newly discovered quasars and 50% of which are independent rediscoveries of previously cataloged quasars. The number of previously cataloged quasars found in the data is used as a benchmark for statistical analysis and to predict what percentage of variability candidates should be expected to be confirmed as quasars. The percentage of known quasars that vary is seen to increase when comparing data from two observing seasons (38%) with data from all three observing seasons (61%). In addition, the colors of objects in the variability list and those of the previously cataloged quasars are studied as a possible means of increasing the efficiency of future spectroscopic observing campaigns.
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