Minute-cadence Observations of the LAMOST Fields with the TMTS: I. Methodology of Detecting Short-period Variables and Results from the first-year Survey

Abstract

Tsinghua University-Ma Huateng Telescopes for Survey (TMTS), located at Xinglong Station of NAOC, has a field of view up to 18 deg2. The TMTS has started to monitor the LAMOST sky areas since 2020, with the uninterrupted observations lasting for about 6 hours on average for each sky area and a cadence of about 1 minute. Here we introduce the data analysis and preliminary scientific results for the first-year observations, which covered 188 LAMOST plates (≈1970 deg2). These observations have generated over 4.9 million uninterrupted light curves, with at least 100 epochs for each of them. These light curves correspond to 4.26 million Gaia-DR2 sources, among which 285 thousand sources are found to have multi-epoch spectra from the LAMOST. By analysing these light curves with the Lomb-Scargle periodograms, we identify more than 3700 periodic variable star candidates with periods below ≈7.5 hours, primarily consisting of eclipsing binaries and δ Scuti stars. Those short-period binaries will provide important constraints on theories of binary evolution and possible sources for space gravitational wave experiments in the future. Moreover, we also identified 42 flare stars by searching rapidly-evolving signals in the light curves. The densely-sampled light curves from the TMTS allow us to better quantify the shapes and durations for these flares.

Observations of the Very Young Type Ia Supernova 2019np with Early-excess Emission

“…High-cadence monitoring is also essential to probe these properties from the outer to inner parts of the ejecta as the photosphere continuously recedes into the exploding WD. Facilitated by the alert streams of modern wide-field, high-cadence transient searches, such as the Zwicky Transient Facility (Bellm et al 2019a,b), ATLAS (Tonry 2011), ASAS-SN (Shappee et al 2014), DLT40 (Tartaglia et al 2018) and TMTS (Lin et al 2022), rapid photometric and spectroscopic follow-up observations will provide a more comprehensive characterization of the early behaviors of SNe Ia. An extensive sample of early SNe Ia will enable stringent tests among various models that may account for the flux excess in their early luminosity evolution.…”

An 18.9-minute Blue Large-Amplitude Pulsator Crossing the "Hertzsprung Gap'' of Hot Subdwarfs

“…The minute-cadence observations by Tsinghua University -Ma Huateng Telescopes for Survey (TMTS) enable the search of variable stars with periods shorter than 1 hr. TMTS J035143.63+584504.2 is such a newly discovered short-period variable, having an 18.9 min period and a peak-to-peak amplitude of ∼ 0.3 mag in white light 3 (Fig. 6).…”

“…The period-amplitude diagram of 24 confirmed BLAPs [1][2][3][4][5][6] and 20 BLAP candidates 4 is shown in Fig. 1.…”

The Spectroscopic Binaries from the LAMOST Medium-resolution Survey. I. Searching for Double-lined Spectroscopic Binaries with a Convolutional Neural Network

“…A subproject toward four K2 plates, namely, the LAMOST-TD survey (Wang et al 2021c), has led to the discovery of a subgiant with an undetected 1-3 M e companion (Yang et al 2021a). Minutecadence photometry is obtained for LAMOST MRS fields, as well to study short-period variables (Lin et al 2022).…”