The Taiwanese-American Occultation Survey: The Multi-Telescope Robotic Observatory

Lehner, M. J.; Wen, C. Y.; Wang, J.-H.; Marshall, Stuart; Schwamb, Megan E.; Zhang, Z.-W.; Bianco, Federica; Giammarco, J.; Porrata, R.; Alcock, C.; Axelrod, T. S.; Byun, Yong−Ik; Chen, W. P.; Cook, K. H.; Davé, Romeel; King, S. K.; Lee, T.; Lin, H. C.; Wang, S.-Y.; Rice, John A.; Pater, Imke de

doi:10.1086/597516

Cited by 25 publications

(15 citation statements)

References 23 publications

(32 reference statements)

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“…We corrected for bias and flat-fielding in the usual manner, and performed standard aperture photometry. The observers except for TAOS 34 used standard filters (B, V, R C , I C ; we write R and I for R C and I C in the main text and figures for brevity. (Extended Data Table 1) and measured magnitudes of V404 Cyg relative to local comparison stars whose magnitudes were measured by A. Henden (sequence 15167RN) from the AAVSO Variable Star Database 35 .…”

Section: Detailed Methods Of Optical Observationsmentioning

confidence: 99%

Repetitive patterns in rapid optical variations in the nearby black-hole binary V404 Cygni

Kimura

Isogai

Katô

et al. 2016

Nature

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How black holes accrete surrounding matter is a fundamental yet unsolved question in astrophysics. It is generally believed that matter is absorbed into black holes via accretion disks, the state of which depends primarily on the mass-accretion rate. When this rate approaches the critical rate (the Eddington limit), thermal instability is supposed to occur in the inner disk, causing repetitive patterns of large-amplitude X-ray variability (oscillations) on timescales of minutes to hours. In fact, such oscillations have been observed only in sources with a high mass-accretion rate, such as GRS 1915+105 (refs 2, 3). These large-amplitude, relatively slow timescale, phenomena are thought to have physical origins distinct from those of X-ray or optical variations with small amplitudes and fast timescales (less than about 10 seconds) often observed in other black-hole binaries-for example, XTE J1118+480 (ref. 4) and GX 339-4 (ref. 5). Here we report an extensive multi-colour optical photometric data set of V404 Cygni, an X-ray transient source containing a black hole of nine solar masses (and a companion star) at a distance of 2.4 kiloparsecs (ref. 8). Our data show that optical oscillations on timescales of 100 seconds to 2.5 hours can occur at mass-accretion rates more than ten times lower than previously thought. This suggests that the accretion rate is not the critical parameter for inducing inner-disk instabilities. Instead, we propose that a long orbital period is a key condition for these large-amplitude oscillations, because the outer part of the large disk in binaries with long orbital periods will have surface densities too low to maintain sustained mass accretion to the inner part of the disk. The lack of sustained accretion--not the actual rate--would then be the critical factor causing large-amplitude oscillations in long-period systems.

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Section: Detailed Methods Of Optical Observationsmentioning

confidence: 99%

Repetitive patterns in rapid optical variations in the nearby black-hole binary V404 Cygni

Kimura

Isogai

Katô

et al. 2016

Nature

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“…The ROTSE-IIIc and TAOS optical observations started around t = 60 s. The ROTSE-IIIc telescope (Akerlof et al 2003) detected the GRB 071112C optical afterglow with brightness R = 17.1 ± 0.2 at t = 90.9 s. At the same time, the optical afterglow was also detected by TAOS-A and TAOS-B telescopes (Lehner et al 2009) with sequences of 1 s and 5 s exposures, respectively. Subsequently, a series of optical multiband follow-up observations were also carried out by Xinglong 0.8 m and 1.0 m telescope in China (Zheng et al 2008), the Lulin One-meter telescope (LOT) in Taiwan Urata et al 2005), and the 0.5 m MITSuME telescope in Japan (Kotani 2005).…”

Section: Optical and X-ray Temporal Analysismentioning

confidence: 87%

GRB 071112c: A Case Study of Different Mechanisms in X-Ray and Optical Temporal Evolution

Huang¹,

Urata²,

Tung³

et al. 2012

ApJ

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We present a study on GRB 071112C X-ray and optical light curves. In these two wavelength ranges, we have found different temporal properties. The R-band light curve showed an initial rise followed by a single power-law decay, while the X-ray light curve was described by a single power-law decay plus a flare-like feature. Our analysis shows that the observed temporal evolution cannot be described by the external shock model in which the X-ray and optical emission are produced by the same emission mechanism. No significant color changes in multi-band light curves and a reasonable value of the initial Lorentz factor (Γ 0 = 275 ± 20) in a uniform interstellar medium support the afterglow onset scenario as the correct interpretation for the early R band rise. The result suggests that the optical flux is dominated by afterglow. Our further investigations show that the X-ray flux could be created by an additional feature related to energy injection and X-ray afterglow. Different theoretical interpretations indicate the additional feature in X-ray can be explained by either late internal dissipation or local inverse-Compton scattering in the external shock.

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“…The zipper-mode data are most suitable to study truly fast varying phenomena such as stellar flaring, but they were not used in the results reported in this paper so will not be discussed further. Technical details of the TAOS operation can be found in Lehner et al (2009).…”

Section: Observations and Data Reductionmentioning

confidence: 99%

The Taiwanese-American Occultation Survey Project Stellar Variability. Ii. Detection of 15 Variable Stars

Mondal

Lin

Chen

et al. 2010

The Astronomical Journal

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The Taiwanese-American Occultation Survey (TAOS) project has collected more than a billion photometric measurements since 2005 January. These sky survey datacovering timescales from a fraction of a second to a few hundred days-are a useful source to study stellar variability. A total of 167 star fields, mostly along the ecliptic plane, have been selected for photometric monitoring with the TAOS telescopes. This paper presents our initial analysis of a search for periodic variable stars from the timeseries TAOS data on one particular TAOS field, No. 151 (RA = 17 h 30 m 6. s 67, Dec = 27 • 17 ′ 30 ′′ , J2000), which had been observed over 47 epochs in 2005. A total of 81 candidate variables are identified in the 3 square degree field, with magnitudes in the range 8 < R < 16. On the basis of the periodicity and shape of the lightcurves, 29 variables, 15 of which were previously unknown, are classified as RR Lyrae, Cepheid, δ Scuti, SX Phonencis, semi-regular and eclipsing binaries.

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The Taiwanese-American Occultation Survey: The Multi-Telescope Robotic Observatory

Cited by 25 publications

References 23 publications

Repetitive patterns in rapid optical variations in the nearby black-hole binary V404 Cygni

Repetitive patterns in rapid optical variations in the nearby black-hole binary V404 Cygni

GRB 071112c: A Case Study of Different Mechanisms in X-Ray and Optical Temporal Evolution

The Taiwanese-American Occultation Survey Project Stellar Variability. Ii. Detection of 15 Variable Stars

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