Intraday Variation of Sagittarius A* at Short Millimeter Wavelengths

Miyazaki, Akira; Tsutsumi, Takahiro; Tsuboi, Masamichi

doi:10.1086/424004

Cited by 94 publications

(123 citation statements)

References 27 publications

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“…Similar flares of Sgr A * were also detected at 1-mm wavelength using the Sub-Millimeter Array (SMA) [12]. Moreover, the intraday variations (IDVs) in the Sgr A * flux density at mm-wavelengths were detected [10]. In recent years, X-ray and infrared flares have also been detected, indicating very short timescales and violent intensity increases (X-rays: [13,14]; IR: [15,16]).…”

Section: Introductionmentioning

confidence: 68%

“…We detected the intraday variation (IDV) of Sgr A * on the 7th March, 2000 [10]. As shown in the upper panel of figure 1, the light curves of Sgr A * in March 2000 indicate particularly strong variability in the 100 and 140 GHz bands in the active phase of Flare II.…”

Section: Intraday Variationmentioning

confidence: 86%

“…The most prominent flare was observed on March 7, 2000 in the 140 GHz band, and the peak flux density at 146 GHz was 3.9 ± 0.8 Jy. On the 7th March, 2000, the Sgr A * flux density have strongly increased during observing session, thus it indicates obviously the IDV [10]. The flux density increases about 30% during 30 minutes, and the twofold timescale of the IDV is estimated to be about 1.5 hours assuming that the increase has a constant gradient [10].…”

Section: Intraday Variationmentioning

confidence: 94%

“…We corrected the measured flux densities of Sgr A * for the decorrelation, and averaged two measured flux densities of Sgr A * which were individually calibrated by each of the two phase calibrators. A more detailed description of the observations and the data calibrations have also been presented in our other papers [9,10,11]. figure 1) with duration of, roughly, one month during the whole observing period [11].…”

Section: Observationsmentioning

confidence: 99%

“…Earlier, in 1990, significant flux variations of Sgr A * at 89 GHz were reported by [6]. Since 1996, we have been monitoring Sgr A * 3-& 2-mm flux densities using the Nobeyama Millimeter Array (NMA), the Nobeyama Radio Observatory 5 , Japan (see figure 1; [7,8,9,10,11]). We detected several Sgr A * flares with typical durations of a few weeks [7,8].…”

Section: Introductionmentioning

confidence: 99%

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Flux monitoring of Sagittarius A* at mm-wavelengths

Miyazaki

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et al. 2006

J. Phys.: Conf. Ser.

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Section: Introductionmentioning

confidence: 68%

Section: Intraday Variationmentioning

confidence: 86%

Section: Intraday Variationmentioning

confidence: 94%

Section: Observationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Flux monitoring of Sagittarius A* at mm-wavelengths

Miyazaki

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et al. 2006

J. Phys.: Conf. Ser.

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Greenland telescope project: Direct confirmation of black hole with sub‐millimeter VLBI

et al. 2014

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A 12 m diameter radio telescope will be deployed to the Summit Station in Greenland to provide direct confirmation of a Super Massive Black Hole (SMBH) by observing its shadow image in the active galaxy M87. The telescope (Greenland Telescope: GLT) is to become one of the Very Long Baseline Interferometry (VLBI) stations at sub-millimeter (submm) regime, providing the longest baseline >9000 km to achieve an exceptional angular resolution of 20 μas at 350 GHz, which will enable us to resolve the shadow size of~40 μas. The triangle with the longest baselines formed by the GLT, the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, and the Submillimeter Array (SMA) in Hawaii will play a key role for the M87 observations. We have been working on the image simulations based on realistic conditions for a better understanding of the possible observed images. In parallel, retrofitting of the telescope and the site developments are in progress. Based on 3 years of opacity monitoring at 225 GHz, our measurements indicate that the site is excellent for submm observations, comparable to the ALMA site. The GLT is also expected to make single-dish observations up to 1.5 THz.

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Flares of Sagittarius A^*at Short Millimeter Wavelengths

Miyazaki

Tsutsumi

Tsuboi

2003

Proceedings of the Galactic Center Workshop 2002

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We have performed monitoring observations of the flux density toward the Galactic center compact radio source, Sagittarius A* (Sgr A*), which is a supermassive black hole, from 1996 to 2005 using the Nobeyama Millimeter Array of the Nobeyama Radio Observatory, Japan. These monitoring observations of Sgr A* were carried out in the 3-and 2-mm (100 and 140 GHz) bands, and we have detected several flares of Sgr A*. We found intraday variation of Sgr A* in the 2000 March flare. The twofold increase timescale is estimated to be about 1.5 hr at 140 GHz. This intraday variability suggests that the physical size of the flare-emitting region is compact on a scale at or below about 12 AU (≈150 RS; Schwarzschild radius). On the other hand, clear evidence of long-term periodic variability was not found from a periodicity analysis of our current millimeter data set. this period, we detected no significant mm-flare in unfavorable weather conditions.Reference [20] reported the presence of a 106 day periodicity in the centimeter flux variability of Sgr A* from the analysis of data observed with the VLA over 20 years. We showed that the millimeter light curve exhibits distinct high and low activity states, by folding our NMA data with this period of 106 days [14]. These results may indicate a quasi-periodic flux variability of Sgr A* at mm-wavelengths. Then we carried out a periodicity analysis using the Lomb-Scargle periodogram method for our NMA data at 3-mm [18]. However, no significant peak in the normalized power spectra is found for the entire 3-mm data set. For the subset of these data after 2000, the power spectra has a peak at 0.0101d −1 corresponding to a ~99 day period, with a significance level of 0.37 (false alarm probability). Thus, from the analysis, this periodicity is not significant for our data [18]. Our current sampling is probably insufficient to detect a periodicity, if we consider possible fluctuations in the period, as indicated in recent analysis of VLA cm-data [21].

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Intraday Variation of Sagittarius A* at Short Millimeter Wavelengths

Cited by 94 publications

References 27 publications

Flux monitoring of Sagittarius A* at mm-wavelengths

Flux monitoring of Sagittarius A* at mm-wavelengths

Greenland telescope project: Direct confirmation of black hole with sub‐millimeter VLBI

Flares of Sagittarius A^*at Short Millimeter Wavelengths

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Intraday Variation of Sagittarius A* at Short Millimeter Wavelengths

Cited by 94 publications

References 27 publications

Flux monitoring of Sagittarius A* at mm-wavelengths

Flux monitoring of Sagittarius A* at mm-wavelengths

Greenland telescope project: Direct confirmation of black hole with sub‐millimeter VLBI

Flares of Sagittarius A*at Short Millimeter Wavelengths

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Flares of Sagittarius A^*at Short Millimeter Wavelengths