The SuperCOSMOS data primarily originate from scans of the UK Schmidt
and Palomar POSS II blue, red and near-IR sky surveys. The ESO Schmidt
R (dec < -17.5) and Palomar POSS-I E (dec > -17.5) surveys have also
been scanned and provide an early (1st) epoch red measurement.
Mirrored here is the source table containing four-plate multi-colour,
multi-epoch data which are merged into a single source catalogue for
general science exploitation. Within the GAVO DC, some column names
have been adapted to local customs (primarily positions, proper
motions).
We present a new technique to measure multi-wavelength "super-deblended" photometry from highly confused images, which we apply to Herschel and ground-based far-infrared (FIR) and (sub-)millimeter (mm) data in the northern field of the Great Observatories Origins Deep Survey (GOODS-N). There are two key novelties. First, starting with a large database of deep Spitzer 24{mu}m and VLA 20cm detections that are used to define prior positions for fitting the FIR/submm data, we perform an active selection of useful priors independently at each frequency band, moving from less to more confused bands. Exploiting knowledge of redshift and all available photometry, we identify hopelessly faint priors that we remove from the fitting pool. This approach significantly reduces blending degeneracies and allows reliable photometry to be obtained for galaxies in FIR+mm bands. Second, we obtain well-behaved, nearly Gaussian flux density uncertainties, individually tailored to all fitted priors for each band. This is done by exploiting extensive simulations that allow us to calibrate the conversion of formal fitting uncertainties to realistic uncertainties, depending on directly measurable quantities. We achieve deeper detection limits with high fidelity measurements and uncertainties at FIR+mm bands. As an illustration of the utility of these measurements, we identify 70 galaxies with z>=3 and reliable FIR+mm detections. We present new constraints on the cosmic star formation rate density at 3<z<6, finding a significant contribution from z>=3 dusty galaxies that are missed by optical-to-near-infrared color selection. Photometric measurements for 3306 priors, including more than 1000 FIR+mm detections, are released publicly with our catalog.
By extending our previous study by Maehara et al. (2012, Cat. J/other/Nat/485.478), we searched for superflares on G-type dwarfs (solar-type stars) using Kepler data for a longer period (500 days) than that (120 days) in our previous study. As a result, we found 1547 superflares on 279 G-type dwarfs, which is much more than the previous 365 superflares on 148 stars. Using these new data, we studied the statistical properties of the occurrence rate of superflares, and confirmed the previous results, i.e., the occurrence rate (dN/dE) of superflares versus flare energy (E) shows a power-law distribution with dN/dE{prop.to}E^-{alpha}^, where {alpha}~2. It is interesting that this distribution is roughly similar to that for solar flares. In the case of the Sun-like stars (with surface temperature 5600-6000K and slowly rotating with a period longer than 10 days), the occurrence rate of superflares with an energy of 10^34^-10^35^erg is once in 800-5000yr. We also studied long-term (500 days) stellar brightness variation of these superflare stars and found that in some G-type dwarfs the occurrence rate of superflares was extremely high, ~57 superflares in 500 days (i.e., once in 10 days). In the case of Sun-like stars, the most active stars show a frequency of one superflare (with 10^34^erg) in 100 days. There is evidence that these superflare stars have extremely large starspots with a size about 10 times larger than that of the largest sunspot. We argue that the physical origin of the extremely high occurrence rate of superflares in these stars may be attributed to the existence of extremely large starspots.
Solar flares are caused by the sudden release of magnetic energy stored near sunspots. They release 10<SUP>29</SUP> to 10<SUP>32</SUP>ergs of energy on a timescale of hours. Similar flares have been observed on many stars, with larger 'superflares' seen on a variety of stars, some of which are rapidly rotating and some of which are of ordinary solar type. The small number of superflares observed on solar-type stars has hitherto precluded a detailed study of them. Here we report observations of 365 superflares, including some from slowly rotating solar-type stars, from about 83,000 stars observed over 120 days. Quasi-periodic brightness modulations observed in the solar-type stars suggest that they have much larger starspots than does the Sun. The maximum energy of the flare is not correlated with the stellar rotation period, but the data suggest that superflares occur more frequently on rapidly rotating stars. It has been proposed that hot Jupiters may be important in the generation of superflares on solar-type stars, but none have been discovered around the stars that we have studied, indicating that hot Jupiters associated with superflares are rare.
Superflares on solar-type stars from TESS first year
Short Name:
J/ApJ/890/46
Date:
21 Oct 2021
Publisher:
CDS
Description:
Superflares, which are strong explosions on stars, have been well studied with the progress of spacetime-domain astronomy. In this work, we present the study of superflares on solar-type stars using Transiting Exoplanet Survey Satellite (TESS) data. Thirteen sectors of observations during the first year of the TESS mission covered the southern hemisphere of the sky, containing 25734 solar-type stars. We verified 1216 superflares on 400 solar-type stars through automatic search and visual inspection with 2 minute cadence data. Our result suggests a higher superflare frequency distribution than the result from Kepler. This may be because the majority of TESS solar-type stars in our data set are rapidly rotating stars. The power-law index {gamma} of the superflare frequency distribution (dN/dE{propto}E^-{gamma}^) is constrained to be {gamma}=2.16+/-0.10, which is a little larger than that of solar flares but consistent with the results from Kepler. Because only seven superflares of Sun-like stars are detected, we cannot give a robust superflare occurrence frequency. Four stars were accompanied by unconfirmed hot planet candidates. Therefore, superflares may possibly be caused by stellar magnetic activities instead of planet-star interactions. We also find an extraordinary star, TIC43472154, which exhibits about 200 superflares per year. In addition, the correlation between the energy and duration of superflares (T_duration_{propto}E^{beta}^) is analyzed. We derive the power-law index to be {beta}=0.42+/-0.01, which is a little larger than {beta} = 1/3 from the prediction according to magnetic reconnection theory.
Redshift measurements, about 1000 of which are new, are presented for 1314 galaxies in a survey toward the apex of the large-scale streaming flow for ellipticals.
We perform the first high-sensitivity soft X-ray long-term monitoring with Swift/XRT of three relatively unexplored supergiant fast X-ray transients (SFXTs), IGR J08408-4503, IGR J16328-4726, and IGR J16465-4507, whose hard X-ray duty cycles are the lowest measured among the SFXT sample, and compare their properties with those of the prototypical SFXTs. The behaviour of J08408 and J16328 resembles that of other SFXTs, and it is characterized by a relatively high inactivity duty cycle (IDC) and pronounced dynamic range (DR) in the X-ray luminosity. Like the SFXT prototypes, J08408 shows two distinct populations of flares, the first one associated with the brightest outbursts (L_X_>=10^35-36^erg/s), the second one comprising less bright events with L_X_<=10^35^erg/s. This double-peaked distribution seems to be a ubiquitous feature of the extreme SFXTs. The lower DR of J16328 suggests it is an intermediate SFXT. We find J16465 is characterized by IDC~5% and DR~40, reminiscent of classical supergiant HMXBs. The duty cycles measured with XRT are found to be comparable with those reported previously by BAT and INTEGRAL, when the higher limiting sensitivities of these instruments are taken into account and sufficiently long observational campaigns are available. We prove that no clear correlation exists between the duty cycles of the SFXTs and their orbital periods, which makes it difficult to interpret the SFXT peculiar variability by only using arguments related to the properties of supergiant star winds. Our findings favour the idea that a correct interpretation of the SFXT phenomenology requires a mechanism to strongly reduce the mass accretion rate onto the compact object during most of its orbit around the companion, as proposed in a number of theoretical works.
We have used previously published observations of the CO emission from the Antennae (NGC 4038/4039) to study the detailed properties of the supergiant molecular complexes with the goal of understanding the formation of young massive star clusters.
We present Herschel/HIFI spectra observed towards two Red Supergiants (NML Cyg, Betelgeuse) and two Yellow Hypergiants (AFGL2343, IRC+10420). The data focus on various transitions of ^12^CO, ^13^CO, ortho- and para- water, as well as some other bonus lines such as SiO, OH or NH_3_.
V, R, and I CCD images are used to investigate the photometric properties and spatial distribution of supergiants in the nearby interacting galaxy NGC 672. Not counting stars imbedded in H II regions, our sample consists of 237 objects. The (V-R,V-I) two-color diagram indicates that the majority of these stars have spectral types between A-K. Statistical tests show that the outer region of NGC 672 contains a redder population of supergiants than the inner region. Comparisons with theoretical evolutionary tracks indicate that the majority of the supergiants in NGC 672 have progenitor masses between 15M_{sun}_ and 25M_{sun}_, and that the inner regions contain stars that are more massive than in the outer disk, indicating that an age gradient is present. The luminosity functions in all three bandpasses follow power laws, and the exponent in V=0.79+/-0.06, in good agreement with other galaxies. The brightest red supergiants occur at V~22.0, from which we derive a distance modulus of 29.5, corresponding to 7.9(+1.0)(-0.9)Mpc.