- ID:
- ivo://CDS.VizieR/J/other/Nat/485.478
- Title:
- Superflares on solar-type stars
- Short Name:
- J/other/Nat/485.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 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.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/890/46
- Title:
- 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.
- ID:
- ivo://CDS.VizieR/J/ApJS/75/241
- Title:
- Supergalactic plane redshift survey
- Short Name:
- J/ApJS/75/241
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/568/A55
- Title:
- Supergiant fast X-ray transients monitoring
- Short Name:
- J/A+A/568/A55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 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.
- ID:
- ivo://CDS.VizieR/J/ApJ/599/1049
- Title:
- Supergiant molecular complexes in the Antennae
- Short Name:
- J/ApJ/599/1049
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/545/A99
- Title:
- 2 supergiants and 2 hypergiants radio spectra
- Short Name:
- J/A+A/545/A99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 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_.
18327. Supergiants in NGC 672
- ID:
- ivo://CDS.VizieR/J/AJ/112/2559
- Title:
- Supergiants in NGC 672
- Short Name:
- J/AJ/112/2559
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 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.
- ID:
- ivo://CDS.VizieR/J/ApJ/865/106
- Title:
- SUPER GOODS. III. ALMA data for SCUBA-2 sources
- Short Name:
- J/ApJ/865/106
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the >4{sigma} sources in the most sensitive 100arcmin^2^ area (rms<0.56mJy) of a SCUBA-2 850{mu}m survey of the GOODS-S and present the 75 band-7 ALMA sources (>4.5{sigma}) obtained from high-resolution interferometric follow-up observations. The raw SCUBA-2 >4{sigma} limit is fainter than 2.25mJy throughout this region, and deboosting corrections would lower this further. Of the 53 SCUBA-2 sources in this sample, only five have no ALMA detections, while 13% (68% confidence range 7%-19%) have multiple ALMA counterparts. Color-based high-redshift dusty galaxy selection techniques find at most 55% of the total ALMA sample. In addition to using literature spectroscopic and optical/near-infrared photometric redshifts, we estimate far infrared photometric redshifts based on an Arp 220 template. We identify seven z>~4 candidates. We see the expected decline with redshift of the 4.5 and 24{mu}m to 850{mu}m flux ratios, confirming these as good diagnostics of z>~4 candidates. We visually classify 52 ALMA sources, finding 44% (68% confidence range 35%-53%) to be apparent mergers. We calculate rest-frame 2-8keV and 8-28keV luminosities using the 7Ms Chandra X-ray image. Nearly all of the ALMA sources detected at 0.5-2keV are consistent with a known X-ray luminosity to 850{mu}m flux relation for star-forming galaxies, while most of those detected at 2-7keV are moderate-luminosity AGNs that lie just above the 2-7keV detection threshold. The latter largely have substantial obscurations of logN_H_=23-24cm^-2^, but two of the high-redshift candidates may even be Compton thick.
- ID:
- ivo://CDS.VizieR/J/ApJ/837/139
- Title:
- SUPER GOODS. I. Ultradeep SCUBA-2 survey
- Short Name:
- J/ApJ/837/139
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this first paper in the SUPER GOODS series on powerfully star-forming galaxies in the two GOODS fields, we present a deep SCUBA-2 survey of the GOODS-N at both 850 and 450{mu}m (central rms noise of 0.28mJy and 2.6mJy, respectively). In the central region, the 850{mu}m observations cover the GOODS-N to near the confusion limit of ~1.65mJy, while over a wider 450arcmin^2^ region-well complemented by Herschel far-infrared imaging-they have a median 4{sigma} limit of 3.5mJy. We present >=4{sigma} catalogs of 186 850{mu}m and 31 450{mu}m selected sources. We use interferometric observations from the Submillimeter Array (SMA) and the Karl G. Jansky Very Large Array (VLA) to obtain precise positions for 114 SCUBA-2 sources (28 from the SMA, all of which are also VLA sources). We present new spectroscopic redshifts and include all existing spectroscopic or photometric redshifts. We also compare redshifts estimated using the 20cm/850{mu}m and the 250cm/850{mu}m flux ratios. We show that the redshift distribution increases with increasing flux, and we parameterize the dependence. We compute the star formation history and the star formation rate (SFR) density distribution functions in various redshift intervals, finding that they reach a peak at z=2-3 before dropping to higher redshifts. We show that the number density per unit volume of SFR>~500M_{sun}_/yr galaxies measured from the SCUBA-2 sample does not change much relative to that of lower SFR galaxies from UV selected samples over z=2-5, suggesting that, apart from changes in the normalization, the shape in the number density as a function of SFR is invariant over this redshift interval.
- ID:
- ivo://CDS.VizieR/J/ApJ/887/23
- Title:
- SUPER GOODS. IV. 850um data of CDFS X-ray sources
- Short Name:
- J/ApJ/887/23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Chandra Deep Field (CDF)-S is the deepest X-ray image available and will remain so for the near future. We provide a spectroscopic (64.5%; 64% with spectral classifications) and photometric redshift catalog for the full 7Ms sample, but much of our analysis focuses on the central (off-axis angles <5.7') region, which contains a large, faint ALMA sample of 75 >4.5{sigma} 850{mu}m sources. We measure the 850{mu}m fluxes at the X-ray positions using the ALMA images, where available, or an ultradeep SCUBA-2 map. We find that the full X-ray sample produces ~10% of the 850{mu}m extragalactic background light. We separate the submillimeter-detected X-ray sources into star-forming galaxies and active galactic nuclei (AGNs) using a star formation rate (SFR) versus X-ray luminosity calibration for high-SFR galaxies. We confirm this separation using the X-ray photon indices. We measure the X-ray fluxes at the accurate positions of the 75 ALMA sources and detect 70% at >3{sigma} in either the 0.5-2 or 2-7keV bands. However, many of these may produce both their X-ray and submillimeter emission by star formation. Indeed, we find that only 20% of the ALMA sources have intermediate X-ray luminosities (rest-frame 8-28 keV luminosities of 10^42.5^-10^44^erg/s), and none has a high X-ray luminosity (>10^44^erg/s). Conversely, after combining the CDF-S with the CDF-N, we find extreme star formation (SFR>300M_{sun}_/yr) in some intermediate X-ray luminosity sources but not in any high X-ray luminosity sources. We argue that the quenching of star formation in the most luminous AGNs may be a consequence of the clearing of gas in these sources.