- ID:
- ivo://CDS.VizieR/J/A+A/625/A21
- Title:
- High contrast images of NZ Lup
- Short Name:
- J/A+A/625/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Planetary systems hold the imprint of the formation and of the evolution of planets especially at young ages, and in particular at the stage when the gas has dissipated leaving mostly secondary dust grains. The dynamical perturbation of planets in the dust distribution can be revealed with high-contrast imaging in a variety of structures. SPHERE, the high-contrast imaging device installed at the VLT, was designed to search for young giant planets in long period, but is also able to resolve fine details of planetary systems at the scale of astronomical units in the scattered-light regime. As a young and nearby star, NZ Lup was observed in the course of the SPHERE survey. A debris disk had been formerly identified with HST/NICMOS. We observed this system in the near-infrared with the camera in narrow and broad band filters and with the integral field spectrograph. High contrasts are achieved by the mean of pupil tracking combined with angular differential imaging algorithms. The high angular resolution provided by SPHERE allows us to reveal a new feature in the disk which is interpreted as a superimposition of two belts of planetesimals located at stellocentric distances of ~85 and ~115au, and with a mutual inclination of about 5{deg}. Despite the very high inclination of the disk with respect to the line of sight, we conclude that the presence of a gap, that is, a void in the dust distribution between the belts, is likely. We discuss the implication of the existence of two belts and their relative inclination with respect to the presence of planets.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/439/2078
- Title:
- High-frequency A-type pulsators
- Short Name:
- J/MNRAS/439/2078
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a survey using the WASP archive to search for high-frequency pulsations in F-, A- and B-type stars. Over 1.5 million targets have been searched for pulsations with amplitudes greater than 0.5 millimagnitude. We identify over 350 stars which pulsate with periods less than 30min. Spectroscopic follow-up of selected targets has enabled us to confirm 10 new rapidly oscillating Ap stars, 13 pulsating Am stars and the fastest known {delta} Scuti star. We also observe stars which show pulsations in both the high-frequency domain and the low-frequency {delta} Scuti range. This work shows the power of the WASP photometric survey to find variable stars with amplitudes well below the nominal photometric precision per observation.
- ID:
- ivo://archive.stsci.edu/hst/hsp
- Title:
- High Speed Photometer
- Short Name:
- HST.HSP
- Date:
- 23 Jul 2020 19:49:53
- Publisher:
- Space Telescope Science Institute Archive
- Description:
- The High Speed Photometer (HSP) was one of the four original axial instruments on the Hubble Space Telescope (HST). The HSP was designed to make very rapid photometric observations of astrophysical sources in a variety of filters and passbands from the near ultraviolet to the visible. The HSP was removed from HST during the First Servicing Mission in December, 1993.
- ID:
- ivo://CDS.VizieR/J/A+A/399/1167
- Title:
- Hipparcos Variability-Induced Movers
- Short Name:
- J/A+A/399/1167
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Hipparcos observations of some variable stars, and especially of long-period (e.g. Mira) variables, reveal a motion of the photocenter correlated with the brightness variation (variability-induced mover, VIM), suggesting the presence of a binary companion. A re-analysis of the Hipparcos photometric and astrometric data (Cat. <I/239>) does not confirm the VIM solution for 62 among the 288 VIM objects (21%) in the Hipparcos catalogue. Most of these 288 VIMs are long-period (e.g. Mira) variables (LPV). The effect of a revised chromaticity correction, which accounts for the color variations along the light cycle, was then investigated. It is based on "instantaneous" V-I color indices derived from Hipparcos and Tycho-2 (Cat. <I/259>) epoch photometry. Among the 188 LPVs flagged as VIM in the Hipparcos catalogue, 89 (47%) are not confirmed as VIM after this improved chromaticity correction is applied. This dramatic decrease in the number of VIM solutions is not surprising, since the chromaticity correction applied by the Hipparcos reduction consortia was based on a fixed V-I color. Astrophysical considerations lead us to adopt a more stringent criterion for accepting a VIM solution (first-kind risk of 0.27% instead of 10% as in the Hipparcos catalogue). With this more severe criterion, only 27 LPV stars remain VIM, thus rejecting 161 of the 188 (86%) of the LPVs defined as VIMs in the Hipparcos catalogue.
- ID:
- ivo://CDS.VizieR/J/A+A/367/297
- Title:
- Hipparcos variable stars
- Short Name:
- J/A+A/367/297
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The data known as the Hipparcos Photometry obtained with the Hipparcos satellite have been investigated to find those stars which are least variable. Such stars are excellent candidates to serve as standards for photometric systems. Their spectral types suggest in which parts of the HR diagrams stars are most constant. In some cases these values strongly indicate that previous ground based studies claiming photometric variability are incorrect or that the level of stellar activity has changed.
- ID:
- ivo://archive.stsci.edu/hut
- Title:
- Hopkins Ultraviolet Telescope
- Short Name:
- HUT
- Date:
- 22 Jul 2020 21:30:05
- Publisher:
- Space Telescope Science Institute Archive
- Description:
- The Hopkins Ultraviolet Telescope (HUT) was a shuttle-borne instrument used to obtain ultraviolet spectra in the far ultraviolet region of the spectrum. It was part of the ASTRO payload complement of three co-mounted instruments that flew in December 1990 and March 1995 as Space Shuttle missions. More than 650 spectra were obtained of 340 targets. In April, 2013, the HUT data was reprocessed to improve calibration, expand metadata, add new data products, and update file formats. The current cone service uses the metadata from these reprocessed files.
- ID:
- ivo://CDS.VizieR/J/AJ/135/1350
- Title:
- Hot variable stars in NGC 330
- Short Name:
- J/AJ/135/1350
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In a sample of 150 hot stars in NGC 330, a SMC cluster containing a high fraction of Be stars, we searched for photometric variables using OGLE II data. At least one third of all stars are variable, with 38 being periodic. We found 27 pulsators ({lambda} Eri variables), six eclipsing systems, two bursting sources, and several stars with unusual photometric behavior. Pulsations are present in ~30% of known Be stars, and they are long lived, lasting more than a decade. The strongest pulsators are associated with stars evolved from the main sequence.
- ID:
- ivo://CDS.VizieR/J/A+A/626/A54
- Title:
- HR4796A dust ring Stokes images
- Short Name:
- J/A+A/626/A54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The scattering properties of the dust originating from debris discs are still poorly known. The analysis of scattered light is however a powerful remote-sensing tool to understand the physical properties of dust particles orbiting other stars. Scattered light is indeed widely used to characterise the properties of cometary dust in the solar system. We aim to measure the morphology and scattering properties of the dust from the debris ring around HR4796A in polarised optical light. We obtained high-contrast polarimetric images of HR4796A in the wavelength range 600-900nm with the SPHERE/ZIMPOL instrument on the Very Large Telescope. We measured for the first time the polarised phase function of the dust in a debris system over a wide range of scattering angles in the optical. We confirm that it is incompatible with dust particles being compact spheres under the assumption of the Mie theory, and propose alternative scenarios compatible with the observations, such as particles with irregular surface roughness or aggregate particles.
- ID:
- ivo://CDS.VizieR/J/ApJ/864/111
- Title:
- HST/ACS one-year observations of M51 stars
- Short Name:
- J/ApJ/864/111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar photometric variability offers a novel probe of the interior structure and evolutionary state of stars. Here we present a census of stellar variability on day to decade timescales across the color-magnitude diagram (CMD) for 73000 stars brighter than M_I,814_=-5 in the Whirlpool Galaxy (M51). Our Cycle 24 Hubble Space Telescope (HST) program acquired V606- and I814-band images over 34 epochs spanning 1 year with pseudo-random cadences enabling sensitivity to periods from days to months. We supplement these data with archival V- and I-band HST data obtained in 1995 and 2005, providing sensitivity to variability on decade timescales. At least 50% of stars brighter than M_I,814_=-7 show strong evidence for variability within our Cycle 24 data; among stars with V_606_-I_814_>2 the variability fraction rises to ~100%. Large amplitude variability (>0.3mag) on decade timescales is restricted to red supergiants (RSGs) and very luminous blue stars. Both populations display fairly smooth variability on month-year timescales. The Cepheid instability strip is clearly visible in our data, although the variability fraction within this region never exceeds ~10%. The location of variable stars across the CMD broadly agrees with theoretical sources of variability, including the instability strip, RSG pulsational instabilities, long-period fundamental mode pulsations, and radiation-dominated envelopes in massive stars. Our data can be used to place stringent constraints on the precise onset of these various instabilities and their lifetimes and growth rates.
- ID:
- ivo://CDS.VizieR/J/ApJ/754/4
- Title:
- HST monitoring of flaring stars in the Galactic bulge
- Short Name:
- J/ApJ/754/4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We utilize the Sagittarius Window Eclipsing Extrasolar Planet Search Hubble Space Telescope/Advanced Camera for Surveys data set for a Deep Rapid Archival Flare Transient Search (DRAFTS) to constrain the flare rate toward the older stellar population in the Galactic bulge. During seven days of monitoring 229293 stars brighter than V=29.5, we find evidence for flaring activity in 105 stars between V=20 and V=28. We divided the sample into non-variable stars and variable stars whose light curves contain large-scale variability. The flare rate on variable stars is ~700 times that of non-variable stars, with a significant correlation between the amount of underlying stellar variability and peak flare amplitude. The flare energy loss rates are generally higher than those of nearby well-studied single dMe flare stars.
