For HD , the gas model in Kral et al. For these systems, more observations are needed and more careful self-consistent modelling must be done to account for shielding to give a coherent CO content. However, for non-detections with much lower masses , we convert the upper limits in mass we found in Section 3.
We note that these CO discs if they exist at all are most likely not self-shielded because the upper limits in surface density we find in Table 6 are at least two orders of magnitude smaller than for HD and checking in Visser et al. In red, we show the extent of upper limits based on non-LTE calculations for a wide range of temperatures and electron densities see Fig.
We conclude that the upper limits we obtained with ALMA are, so far, not at odds with the composition of Solar system comets. Assuming that the LTE upper limits are correct and using the width of belts obtained from other studies Churcher et al.
This result for HR A was already pointed out in Kennedy et al. Photodissociation time-scales are mainly driven by the ISRF. It leads to much stronger constraints when comparing to measured outgassing rates in our Solar system. We note that these calculations assumed no shielding for either CO or CN and that the emission is optically thin ; CO could self-shield and carbon could shield CO even more, but CN should be less affected. These results could be explained by different scenarios.
The latter is certainly true for HD and should be checked further for HD The coordinates of the brightest pixel of the CO emission are RA However, the PA of the CO putative detection seems to be almost perpendicular to the PA of the continuum, so the CO may be due to a cloud along the line of sight.
But we note that the cloud is roughly at the stellar velocity and the spectrum shows a double-peaked profile, which is usually due to circumstellar discs. We just report this unexplained CO detection without finding convincing explanations owing to its origin.
If it is a cloud then its intracloud motions could be complex enough to create a double-peaked profile and if it is circumstellar then the PA of the gas disc is definitely not well oriented compared to the PA of the dust disc. Further observations at higher resolution would be needed to confirm whether or not this CO is bound to the star and start investigating different possible scenarios. We looked for dust, as well as gas emission CO and CN.
For instance, we provide the first detection in the mm for HD , which we also resolve see Fig. We detect emission from the star HD located at This is the first detection of gas around HD and around any G-type star. This detection around a star similar to our Sun raises questions as to whether gas could also have been released early in the Solar system lifetime and contributed to feeding the atmospheres of its 8 giant and terrestrial planets early-on with gas released by its early planetesimal belts Kral et al.
We speculate that this discrepancy may be explained from CO self-shielding and shielding from carbon that would prolong the CO lifetime and allow CO to viscously spread in the inner region see Kral et al.
For the systems with no CO detections, we derive upper limits in CO mass as well as upper limits on the CO content in planetesimals of these belts. We find systems assuming LTE where the CO ice mass fraction is already low compared to Solar system comets HD , HD , HD , HR A , which may indicate that the CO content in these planetesimals is very different than in our Solar system or that CO is not released at all or much less efficiently in these systems for reasons that are yet to be understood.
We thank the referee for their very thoughtful report that improved the paper. ALMA Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. However, this non-detection puts a constraint on the slope of the modified blackbody and hence size distribution of the grains that fits the SED as explained further in Section 4. HD is surrounded by warm dust very close to its host star, which yields almost no emission at 1.
For the radius of HD , we assumed a real to blackbody radius ratio of 2. With no carbon observations at hand, we cannot say that carbon shielding is non-existent. If carbon is present in sufficient quantity to shield CO then we would predict even lower amount of CO ice trapped on the grains, hence our upper limits would still be valid. Allison A. Beichman C. Beust H. Bohren C. Brandeker A. Burns J. Cataldi G. Cavallius M. Chen C.
Churcher L. Collings M. Cordiner M. Astron Czechowski A. De Rosa R. Dent W. Dickinson A. Dohnanyi J. Draine B. Dullemond C. Google Scholar. Google Preview. Engler N. Foreman-Mackey D. Gaia Collaboration et al. Gibbs A. Gontcharov G. Goodman J. Greaves J. Grigorieva A. Higuchi A. Holland W. Hom J. Hughes A. Husser T. Jackson A.
Kalas P. Kennedy G. Kharchenko N. Kral Q. Krivov A. Lagrange A. Lieman-Sifry J. Liseau R. MacGregor M. Marino S. Marton G. Matthews E. Melis C. Nesvold E. Nilsson R. Ren B. Ricci L. Riviere-Marichalar P. Roberge A. Schneider G. Sibthorpe B. Smith R. Tanner A. Vican L. Visser R. Wahhaj Z. Wilson P. Zuckerman B. Irradiation of the discs for our sample of 10 stars. Oxford University Press is a department of the University of Oxford. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide.
Sign In or Create an Account. Sign In. Advanced Search. Search Menu. Article Navigation. Close mobile search navigation Article Navigation. Volume Quentin Kral , Quentin Kral. E-mail: quentin. Oxford Academic. Grant M Kennedy. Department of Physics, University of Warwick. Centre for Exoplanets and Habitability, University of Warwick. Sebastian Marino. Max Planck Institute for Astronomy.
First, you can use Orion's Belt to find Sirius, the brightest star in the sky. Sirius is just 8. Continue from Orion's Belt drawing a straight line until you reach a bright star — that's Sirus.
Another noticeable star you can find using Orion's Belt is Aldebaran, a red giant star located in the constellation Taurus. To identify Aldebaran, follow Orion's Belt in the opposite direction from east to west from how you identified Sirius.
Aldebaran has a reddish hue to help you know you're looking at the right star. Last, but certainly not least, you can use Orion's Belt to identify two other bright stars in the constellation Orion: Betelgeuse and Rigel. Betelgeuse, another reddish star is usually the tenth-brightest star in the night sky it's also a variable star so it sometimes dims and loses that spot on the list , whereas Rigel is a blue supergiant and ranks No. To find each one, look to the north of Orion's Belt to spot Betelgeuse, and equally distant to the south to find Rigel.
Note: These directions work if you are viewing Orion's Belt in the Northern Hemisphere, facing south. While Orion's Belt looks like three stars, it actually comprises six stars! Alnilam is a supergiant, Mintaka is a double star and Alnitak is a triple-star system. The size and distance of these star systems are part of what makes them bright and appear as just three points of light in the sky. Sign up for our Newsletter!
Mobile Newsletter banner close. Mobile Newsletter chat close. Mobile Newsletter chat dots. Mobile Newsletter chat avatar. Mobile Newsletter chat subscribe. The constellation of Orion looks a little like a human figure with an arrow. The age estimates of most stars, which are based on lithium abundances, H-R diagram location, moving group MG association, chromospheric activity, etc.
Due to these inconsistencies we have adopted probable approximate ages with upper and lower limits that encompass the range of published values from different methods.
Consequently, our ability to resolve details about the temporal evolution of disk properties in the young Myr systems, where terrestrial planet formation could still be in progress, according to, e.
Observations of the targets presented in Table 1 were obtained between June 4 and October 22, , amounting to roughly 80 out of allocated hours of this Large Programme. Several individual 7. In-between these scans, skydips to determine the correction for the atmospheric opacity , flux calibration, and measurements of pointing accuracy and focussing were performed on selected calibration objects.
Table 1: Observing log with stellar properties and integration times. As all of the sources were relatively faint we used filtering and settings optimised for point source extraction, with full beam smoothing, resulting in clean maps with effective resolution. The general reduction steps involve flux calibration opacity correction and counts-to-Jy conversion , flagging of bad unresponsive, very noisy, or those that were too fast or too slow channels, correlated noise removal, despiking, data weighting, and map making.
Siringo et al. Table 2: Integrated flux density, root-mean-square noise levels, and derived dust temperature, power-law exponent of the opacity law, mass, fractional dust luminosity, and characteristic radial dust distances for the 22 stars observed at m. The final m flux-density maps of the detected and marginally detected objects are found in Fig.
The dotted contour represents the 1 -level and the first solid contour outlines the 2 -level, with subsequent contour lines spaced by 1. A circle representing the effective beam size after smoothing, and a line showing the angular size subtended by AU at the distance of the object, has been inserted in the lower left corner. Several significant flux density peaks can be found surrounding the position of the observed star, also in parts of the LABOCA field-of-view outside the plotted maps.
This also effects the interpretation of our results for HD and HD , which appear spatially resolved even with our rather large effective beam which had been optimised for point source extraction in the reductions. These issues are discussed further in Appendix A. The measured integrated fluxes and RMS noise levels are listed in Table 2 , together with the disk parameters temperature, power-law exponent of the opacity law, dust mass, fractional dust luminosity, and characteristic radial distance of the dust derived from the analysis outlined in Sect.
For undetected sources, an upper 3 limit on the dust mass is given. Each map has been smoothed with a circular Gaussian corresponding to the FWHM of the beam, and the resulting effective FWHM image resolution of 27 is shown as a circle in the maps. In addition, a scale bar corresponding to AU at the distance of the star is inserted. The first solid contour represents 2 flux levels, with the following contours at increments of 1 or 2 for HD and HD , while the dotted contour outlines the 1 level.
The position of the star is at. Multiple stars have previously been deliberately left out from most debris disk surveys under the assumption that the formation of planetesimals in such systems would be inhibited. Our results confirm these trends, since the four multiple star systems in our sample are three wide binaries and one spectroscopic tight binary HD These results should however be taken with caution because of the morphological states of these four multiple stars systems.
The main one is that all four systems are young Myr old and thus should naturally have a higher probability of possessing massive debris disks see discussion in Sect. This bias towards young stars in our sample of multiple star systems make it difficult to infer trends related to the binarity. This cannot only be explained by higher instrument sensitivity but is most likely due to a selection effect, having chosen an initial sample of stars with high far-IR excesses, and we are not expecting such a high detection rate from our ongoing Large Programme observations.
Based on results from previous deep galaxy surveys at mm and submm wavelengths e. Clements et al. This is consistent with the average number of four 3 peaks within a 4 radius around the central position of the source that we observe in our final maps. Although the risk of a background galaxy falling within the central beam is so low, the probability that it does must be considered, as it could produce a false disk detection or a seemingly extended disk.
The total modelled SEDs of detected objects are shown as a solid black line, with the stellar and disk components represented by red dashed and dotted lines, respectively.
Our obtained m integrated flux density is given by a green square, while blue circular markers and triangles symbolizing upper limits are data from the literature. Fits which yield exceptionally high values and other special cases are discussed in Sect. Although only the best-fit parameter is quoted without errors , we note that in almost all fits a value between 0. The difficulty in determining is due to relatively large errors in measured submm and longer wavelength data, in addition to the possible existence of colder dust that would have been better modelled with a second dust component, but now instead shifts in a single component fit towards zero.
One example is HD which clearly cannot be modelled with a single component dust disk. For this star we added a second disk with a lower temperature limited by the maximum extent of the unresolved disk AU and upper limit constrained by the two IR points at 13 and 33 m Chen et al. The fit shown in Fig. This is in agreement with previous results by e. In three cases the SED modelling does not yield a good fit.
For the quadruple system HD Fig. It can not be excluded that processes related to the orbital phase of the tight 1 AU binary HD B cause this seemingly bimodal flux variation of its circumbinary disk. Photometric variability has been found at shorter wavelengths Soderblom et al. In any case, this unusual system of two eccentric binaries orbiting each other with highly inclined orbital planes see e. For HD the mid-IR flux is difficult to fit consistently with longer wavelength data in a simple disk model, however our results are very similar to those of Sheret et al.
The photometry data of HD AK Sco can clearly not be fitted with a simple modified blackbody emitting disk. In Fig. This is indicative of hot dust in the system's young circumbinary disk, and it is probably still in its protoplanetary or transitional disk stage. Although more detailed modelling of the SED could have been performed and for some sources previously has been made by other authors the lack of sensitive photometry at wavelengths between m still hampers our ability to accurately determine grain properties and size distributions in cold debris disks.
With such data, any deviation from the theoretical power law size distribution of observable dust, e. For an optically thin disk at submm wavelengths we can make an estimate of the mass of large and cool dust grains which contain most of the dust mass , providing a lower limit on the total dust mass required to reproduce the measured flux Hildebrand :.
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