Semiclassical Strings in AdS_5 x S^5 and Automorphic Functions

Using AdS/CFT we derive from the folded spinning string ordinary differential equations for the anomalous dimension of the dual N=4 SYM twist-two operators at strong coupling. We show that for large spin the asymptotic solutions have the Gribov-Lipatov recirocity property. To obtain this result we use a hidden modular invariance of the energy-spin relation of the folded spinning string. Further we identify the Moch-Vermaseren-Vogt (MVV) relations, which were first recognized in plain QCD calculations, as the recurrence relations of the asymptotic series ansatz.Comment: 4 page

The Big Sibling of AU Mic: A Cold Dust-rich Debris Disk around CP-72 2713 in the β Pic Moving Group

Analyzing Spitzer and Herschel archival measurements we identified a hitherto unknown debris disk around the young K7/M0 star CP-72 2713. The system belongs to the 24Myr old $\beta$ Pic moving group. Our new 1.33mm continuum observation, obtained with the ALMA 7-m array, revealed an extended dust disk with a peak radius of 140au, probably tracing the location of the planetesimal belt in the system. The disk is outstandingly large compared to known spatially resolved debris disks and also to protoplanetary disks around stars of comparable masses. The dynamical excitation of the belt at this radius is found to be reconcilable with planetary stirring, while self-stirring by large planetesimals embedded in the belt can work only if these bodies form very rapidly, e.g. via pebble concentration. By analyzing the spectral energy distribution we derived a characteristic dust temperature of 43K and a fractional luminosity of 1.1$\times$10$^{-3}$. The latter value is prominently high, we know only four other similarly dust-rich Kuiper-belt analogs within 40pc of the Sun

Stirring in massive, young debris discs from spatially resolved Herschel images

A significant fraction of main-sequence stars are encircled by dusty debris discs, where the short-lived dust particles are replenished through collisions between planetesimals. Most destructive collisions occur when the orbits of smaller bodies are dynamically stirred up, either by the gravitational effect of locally formed Pluto-sized planetesimals (self-stirring scenario), or via secular perturbation caused by an inner giant planet (planetary stirring). The relative importance of these scenarios in debris systems is unknown. Here we present new Herschel Space Observatory imagery of 11 discs selected from the most massive and extended known debris systems. All discs were found to be extended at far-infrared wavelengths, five of them being resolved for the first time. We evaluated the feasibility of the self-stirring scenario by comparing the measured disc sizes with the predictions of the model calculated for the ages of our targets. We concluded that the self-stirring explanation works for seven discs. However, in four cases, the predicted pace of outward propagation of the stirring front, assuming reasonable initial disc masses, was far too low to explain the radial extent of the cold dust. Therefore, for HD 9672, HD 16743, HD 21997, and HD 95086, another explanation is needed. We performed a similar analysis for {\ss} Pic and HR 8799, reaching the same conclusion. We argue that planetary stirring is a promising possibility to explain the disk properties in these systems. In HR 8799 and HD 95086 we may already know the potential perturber, since their known outer giant planets could be responsible for the stirring process. Our study demonstrates that among the largest and most massive debris discs self-stirring may not be the only active scenario, and potentially planetary stirring is responsible for destructive collisions and debris dust production in a number of systems.Comment: Accepted for publication in MNRAS, 22 pages, 7 figures, 6 tables (abstract abridged due to arXiv requirements

One-loop spectroscopy of semiclassically quantized strings: bosonic sector

We make a further step in the analytically exact quantization of spinning string states in semiclassical approximation, by evaluating the exact one-loop partition function for a class of two-spin string solutions for which quadratic fluctuations form a non-trivial system of coupled modes. This is the case of a folded string in the SU(2) sector, in the limit described by a quantum Landau–Lifshitz model. The same applies to the full bosonic sector of fluctuations over the folded spinning string in AdS5 with an angular momentum J in S5. Fluctuations are governed by a special class of fourth-order differential operators, with coefficients being meromorphic functions on the torus, which we are able to solve exactly

YETI observations of the young transiting planet candidate CVSO 30 b

CVSO 30 is a unique young low-mass system, because, for the first time, a close-in transiting and a wide directly imaged planet candidates are found around a common host star. The inner companion, CVSO 30 b, is the first possible young transiting planet orbiting a previously known weak-lined T-Tauri star. With five telescopes of the 'Young Exoplanet Transit Initiative' (YETI) located in Asia, Europe and South America we monitored CVSO 30 over three years in a total of 144 nights and detected 33 fading events. In two more seasons we carried out follow-up observations with three telescopes. We can confirm that there is a change in the shape of the fading event between different observations and that the fading event even disappears and reappears. A total of 38 fading event light curves were simultaneously modelled. We derived the planetary, stellar, and geometrical properties of the system and found them slightly smaller but in agreement with the values from the discovery paper. The period of the fading event was found to be 1.36 s shorter and 100 times more precise than the previous published value. If CVSO 30 b would be a giant planet on a precessing orbit, which we cannot confirm, yet, the precession period may be shorter than previously thought. But if confirmed as a planet it would be the youngest transiting planet ever detected and will provide important constraints on planet formation and migration time-scales.Comment: 14 pages (20 with appendix), 7 figures (16 with appendix), 6 tables (7 with appendix

Characterizing the morphology of the debris disk around the low-mass star GSC 07396-00759

Context. Debris disks have commonly been studied around intermediate-mass stars. Their intense radiation fields are believed to efficiently remove the small dust grains that are constantly replenished by collisions. For lower-mass stars, in particular M-stars, the dust removal mechanism needs to be further investigated given the much weaker radiation field produced by these objects. Aims. We present new polarimetric observations of the nearly edge-on disk around the pre-main sequence M-type star GSC 07396-00759, taken with VLT/SPHERE IRDIS, with the aim to better understand the morphology of the disk, its dust properties, and the star-disk interaction via the stellar mass-loss rate. Methods. We model our observations to characterize the location and properties of the dust grains using the Henyey-Greenstein approximation of the polarized phase function and evaluate the strength of the stellar winds. Results. We find that the observations are best described by an extended and highly inclined disk (i\approx 84.3\,^{\circ}\pm0.3) with a dust distribution centered at a radius $r_{0}\approx107\pm2$ au. The polarized phase function $S_{12}$ is best reproduced by an anisotropic scattering factor $g\approx0.6$ and small micron-sized dust grains with sizes $s>0.3\,\mathrm{\mu}$m. We furthermore discuss some of the caveats of the approach and a degeneracy between the grain size and the porosity. Conclusions. Even though the radius of the disk may be over-estimated, our results suggest that using a given scattering theory might not be sufficient to fully explain key aspects such as the shape of the phase function, or the dust grain size. With the caveats in mind, we find that the average mass-loss rate of GSC 07396-00759 can be up to 500 times stronger than that of the Sun, supporting the idea that stellar winds from low-mass stars can evacuate small dust grains from the disk

Abundant sub-micron grains revealed in newly discovered extreme debris discs

This is the author accepted manuscript. The final version is available from Oxford University Press via the DOI in this record DATA AVAILABILITY: The VISIR data used in this paper are publicly available at ESO Archive (http://archive.eso.org/eso/eso_archive_main. html).Extreme debris discs (EDDs) are bright and warm circumstellar dusty structures around main sequence stars. They may represent the outcome of giant collisions occuring in the terrestrial region between large planetesimals or planetary bodies, and thus provide a rare opportunity to peer into the aftermaths of these events. Here, we report on results of a mini-survey we conducted with the aim to increase the number of known EDDs, investigate the presence of solid-state features around 10 μm in eight EDDs, and classify them into the silica or silicate dominated groups. We identify four new EDDs and derive their fundamental properties. For these, and for four other previously known discs, we study the spectral energy distribution around 10 μm by means of VLT/VISIR photometryin three narrow-band filters and conclude that all eight objects likely exhibit solid-state emission features from sub-micron grains. We find that four discs probably belong to the silicate dominated subgroup. Considering the age distribution of the entire EDD sample, we find that their incidence begins to decrease only after 300 Myr, suggesting that the earlier common picture that these objects are related to the formation of rocky planets may not be exclusive, and that other processes may be involved for older objects (≳100 Myr). Because most of the older EDD systems have wide, eccentric companions, we suggest that binarity may play a role in triggering late giant collisions.Hungarian National Research, Development and Innovation OfficeHungarian National Research, Development and Innovation OfficeBolyai+Royal SocietyNASANASAHungarian Academy of Science

High resolution ALMA and HST imaging of κ CrB : a broad debris disc around a post-main sequence star with low-mass companions

κ CrB is a ~2.5 Gyr old K1 sub-giant star, with an eccentric exo-Jupiter at ~2.8 au and a debris disc at tens of au. We present ALMA Band 6 (1.3 mm) and HST scattered light (0.6 μm) images, demonstrating κ CrB's broad debris disc, covering an extent 50 - 180 au in the millimetre (peaking at 110 au), and 51 - 280 au in scattered light (peaking at 73 au). By modelling the millimetre emission, we estimate the dust mass as ~0.016 M⊕, and constrain lower-limit planetesimal sizes as Dmax ≳ 1 km and the planetesimal belt mass as Mdisc ≳ 1 M⊕. We constrain the properties of an outer body causing a linear trend in 17 years of radial velocity data to have a semi-major axis 8 - 66 au and a mass 0.4 - 120 MJup. There is a large inner cavity seen in the millimetre emission, which we show is consistent with carving by such an outer massive companion with a string of lower mass planets. Our scattered light modelling shows that the dust must have a high anisotropic scattering factor (g ~ 0.8 - 0.9) but an inclination (i ~ 30 - 40○) that is inferred to be significantly lower than the i ~ 61○ millimetre inclination. The origin of such a discrepancy is unclear, but could be caused by a misalignment in the micron and millimetre sized dust. We place an upper limit on the CO gas mass of MCO < (4.2 - 13) × 10-7 M⊕, and show this to be consistent with levels expected from planetesimal collisions, or from CO-ice sublimation as κ CrB begins its giant branch ascent

The debris disc of HD 131488: bringing together thermal emission and scattered light

This is the final version. Available from Oxford University Press via the DOI in this record. DATA AVAILABILITY: The data underlying this article will be shared on request to the corresponding author. The ALMA and VLT/SPHERE data are publicly available and can be queried and downloaded directly from the ALMA archive: https://almascience.nrao.edu/asax/ and the SPHERE archive: https://archive.eso.org/wdb/wdb/eso/sphere/.We show the first SPHERE/IRDIS and IFS data of the CO-rich debris disc around HD 131488. We use N-body simulations to model both the scattered light images and the spectral energy distribution of the disc in a self-consistent way. We apply the Henyey–Greenstein approximation, Mie theory, and the Discrete Dipole Approximation to model the emission of individual dust grains. Our study shows that only when gas drag is taken into account can we find a model that is consistent with scattered light as well as thermal emission data of the disc. The models suggest a gas surface density of 2 × 10−5 M⊕ au−2 which is in agreement with estimates from ALMA observations. Thus, our modelling procedure allows us to roughly constrain the expected amount of gas in a debris disc without actual gas measurements. We also show that the shallow size distribution of the dust leads to a significant contribution of large particles to the overall amount of scattered light. The scattering phase function indicates a dust porosity of ∼0.2…0.6 which is in agreement with a pebble pile scenario for planetesimal growth.Agence Nationale de la RechercheSwiss National Science Foundation (SNSF)CNR