Sublimation-Driven Activity in Main-Belt Comet 313p/Gibbs

We present an observational and dynamical study of newly discovered main-belt comet 313P/Gibbs. We find that the object is clearly active both in observations obtained in 2014 and in precovery observations obtained in 2003 by the Sloan Digital Sky Survey, strongly suggestingthat its activity is sublimation-driven. This conclusion is supported by a photometric analysis showing an increase in the total brightness of the comet over the 2014 observing period, and dust modeling resultsshowing that the dust emission persists over at least three months during both active periods, where we find start dates for emission nolater than 2003 July 24 ± 10 for the 2003 active period and 2014 July 28 ± 10 for the 2014 active period. From serendipitous observations by the Subaru Telescope in 2004 when the object was apparently inactive, we estimate that the nucleus has an absolute R-band magnitude of HR = 17.1 ± 0.3, corresponding to aneffective nucleus radius of re ∼ 1.00 ± 0.15 km.The object’s faintness at that time means we cannot rule out the presence of activity, and so this computed radius should be consideredan upper limit. We find that 313P’s orbit is intrinsically chaotic, having a Lyapunov time of Tl = 12,000 yr and beinglocated near two three-body mean-motion resonances with Jupiter andSaturn, 11J-1S-5A and 10J+12S-7A, yet appears stable over >50 Myr in an apparent example of stable chaos. We furthermore find that 313P is the second main-belt comet, after P/2012 T1 (PANSTARRS), to belong tothe ∼155 Myr old Lixiaohua asteroid family.

A Hundred Comets: The Visual-Wavelength Observations of the Survey of Ensemble Physical Properties of Cometary Nuclei (SEPPCoN)

We present new results from SEPPCoN, a Survey of Ensemble Physical Properties of Cometary Nuclei. This project is currently surveying 100 Jupiter-family comets (JFCs) to measure the mid-infrared thermal emission and visible reflected sunlight of the nuclei. The scientific goal is to determine the distributions of radius, geometric albedo, thermal inertia, axial ratio, and color among the JFC nuclei. In the past we have presented results from the completed mid-IR observations of our sample [1]; here we present preliminary results from ongoing, broadband visible-wavelength observations of nuclei obtained from a variety of ground-based facilities (Mauna Kea, Cerro Pachon, La Silla, La Palma, Apache Point, Table Mtn., and Palomar Mtn.), including contributions from the Near Earth Asteroid Telescope project (NEAT) archive. The nuclei were observed at high heliocentric distance (usually over 4 AU) and so many comets show either no or little contamination from dust coma. While several nuclei have been observed as snapshots, we have multiepoch photometry for many of our targets. With our datasets we are building a large database of photometry, and such a database is essential to the derivation of albedo and shape of a large number of nuclei, and to the understanding of biases in the survey. Support for this work was provided by NSF and the NASA Planetary Astronomy program. Reference: [1] Fernandez, Y.R., et al. 2007, BAAS 39, 827.

ESO observations of the Nucleus of Rosetta Target 67P/C-G

Rosetta is ESA's new comet orbiter mission, launched in March 2004 and currently en route to Jupiter-family comet 67P/Churyumov-Gerasimenko. The probe will rendezvous with the comet in 2014 and remain in orbit around the nucleus for on-going detailed physical and compositional analysis. Pre-encounter observations of the target are important for characterization of the heliocentric light-curve behaviour and the physical properties of the nucleus, information that is critical for mission planning. The nucleus was first characterized using HST observations in 2003 (Lamy et al. 2006) and observed directly in May 2005 by ground based telescopes (Lowry et al. 2006) when it was at 5.6 AU from the Sun. An extensive database of nucleus observations have since been acquired, not only from large ground-based telescopes like the ESO VLT (Tubiana et al. 2008 & 2011), but also from Spitzer (Kelley et al. 2006 & 2009; Lamy et al. 2008).

On the alignment of debris discs and their host stars' rotation axis - implications for spin-orbit misalignment in exoplanetary systems

It has been widely thought that measuring the misalignment angle between the orbital plane of a transiting exoplanet and the spin of its host star was a good discriminator between different migration processes for hot-Jupiters. Specifically, well-aligned hot-Jupiter systems (as measured by the Rossiter-McLaughlin effect) were thought to have formed via migration through interaction with a viscous disc, while misaligned systems were thought to have undergone a more violent dynamical history. These conclusions were based on the assumption that the planet-forming disc was well-aligned with the host star. Recent work by a number of authors has challenged this assumption by proposing mechanisms that act to drive the star-disc interaction out of alignment during the pre-main-sequence phase. We have estimated the stellar rotation axis of a sample of stars which host spatially resolved debris discs. Comparison of our derived stellar rotation axis inclination angles with the geometrically measured debris-disc inclinations shows no evidence for a misalignment between the two.

Indications for an influence of hot Jupiters on the rotation and activity of their host stars

Context. The magnetic activity of planet-hosting stars is an importantfactor for estimating the atmospheric stability of close-in exoplanetsand the age of their host stars. It has long been speculated thatclose-in exoplanets can influence the stellar activity level. However,testing for tidal or magnetic interaction effects in samples ofplanet-hosting stars is difficult because stellar activity hindersexoplanet detection, so that stellar samples with detected exoplanetsshow a bias toward low activity for small exoplanets.

Aims: Weaim to test whether exoplanets in close orbits influence the stellarrotation and magnetic activity of their host stars.

Methods: Wedeveloped a novel approach to test for systematic activity-enhancementsin planet-hosting stars. We use wide (several 100 AU) binary systems inwhich one of the stellar components is known to have an exoplanet, whilethe second stellar component does not have a detected planet andtherefore acts as a negative control. We use the stellar coronal X-rayemission as an observational proxy for magnetic activity and analyzeobservations performed with Chandra and XMM-Newton.

Results: Wefind that in two systems for which strong tidal interaction can beexpected the planet-hosting primary displays a much higher magneticactivity level than the planet-free secondary. In three systems forwhich weaker tidal interaction can be expected the activity levels ofthe two stellar components agree with each other.

Conclusions:Our observations indicate that the presence of Hot Jupiters may inhibitthe spin-down of host stars with thick outer convective layers. Possiblecauses for this effect include a transfer of angular momentum from theplanetary orbit to the stellar rotation through tidal interaction, ordifferences during the early evolution of the system, where the hoststar may decouple from the protoplanetary disk early because of a gapopened by the forming Hot Jupiter.

A search for star-planet interactions in the υ Andromedae system at X-ray and optical wavelengths

Context. Close-in, giant planets are expected to influence their host stars via tidal or magnetic interaction. But are these effects in X-rays strong enough in suitable targets known so far to be observed with today's instrumentation? Aims: The υ And system, an F8V star with a Hot Jupiter, was observed to undergo cyclic changes in chromospheric activity indicators with its innermost planet's period. We aim to investigate the stellar chromospheric and coronal activity over several months. Methods: We therefore monitored the star in X-rays as well as at optical wavelengths to test coronal and chromospheric activity indicators for planet-induced variability, making use of the Chandra X-ray Observatory as well as the echelle spectrographs FOCES and HRS at Calar Alto (Spain) and the Hobby-Eberly Telescope (Texas, US). Results: The stellar activity level is low, as seen both in X-rays as in Ca ii line fluxes; the chromospheric data show variability with the stellar rotation period. We do not find activity variations in X-rays or in the optical that can be traced back to the planet. Conclusions: Gaining observational evidence of star-planet interactions in X-rays remains challenging.

51 Pegasi - a planet-bearing Maunder minimum candidate

We observed 51 Peg, the first detected planet-bearing star, in a 55 ks XMM-Newton pointing and in 5 ks pointings each with Chandra HRC-I and ACIS-S. The star has a very low count rate in the XMM observation, but is clearly visible in the Chandra images due to the detectors' different sensitivity at low X-ray energies. This allows a temperature estimate for 51 Peg's corona of T⪉ 1 MK; the detected ACIS-S photons can be plausibly explained by emission lines of a very cool plasma near 200 eV. The constantly low X-ray surface flux and the flat-activity profile seen in optical Ca II data suggest that 51 Peg is a Maunder minimum star; an activity enhancement due to a Hot Jupiter, as proposed by recent studies, seems to be absent. The star's X-ray fluxes in different instruments are consistent with the exception of the HRC Imager, which might have a larger effective area below 200 eV than given in the calibration.

A magnetic cycle of τ Bootis? The coronal and chromospheric view

τ Bootis is a late F-type main sequence star orbited by a Hot Jupiter. During the last years spectropolarimetric observations led to the hypothesis that this star may host a global magnetic field that switches its polarity once per year, indicating a very short activity cycle of only one year duration. In our ongoing observational campaign, we have collected several X-ray observations with XMM-Newton and optical spectra with TRES/FLWO in Arizona to characterize τ Boo's corona and chromosphere over the course of the supposed one-year cycle. Contrary to the spectropolarimetric reconstructions, our observations do not show indications for a short activity cycle.

Do exoplanets spin up their host stars?

We have collected initial evidence that tidal interaction between a late-type star and its close-in, massive planet can lead to a spin-up of the host star. We propose to explore this further by studying a small sample of proper motion pairs in which one of the stars is orbited by a Hot Jupiter. We will determine if the activity-estimated age appears to be strongly different for the two stars, which would indicate a tidal spin up of the Hot Jupiter host star. We propose to observe 4 such systems with Chandra/ACIS-S, and to perform a similar observation of one additional system with large angular separation using XMM-Newton/EPIC. The total proposed exposure times are 141 ks (Chandra) and 38 ks (XMM).

Planets spinning up their host stars

We have collected initial evidence that tidal interaction between a late-type star and its close-in, massive planet can lead to a spin-up of the host star. We propose to explore this further by studying a small sample of proper motion pairs in which one of the stars is orbited a Hot Jupiter. We will determine if the gyrochronal age is different for the two stars, which would indicate a tidal spin up of the planet host star. We propose to observe 3 such systems with XMM, and to perform similar Chandra observations of 3 more systems with angular separations

Modeling the Rossiter-McLaughlin Effect: Impact of the Convective Center-to-limb Variations in the Stellar Photosphere

bservations of the Rossiter–McLaughlin (RM) effect provide information on star–planet alignments, which can inform planetary migration and evolution theories. Here, we go beyond the classical RM modeling and explore the impact of a convective blueshift that varies across the stellar disk and non-Gaussian stellar photospheric profiles. We simulated an aligned hot Jupiter with a four-day orbit about a Sun-like star and injected center-to-limb velocity (and profile shape) variations based on radiative 3D magnetohydrodynamic simulations of solar surface convection. The residuals between our modeling and classical RM modeling were dependent on the intrinsic profile width and v sin i; the amplitude of the residuals increased with increasing v sin i and with decreasing intrinsic profile width. For slowly rotating stars the center-to-limb convective variation dominated the residuals (with amplitudes of 10 s of cm s−1 to ~1 m s−1); however, for faster rotating stars the dominant residual signature was due a non-Gaussian intrinsic profile (with amplitudes from 0.5 to 9 m s−1). When the impact factor was 0, neglecting to account for the convective center-to-limb variation led to an uncertainty in the obliquity of ~10°–20°, even though the true v sin i was known. Additionally, neglecting to properly model an asymmetric intrinsic profile had a greater impact for more rapidly rotating stars (e.g., v sin i = 6 km s−1) and caused systematic errors on the order of ~20° in the measured obliquities. Hence, neglecting the impact of stellar surface convection may bias star–planet alignment measurements and consequently theories on planetary migration and evolution.

Comet 322P/SOHO 1: An asteroid with the smallest perihelion distance?

We observed comet 322P/SOHO 1 (P/1999 R1) from the ground and with the Spitzer Space Telescope when it was between 2.2 and 1.2 AU from the Sun. These are the first observations of any SOHO-discovered periodic comet by a non-solar observatory, and allow us to investigate its behavior under typical cometary circumstances. 322P appeared inactive in all images. Its lightcurve suggests a rotation period of 2.8+/-0.3 hr and has an amplitude greater than ~0.3 mag, implying a density of at least 1000 kg m$^{-3}$, considerably higher than that of any known comet. It has average colors of g'-r' = 0.52+/-0.04 and r'-i' = 0.04+/-0.09. We converted these to Johnson colors and found that the V-R color is consistent with average cometary colors, but R-I is somewhat bluer; these colors are most similar to V- and Q-type asteroids. Modeling of the optical and IR photometry suggests it has a diameter of 150-320 m and a geometric albedo of 0.09-0.42, with diameter and albedo inversely related. Our upper limits to any undetected coma are still consistent with a sublimation lifetime shorter than the typical dynamical lifetimes for Jupiter Family Comets. These results suggest that it may be of asteroidal origin and only active in the SOHO fields of view via processes different from the volatile-driven activity of traditional comets. If so, it has the smallest perihelion distance of any known asteroid.

Épître en vers de Charles VIII à François Ier, avec dédicace à Louise de Savoie.

Commençant par : « Clyo, fille legitime du souverain roy Jupiter et de dame Memoire, seur et compaigne des Muses heliconicques... ». Épître : « Amour me exorte et gloire m'admouneste, O roy Françoys, prince doulx et houneste... » et finissant par : « De ton parent, que par escript congnoyz, Charles huytain, surnommé de Valloys » .

Recueil d'épitaphes, précédé d'un journal des principaux événements arrivés à Paris de 1557 à 1590.

Contient : 1 Journal autographe de JEHAN DE LA FOSSE, où sont notés mois par mois les principaux événements des années 1557 à 1590, arrivés en France et particulièrement à Paris, où vivait l'auteur, curé de St-Leu et de St-Barthélemy ; 2 Recueil d'épitaphes ; « Cavendish,... general Norris,... docter Story,... mylord Treasurer,... Frier Andrew,... Ellis,... earle of Essex, beheaded in the tower », Joannes Rekingale, episcopus Cicestriensis, Gulielmus de Blitz, archidiaconus Nodovicensis ; Thomas Linaerus, regis Henrici VIII medicus, Antonius Riccius Faventiae, « Mr Hofkins », Lucretia Borgia, Honorius P. M., Johannes Riberius ; Galfridus Chaucer, Corythus, filius Oenones et Paridis, Ninus, Assyriae monarcha, Pyramis, lateritia Asychis, Aegypti regis ; Bartholomaeus Platina, Petrus Pomponatius, Pompeius Magnus, Capys, Ennius, Hannibal ; Marcus Antonius Turrianus, Marcus Antonius Coccius, Marcus Antonius Casanova, Sardanapalus, Rufus, Julius Caesar, Augustus Caesar ; Petrus Ciaconius, Nicolaus Macchiavellus, Gulielmus Rondeletus, medicus, Anicia, foemina romana, Callicratea ; Johannes Coletus, Rembertus Dodonaeus, medicus Maximiliani II et Rodolphi imperatorum, Alcaeus poeta, Scipio Africanus ; Paracelsus, Gerardus Noviomagus et Andreas Hyperius, Didacus de Valdes, Albericus de Vere et Gulielmus, primus comes Oxoniensis, Robertus Buc ; Hieronymus Cagnolus Vercellensis, Johannes Stofflerus, mathematicus Tubingae, Remigius Bellaqueus, Pallas, Evandri filius, Zarmanochegas indus, de Bargosa ; Johannes Rivius Attbend, Petrus Bembus, Lucius P. M. Veronae, Gulielmus Norselez, decanus quondam ecclesiae S. Pauli Londini, Mathias Corvinus, rex Pannoniae ; Philippus Callimachus Cracoviae, in aede S. Trinitatis, Ludovicus Bologninus, Bononiae, Rachel, uxor Jacobi Bethleem, Aratus, Plato, Aeschylus ; Joannes Zonaras, Homerus, Menander, Epictetus ; Berengarius, archidiaconus Andegavensis, Andreas Fanzonius, Cyrus, Persarum monarcha, Midas ; Hugo S. Victoris Parisiensis, S. Bernardus, abbas claraevallensis, Petrus de Toledo, Psittacus, Musaeus poeta, Linus, thebanus poeta, Orpheus ; Petrus Lombardus, Petrus Comestor, Pallas, libertus Romae, Megista, Spartanus vates ; Aegidius de Roma, archiepiscopus Bituricensis, Johannes Gerson, Aristocrates, perfidus in Lycaei Jovis luco, Setho, sacerdos Vulcani et Aegypti rex, Rosamunda Cliffordensis, Petrus Aretinus ; Nicolaus de Lyra, Jacobus Pisaurus, Paphi episcopus, Cedwalla, rex Sussexiae ; Alphonsus Tostadus, hispanus, Abulensis episcopus, Albertus Pius de Sabaudia, princeps Carporum, Similis, praefectus praetorianorum, Jupiter, Osyris, Isis ; Aeneas Sylvius, Christophorus Colombus, Hermes, Apollo, Timon, Darius ; Robertus Gaguinus, Johannes de Sacro Busto, Darius, Hystaspis filius, Simandius, Aegypti rex, Idomeneus et Myrio, filii Deucalionis, Semiramis ; Alexander Piccolomineus, Justina, pulchra foemina, quam maritus zelotypus nefarie decollavit, Claudia, nobilis foemina Romae, Carolus Magnus, Carolus V, imperator ; Actius Plautus, Johannes Boccacius, Franciscus Ximenes, cardinalis Hispaniae, Federicus imperator, Sylla, Ricardus I, rex Anglorum ; Johannes Stadius, math. belga, C. Manlia camertina, Johannes de Mandeville, Patricius, Brigida et Columda in Hibernia, la reine d'Angleterre, femme de Jacques Ier ; Johannes Glandorp, Jodocus, medicus Romae, Urandus, sive Durandus, Johannes Jacobus Trivultius, Ludovicus VIII, rex Francorum ; Antonius quidam italus, Fin dal Finale, Battistina Senensis, puella elegantissima ; Chalonerus Dubliniae, Askew Lincolniensis, Christophorus Hatton, Robertus, comes Leicestriae ; Johannes Chidley, Walterus Ralegh, Arturus Gorges, Johannes Parkar, Maria Stafford, Charitas et Carolus Ho., Thomas Wals, Sylvanus Scorus, Johannes Horo et Edwardus Nymark, Edwardus Stanhop, Franciscus Wal ; Philippus Sydney, Franciscus Walsinghan, N. Marsonius, jurisconsultus, Christophorus H, Gulielmus, comes Penbrok, Angliae marescallus, Antonius Deny, frater Lubinus ; Fratislaus, dux Bohemiae, countess of Penbrok, Edward Spenser, Henry Abyngdon, Thomas Nash, N. Dobson ; Dr Hugh a price, Johannes Vitulus, Dr Bently, Hor. Pallavicin, Margaret Ratcliff ; Howlet, Elian, Henry Barron ; James Stuart, Thomas Sackville, Penelope d'Evreux, uxor domini Bar. Rich, pellicis comitis Devonshire, Robert Cecil, Ricardus Bancroft, archiepiscopus Cantuariensis ; Godefridus de Bulion, Balduinus, rex Jerusalem, Allicia, pulchra foemina anglica et forte meretrix, Theobaldus, comes Campaniae, qui vixit tempore regis Angliae Stephani ; Fernandus de Castro, hispanus in Anglia exulans et moriens ob fidem in Dominum Petrum, regem Castellae, Johannes Taylor de Colman street, usurarius, Petrus Miago Vallisoleti, in templo Sancti Stephani, Franciscus Duarte de Mendico, a proveedor de los exercitos y armadas del emperador Carlo V, Henricus, Walliae princeps ; Milo, comes de Anglera, pater Rolandi, a Mauris juxta ripam Ceae occisus, Hecuba, S. Edmundus, rex et martyr, Pindarus, poeta lyricus, Stesichorus, Anacreon, poeta vinosus, Leonidas, dux Lacedemoniorum ad Thermopylas occisus contra Persas, Timotheus, citharedus milesius ; Timocreon Rhodius, Laïs, meretrix Corinthia, sepulta in Thessalia, juxta Peneum fluvium, Acron, antiquissimus medicus Agrigentinus

Le Mystère de Ste Barbe.

Commençant par : « Primo Dyoscorus rex, pater beate Barbare, incipit : « Ha, Jupiter et Baratron, Cahu mon souverain patron... » et finissant par : « Et allons sejourner plus Chantant Te Deum laudamus. Explicit vita beate Barbare » .