Stellar activity and planetary atmosphere evolution in tight binary star systems

Context. In tight binary star systems, tidal interactions can significantly influence the rotational and orbital evolution of both stars, and therefore their activity evolution. This can have strong effects on the atmospheric evolution of planets that are orbiting the two stars. Aims. In this paper, we aim to study the evolution of stellar rotation and of X-ray and ultraviolet (XUV) radiation in tight binary systems consisting of two solar mass stars and use our results to study planetary atmosphere evolution in the habitable zones of these systems. Methods. We have applied a rotation model developed for single stars to binary systems, taking into account the effects of tidal interactions on the rotational and orbital evolution of both stars. We used empirical rotation-activity relations to predict XUV evolution tracks for the stars, which we used to model hydrodynamic escape of hydrogen dominated atmospheres. Results. When significant, tidal interactions increase the total amount of XUV energy emitted, and in the most extreme cases by up to factor of $\sim$50. We find that in the systems that we study, habitable zone planets with masses of 1~M$_\oplus$ can lose huge hydrogen atmospheres due to the extended high levels of XUV emission, and the time that is needed to lose these atmospheres depends on the binary orbital separation.For some orbital separations, and when the stars are born as rapid rotators, it is also possible for tidal interactions to protect atmospheres from erosion by quickly spinning down the stars. For very small orbital separations, the loss of orbital angular momentum by stellar winds causes the two stars to merge. We suggest that the merging of the two stars could cause previously frozen planets to become habitable due to the habitable zone boundaries moving outwards.Comment: Accepted for publication by A&

A Physical Limit to the Magnetic Fields of T Tauri Stars

Recent estimates of magnetic field strengths in T Tauri stars yield values $B=1$--$4\,{\rm kG}$. In this paper, I present an upper limit to the photospheric values of $B$ by computing the equipartition values for different surface gravities and effective temperatures. The values of $B$ derived from the observations exceed this limit, and I examine the possible causes for this discrepancy

Accelerator performance analysis of the Fermilab Muon Campus

Fermilab is dedicated to hosting world-class experiments in search of new physics that will operate in the coming years. The Muon g-2 Experiment is one such experiment that will determine with unprecedented precision the muon anomalous magnetic moment, which offers an important test of the Standard Model. We describe in this study the accelerator facility that will deliver a muon beam to this experiment. We first present the lattice design that allows for efficient capture, transport, and delivery of polarized muon beams. We then numerically examine its performance by simulating pion production in the target, muon collection by the downstream beam line optics, as well as transport of muon polarization. We finally establish the conditions required for the safe removal of unwanted secondary particles that minimizes contamination of the final beam.Comment: 10 p

Letter from E. McD Johnstone to John Muir, 1893 May 3.

E. McD. JOHNSTONE.R.K. Johnson.WM. V. BRYAN.$1.00 a Year.WITH THE TOURIST,$1.50 a YEAR.AN ILLUSTRATED MONTHLY JOURNAL OF TRAVEL ANDRECREATION.Information and printed matter concerning Hotels, Summer and Winter Resorts, Railways or Steamship Lines,will be furnished without charge by THE TRAVELER\u27S BUREAU OF INFORMATION OFFICE:602 MARKET STREET (IN STATE BOARD OF TRADE ROOMS, CROCKER BUILDING).SAN FRANCISCO,CAL.................May 3,1893John Muir,Esq,Martinez, Cal.My dear Mr. Muir:-I see by the morning paper that you are contemplating a trip abroad. There are two or three favors I would like to ask of you before you go,and when you do go,I will throw the best old boot after you I have got in my possession,and I have quite a number.First,I want your photograph,possibly for reproduction in The Traveler ,if you don\u27t object,and the privilege of using something from picturesque California\u27from you. Then I beg of you to spare enough of your valuable time to take a run out to the Golden Gate Park before you go .May I hear from you at an early date,and if you have decided to leave very soon,I would take a day and run up to see you.Very truly,THE TRAVELER,0144

Cyanobacteria blooms cannot be controlled by effective microorganisms (EM) from mud- or Bokashi-balls

In controlled experiments, the ability of ‘‘Effective Microorganisms (EM, in the form of mudballs or Bokashi-balls)’’ was tested for clearing waters from cyanobacteria. We found suspensions of EM-mudballs up to 1 g l-1 to be ineffective in reducing cyanobacterial growth. In all controls and EM-mudball treatments up to 1 g l-1 the cyanobacterial chlorophyll-a (Chl-a) concentrations increased within 4 weeks from&120 to 325–435 lg l-1. When pieces of EM-mudballs (42.5 g) were added to 25-l lake water with cyanobacteria, no decrease of cyanobacteria as compared to untreated controls was observed. In contrast, after 4 weeks cyanobacterial Chl-a concentrations were significantly higher in EM-mudball treatments (52 lg l-1) than in controls (20 lg l-1). Only when suspensions with extremely high EM-mudball concentrations were applied (i.e., 5 and 10 g l-1), exceeding the recommended concentrations by orders of magnitude, cyanobacterial growth was inhibited and a bloom forming concentration was reduced strongly. In these high dosing treatments, the oxygen concentration dropped initially to very low levels of 1.8 g l-1. This was most probably through forcing strong light limitation on the cyanobacteria caused by the high amount of clay and subsequent high turbidity of the water. Hence, this study yields no support for the hypothesis that EM is effective in preventing cyanobacterial proliferation or in terminating blooms. We consider EM products to be ineffective because they neither permanently bind nor remove phosphorus from eutroficated systems, they have no inhibiting effect on cyanobacteria, and they could even be an extra source of nutrients

Colliding Winds in Low-Mass Binary Star Systems: wind interactions and implications for habitable planets

Context. In binary star systems, the winds from the two components impact each other, leading to strong shocks and regions of enhanced density and temperature. Potentially habitable circumbinary planets must continually be exposed to these interactions regions. Aims. We study, for the first time, the interactions between winds from low-mass stars in a binary system, to show the wind conditions seen by potentially habitable circumbinary planets. Methods. We use the advanced 3D numerical hydrodynamic code Nurgush to model the wind interactions of two identical winds from two solar mass stars with circular orbits and a binary separation of 0.5 AU. As input into this model, we use a 1D hydrodynamic simulation of the solar wind, run using the Versatile Advection Code. We derive the locations of stable and habitable orbits in this system to explore what wind conditions potentially habitable planets will be exposed to during their orbits. Results. Our wind interaction simulations result in the formation of two strong shock waves separated by a region of enhanced density and temperature. The wind-wind interaction region has a spiral shape due to Coriolis forces generated by the orbital motions of the two stars. The stable and habitable zone in this system extends from approximately 1.4 AU to 2.4 AU. (TRUNCATED)Comment: 15 pages, 11 figures, to be published in A&

Letter from E. McD. Johnstone to John Muir, 1887 Jul 26.

[3]You under your own mine and fig[illegible]Iremain Yours respyMcD Johnstone[illegible] S.P.C. Blde01271[1]San Francisco July 26/87Mr John Muir Martinez Cal. My Dear SirI mail you today the small book on Shasta to which there will be soon added 15 pages devoted to Oregon Scenery, a copy of which I will send you. I regret that I could not have [stricken word] met you before its publication.I am now [2] working up. something of the same kind for Tahoe and would be greatly pleased if you would make any suggestions in that Connection.Have you ever published your entire works on this Coast? if not, why not? There has never in my humble opinion been any =thing written in your line that anywhere near approaches you in general excellence Still hoping that I may have the pleasure of meetin

Letter from E. McD Johnstone to John Muir, 1894 Nov 20.

OFFICE: 602 MARKET STREET,CROCKER BUILDING.SAN FRANCISCO, CAL. November 20, l894.Dear Mr. Muir: -When are you coming to make a day with Keith and myself to Stanford University and our Log Cabin ? How about some day the early part of next week,say Tuesday or Wednesday ? If this is agreeable to you kindly drop me a note a few days ahead so that I will notify Keith and be prepared to guide you around Palo Alto and San Mateo.Wife and I have been reading Mountains in California ,by John Muir Found it exceedingly interesting. I have clipped from this book a column of the Water Ouzel, for December No. which I think will interest childrenas well as grown folk. I am sorry not to be able to illustrate the short article,I am also sorry that your book was not better illustrated,but of that we will talk at greater length when you come down our way.Yours very truly,[illegible]0187