64,202 research outputs found

    Long-term IR Photometry of Seyferts

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    Long-term (up to 10000d) monitoring has been undertaken for 41 Seyferts in the near-IR (JHKL). All but 2 showed variability, with K ampl in the range <0.1 to > 1.1 mags. The timescale for detectable change is from about one week to a few years. A simple cross-correlation study shows evidence for delays of up to several hundred days between the variations seen at the shortest wavelengths and the longest in many galaxies. In particular, the data for F9 now extend to twice the interval covered earlier and the delay between its UV and IR outputs persists. An analysis of the fluxes shows that, for any given galaxy, the colours of the variable component are usually independent of the level of activity. The state of activity can be parameterized. Taken over the whole sample, the colours of the variable components fall within moderately narrowly defined ranges. In particular, the H-K colour is appropriate to a black body of temperature 1600K. The H-K excess for a heavily reddened nucleus can be determined and used to find E_{B-V}, which can be compared to the values found from the visible region broad line fluxes. Using flux-flux diagrams, the flux within the aperture from the underlying galaxy can often be determined without the need for model surface brightness profiles. In many galaxies it is apparent that here must be an additional constant contribution from warm dust.Comment: Better quality available from ftp://ftp.saao.ac.za/pub/isg/seyf.pd

    Period-magnitude relations for M giants in Baade's Window NGC6522

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    A large and complete sample of stars with K < 9.75 in the NGC6522 Baade's Window is examined using light curves from MACHO and IJK from DENIS. All 4 of the sequences ABCD in the K vs logP diagram of the LMC are seen in the Bulge. The Bulge sequences however show some differences from the Magellanic Clouds. The sequences may be useful as distance indicators. A new diagram of the frequency of late-type variables is presented. The catalogued SR variables of the solar nbd are found to be a subset of the total of SRs, biased towards large amplitude.Comment: 11 pages 11 fig

    Composition of Integers with Bounded Parts

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    In this note, we consider ordered partitions of integers such that each entry is no more than a fixed portion of the sum. We give a method for constructing all such compositions as well as both an explicit formula and a generating function describing the number of k-tuples whose entries are bounded in this way and sum to a fixed value g

    Joyce, Bloomsday, and diasporic identity: a report from Melbourne

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    On Pi Day, A Serving of Why We Need Math

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    Today, our Facebook feeds will be peppered with references to Pi Day, a day of celebration that has long been acknowledged by math fans and that Congress recognized in 2009. Every high schooler learns that pi is the ratio of the circumference of a circle to its diameter and that its decimal expansion begins 3.14 and goes on infinitely without repeating. [excerpt

    Klein Four Actions on Graphs and Sets

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    We consider how a standard theorem in algebraic geometry relating properties of a curve with a (ℤ/2ℤ)2-action to the properties of its quotients generalizes to results about sets and graphs that admit (ℤ/2ℤ)2-actions

    Fair-Weather Fans: The Correlation Between Attendance and Winning Percentage

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    In Rob Neyer\u27s chapter on San Francisco in his Big Book of Baseball Lineups, he speculates that there aren\u27t really good baseball cities, and that attendance more closely correlates with winning percentage than with any other factor. He also suggests that a statistically minded person look at this. I took the challenge and have been playing with a lot of data

    Solving the Debt Crisis on Graphs - Solutions

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    We begin by noting that solutions to these puzzles are not unique. In particular, doing the `lending\u27 action from each of the vertices once brings us back to where we started. Moreover, the act of doing the `borrowing\u27 action from one vertex is equivalent to doing the`lending\u27 action from each of the other vertices. In particular, without loss of generality one can assume that there is (at least) one vertex for which you do neither action and for all other vertices you do the `lending\u27 action a nonnegative number of times. Below we give possible solutions to four of the puzzles by showing the number of times one lends from each vertex in order to eliminate all debt
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