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Jay Cross
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Attended Rensselaer Polytechnic Institute
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Astronomy Papers That Caught My Eye In Today's arXiv

There are 87 papers today (Wednesday), not counting replacements. 

Topics: Void Stacking, Dark Matter in the Dark Ages, IMBH?

Void Stacking http://arxiv.org/abs/1509.00010 The precision of our cosmology has been improving over the decades. Gone are the days when 1=10 was valid cosmology. One area that still leaves some room for doubt about the precise numbers has to do with the effects of voids, and our relative placement near/within them and the observable cosmological factors (like the perhaps direction-dependent redshift-distance relationship). This paper looks at a new method for stacking voids and their effects so as to be able to better measure these factors taking the voids into account.

Dark Matter in the Dark Ages http://arxiv.org/abs/1509.00029 One of the current big topics in astro- and particle physics is the question of what Dark Matter is. It has so far proved elusive when sought as a very weakly interacting massive particle in deep underground detectors, but there may be other new ways to observe it and have some way to discern properties of the particle based on observation. This paper is a proposal for such an effort that might be accomplished using the SKA looking at how the gravitational interactions of dark matter on normal matter's motion results in heating of he normal matter in ways that should be detectable in the 21 cm radiation from that era with a table of possible results based on the mass of the dark matter individual particles. Answers in 10-20 years.

IMBH? http://arxiv.org/abs/1509.00329 CXO J122518.6+144545 is a transient x-ray source. It appears to be about 500 million lightyears away, and is about 100 million times as bright as the Sun. This is the second Hyperlouminous X-Ray source (HLX) yet discovered. It has now been observed by Chandra, and the optical counterpart has been observed with Hubble's WFC3. Based on its properties, this object is a strong candidate to be a flaring Intermediate Mass Black Hole (IMBH).
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Astronomy Papers That Caught My Eye In Today's arXiv

There are 82 papers today (Tuesday), not counting replacements. 

Topics: HAWC & GRBs, ComPair, IBEX Ribbon

HAWC & GRBs http://arxiv.org/abs/1508.07325 It is unlikely that multiple photons above 100 GeV will be seen from a single GRB using any equipment in use now, except HAWC. Most other Atmospheric Cherenkov Telescopes need to be slewed in the direction of the GRB to detect photons, but HAWC has a fairly wide angle, and will be in the line of sight for nearly 20 GRBs per year, and from them should detect photons from one or two per year, based on the current size of the project. If there are positive detections, it may prove worthwhile to expand it. These results could potentially start to give insight as to the mechanism by which these GRBs create such energetic photons. This paper looks at how such events are detected and analysed.

ComPair http://arxiv.org/abs/1508.07349 This is a proposed new mission to put a probe up that studies gamma rays from 200 keV (nuclear transitions) up to a few hundred MeV (very high temperatures), using a technology that will give excellent angular and spectral resolution. This paper describes the mission and compares it to other previous missions in overlapping energy ranges such as Fermi-LAT.

IBEX Ribbon http://arxiv.org/abs/1508.07815 There are a few IBEX papers in this batch. You might remember this probe was launched a few years ago and detected a surprising ribbon shaped zone of neutral atoms from the interstellar medium hitting the outer heliosphere. This paper takes a closer look at this result and what it seems to imply about the sources of these atoms.
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Astronomy Papers That Caught My Eye In Today's arXiv

There are 63 papers today (Monday), not counting replacements. Includes several papers about VERITAS.

Topics: Bulge-Black Hole Relation, Infall-Orbit Transition, LGRB Luminosity Function, Lorentz Violation Constraints

Bulge Black Hole Relation http://arxiv.org/abs/1508.06997 About 17 years ago there was a paper published showing that there is a fairly consistent linear relationship between the mass of the central black hole and the mass of the bulge in the center of the galaxy. More recently it has been noticed that about ten billion solar masses, there is a break in this relation for lower mass galaxies. This paper looks at how the impact of this break has changed over time, and speculates about what this means about BH-Galaxy coevolution.

Infall-Orbit Transition http://arxiv.org/abs/1508.07013 Protostars have gas and dust falling into them, but at some point in some of the fall, the material has to start orbiting the star. This paper is about ALMA's millimeter-wave observations of TMC-1A (a nearby protostar) observing the radius from the core at which material begins having a Keplerian orbit. Many unknown factors, including magnetism are looked at as possible explanations, and targets for further study.

LGRB Luminosity Function http://arxiv.org/abs/1508.07094 What is the relationship between long GRB's luminosity and the age of the universe when they exploded? There are a few surprises in the data, including a dark period (redshift desert). This paper looks at possible selection effects, and shows that the desert is mostly a selection effect and is not present when only looking at he brighter GRBs. Also, this luminosity function has the ability to tell us some important things about galaxy evolution.

Lorentz Violation Constraints http://arxiv.org/abs/1508.07007 String Theory, Loop Quantum Gravity, and other incomplete candidate models have some parameters that suggest that the highest energy gamma rays might travel a little slower than c. How much slower is model, energy, and other parameter dependent. This paper takes a good look at what we can tell about those parameter constraints based on existing observations, and from future methods.
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Astronomy Papers That Caught Fred's Eye In Today's arXiv
 
There are seventy-one new paper accepted into Astro-archives today. Eye-catching topics selected include: Modified gravity, Aurora Borealis, Asteroid astrometrics, Binary black holes.


On Nonlocal Modified Gravity and Cosmology http://arxiv.org/abs/1508.06584 This is fun, because I have a draft sitting in my computer in which the first line is almost identical to the first line in the abstract. This is a theoretical work on non-local gravity. It is disappointing in that I cannot find any discriminators within the text: A theory without predictive powers and only explains what we see is little more that a turtle in a stack of turtles.

The Grand Aurorae Borealis Seen in Colombia in 1859 http://arxiv.org/abs/1508.06365 Interesting historical footnote. The magnetic north pole was at a much lower latitude that it is today, possibly allowing such an incredible event.

Precise Distances for Main-Belt Asteroids in Only Two Nights http://arxiv.org/abs/1508.06331 These authors have exploited the earth's axial rotation to lock in the subtle variations in the asteroids positions; identifying the position with an accuracy within 1.7% of other established methods.

A probable Milli-Parsec Supermassive Binary Black Hole in the Nearest Quasar Mrk 231 http://arxiv.org/abs/1508.06292 A binary black hole. Worse, I suppose to fly into than a double hurricane.
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Astronomy Papers That Caught My Eye In Today's arXiv

There are 62 papers today (Wednesday), not counting replacements. Many of today's papers are about the Cherenkov Telescope Array results.

Topics: Categorizing SN Ia, First Low Mass Stars, Constraints From the Stability of the FSC

Categorizing SN Ia http://arxiv.org/abs/1508.05961 Type Ia Supernovae are one of the big hopes for getting relatively solid distance measurements over cosmological distances. But there is some scatter in their brightness, most likely from differences in their progenitor systems. This paper looks at some metalicity tests visible about 30 days after the explosion which might separate the two types of systems, making it possible to (hopefully) get a subset of these standard candles that really are standard.

First Low Mass Stars http://arxiv.org/abs/1508.06137 The very first stars (it is thought) were huge. The very next batch of stars included large and small stars that still had very low fractions of heavier elements in them. This paper looks at the models of early stellar formation, and what the original dwarf stars had in them, and what they should look like now (some of these stars may have been studied already).

Constraints From the Stability of the FSC http://arxiv.org/abs/1508.06157 Years ago there was some thought that the Fine Structure Constant (FSC) might have changed a few parts per million since the early days of the universe. Measuring this is very difficult, but more recent measurements show those early conclusions were wrong, and the FSC is much more stable that thought at that time. This paper looks at what the stability of this constant means for constraints on Dark Energy and also the Weak Equivalence Principle.
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Astronomy Papers That Caught My Eye In Today's arXiv

There are 69 papers today (Tuesday), not counting replacements.

Topics: Neutron Star Properties, Age of the Big Dipper, Central DM Density

Neutron Star Properties http://arxiv.org/abs/1508.05493 There are some indirect ways of guessing the equation of state of the high density matter than makes up neutron stars, including knowing what the most and least massive neutron stars are, or knowing their mass and fastest spin rates. These narrow the ranges of the parameters, but there is still a wide rage of stiffness, or compressibility, or fluidity of the materials. This paper proposes ways to tell more details based on the gravitational waves emitted when two neutron stars merge. It is interesting to read how the future results of LIGO will be applied.

Age of the Big DIpper http://arxiv.org/abs/1508.05643 How old are the seven bright A-class stars in the Big Dipper? These are nearby stars, which means we have the ability using interferometry to determine how oblate they are, and we can apply the usual means for determining how fast they are spinning. Applying this to stellar evolution models, this team gets that this group of stars are 414 +/- 28 million years old. This is the most precise age estimate for these stars so far.

Central DM Density http://arxiv.org/abs/1508.05725 How much Dark Matter is there in the immediate vicinity of Sgr A-star? Knowing this could help determine something about the cuspiness of the dark matter, which would help give guidance about dark matter models. It would also support or refute the apparent signal that might be associated with DM decay or self-annihilation. This paper looks at future precise measurement of the orbits of the S stars, especially S0, which orbit closely the central black hole in our galaxy, and using the precession of those orbits to get a concrete number for the total amount of dark matter in the inner few light years. Side note: The paper assumes that the cusp's center overlaps the position of the black hole. This is reasonable for most current models of galaxy evolution... but not certain. The black hole could orbit the cusp if the cusp is deep enough and far enough from the black hole. 
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Jay Cross

Astronomy  - 
 
Astronomy Papers That Caught My Eye In Today's arXiv

There are 87 papers today (Wednesday), not counting replacements. 

Topics: Void Stacking, Dark Matter in the Dark Ages, IMBH?

Void Stacking http://arxiv.org/abs/1509.00010 The precision of our cosmology has been improving over the decades. Gone are the days when 1=10 was valid cosmology. One area that still leaves some room for doubt about the precise numbers has to do with the effects of voids, and our relative placement near/within them and the observable cosmological factors (like the perhaps direction-dependent redshift-distance relationship). This paper looks at a new method for stacking voids and their effects so as to be able to better measure these factors taking the voids into account.

Dark Matter in the Dark Ages http://arxiv.org/abs/1509.00029 One of the current big topics in astro- and particle physics is the question of what Dark Matter is. It has so far proved elusive when sought as a very weakly interacting massive particle in deep underground detectors, but there may be other new ways to observe it and have some way to discern properties of the particle based on observation. This paper is a proposal for such an effort that might be accomplished using the SKA looking at how the gravitational interactions of dark matter on normal matter's motion results in heating of he normal matter in ways that should be detectable in the 21 cm radiation from that era with a table of possible results based on the mass of the dark matter individual particles. Answers in 10-20 years.

IMBH? http://arxiv.org/abs/1509.00329 CXO J122518.6+144545 is a transient x-ray source. It appears to be about 500 million lightyears away, and is about 100 million times as bright as the Sun. This is the second Hyperlouminous X-Ray source (HLX) yet discovered. It has now been observed by Chandra, and the optical counterpart has been observed with Hubble's WFC3. Based on its properties, this object is a strong candidate to be a flaring Intermediate Mass Black Hole (IMBH).
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Jay Cross

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Astronomy Papers That Caught My Eye In Today's arXiv

There are 82 papers today (Tuesday), not counting replacements. 

Topics: HAWC & GRBs, ComPair, IBEX Ribbon

HAWC & GRBs http://arxiv.org/abs/1508.07325 It is unlikely that multiple photons above 100 GeV will be seen from a single GRB using any equipment in use now, except HAWC. Most other Atmospheric Cherenkov Telescopes need to be slewed in the direction of the GRB to detect photons, but HAWC has a fairly wide angle, and will be in the line of sight for nearly 20 GRBs per year, and from them should detect photons from one or two per year, based on the current size of the project. If there are positive detections, it may prove worthwhile to expand it. These results could potentially start to give insight as to the mechanism by which these GRBs create such energetic photons. This paper looks at how such events are detected and analysed.

ComPair http://arxiv.org/abs/1508.07349 This is a proposed new mission to put a probe up that studies gamma rays from 200 keV (nuclear transitions) up to a few hundred MeV (very high temperatures), using a technology that will give excellent angular and spectral resolution. This paper describes the mission and compares it to other previous missions in overlapping energy ranges such as Fermi-LAT.

IBEX Ribbon http://arxiv.org/abs/1508.07815 There are a few IBEX papers in this batch. You might remember this probe was launched a few years ago and detected a surprising ribbon shaped zone of neutral atoms from the interstellar medium hitting the outer heliosphere. This paper takes a closer look at this result and what it seems to imply about the sources of these atoms.
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Jay Cross

Astronomy  - 
 
Astronomy Papers That Caught My Eye In Today's arXiv

There are 63 papers today (Monday), not counting replacements. Includes several papers about VERITAS.

Topics: Bulge-Black Hole Relation, Infall-Orbit Transition, LGRB Luminosity Function, Lorentz Violation Constraints

Bulge Black Hole Relation http://arxiv.org/abs/1508.06997 About 17 years ago there was a paper published showing that there is a fairly consistent linear relationship between the mass of the central black hole and the mass of the bulge in the center of the galaxy. More recently it has been noticed that about ten billion solar masses, there is a break in this relation for lower mass galaxies. This paper looks at how the impact of this break has changed over time, and speculates about what this means about BH-Galaxy coevolution.

Infall-Orbit Transition http://arxiv.org/abs/1508.07013 Protostars have gas and dust falling into them, but at some point in some of the fall, the material has to start orbiting the star. This paper is about ALMA's millimeter-wave observations of TMC-1A (a nearby protostar) observing the radius from the core at which material begins having a Keplerian orbit. Many unknown factors, including magnetism are looked at as possible explanations, and targets for further study.

LGRB Luminosity Function http://arxiv.org/abs/1508.07094 What is the relationship between long GRB's luminosity and the age of the universe when they exploded? There are a few surprises in the data, including a dark period (redshift desert). This paper looks at possible selection effects, and shows that the desert is mostly a selection effect and is not present when only looking at he brighter GRBs. Also, this luminosity function has the ability to tell us some important things about galaxy evolution.

Lorentz Violation Constraints http://arxiv.org/abs/1508.07007 String Theory, Loop Quantum Gravity, and other incomplete candidate models have some parameters that suggest that the highest energy gamma rays might travel a little slower than c. How much slower is model, energy, and other parameter dependent. This paper takes a good look at what we can tell about those parameter constraints based on existing observations, and from future methods.
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Astronomy Papers That Caught Fred's Eye In Today's arXiv
 
There are forty-nine new papers listed in Astro-archives today. These topics caught my eye: *Gravitational waves, LOFAR, TeV flares,
Modified Maxwell Equations*

Gravitational Waves from Neutron Stars: A Review http://arxiv.org/abs/1508.06643 This review covers the expectations of the Advanced LIGO's first science run started August 17 . LIGO runs to date have been used to rule-out compact binary coalescences as sources of local gamma ray bursts because no gravitational waves have been detected. If the current generation of LIGO antenna/telescopes do not identify many coalescent events, it is time to revisit the fundamental theory. https://ligo.caltech.edu/

Galactic interstellar filaments as probed by LOFAR and Planck http://arxiv.org/abs/1508.06652 The magnetic fields of interstellar space are pathetically weak, so it is quite unexpected to find a column of dust closely aligned with a magnetic filament: But there it is; in living radio waves. Perhaps the 'magnetic dust' is not what we think it is.

VERITAS observations of exceptionally bright TeV flares from LS I +61$^\circ$ 303 http://arxiv.org/abs/1508.06800 Now that Advanced LIGO is up-and-running; it would be nice to have another toenail flare-up like this one: Good constraint on gravitational waves, if not an out-right detection.

Electrodynamics on Cosmological Scales http://arxiv.org/abs/1508.06910 The universe is a tough place for Maxwell, his field equations work well at your local radio station, but run into vanishing limits on cosmic scales. With a need for cosmic acceleration; there are also reasons to define matter at the fields associated with it in ways the are consistent with dark energy science. (If this paragraph sounds like so much smoke and mirrors, you have broken the code.)
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Jay Cross

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Astronomy Papers That Caught My Eye In Today's arXiv

There are 62 papers today (Wednesday), not counting replacements. Many of today's papers are about the Cherenkov Telescope Array results.

Topics: Categorizing SN Ia, First Low Mass Stars, Constraints From the Stability of the FSC

Categorizing SN Ia http://arxiv.org/abs/1508.05961 Type Ia Supernovae are one of the big hopes for getting relatively solid distance measurements over cosmological distances. But there is some scatter in their brightness, most likely from differences in their progenitor systems. This paper looks at some metalicity tests visible about 30 days after the explosion which might separate the two types of systems, making it possible to (hopefully) get a subset of these standard candles that really are standard.

First Low Mass Stars http://arxiv.org/abs/1508.06137 The very first stars (it is thought) were huge. The very next batch of stars included large and small stars that still had very low fractions of heavier elements in them. This paper looks at the models of early stellar formation, and what the original dwarf stars had in them, and what they should look like now (some of these stars may have been studied already).

Constraints From the Stability of the FSC http://arxiv.org/abs/1508.06157 Years ago there was some thought that the Fine Structure Constant (FSC) might have changed a few parts per million since the early days of the universe. Measuring this is very difficult, but more recent measurements show those early conclusions were wrong, and the FSC is much more stable that thought at that time. This paper looks at what the stability of this constant means for constraints on Dark Energy and also the Weak Equivalence Principle.
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Jay Cross

Astronomy  - 
 
Astronomy Papers That Caught My Eye In Today's arXiv

There are 69 papers today (Tuesday), not counting replacements.

Topics: Neutron Star Properties, Age of the Big Dipper, Central DM Density

Neutron Star Properties http://arxiv.org/abs/1508.05493 There are some indirect ways of guessing the equation of state of the high density matter than makes up neutron stars, including knowing what the most and least massive neutron stars are, or knowing their mass and fastest spin rates. These narrow the ranges of the parameters, but there is still a wide rage of stiffness, or compressibility, or fluidity of the materials. This paper proposes ways to tell more details based on the gravitational waves emitted when two neutron stars merge. It is interesting to read how the future results of LIGO will be applied.

Age of the Big DIpper http://arxiv.org/abs/1508.05643 How old are the seven bright A-class stars in the Big Dipper? These are nearby stars, which means we have the ability using interferometry to determine how oblate they are, and we can apply the usual means for determining how fast they are spinning. Applying this to stellar evolution models, this team gets that this group of stars are 414 +/- 28 million years old. This is the most precise age estimate for these stars so far.

Central DM Density http://arxiv.org/abs/1508.05725 How much Dark Matter is there in the immediate vicinity of Sgr A-star? Knowing this could help determine something about the cuspiness of the dark matter, which would help give guidance about dark matter models. It would also support or refute the apparent signal that might be associated with DM decay or self-annihilation. This paper looks at future precise measurement of the orbits of the S stars, especially S0, which orbit closely the central black hole in our galaxy, and using the precession of those orbits to get a concrete number for the total amount of dark matter in the inner few light years. Side note: The paper assumes that the cusp's center overlaps the position of the black hole. This is reasonable for most current models of galaxy evolution... but not certain. The black hole could orbit the cusp if the cusp is deep enough and far enough from the black hole. 
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I'm a technical trainer for enterprise software systems
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One of a long line of Renaissance Men
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Publicly, I post a lot of astronomy stuff. I also post about politics, my life, the future, and links to my photo journal to people in specific circles.

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It seems impolite for me to say all the great stuff I've been lucky enough to do.
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  • Rensselaer Polytechnic Institute
    Physics, 1973 - 1979
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I've gone by "antoniseb" on the web, and in the Society for Creative Anachronism, I'm called "Anton of Winteroak"