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Thread: A Path to Superluminous type 1a's?

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    A Path to Superluminous type 1a's?

    According to standard fare calculations, the limit on the mass of a white dwarf as a progenitor to going type 1a, single degenerate-style, with a bloated companion, is 1.4 stellar masses....The Chandrasekhar Limit. These guys consider the implications of a stronger magnetic field than is usually implied and found a new limiting mass of about 2 solar masses....beyond the Chandrasekhar limit, and more fitting to some of the models of progenitors of superluminal type 1a's. SEE:https://arxiv.org/abs/1702.00571

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    The field strength they use to allow for a 2 solar mass WD is around 10^14 Gauss. Can WDs be as strong as magnetars?
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    Another blow to the idea of standard candles?

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    The idea that Type Ia supernovae are standard candles has been dead for many years.

    The idea that Type Ia supernovae are standard-izable candles is alive and well.

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    I was not aware there were white dwarfs with weak magnetic fields. Missed something there.
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    Quote Originally Posted by StupendousMan View Post
    The idea that Type Ia supernovae are standard candles has been dead for many years.

    The idea that Type Ia supernovae are standard-izable candles is alive and well.
    Are you simply saying that some Type Ia SN can be determined to be effective candles, but not all?
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    Quote Originally Posted by George View Post
    Are you simply saying that some Type Ia SN can be determined to be effective candles, but not all?
    He means that people have a weird idea of what it means to be a "standard candle." All it means is that you can infer the absolute brightness somehow, and use that to get distance, it never meant that all the objects you use it on have the same brightness. For some reason, when "standard candle" was applied to type Ia SN, it took on that latter meaning, but that was never the correct requirement for a "standard candle." So if you can have a big magnetic field, and change the luminosity, then it can still be a standard candle as long as there is some observational way to tell that it's luminosity will be higher.

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    Quote Originally Posted by Ken G View Post
    He means that people have a weird idea of what it means to be a "standard candle." All it means is that you can infer the absolute brightness somehow, and use that to get distance, it never meant that all the objects you use it on have the same brightness. For some reason, when "standard candle" was applied to type Ia SN, it took on that latter meaning, but that was never the correct requirement for a "standard candle."
    So some but not all or is the inferring part a nuance that creates less accuracy, unlike candle measurements?
    So if you can have a big magnetic field, and change the luminosity, then it can still be a standard candle as long as there is some observational way to tell that it's luminosity will be higher.
    I guess if they were intra galactic we could.
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    Ken G explained what I meant very nicely. Not all type Ia supernovae have exactly the same luminosity, so, in one sense, they aren't "standard candles." On the other hand, if we can acquire the spectrum of a type Ia supernova, and sample its light curve well, then we can

    a) recognize that it might be peculiar, and put it in the discard bin, or

    b) note that it has properties similar to some other instances of type Ia SNe, and so, based on our knowledge of THOSE events, assign it a luminosity with some degree of confidence

    In short, for many type Ia supernovae, we can use spectra and light curves to determine luminosity ... and then compare luminosity to apparent brightness to estimate distance.

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    Quote Originally Posted by StupendousMan View Post
    Ken G explained what I meant very nicely. Not all type Ia supernovae have exactly the same luminosity, so, in one sense, they aren't "standard candles." On the other hand, if we can acquire the spectrum of a type Ia supernova, and sample its light curve well, then we can

    a) recognize that it might be peculiar, and put it in the discard bin, or

    b) note that it has properties similar to some other instances of type Ia SNe, and so, based on our knowledge of THOSE events, assign it a luminosity with some degree of confidence
    Yes, and that's what I meant by "some but not all". Is there something you see I'm implying that I'm missing?

    It may be of interest to note that this is somewhat true for actual candles. Paraffin candles, for instance, are about 20% brighter than "standard candles". In colonial times, crystallized sperm whale wax was the "standard" candle, but this was more functionality and aroma than a luminosity standard, I suppose.
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    This was a hot topic a few years ago. Basically, some SN1a (not much Hydrogen in the spectrum) are single degenerate and have about 1.4 solar masses. Some are double degenerate with two smaller white dwarfs merging... currently thought to be the more common variation. But these double degenerate SN1a are also likely to be in a narrow range of combined masses, so their luminosity will still be usually only tens of percents away from the theoretical standard candle. This paper about highly magnetic white dwarfs is similar to a paper a few years back about very rapidly rotating single degenerate white dwarfs possibly collecting more than 1.4 solar masses before the big event. It is worth noting that we have not observed ANY white dwarfs with masses over the Chandrasekhar limit, so while highly magnetic or rapidly rotating super-Chandrasekhar white dwarfs MIGHT happen they are apparently very rare. ... as are super-luminous SN1a events.

    Concerning the matter of some subset being usable as standard candles, there have been (at least partially) successful efforts to find spectral and other indicators to distinguish the various progenitor types, and eliminate non-standard candles from efforts where higher precision is needed.
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    Quote Originally Posted by antoniseb View Post
    This was a hot topic a few years ago. Basically, some SN1a (not much Hydrogen in the spectrum) are single degenerate and have about 1.4 solar masses. Some are double degenerate with two smaller white dwarfs merging... currently thought to be the more common variation. But these double degenerate SN1a are also likely to be in a narrow range of combined masses, so their luminosity will still be usually only tens of percents away from the theoretical standard candle. This paper about highly magnetic white dwarfs is similar to a paper a few years back about very rapidly rotating single degenerate white dwarfs possibly collecting more than 1.4 solar masses before the big event. It is worth noting that we have not observed ANY white dwarfs with masses over the Chandrasekhar limit, so while highly magnetic or rapidly rotating super-Chandrasekhar white dwarfs MIGHT happen they are apparently very rare. ... as are super-luminous SN1a events.
    But there have been reports of superluminous Type 1a SN, right? This may mean, however, that they resolved to normal SN luminosities after all the factors (e.g. dust extinctions) were taken into account.

    Concerning the matter of some subset being usable as standard candles, there have been (at least partially) successful efforts to find spectral and other indicators to distinguish the various progenitor types, and eliminate non-standard candles from efforts where higher precision is needed.
    Thanks, and I recall the double degeneracy issue. What I have been curious to see is how much our advanced knowledge of Type Ia supernovae has impacted the results of both teams that gave us acceleration?
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    Quote Originally Posted by George View Post
    ... What I have been curious to see is how much our advanced knowledge of Type Ia supernovae has impacted the results of both teams that gave us acceleration?
    So far, the accelerated expansion of the universe is strongly supported, but not well enough characterized to decide between competing models to explain it.
    Hopefully the upcoming Euclid mission will get enough data to make that possible.
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    Thanks.
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    Let me throw this out there and see what anyone thinks.

    One could say that very distant supernovae are like the blobs of light that folks photograph and wind up calling a UFO.
    It could be a star very far out--it might be Venus--or the light of an aircraft. All you really know is that it is a blob of light.

    Now, very far away, perhaps you have a collision, and the explosion is more powerful than expected--you are seeing spectra from two objects--but it might wind up looking like..say..one supernova, when maybe two went up striking each other. They may have been close for so long that they shared material--and--being in another galaxy--this isn't really evident.

    Possible?

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    Quote Originally Posted by publiusr View Post
    ...Possible?
    Not easily. Supernovae have quite distinct light curves and spectral features. It'd be pretty unlikely for some other phenomenon to precisely mimic that.

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    Quote Originally Posted by Ken G View Post
    He means that people have a weird idea of what it means to be a "standard candle." All it means is that you can infer the absolute brightness somehow, and use that to get distance, it never meant that all the objects you use it on have the same brightness. For some reason, when "standard candle" was applied to type Ia SN, it took on that latter meaning, but that was never the correct requirement for a "standard candle." So if you can have a big magnetic field, and change the luminosity, then it can still be a standard candle as long as there is some observational way to tell that it's luminosity will be higher.
    There is not "some reason", there is an actual history. When people use the term "standard candle," they usually do mean something that has a standard brightness. For years, for good reasons, it was expected that type Ia supernovae were standard candles. There are many papers about this.

    The current state of affairs is that there are identifiable sub-types of type Ia with identifiable relationships between brightness and their changes in brightness over time. One can use this relationship to determine brightness and thus determine actual distance. The development of this relationship and the ultimate rejection that these events were standard candles began to be established with a paper by Philips in 1993. ("The Absolute Magnitudes of Type Ia Supernovae, Astrophysical Journal, 413: L105-L108, 1993 Aug 08)

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    Quote Originally Posted by Kwalish Kid View Post
    There is not "some reason", there is an actual history. When people use the term "standard candle," they usually do mean something that has a standard brightness. For years, for good reasons, it was expected that type Ia supernovae were standard candles. There are many papers about this.

    The current state of affairs is that there are identifiable sub-types of type Ia with identifiable relationships between brightness and their changes in brightness over time. One can use this relationship to determine brightness and thus determine actual distance. The development of this relationship and the ultimate rejection that these events were standard candles began to be established with a paper by Philips in 1993. ("The Absolute Magnitudes of Type Ia Supernovae, Astrophysical Journal, 413: L105-L108, 1993 Aug 08)
    Kwalish Kid. Actually, part of the development of the idea that these events were not standard candles began at MIT in the winter of 91-92. MIT offered a Winter Course on Nuclear and Particle Physics for Massachusetts High School Teachers. About 100 applied: I was fortunate to participate there. Notable speakers from several areas, including Larry Sulak from the IMB, B.U. Physics, delineated the state of the art. As a course requirement, we had the option of several tasks, including a short paper. I wrote one read by PhD Betty Sapp, the course coordinator, wife of the director of the Bates Linear Accelerator, Wade Sapp. The title was "Parity, Pulsars, and Supernova Remnants". She noted that the ideas were "Original!" on the cover page. So, I decided to give my first science talk at a conference on it that fall.....the Vassar College, Nov.92 Meeting of the American Association of Physics Teachers.
    You had to write a short summary of the conceptual outline of the talk, which I did, and it was published as part of the proceedings therein. It went like this.

    My interest was in particle physics, and supernovae in general. I was aware that better instrumentation and detector technology,coupled with improved image processing algorithms gave vastly better data of more sensitive, distant objects. I regularly attended the Physics Colloquia and Astrophysics Colloquia @ MIT, courtesy of the Dept, as a science teacher. In the course of examining radio images of supernovae remnants from an article by M.J.Kesteven and R. N. Manchester, Molonglo Observatory, N.S.W (Australian Journal of Physics), I realized that the great majority of remnants were barrel-shaped, not spheres...~85%. The ones that look spherical were happenstances where you looked along the axis of the barrel. Then, they looked spherical.
    But, the talk at the time was of using them for standard candles in scales of the universe. It's obvious that the viewing angle of the observer plays a role in the light curve. what could be causing the explosions/deflagrations to proceed with an inherent asymmetry? Parity effects. Any time weak interactions are involved, they respond asymmetrically to the presence of a strong magnetic field. This was shown to be true in the famous resolution of the Tau-Theta Problem by T.D.K Lee and C. N. Yang in the fifties, where their research showed that not only was it true with K mesons, it was in every run of every experiment that could have shown it....and nobody had ever checked..(Martin Gardner..."Mirror Asymmetry and Time Reversed Worlds". When, in particular, a supernova is type 2, the pulsar will always eject from the same pole, and even in type1 a's, there will be a North/South asymmetry.
    MIT was in the process of running a parity effect experiment using an expensive highly polarized target of He-3....showed a distinct parity effect.

    Two years later, gave the talk in May AAPT at Harvard's Olney Science Center, combining the numerical work of the Russians, Leinson & Oraevskii, with an increase of 30% of the scattering of neutrinos off spin waves, magnons, in the explosion, yielding a successful supernova, with an asymmetry of ~ 4% due to parity effects, ejecting a pulsar at typical nascent velocities..50-500 km/sec. Fun. (Matt D. & Ben Affleck in the back row...they played golf with my sister's boyfriend @ Andover C.C.) not all the liars in the world live in white houses...... pete

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    Ooooh, history anecdotes! Let me play, too.

    One of the critical steps in the process of finding a way to account for the difference in the absolute magnitudes of (some of) Type Ia supernovae was the discovery and measurement of two particular objects in 1991. SNe 1991T and 1991bg were both relatively nearby and bright, and each was studied in detail -- via both photometry and spectroscopy. The first (1991T) was peculiar in one way: it was more luminous than the usual Type Ia event, somewhat bluer at peak, and also declined after maximum light more slowly. The other (1991bg) was almost its opposite: it was considerably less luminous than most, much redder at peak, and declined quickly after reaching maximum light.

    The combination of two such unusual SNe with well-sampled light curves and spectra gave astronomers a chance to look for some patterns in the deviation of individual events from the typical properties. Mark Phillips was one of the first to come up with the notion that there was a "family" of Type Ia SNe, in which members at the bright end of the group shared one set of properties, and those at the faint end a different set. I remember going out to lunch at Blondie's Pizza with him and Alex Filippenko (my graduate advisor): he pulled out a graph showing a correlation between absolute luminosity and decay rate, which later appeared as Figure 1 in his 1993 paper (mentioned above). You can see a copy on ADS at

    http://articles.adsabs.harvard.edu//...00107.000.html

    Sigh. I was skeptical of the connection at the time. Missed my chance to get in at the ground floor :-)

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    Quote Originally Posted by Kwalish Kid View Post
    There is not "some reason", there is an actual history. When people use the term "standard candle," they usually do mean something that has a standard brightness.
    And that's what is just plain wrong. For example, a crucial application of the "standard candle" concept is Cepheid variables, which were so important for understanding the distance to other galaxies and the Hubble Law. Cepheids are not a class of stars that all have the same intrinsic brightness, they are a class that you can infer their intrinsic brightness-- that's generally what a standard candle is! For example, look here: https://universe-review.ca/R02-07-candle.htm. What you will see is the following list of "standard candles:"
    Cepheids
    Tully-Fisher effect
    Type Ia SN

    Please notice that not a single one of those would be a "standard candle" by your meaning. So it's just a kind of myth that "standard candle" means "class of objects that all have the same intrinsic brightness", it totally undersells the true sophistication of the standard candle concept in astronomy.
    Last edited by Ken G; 2017-Feb-15 at 11:20 PM.

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    Pardon the interruption, but there are a number of papers on supernovae in the new list of fun arVix papers....

    https://forum.cosmoquest.org/showthr...01#post2392001
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    Quote Originally Posted by Ken G View Post
    So it's just a kind of myth that "standard candle" means "class of objects that all have the same intrinsic brightness", it totally undersells the true sophistication of the standard candle concept in astronomy.
    I had some extra time this evening, so I spent a bit of it using the excellent "Bumblebee" version of the Astrophysics Data Service to investigate the use of the term "standard candle" in the astronomical literature. You can find Bumblebee at

    https://ui.adsabs.harvard.edu/

    The term occurs frequently between 1850 and 1930 or so to refer to a literal candle: a small cylinder of a waxy substance surrounding a wick, used to produce a burning flame. Several firms worked hard to produce candles of very particular sizes and properties, and scientists adopted several models to serve as standards for illumination. The terms "standard candle", "international candle" and "Hefner candle" refer to items of this sort. The phrase "standard candle" appears often in descriptions of astronomical photography and photometry.

    The use of "standard candle" to refer to metaphorical candles -- that is, to refer to a class of stars or galaxies or other celestial objects which may act as references -- first appears in 1970 in a pair of papers.

    http://adsabs.harvard.edu/cgi-bin/np...&link_type=GIF
    http://articles.adsabs.harvard.edu/f...J.....75...21L

    Each paper discusses cosmology, and uses "standard candle" to mean "one of a set of objects which have identical properties." For example, here's a portion of the sentence from the second article, by Lasker:

    as “standard candles” (i.e., as a set of sources of fixed and given intensity),
    In the 1970s, the use of this term exploded in the astronomical literature.

    So, when Kwalish Kid stated that the term had a history, and referred to something with a standard brightness, he was absolutely right.

    On the other hand, in recent years, the phrase "standard candle" has come to be used in a more general sense, to refer to a class of objects which, although not having exactly the same luminosity, emit amounts of light which can be estimated accurately from other observables; so Ken G. has some justification for his point of view.

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    Quote Originally Posted by StupendousMan View Post
    I had some extra time this evening, so I spent a bit of it using the excellent "Bumblebee" version of the Astrophysics Data Service to investigate the use of the term "standard candle" in the astronomical literature. You can find Bumblebee at

    https://ui.adsabs.harvard.edu/
    That's really cute, it's a useful function.

    The phrase "standard candle" appears often in descriptions of astronomical photography and photometry.
    And the one thing we can say about this term is that it always means comparing what you see to an intrinsic brightness you know, and using the result to infer distance. That's just what the term always means in astronomy.
    The use of "standard candle" to refer to metaphorical candles -- that is, to refer to a class of stars or galaxies or other celestial objects which may act as references -- first appears in 1970 in a pair of papers.

    http://adsabs.harvard.edu/cgi-bin/np...&link_type=GIF
    http://articles.adsabs.harvard.edu/f...J.....75...21L
    But this is not the point-- every term has a history, that's not what matters. Its current meaning is what matters.
    Each paper discusses cosmology, and uses "standard candle" to mean "one of a set of objects which have identical properties." For example, here's a portion of the sentence from the second article, by Lasker:



    In the 1970s, the use of this term exploded in the astronomical literature.

    So, when Kwalish Kid stated that the term had a history, and referred to something with a standard brightness, he was absolutely right.
    Ah, but that's not what Kwalish Kid said that I objected to. Had he said that "standard candle" used to mean that, but has stopped meaning that in modern astronomical parlance, then he would have been completely correct. But instead, he said "When people use the term "standard candle," they usually do mean something that has a standard brightness." I suppose it depends on what "people" he means, I took it to mean "people relevant to this forum," because it is on this forum that we are talking about standard candles. So it's the astronomy meaning that matters here, not what glass blowers mean, etc. That meaning is clear enough, as used today by astronomers, as you can see if you restrict your Bumblebee search on "standard candle" to astronomical papers after 1990, when the term really took off. You'll see lots of application of the term to variable stars, which is a class of stars that tell us their intrinsic brightness based on their variability, but they are certainly not a class of stars of fixed intrinsic brightness. You'll also see lots of type Ia supernovae references, also not the old meaning. And you'll find a host of other uses, always about inferring the instrinsic brightness and comparing it to the apparent brightness, but very very rarely from any kind of object with fixed brightness-- simply because astronomy rarely gives us those. So we have the single most important way to infer large distances, the "standard candle" idea, being applied in a host of places-- and almost none of them could be understood if people are thinking about the old-fashioned meaning of the term. Hence, it is vastly misleading to use that old meaning.
    On the other hand, in recent years, the phrase "standard candle" has come to be used in a more general sense, to refer to a class of objects which, although not having exactly the same luminosity, emit amounts of light which can be estimated accurately from other observables; so Ken G. has some justification for his point of view.
    Right, I am only talking about what the term means today, because that's what is relevant to type Ia SNe. When people say that type Ia supernovae are "not standard candles", they are saying it today, and they are wrong-- given what that term means in astronomy today. It's a common misconception that does type Ia SN research a terrible disservice, even if they are themselves to blame for co-opting a term that used to mean something quite different, and people who don't know better often get the two meanings confused.
    Last edited by Ken G; 2017-Feb-16 at 08:00 PM.

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    I stand by my comments. Cepheids are a set of different standard candles. SN Ia are not standard candles, but individual events can be used as effective standard candles.

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    Quote Originally Posted by Kwalish Kid View Post
    I stand by my comments. Cepheids are a set of different standard candles. SN Ia are not standard candles, but individual events can be used as effective standard candles.
    I agree. That being said I also respect Ken G and his desire to have things worded very precisely. I wouldn't take his clarification to imply that you were wrong somehow.
    Forming opinions as we speak

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    Quote Originally Posted by Kwalish Kid View Post
    I stand by my comments. Cepheids are a set of different standard candles. SN Ia are not standard candles, but individual events can be used as effective standard candles.
    In what way do you think Cepheids are standard candles, that type Ia SN are not? This is what you need to answer.

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    Quote Originally Posted by Ken G View Post
    In what way do you think Cepheids are standard candles, that type Ia SN are not? This is what you need to answer.
    I'm going to take a wild guess that he meant "standard candles" in the sense that I described in post 22 in this thread; you know, the sense that is based in history. My guess is based on the fact that he used the words "there is an actual history" in his original post.

    Could we stop arguing about semantics and get back to talking about the properties of supernovae, please? As my contribution to the topic of "Superluminous supernovae", let me offer some notes I took during a two-day colloquium on superluminous supernovae at STScI last summer:

    http://spiff.rit.edu/richmond/sne/sl...lsne_2016.html

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    Quote Originally Posted by StupendousMan View Post
    I'm going to take a wild guess that he meant "standard candles" in the sense that I described in post 22 in this thread; you know, the sense that is based in history. My guess is based on the fact that he used the words "there is an actual history" in his original post.
    I don't understand-- Cepheids are certainly not "standard candles" in the historical sense that Kwalish Kid talked about.
    Could we stop arguing about semantics and get back to talking about the properties of supernovae, please?
    The relevance is, people need to understand that type Ia SN are standard candles in exactly the same way that Cephieds are. I don't really care much about the term "standard candle", I care that type Ia SNs give us distances in exactly the same way that Cepheids do, but people don't have some kind of cow every time a new class of Cepheids appears!
    As my contribution to the topic of "Superluminous supernovae", let me offer some notes I took during a two-day colloquium on superluminous supernovae at STScI last summer:

    http://spiff.rit.edu/richmond/sne/sl...lsne_2016.html
    You take good notes!

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