What is the New White Dwarf Mass Limit?

[|Glitch|]

For the last 88 years we have used Subrahmanyan Chandrasekhar's calculations to determine the maximum mass of a white dwarf. As a result of that calculated mass limit, a peak brightness was derived and the Standard Candle was born. However, those calculations were made based upon certain assumptions, namely that the white dwarf was not rotating and had no magnetic field. More recent discoveries have demonstrated that those assumptions made in 1930 may not be valid in some cases.

In the last 15 years we have discovered both sub- and super-Chandrasekhar Type Ia SNe, each with varying absolute magnitudes. In the case of the sub-Chandrasekhar Type Ia SNe, they were classified as Type Iax SNe in March 2013 with an absolute magnitude range between -14.2 < M_B < -18.9, and none of them are suspected of exceeding the 1.4 M_☉ established by Chandrasekhar.¹ In the case of super-Chandrasekhar Type Ia SNe (specifically, SNLS-03D3bb, SN 2003fg, SN 2006gz, SN 2007if, and SN2009d) they all showed an exceptionally large mass of ⁵⁶Ni in their ejecta.² Larger than should be possible for a 1.4 M_☉ white dwarf progenitor. The white dwarf mass prior to SN 2007if's deflagration, for example, was estimated to be 2.4 M_☉ based upon the amount of ⁵⁶Ni detected in its ejecta.³

In 2013 it was suggested that these super-Chandrasekhar Type Ia SNe were the result of highly magnetic white dwarfs. Upasana Das and Banibrata Mukhopadhyay, from the Indian Institute of Science, proposed a new white dwarf maximum limit of 2.58 M_☉.⁴ However, these suggested white dwarfs progenitors were also assumed to be not rotating. In 2015 Mukhopadhyay corrected this oversight and calculated the mass range for various rotational periods and various intensities of magnetic field. Mukhopadhyay now proposes a white dwarf maximum limit range between 2.3 and 2.8 M_☉.⁵ The idea behind these papers was that both a very strong magnetic field and/or rapidly rotating white dwarf would be able to counteract the inward pull of gravity to a certain degree, allowing the white dwarf to accumulate additional mass before deflagration.

If rapidly rotating and/or highly magnetic white dwarfs can exceed the Chandrasekhar Limit of 1.4 M_☉, then it would have a significant effect on our prior assumptions. Magnetars, for example, could be highly magnetic white dwarfs, and not neutron stars as currently believed. A 2.8 M_☉ white dwarf would also be more massive than the most massive neutron star yet observed.

One of the first casualties of these new discoveries of both sub- and super-Chandrasekhar Type Ia SNe has to be what we have assumed was a “Standard Candle.” This would also call into question the ΛCDM model considering that it is based upon the observations of 30 Type Ia SNe at z = 0.5 and 10 Type Ia SNe at z = 1 made prior to 2003.⁶ At the very least we need to be certain that the data for Type Ia SNe collected prior to 2013 is sufficient to rule out any possibility of sub- or super-Chandrasekhar Type Ia SNe before assuming it has a fixed absolute magnitude.

Sources:http://iopscience.iop.org/article/10.1088/0004-637X/767/1/57/meta

1. Type Iax Supernovae: A New Class of Stellar Explosion - The Astrophysical Journal, Volume 767, Number 1, March 2013 (free issue)
2. The Type Ia Supernova SNLS-03D3bb from a Super-Chandrasekhar-Mass White Dwarf Star - Lawrence Berkeley National Laboratory, April 2008 (open access)http://iopscience.iop.org/article/10.1088/0004-637X/713/2/1073/meta
3. Nearby Supernova Factory Observation of SN 2007if: First Total Mass Measurement of a Super-Chandrasekhar-Mass Progenitor - The Astrophysical Journal, Volume 713, Number 2, March 2010 (free issue)http://www.worldscientific.com/doi/abs/10.1142/S0218271813420042
4. New Mass Limit of White Dwarfs - International Journal of Modern Physics D, Volume 22, Issue 12, October 2013 (free preprint)https://arxiv.org/abs/1509.09008
5. Over-Luminous Type Ia Supernovae - arXiv : 1509.09008, September 2015http://iopscience.iop.org/article/10.1086/306308/meta
6. The High-Z Supernova Search: Measuring Cosmic Deceleration and Global Curvature of the Universe Using Type Ia Supernovae - The Astrophysical Journal, Volume 507, Number 1, 1998 (free preprint)

 

[phyzguy]

At the very least we need to be certain that the data for Type Ia SNe collected prior to 2013 is sufficient to rule out any possibility of sub- or super-Chandrasekhar Type Ia SNe before assuming it has a fixed absolute magnitude.

The use of SN1A for cosmology does not assume that these supernovae have a fixed absolute magnitude. This is a common misconception. Instead, the Philips relationship is used to determine the peak intrinsic brightness by measuring the decay rate of the light curve. The Philips relationship has been empirically verified, so in this sense the details of the SN1A explosions don't really matter. They are still usable as "standardizable candles". So your objections don't really apply.

 

[|Glitch|]

The use of SN1A for cosmology does not assume that these supernovae have a fixed absolute magnitude. This is a common misconception. Instead, the Philips relationship is used to determine the peak intrinsic brightness by measuring the decay rate of the light curve. The Philips relationship has been empirically verified, so in this sense the details of the SN1A explosions don't really matter. They are still usable as "standardizable candles". So your objections don't really apply.

Cosmology does assume that all Type Ia SNe have a fixed absolute magnitude. Without that assumption there can be no Standard Candle. Astronomers use the Phillips relationship as a tool to help them identify Type Ia SNe. The Phillips relationship does not provide absolute magnitude, which is required to determine distance. It merely assumes it based upon the light curve.

We will need more data than just the light curve. Both sub- and super-Chandrasekhar Type Ia SNe have almost identical light curves. Which is where the bulk of the problem lies. Many have merely assumed they were Type Ia SNe, particularly those SNe beyond z = 1, because of their light curve and nothing else. Type Ia SNe are only usable as Standard Candles once you have removed any possibility that it may be either a sub- and super-Chandrasekhar Type Ia SNe. If there is insufficient data to make that determination, then there is no Standard Candle. Between 18% and 48% of all Type Ia SNe prior to 2013 have been misclassified and should actually be the much dimmer sub-Chandrasekhar Type Ia SNe, or Type Iax SNe. That alone calls into question the ΛCDM model.

 

[Bandersnatch]

Cosmology does assume that all Type Ia SNe have a fixed absolute magnitude.

I agree with @phyzguy - this is simply not true. It hasn't been true for at least a quarter of a century, if not longer. Even your own source [6] talks about it (pt. 3).

This would also call into question the ΛCDM model considering that it is based upon the observations of 30 Type Ia SNe at z = 0.5 and 10 Type Ia SNe at z = 1 made prior to 2003

We have 2018 now. There's been more surveys since then, and the Hubble graph is well populated at those distances.

 

[|Glitch|]

I agree with @phyzguy - this is simply not true. It hasn't been true for at least a quarter of a century, if not longer. Even your own source [6] talks about it (pt. 3).We have 2018 now. There's been more surveys since then, and the Hubble graph is well populated at those distances.

You cannot determine absolute magnitude from a light curve, which is all the Phillips relationship gives you. The Phillips relationship merely helps identify a potential Type Ia SNe, it says absolutely nothing about absolute magnitude. My source does not reference the Phillips relationship anywhere in the paper. It does, however, make reference to the Hubble diagram, but they even acknowledge what I original posted, that it is insufficient without additional data.

At maximum light, SN Ia have an intrinsic range of > 2 mag in B and > 1 mag in V. Although this is an interesting result for supernova physics, it does not bode well for using SN Ia as high-precision distance indicators without additional information.

Keep in mind that the Phillips relationship, and the comments in the Schmidt, et al. (1998) paper above, where made before we discovered sub- and super-Chandrasekhar Type Ia SNe.

 

[Chronos]

Science is a self-policing discipline. For every remarkable finding there is an equally remarkable number of dispassionate [jealous] colleagues scavenging for any trace of error, omission, dubious assumption or other hint of human frailty. Fame carries a price, and thar price is a relentless flock of buzzards. The mere thought of felling a giant like the Sne1a distance ladder inspires visions of ilfetime leisure and a to die for collection of luxury hotel towels from keynote speaking engagements.Yes, Virginia, even scientists are not immune to banality. The Sne1a luminosity distance ladder is subject to adjustments based on a variety of factors and observational data. It is still subject to uncertainties, but, have been reduced significantly over the past century. There is less a question of their peak luminosity than progenitor mass. Independent indicators, such as the SZ effect and gravitational lensing of quasars, are available to calibrate and confirm distance calculations. So, viewing Sne1s as a one trick pony in the cosmologists tool kit is fallacious.

 

[|Glitch|]

Science is a self-policing discipline. For every remarkable finding there is an equally remarkable number of dispassionate [jealous] colleagues scavenging for any trace of error, omission, dubious assumption or other hint of human frailty. Fame carries a price, and thar price is a relentless flock of buzzards. The mere thought of felling a giant like the Sne1a distance ladder inspires visions of ilfetime leisure and a to die for collection of luxury hotel towels from keynote speaking engagements.Yes, Virginia, even scientists are not immune to banality. The Sne1a luminosity distance ladder is subject to adjustments based on a variety of factors and observational data. It is still subject to uncertainties, but, have been reduced significantly over the past century. There is less a question of their peak luminosity than progenitor mass. Independent indicators, such as the SZ effect and gravitational lensing of quasars, are available to calibrate and confirm distance calculations. So, viewing Sne1s as a one trick pony in the cosmologists tool kit is fallacious.

Science is also always evolving with each new discovery. Refining the data over the past century does nothing if new discoveries demonstrates that the old assumptions were incorrect or incomplete. There are significant questions as to their absolute magnitude, when it can range anywhere from between -14.2 and -22.3. Just because the SN has the correct light curve for a Type Ia SN does not mean it is at the distance assumed. Without additional information, such as the rate and composition of the ejecta, we cannot be certain of its distance. When it comes to determining distances beyond a million parsecs Type Ia SNe are a "one trick pony", which is why it is critical that we get all the information we can about them before making pronouncements about their distance.

I suppose red shift could also be used for determining distances beyond a million parsecs, but not very accurately. It will get you in the ballpark anyway, plus or minus a few tens of millions of light years.

 

[phyzguy]

You cannot determine absolute magnitude from a light curve, which is all the Phillips relationship gives you. The Phillips relationship merely helps identify a potential Type Ia SNe, it says absolutely nothing about absolute magnitude. My source does not reference the Phillips relationship anywhere in the paper. It does, however, make reference to the Hubble diagram, but they even acknowledge what I original posted, that it is insufficient without additional data.

@|Glitch| Why do you continue to propagate misinformation? Have you even read the links you posted or the Wikipedia article on the Philips relationship that I posted? The whole point of the Philips relationship is that it does allow you to determine the absolute magnitude from the shape of the light curve.

Below are two quotes from Reference 6 in your OP (bolding mine):

"Type Ia supernovae (SN Ia) have long been considered promising tools for measuring extragalactic luminosity distances, but only recent searches, the resulting sets of light curves and spectra, and new methods of analysis (Phillips 1993 [P93]; Hamuy et al. 1995, 1996a-d [H95,H96a-d]; Riess, Press, & Kirshner 1995, 1996a [RPK95, RPK96]) have quantified the nature, power, and limitations of SN Ia as distance indicators."

"Although their brightness at maximum light has a moderately large scatter, SN Ia do exhibit a correlation (σ ≈ 0.15 mag) between the rate at which their luminosity declines and absolute magnitude. P93 demonstrated this relationship by plotting the absolute magnitude of ten nearby SN Ia which had dense photoelectric or CCD coverage, versus the parameter ∆m15(B), the amount by which the SN decreased in brightness in the B band over the 15 days following maximum light. The sample showed a correlation, which when taken into account, dramatically improved the predictive power of SN Ia."

 

[|Glitch|]

@|Glitch| Why do you continue to propagate misinformation? Have you even read the links you posted or the Wikipedia article on the Philips relationship that I posted? The whole point of the Philips relationship is that it does allow you to determine the absolute magnitude from the shape of the light curve.

Below are two quotes from Reference 6 in your OP (bolding mine):

"Type Ia supernovae (SN Ia) have long been considered promising tools for measuring extragalactic luminosity distances, but only recent searches, the resulting sets of light curves and spectra, and new methods of analysis (Phillips 1993 [P93]; Hamuy et al. 1995, 1996a-d [H95,H96a-d]; Riess, Press, & Kirshner 1995, 1996a [RPK95, RPK96]) have quantified the nature, power, and limitations of SN Ia as distance indicators."

"Although their brightness at maximum light has a moderately large scatter, SN Ia do exhibit a correlation (σ ≈ 0.15 mag) between the rate at which their luminosity declines and absolute magnitude. P93 demonstrated this relationship by plotting the absolute magnitude of ten nearby SN Ia which had dense photoelectric or CCD coverage, versus the parameter ∆m15(B), the amount by which the SN decreased in brightness in the B band over the 15 days following maximum light. The sample showed a correlation, which when taken into account, dramatically improved the predictive power of SN Ia."

What misinformation? I cited valid and verifiable sources. You are making demonstrably false accusations because you do not like what I am saying, but everything I have posted is factual and verifiable. There is no misinformation being presented by me.

 

[berkeman]

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