A New Pulsar Planet?

Dates back October 2010. A possible gas giant revolving the neutron star PSR J1719-14. We eager wait for a publication paper!

http://adsabs.harvard.edu/abs/2010xmm..prop..203P

Quote :

A binary msp with a planetary mass companion has been recently discovered. For a psr mass of 1.4Msun, we infer a companion mass of 1.3 Jovian masses, which is ten times smaller than that of any other known stellar companion to a msp. This psr is likely the first long-sought example of a msp which descended from an Ultra Compact Accreting X-ray MSP. In the context of a multi-wavelength campaign, we request a 25 ks exposure (sampling 3 orbits of the system) with the aims of:i) identifying the X-ray counterpart;ii) comparing X-ray fluxes and spectra with those of other binaries with other kinds of companions and/or have undergone other evolutionary paths;iii) searching for orbital variations in the X-ray flux, in order to investigate if the new binary can be the progenitor of an isolated msp.

Question would be whether this is a bona-fide planet or a remnant of a tidally-disrupted star...

Lazarus wrote:

Question would be whether this is a bona-fide planet or a remnant of a tidally-disrupted star...

So undermassive? Another question is the orbital period. If very short (P<<0.1 days), the He-WD option would be likely.

Edasich wrote:

So undermassive?

Don't see why not. If companion stars get completely destroyed (as suggested by the existence of single MSPs), then presumably there is a stage at which they will have very low masses...

Well this is a weird one, apparently it is a Jupiter-mass diamond "planet" orbiting the millisecond pulsar PSR J1719−1438.

From the abstract: "its minimum density of 23 g cm⁻³ suggests that it may be an ultra-low-mass carbon white dwarf."

News release
More discussion at Dynamics of Cats

Well, quite an exotic second generation planet, if we want to consider it as "planet"

600000km away from pulsar quite nice place

tommi59 wrote:

600000km away from pulsar quite nice place

Roughly 0.0043 AUs away, nearly twice the Earth-Moon separation. Just figure out the irradiation...

I wonder how far from spherical this object is. The tidal forces from the (very) nearby pulsar must be enormous. On the other hand, with a density of at least 23 g cm^-3 and a mass equal to that of Jupiter, the surface gravity must be immense as well.

So on looking at this further, the "diamond" idea doesn't seem to work particularly well.

The most common type of white dwarf is a carbon-oxygen white dwarf, in which the core of the white dwarf is made up of carbon and oxygen. This is then usually (but not always) surrounded by layers of hydrogen and helium.

Oxygen is heavier than carbon and apparently crystallises at higher temperatures, therefore the inner part of the core is very oxygen-rich, with carbon-rich material further out. This applies even to the diamond star BPM 37093 that was announced in 2004: the best-fitting model is for an oxygen core.

So if this object is indeed the core of a white dwarf star, we should probably expect there to be a lot of oxygen in there...

Transformation of a Star into a Planet in a Millisecond Pulsar Binary
http://arxiv.org/abs/1108.5201

Quote :

Millisecond pulsars are thought to be neutron stars that have been spun-up by accretion of matter from a binary companion. Although most are in binary systems, some 30% are solitary, and their origin is therefore mysterious. PSR J1719-1438, a 5.7 ms pulsar, was detected in a recent survey with the Parkes 64m radio telescope. We show that it is in a binary system with an orbital period of 2.2 h. Its companion's mass is near that of Jupiter, but its minimum density of 23 g cm$^{-3}$ suggests that it may be an ultra-low mass carbon white dwarf. This system may thus have once been an Ultra Compact Low-Mass X-ray Binary, where the companion narrowly avoided complete destruction.

Listed at EPE

http://exoplanet.eu/star.php?st=PSR+1719-14

Formation of the planet around the millisecond pulsar J1719-1438

Still think it's better to call the companion a white dwarf rather than a planet.

As I foresaw some low-mass substellar companions to neutron stars have been listed in EPE...

http://exoplanet.eu/catalog/psr_j1807-2459_b/
http://exoplanet.eu/catalog/psr_b1957%2B20_b/
http://exoplanet.eu/catalog/psr_j2051-0827_b/
http://exoplanet.eu/catalog/psr_j2241-5236_b/

...along with the K2 white dwarf with transiting planetesimal...

http://exoplanet.eu/catalog/wd_1145%2B017_b/

I can understand the pulsar companions based on precedent, but the WD asteroid? Really?

Why not?

If so I have more pulsar and WDs with very low-mass companions even at longer orbital periods (>1-2 days).

Me too. A lot of cataclysmic variables have substellar secondaries.

Thread bump for recent addition to EPE: PSR J0636+5129 b

Likely another "diamond planet"

Ordinary X-rays from Three Extraordinary Millisecond Pulsars: XMM-Newton Observations of PSRs J0337+1715, J0636+5129, and J0645+5158

Quote :

We present the first X-ray observations of three recently discovered millisecond pulsars (MSPs) with interesting characteristics: PSR J0337+1715, PSR J0636+5129, and PSR J0645+5158. PSR J0337+1715 is a fast-spinning, bright, and so-far unique MSP in a hierarchical triple system with two white dwarf (WD) companions. PSR J0636+5129 is a MSP in a very tight 96-min orbit with a low-mass, 8 M_J companion. PSR J0645+5158 is a nearby, isolated MSP with a very small duty cycle (1-2%), which has led to its inclusion in high-precision pulsar timing programs. Using data from XMM-Newton, we have analyzed X-ray spectroscopy for these three objects, as well as optical/ultraviolet photometry for PSR J0337+1715. The X-ray data for each are largely consistent with expectations for most MSPs with regards to the ratios of thermal and non-thermal emission. We discuss the implications of these data on the pulsar population, and prospects for future observations of these pulsars.

Quote :

PSR J0636+5129 (hereafter PSR J0636) is an MSP with a very low-mass companion that was discovered in GBNCC data in a 96 min orbit: one of the tightest MSP binary systems known (Stovall et al. 2014). The companion, which has a minimum mass of 7.4 M_J (for an assumed neutron star mass of 1.4 M_Sol), does not show any signs of current mass loss (cf. Romani et al. 2012) and appears similar in nature to the “diamond planet” orbiting PSR J1719–1438 (Bailes et al. 2011). This suggests that PSR J0636 will evolve into an isolated MSP following a period of mass-transfer/loss in an ultra-compact X-ray binary.