No Pulsar Left Behind. I. Timing Solutions, Pulse-sequence Polarimetry, and Emission Morphology for 12 pulsars. (2024)

2.1 PSR J2053+1718

PSRJ2053+1718 has a much smaller spin periodderivative and is clearly much older than the other pulsars in this sample.A first simple fit for $\nu$, $\dot{\nu}$, $\alpha$, $\delta$ and propermotion along these two directions ($\mu_{\alpha}$ and $\mu_{\delta}$)yields a reduced $\chi^{2}$ of 1.80, and visible trends inthe residuals. Given the low frequency used in the timing and the relatively highprecision of the measurements, these are likely due to variations in DM caused bythe Earth’s and the pulsar’s movement through space. We used the DMX model(2013ApJ...762...94D) to measure the DM variations (displayedin Fig.2) and subtract them; once this is done thereduced $\chi^{2}$ decreases to 1.34. In this model we obtain$\mu_{\alpha}\,=\,1.0\,\pm\,2.3\,\rm mas$ $yr^{-1}$and $\mu_{\delta}\,=\,+6.9\,\pm\,2.8\,\rm mas$ $yr^{-1}$.The NE 2001 model places this pulsar at a distance of 1.9 kpc,which implies a transverse velocity of $(63\,\pm\,25)\,\rm km\,s^{-1}$,which is typical among recycled pulsars (e.g., 2011ApJ...743..102G).This proper motion allows for a correction of the observed $\dot{P}$, where wesubtract the Shklovskii effect (1970SvA....13..562S) and the Galacticacceleration of this pulsar relative to that of Solar System, projected along theline of sight (1991ApJ...366..501D) (this was calculated using the latestmodel for the rotation of the Galaxy from2014ApJ...783..130R). These terms mostly cancel each other, so thatthe intrinsic spin-down, $\dot{P}_{\rm int}\,=\,2.8\times 10^{-19}\,\rm s\,s^{-1}$, is very similar to the observed $\dot{P}$. This implies a low B-field of$\sim\,5.8\,\times\,10^{9}\,$G and a characteristic age of $\sim\,6.7\,$Gyr. The origin of this pulsar is discussed in §4.

2.2 PSRJ0627+0706

With a characteristic age of only 250 kyr PSRJ0627+0706 is two orders of magnitudeyounger than any other pulsar in this group; its spin-down power is more than 220 timeslarger than any other pulsar in this sample. This object displays a prominent interpulse,suggesting an orthogonal rotator. It also has significant timing noise, which isagain typical of young pulsars. This is the reason for the very high reduced$\chi^{2}$ of its solution.

2003PhDT.........2C remarked that this pulsar lies, in projection,within $3^{\circ}$ of the centre of the old, large Monoceros supernova remnant (SNR G205.5+0.5);which is located at $\alpha\,=\,06^{\rm h}\,39^{\rm min},\,\delta\,=\,+06^{\circ}\,30\arcmin$.For this reason they proposed that, if PSRJ0627+0706 has an age similar to thatof SNR G205.5+0.5 (30 to 100 kyr, 1986MNRAS.220..501L), it could be acandidate in association with that SNR (they point out that the positional offsetis possible given the age of the SNR and the proper motions of other pulsarsobserved in the Galaxy).

The age we and 2013MNRAS.429..579Bmeasure for PSRJ0627+0706 is larger by a factor of 2.5 to 8. However, this is notvery constraining: pulsars can be substantially younger than their characteristic ageif they are born with a spin period similar to their current spin period.

Another way of verifying the association is through distance measurements.The estimated distance to the Monoceros SNR, 1.6 kpc (1986ApJ...301..813O),is much smaller than the estimated distance to this pulsar, 4.5 kpc, whichis based on its unusually large DM relative to other pulsars in the Galactic anticentre.This, again, is not necessarily an indication that the pulsar is much more distant thanthe SNR: the large amount of ionized gas in the vicinity of this SNR could be itselfan explanation for the large DM of the pulsar.

We note that this area of the Galaxy has an abundance ofrelatively young pulsars that could potentially be associated withSNR G205.5+0.5. In particular, the “radio quiet” gamma-ray pulsar PSRJ0633+0632, discoveredin data from the Fermi satellite (2009Sci...325..840A), was listed inthe latter paper as a “plausible” association with SNR G205.5+0.5based on its location within $\sim 1.5^{\circ}$ of the SNR centre.Later 2011ApJS..194...17R measured the characteristic age of PSRJ0633+0632 (59 kyr)which is also more compatible with the estimated age of the SNR.

We conclude therefore that PSRJ0633+0632 is more likely to be associatedto SNR G205.5+0.5 than PSRJ0627+0706.

3.1 Polarimetry and Fluctuation-spectral Analysis

J0435+2749 has a clear triple profile at both frequencies as shownin FigureA1, though the L-band one is of better quality.The leading and trailing components have very different spectralindices: the trailing component is much stronger at 327 MHz, but the leadingis much stronger at L-band.The fractional linearpolarization is low in both profiles such that the polarization-angle traverse is welldefined only at the higher frequency. The power under the leading component mayrepresent a different orthogonal polarization mode (OPM) than the others, suggestinglittle position angle (PPA) rotation across the profile. Both fluctuation spectra showbroad peaks at about 0.05 cycles/period, primarily in the two outer components, whichsuggest a 20-period conal modulation.

J0517+2212 has a double component profile at L-band, whereas itsP-band profile shows some structure in the second component. The polarizationtraverse show little rotation at P band apart from the two 90°“jumps” and thebehaviour seems similar at L band but less well resolved perhaps because of thediminished fractional linear polarization. The fluctuation spectra show a peaks around 0.12cycles/period, suggesting an 8 rotation-period modulation.

J0627+0706 has a bright interpulse, a component-peak separationof 177°(main pulse minus interpulse peak longitudes) as can be seen inFig.A3. Because both features have structure, more detailed interpretationis needed to assess how close to 180°they fall; however, given the narrownessof both features, it seems likely that they represent emission from the stars two poles,implying an orthogonal geometry where $\alpha$ is close to 90°. PPA tracksgive hints about the geometry only at L band, and here little to go on apart from aprobable 90°“jump” under the main pulse. The main pulse might have threecomponents and the interpulse two. The fluctuation spectra are not displayed becausethey showed only flat “white” fluctuations.

J0927+2345 shows an interesting feature at P-band approximately180°away from the main pulse (Fig.A4). This apparent interpulse isdiscernible only in the P-band profile, and disappears in the L-band profile. Again, bothprofiles show so little linear polarization that a reliable PPA rate can be estimated foronly a narrow longitude interval at P band. The main pulse appears to have threeclosely spaced features. The fluctuation spectra are not given for this pulsar either because theyshowed no discernible features.

J0943+2253 nulls as seen in Fig.1 above, but the fluctuationspectra show no quasiperiodic behavior. The polarization is slight and the PPA trackshows what appears to be a 90°“jump” within the narrow interval where it isclearly defined.

J0947+2740 shows three components at both frequencies, though theleading region may be more complex at the lower frequency, probably representinga core and closely spaced inner cone. At L-band the conal components are weaker, andthe PPA traverse is more complex, perhaps showing a 90°“jump” in the region ofrapid PPA rotation. RVM behaviour, and the slope of it’s polarization traverse could notbe determined. This pulsar is also known to exhibit sporadic emission between intervalsof weakness or nulls as in Fig.1. The fluctuation spectra seem to hint at fluctuationpower at periods longer than about 3 or 4 pulses.

J1246+2253 has a single component at P band, which develops into aresolved triple form at L band in what may be the characteristic core-single manner.The fractional linear polarization at both frequencies is low, so little can be discernedreliably from the PPA tracks. Also no clear features are seen in the fluctuation spectraas is often the case for core-single profiles.

J1404+1159 exhibits a narrow peak in its fluctuation spectra around 0.2cycles/period, suggesting a modulation period $P_{3}$ of some 5 rotation periods. Adisplay of its individual pulses bears this out, and a display of the its emission foldedat $P_{3}$ shows that the modulation is highly regular. The PPA rate at the profilecenter suggests an outside sightline traverse as is usual for conal single “drifters”.See FigureA8.

J1756+1822 appears to have two profile components, and its profilebroadens perceptibly with wavelength, suggesting a conal double configuration. TheP-band polarization is negligible, whereas a hint of a moderately steep negative PPAtraverse is seen at L-band. The fluctuation spectra showed no features and were thusomitted.

J1935+1159’s long nulls (see Fig.1) make this pulsar difficult toobserve sensitively, and neither clear profile structure nor polarization signature is seenat either frequency. Similarly, fluctuation spectra showed nothing useful.

J2050+1259 also exhibits frequent nulls as seen above in Fig.1.However, its single profile at L band broadens and bifurcates at P band in the usualconal double manner, and a steep PPA traverse is seen at the lower frequency. Finally,here we do see strong low frequency features in the fluctuation spectra indicative ofmodulation on a scale of 50 rotation periods or longer.

J2053+1718 Our P and L band observations donot provide much polarization information or fluctuation-spectral information apartits having a single profile at both frequencies.

3.2 Quantitative Geometry

We have also attempted to classify the profiles where possible and conduct aquantitative geometrical analysis following the procedures of the core/double-conemodel in Rankin (1993a,b; hereafter ETVI). Outside half-power (3-db) widths aremeasured for both conal components or pairs—and where possible estimated forcores. Core widths can be used to estimate $\alpha$, PPA-traverse central rates$R=\sin\alpha/\sin\beta$ can be used to compute $\beta$, and the conal widths can be used to computeconal beam radii using eqs. (1) through (6) of the above paper.

The notes to Table5 summarize our measurements, and the table values show theresults of the geometrical model for the pulsar’s emission beams. The profiles classis given in the first column, $\alpha$ and $\beta$ in next two per the $R$ value whenpossible. The conal component profile widths $w$, conal beam radii $\rho$, andcharacteristic emission heights $h$ are tabulated in the rightmost three columns.

J0435+2749’s average profile has a triple component configurationat both frequencies, and the observed conal spreading suggests a core/outer conegeometry. The core width can only be estimated at the higher frequency at perhaps9°maximum, implying that $\alpha$ is less that some 1.4°per ETVI, eq.(1).

The PPA traverse shows a much more complex behavior than the Rotation VectorModel (RVM) describes; however, the roughly 90°rotation near the center ofthe pulse may be so interpreted. The spherical geometric beam model in Table5seems compatible with a core-cone triple T classification.

J0517+2212’s profile shows two primary components. There is morestructure at L-band, as well as overall pulse narrowing. These factors, along with thelack of PPA traverse suggest that $\beta\sim 0$ and imply the outer conal beamgeometry shown in Table5.

J0627+0706’s main-pulse profile may have two or three closely spacedcomponents. The pulse width at half maximum interestingly widens from P-bandto L-band suggesting a core-single configuration where the conal emission is seenmainly at high frequency. The polarization traverse is clearer at L-band, marked byprominent 90°modal “jumps”. It thus seems likely that $\beta$ is small for themain pulse and perhaps larger for the inter pulse, but that $\alpha$ is close to 90°,yielding the classifications and model values in Table5. The emission heights given forboth the main pulse and interpulse suggest that it is inner conal emission.

J0927+2345’s average profile has two clear components and possiblyan unresolved trailing one as well. Its half width interestingly broadens from P-bandto L-band suggesting a core single evolution where conal “outriders” appear or becomemore prominent at high frequency. The polarization traverse is well defined only fora short interval at L band, which provides a useful $R$ value that leads to thegeometric beam model in Table5. If this profile were triple, the central component wouldbe $2.8\degr$ wide.

J0943+2253’s average profile also has two closely spaced componentsand perhaps and unresolved weak feature on its leading edge, suggesting a doubleor triple configuration. We only have a P-band observation so cannot see how theprofile evolves, and the linear polarization is slight and difficult to interpret. However,we can guess a central PPA rate of 7°/°in order to compute the geometricmodel parameters in Table5, which suggest an inner-conal configuration.

J0947+2740’s profile is comprised by three main components, and the fact that itswidth increases with wavelength indicates an outer-conal configuration. Its PPA traverseseems interpretable per the RVM model at P band, but its L-band traverse seems to bedistorted by what may be a 90°“jump” just prior to the profile center. Its profilethen seems to be a core/outer cone triple, and the quantitative beam geometry modelis shown in Table5. The core width is estimated around $2.65\degr$, which is muchmore narrow than the central component of the profile ($7.92\degr$ at P-band and $10.08\degr$ at L-band), which indicates that thecentral component contains both core and conal emission.

J1246+2253’s single profile at P band becoming triple at L band stronglysuggests a core single configuration. Despite the low fractional linear polarization, thetrailing positive traverse through roughly 90°was used to computer the geometricalmodel in Table5. The core width is estimated at $3.55\degr$.

J1404+1159 has a single component profile at both frequencies, and its narrowfluctuation feature identifies it as having regular drifting subpulses as shown in Fig.A8.The pulsar then appears to have a classic conal single profile. Both PPA tracks show anegative-going traverse with a central slope of about –12°/°. Here we also giveshort pulse-sequences folded at the modulation period of some 0.2 rotation-periods/cycle.

J1756+1822 has an interestingly shaped profile that appears to have twoseparate components. The P and L-band profiles have similar forms with the longerwavelength one somewhat broader in the usual pattern of the conal double class.The fractional linear profiles is low at both frequencies, but at L-band there seems to bea hint of a traverse through more than 90°across the profile. The fluctuation spectraare not shown as no features could be discerned.

J1935+1159 Appears to be a five component pulsar; even though only twoindividual components can be resolved, it appears to be filled which could hide additional components.According to the emission heights, and the profile narrowing from P-band to L-band, indicate that thisis an outer cone which is filled with inner conal and/or core emission. For the geometric computations,we have estimated a central traverse of $10\degr/\degr$.

J2050+1259’s profile has a single component at Lband and two closelyspaced components at P band as seen in Figs.1 and A11. Its profile isbroader at the lower frequency, and strong hints of a roughly 180°PPA traverse areseen in both profiles, suggesting that this is a conal single profile with a small impactangle with the beaming parameters as given in Table5.

J2053+1718 show a single component at both frequencies, though in thehigher frequency observation the time resolution was poor with only 232 samples acrossthe rotation cycle. The polarization information and fluctuation spectra do not give muchto go on either. Curiously, this pulsar has a wider profile in L-band than in P-band, howevermuch of this can probably be attributed to the quality of the observation. Its short 119-ms rotation periodand single profile do suggest acore-single classification.