[Lofarpwg] [DKIM: Failed] Re: LOTAAS binary pulsar + 20 timing paper
Vlad Kondratiev
kondratiev at astron.nl
Fri Aug 30 12:27:29 UTC 2019
Hi Chia Min,
Sorry for the large delay with the comments, please find them attached,
they are mostly minor.
It'd be probably worth another reading once you incorporate all the
comments.
cheers,
Vlad
On Mon, 26 Aug 2019 at 16:24, Daniele <danielemichilli at gmail.com> wrote:
> Hi Chia Min,
>
> I am sorry for the huge delay in my comments. I enjoyed reading the paper,
> I think it is very clear and thoughtful.
> My main comments (more questions actually) are the following.
>
> - I am sure this came out before but I am not aware (it is difficult for
> me to attend the PWG telecons because of the time zone, I am sorry about
> that). Have you considered presenting the binary pulsar into a separate
> paper? With respect to the rest of the sample, the observations are
> different, the analysis overlaps only very partially, conclusions and
> discussions are mostly separated. Therefore, I think it could make much
> sense to have a separate paper specifically about the binary, where you
> might also include information not presented here (e.g. "the study of the
> scintillation properties of the pulsar will be presented in a separate
> paper").
>
> - Regarding J0421, you attribute the strong timing noise to mode
> switching. However, even after excluding the two points with the largest
> offset in Fig.1, the noise is still very high. To me, it looks that both
> the different profiles and the timing noise could be due to a wrong timing
> solution. Have you considered this possibility? I mention it because a
> couple of pulsars in my sample showed a similar behavior that disappeared
> later on when I added more observations. What is the chance of the timing
> solution to be degenerate giving the small number of TOAs?
>
> - The characteristics of the profile of PSR J1658 (Fig. 10) and its
> relatively strong DM variation (Fig. 9) suggest this pulsar as a good
> candidate for a detection of profile variation with time. I suggest you to
> carefully compare pulse profiles at different epochs to check if the weak
> postcursor or any other feature varies with intensity with respect to the
> main peak. In order to do so quickly and accurately, you could normalize
> the main peak of the integrated profile of each LOFAR observation and
> subtracting one of the profiles from the rest. I can do that myself if you
> prefer.
> In any case, have you checked with Joris about the DM variation? Since the
> pulsar DM is so low, the fractional variation could be pretty large,
> suggesting a very turbulent medium. By looking at other studies of ISM
> turbulence in the local bubble (such as
> http://adsabs.harvard.edu/abs/2010AAS...21541509Sm
> <http://mailsweeper.astron.nl:32224/?dmVyPTEuMDAxJiZmYjZlZjgyOGQ5NWE5NGYyMD01RDYzRUJCQ181ODczXzM5MzRfMSYmYmMxZTU5NjMzNThmOTVjPTEyMjMmJnVybD1odHRwJTNBJTJGJTJGYWRzYWJzJTJFaGFydmFyZCUyRWVkdSUyRmFicyUyRjIwMTBBQVMlMkUlMkUlMkUyMTU0MTUwOVNt>),
> this looks a very promising candidate, especially considering that it is a
> binary. I wonder whether we should try some analysis ourselves before
> publishing the DM variation.
>
>
> The rest of my comments are very minor.
>
> - Sec. 2, "An archive file is produced from each observation". This could
> be a good place to first cite PSRCHIVE
> - Sec. 2, "To model the binary orbit [...] These data were recorded and
> processed using the same method as the monthly timing observations." It is
> difficult for me to follow the numerous observations performed of this
> pulsar, I suggest including a second summary table specifically for this
> source.
> - Sec. 3, "However, PSRs J0210+5845 and J0421+3255 showed large timing
> residuals". I do not see J0210+5845 showing large residuals.
> - Fig. 2, What is the purpose of indicating the binary pulsar with a
> different style?
> - Fig. 4, How are the profiles normalized with respect to one another?
> - Fig. 4, "The phase of the pulses in the observations where the offset
> occurred coincides with the leading peak of the integrated pulse profile."
> I do not understand this sentence.
> - Sec. 5, "We estimated the average RFI fraction of each observation at
> 1532 MHz to be 20 per cent of the bandwidth and 5 per cent of the observing
> length, while at 334 MHz, the fraction is 20 per cent of the bandwidth and
> 20 per cent of the observing length." Are these the final values you are
> going to use? I need to check that we are using consistent numbers.
> - Sec. 5, "The measured spectral indices of the pulsars are also shown in
> Table 6." You already mentioned Table 6 at the beginning of the paragraph.
> - Sec. 5, I think that showing the plots of flux as a function of
> frequency could be worth for each pulsar.
> - Fig. 5, I see that you are considering the error on the slope of the
> line but not on the intercept. I did the same at the beginning but then I
> decided to also consider the intercept error. What do you think about this?
> - Fig. 6, I don't see some of the figures to be referenced in the text,
> such as 3, 6 and 7 (I am sorry if I am missing them). Specifically about
> Fig. 6, I am unsure it is necessary to show every observation, one or two
> examples may suffice.
> - Tab. 7, I would specify that these are LOFAR observations.
> - Sec 6.2, this could easily be a separate section.
> - Sec 6.2, "Later, we found that the position [...] observation taken in
> 2014." The way this is phrased may seem to suggest that the initial
> position was wrong. I suggest removing "later" and explicitly stating that
> we measured a proper motion from the different positions of the source
> measured at an interval of 14 years.
> - Sec 6.2, "The diffractive scintillation and possibly refractive
> scintillation will result in variation in the flux densities." What is the
> expected band of the scintles for this pulsar?
>
> On Tue, 20 Aug 2019 at 08:22, Michael Kramer <mkramer at mpifr-bonn.mpg.de>
> wrote:
>
>> Dear Chia Min,
>>
>> I read the paper and have some comments which are hopefully useful.
>> Please, let me know if
>> my handwriting is difficult.
>>
>> Please, note my comments about the reference to spectra paper - which is
>> also relevant for
>> the census papers (I’ll read those shortly). The problem with the cited
>> Bates et al. and
>> Jankowski et al references is, that the spectra in both papers were
>> derived for a relatively
>> small frequency range, which is well above the the LOFAR frequencies.
>> When you make
>> comparisons it is probably more appropriate to refer to samples which are
>> drawn from
>> data covering the whole frequency range. Here the best reference is
>> probably still Maron et al.
>>
>> Anyway, I hope the comments are useful.
>>
>> Cheers, Michael
>>
>>
>>
>> > On 6 Aug 2019, at 15:17, Cees Bassa <cbassa at gmail.com> wrote:
>> >
>> > Hi Chia Min,
>> >
>> > Thanks for sending the draft around. There's some nice work in the
>> paper.
>> >
>> > Below are comments up to section 4. I'll try to get my comments on the
>> > rest of the paper by the end of the week.
>> >
>> > Regards,
>> > Cees
>> >
>> > Title:
>> >
>> > * The title is perhaps a bit long. Since the title of Daniele's paper
>> > was: "LOTAAS: Characterization of 20 pulsars", you could use
>> > "LOTAAS: Timing of 21 pulsars", though I agree that having the
>> > binary MSP in the title is a plus.
>> >
>> > SECTION 1:
>> >
>> > * I think the introduction needs a bit more work. Right now, the
>> > information motivating this paper (pulsar properties from timing,
>> > spectral indices from multi-frequency follow-up, pulse profile
>> > evolution) is available, but it is not in a logical order. My
>> > suggestion would be that you start with a general overview of pulsar
>> > science, which has sofar been predominantly done at higher
>> > frequencies and the importance of observing at lower
>> > frequencies. You can then provide some information of low-frequency
>> > studies of known pulsars (Pilia profiles, LOFAR Census, MSP Census,
>> > Sobey RM study). This naturally leads into LOTAAS as the first real
>> > low frequency pulsar search, and that this paper presents some of
>> > the first timing and multi-frequency results of pulsars discovered
>> > at these low frequencies.
>> >
>> > SECTION 2:
>> >
>> > * In the first paragraph it would be good to compare the setup of the
>> > timing observations to that of the search observations in terms of
>> > number of stations, bandwidth and integration time.
>> >
>> > * Mention psrchive (with Hotan ref) after dspsr.
>> >
>> > * Did you not use any ROACH data from Jodrell? Certainly for the
>> > 334MHz observations the coherent dedispersion will be important.
>> >
>> > * I would also restructure section 2 somewhat, as right now the
>> > information is spread about. Perhaps a subsection for timing
>> > observations, timing of the binary, and follow up observations for
>> > profile evolution and spectral properties. Another approach would be
>> > to split it in LOFAR core, Jodrell and GLOW observations.
>> >
>> > * The paragraphs about J1658 are also confusing, and I think all this
>> > information can be distilled into a table. You also need to clarify
>> > the timing procedure a bit, in that we start off with binary
>> > parameters determined from variations in the spin period (an
>> > incoherent timing solution), to a coherent timing solution where you
>> > account for all rotations of the pulsar. You might also clarify the
>> > 'accounting for all rotations' at the start of section 2 when
>> > discussing the timing of normal pulsars.
>> >
>> > * Table 1: miutes -> minutes
>> >
>> > * Table 1: Somewhere in the paper we need to provide the JXXXX+YY
>> > names from the LOTAAS overview paper to these timing names. This
>> > naturally fits in table 1.
>> >
>> > SECTION 3:
>> >
>> > * For determining the template, you need to specify to which profile
>> > you fitted the von Mises profiles. Was it the single observation
>> > with the highest S/N or some average of profiles?
>> >
>> > * Add how many von Mises functions you had to use (just give the
>> > minimum and maximum).
>> >
>> > * "are split into 2 frequency channels" -> "are averaged into two
>> > frequency channels".
>> >
>> > * I'm a bit worried by only using two frequency channels to measure
>> > DM, as you are using two measurements to obtain two parameters (TOA
>> > and DM).
>> >
>> > * How were the templates at different frequencies referenced to
>> > absolute phase? If scattering or intrinsic profile evolution is
>> > present then you could impart a DM offset by this approach.
>> >
>> > * You need to clarify what is meant by a jump. That is not
>> > nomenclature that non-pulsar astronomers know. Also change "Any
>> > offsets" to "Any time offsets", and perhaps specify what causes
>> > these (cable length differences etc).
>> >
>> > * In paragraph 2 "In order to...", you may want to make it clear that
>> > the dense campaigns were meant to remove ambiguities in the number
>> > of pulse rotations between consecutive observations, and that
>> > getting phase connection on short timescales allowed extrapolating
>> > the timing solution to longer timescales without introducting
>> > ambiguities.
>> >
>> > * I mentioned this for section 2 as well, but for the timing solution
>> > of J1658; explain that you got initial orbital parameters by
>> > modelling the spin period variations, and used those to obtain a
>> > phase coherent timing solution.
>> >
>> > * I am not sure a reference exists for FITORBIT, in which case you may
>> > have to explain in a bit more detail what the software does.
>> >
>> > * "... is a low S/N pulsar" is an incorrect statement. low S/N is a
>> > property of the telescope, not really the pulsar. Maybe rewrite to
>> > "In the initial timing observations of PSR J1643+1338 it was
>> > detected at low S/N."
>> >
>> > * Section 3 is mixing observations and their analysis with
>> > results. This may be a large change, but I think the first 4
>> > paragraphs could be joined with section 2 to make a "Observations
>> > and timing analysis" section. This resolves some of the duplicity of
>> > the statements between section 2 and 3. The rest of section 3 could
>> > be called "Timing properties".
>> >
>> > Sections 4 and 5 also mix analysis and results. I think it would be
>> > more logical to include the first paragraph of section 4 in section
>> > 2, and similarly the first few paragraphs of section 5 also fit
>> > better in section 2.
>> > _______________________________________________
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>>
>>
>> ----------------------------------------------------------------------------------------------------------
>> Prof. Dr. Michael Kramer
>> Director - Max-Planck-Institut für Radioastronomie, Bonn, Germany
>> Professor for Astrophysics - University of Manchester, UK
>> Professor (Hon-Prof.) - University of Bonn, Germany
>>
>> Address: MPI fuer Radioastronomie
>> Auf dem Huegel 69
>> 53121 Bonn, Germany
>>
>> Phone: +49-228-525-278 (direct)
>> +49-228-525-299 (secretary)
>>
>> EMAIL: mkramer at mpifr-bonn.mpg.de / michael.kramer at manchester.ac.uk
>>
>> ----------------------------------------------------------------------------------------------------------
>>
>>
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--
Vlad Kondratiev
ASTRON Junior Scientist
P.O. Box 2, 7990 AA Dwingeloo
The Netherlands
tel: +31 (0) 521-595-767
fax: +31 (0) 521-595-101
kondratiev at astron.nl
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* Title
how about changing it to:
"The LOFAR Tied-Array All-Sky Survey: timing of the 21 pulsars including first LOFAR binary PSR J1658+3630"
* Intro
- This meant -> This means
- for new pulsar discoveries -> for new pulsars
- is required to model them -> are required to model them
- distribution found suggests -> distribution suggests
- at lower frequencies are higher, with -> at lower frequencies is higher, with
- Michilli et al 2019 -> Michilli et al. 2019
- longer spin period -> longer spin periods
- smaller spin period derivative -> smaller spin period derivatives
- is older than -> are older than
* Section 2
- The data are recorded in dual-polarization, complex frequency channels
->
The complex-voltage data are recorded in dual-polarization frequency channels
- You have 3 similar sentences where you refer to Table 1 that lists observation lengths
of the timing observations. Leave only one of them.
- "The interim timing solution of PSR J1658+3630 showed
that the binary companion has a large minimum mass of
0.87M_sun"
It is a result, and I would move it from this section. All observations and campaingns
for J1658 I would put into the separate subp-section, so the Section 2 is not overwhlemed
with many details. Maybe it'd be also worth to put this in a Table?..
- The data were recorded as complex frequency channels -> The complex-voltage data were recorded
* Section 4
- PSRs, J0454+4529, J1017+3011, J1638+4005 and J1745+1252, shows
->
PSRs J0454+4529, J1017+3011, J1638+4005, and J1745+1252 show
- The detections at 334 MHz for PSRs, J0454+4529 -> The detections at 334 MHz for PSRs J0454+4529
- The profiles of PSRs J0210+5845 and J1745+1252 shows signs -> The profiles of PSRs J0210+5845 and J1745+1252 show signs
- The other 5 pulsars, PSRs J0107+1322, J1643+1338, J1749+5952, J1810+0705 and J1916+3224 are detected with
->
The other 5 pulsars~-- J0107+1322, J1643+1338, J1749+5952, J1810+0705, and J1916+3224~-- are detected with
* Figure 4, caption
- expect -> except
* Table 5, 3rd column, last value
- 10.9(12) -> 10.90(12)
* Section 5
- The Gain G of the receiver -> The gain, G, of the receiver
* Table 6, caption
- Flux densities measurements of each pulsar -> Flux density measurements of each pulsar
* Table 6
- several measurements in the Table have only 1 digit after the comma, but two digits for the uncertainty.
Be careful with this, as for example what does this mean "2.8(10)"? Does it mean, that within 1sigma, the value
changes between 2.7 and 2.9, or between 1.8 and 3.8?? If former, than you should use "2.80(10)" instead.
* Section 6.1
- densityat -> density at
* Section 6.2
- The low eccntricity -> The low eccentricity
- is possibly -> is possible
- and the nearness -> and pulsar proximity
* Table 8
- In the Derived part of the table also add the measurement of the spectral index that you give in the
text at the end of Sect. 6.2.
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