[Lofarpwg] [DKIM: Failed] Re: LOTAAS binary pulsar + 20 timing paper

Tue Aug 20 12:21:51 UTC 2019

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

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> 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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