Does the GRB Duration Depend on Redshift?
Round 1
Reviewer 1 Report
Report on Horvath et al "Does the GRB duration depend on redshift?"
Below are some suggestions for the authors.
line 3: In this paper we "analyse"
line 32: "duration (T90)" perhaps "(in T90)". Please define T90.
Fig 4: should be: T90>5 s
line 70 and Fig. 5: In this paragraph the authors mention short GRBs. From figure 5 it looks like they already disregarded short GRBs in this sample and they already discussed that sGRBs have a different redshift distribution. I suggest a log color scale, because it's unclear if the red part is 1e-5 or 1e-1. Also the AREA1 region is hard to find. I suggest marking these areas on the figure.
section "summary & conclusions":
The authors should discuss what their results imply, even if not found with a high significance. E.g. At least speculate on some possible reasons why GRBs with 9 s<T90<21 s are farther than the GRBs with T90 not in this range?
line 107: The authors mention non-independent KS tests, and they indeed perform many tests that do not seem independent. They should address this quantitatively: by how much does the p-value increase when considering independent tests only? (e.g. estimate the number of effective tests). What is the role (if any) of the look-elsewhere effect (trials factor)?
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The authors have analyzed several hundreds GRBs both with the detected redshifts and well-defined durations. They found that the short GRBs (T90 < 5s in this article) could be in a aera deviating from the non-short GRBs. For the non-short GRBs, they found three distinct areas according dataset of the T90-vs-redshift using Kolmogorov-Smirnov test. The paper can be accepted after the minor revision.
1> Figure 3. Please present "interval starting point (k)" in detail, which is different from the "n", as well as in the main text.
2> Figure 4. ... non-short GRBs (T90 < 5s)... ==> non-short GRBs (T90 > 5s)
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
This paper aims to find any dependence between observed GRB duration and redshift in a certain area. It is well known that the redshift distribution of short GRBs is different from that of long GRBs. By sampling T_90 and redshift and performing the KS test, the authors search for other suspicious areas that show the deviation in distributions between the sub-sample and the rest. I have several major comments on this work.
Major comments
- In the introduction, the scientific motivation for this project is not well described. Why do we want to find out any dependence between the duration and redshift of GRBs?
- This paper does not review any redshift-related studies. It focuses on the angular distribution of GRBs, which is not directly relevant to this paper.
- This paper uses the observed GRB duration. However, if we want to find any dependence between the GRB duration and redshift, it would be more appropriate to use the intrinsic duration, especially in the second study (section 2.3).
- As we know, there are two methods for estimating the redshift: photometric and spectroscopic. Sometimes, the two values from the same object are quite different from one another. Do you use the redshifts from the same method? If not, do you consider any systematic effect from this?
- Related to the previous one, when you adopt the duration of GRBs, the T90 of GRBs are measured from the same energy band? e.g., in the case of BAT, they used to estimate T90 of a burst in 15-350 keV, whereas the GBM team compute T90 in 50-300 keV. I expect there is a systematic effect from this as well.
- This paper does not contain any discussion on their results. They found several suspicious regions, but the possible scientific region for this is not discussed. Does it related to cosmology? Why do we see such deviation in GRBs occurring in several epochs of the Universe?
Minor comments
- The definition of T90 is not in the paper.
- Could you make the z-axis of Figure 5 and Figure 8 be in logarithm?
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
