The Apparent Tidal Decay of WASP-4 b Can Be Explained by the Rømer Effect

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

(1) Authors present a study on the light-time effect for transit timing variations of WASP-4b. It is a well written paper. However, the current title of the paper is misleading.

As the authors state, there is no conclusive answer.

Authors can consider a different title. One  example is:  

Studying transit timing variations with the light-time effect of exoplanet WASP-4b

     (2) The machine-readable form (ascii files) of tables in Appendix B (Table A1, A2 ? or shall be Table B1, B2 ?) can be made available to readers. It will be great if the journal can provide links to  these files at appropriate places of the paper.

Comments on the Quality of English Language

(1) Page 4, Line 143,   "and parameters"

shall be "any parameters" ?

(2) Page 8, Line 187,  "This results" shall be 

"This result" ?  It seems there is no verb in this sentence.

 

Authors shall go through the whole paper to check if there are other minor mistakes.  

Author Response

Dear reviewer,

we want to thank you for your helpful comments, that improve the clarity of our manuscript.

Comments/suggestions: - (1) The title in its current form does not rule out that other explanations are possible. We would prefer to keep it as is, with some changes in the abstract and conclusions sections to make this clearer and more cohesive. If there is still an issue, we will consider adjusting the title.   - (2) I will provide the files to the journal or upload them on their recommended site.   Comments on the Quality of the English Language: - (1) To clarify the sentence, I changed it to: "The priors for, and results from the combined ...".   - (2) The sentence is correct as is, with "results" being the verb.   Thank you again!   Best regards, Jan-Vincent Harre

 

Reviewer 2 Report

Comments and Suggestions for Authors

Rereferee's report

Universe ID: universe-2731231

Title: The apparent tidal decay of WASP-4 b can be explained by the Rømer effect
Authors:Jan-Vincent Harre , Alexis M. S. Smith

The context of this manuscript is the study of tidal orbital decay experienced by hot Jupiters orbiting very close their host star. This phenomenon has been detected and confirmed only on few candidates (probably just one), but the reasons are still under discussion among the experts.

I think that the article is very interesting and it deserves the publication, since I believe that the stellar physics and exoplanets communities will find in it a lot of food for thought.
The authors clearly argue on the possible scenarios foreseen by applying different models.

Nevertheless, I have a couple of  concerns, not in the procedure of the analysis, but in the way the results are presented. On this purpose, I would suggest the authors to consider the minor general points addressed below in order to
improve the manuscript:

1)Title, abstract and conclusion: I think that title, abstract and conclusions
need to be uniformly formulated.
I find quite confusing the fact that the title refers to the Romer effect as a possible explanation for the tidal decay while the conclusions, citing the text itself, 'leave us with no conclusive answer about the origin of the TTV....but probably a mix of all the effects including the tidal decay...'
Hence I suggest to find a different title and abstract in agreement with the conclusions. It is evident that the Romer effect is just one of the reasons examined in order to explain the peculiar TTV.

2)In the Introduction: The authors should explain the difference in the measurements  obtained by different authors for the tidal orbital decay. Are the differences rising by different observations, different models or what else?

3) Fig. 1: Please enhance symbols which appear barely visible.

4) Fiig. 2: give more deatils of the light curve in the caption and in the text

5) Section 4: Are all the results for the orbital decay obtained by using different models in agreement with each other and with previous results? Can you comment on the results shown in Fig. 3 and 4

6) The Bottom panels of Fig. 3 and 4 (and also A1 and A2) need the use of different colors. It is impossible to distinguish the two kind of reds.
Is there a possibility to put plots of Fig. 3 and 4 in the same Figure in order to make a comparison?

7) It is not clear to me the reasons for Appendix A being without text. This should be probably considered by the Editors. Appendix B, will probably include the data, but this is not clear.

Author Response

Dear reviewer,

we want to thank you for your helpful comments, which clarify the manuscript and make the figures easier to understand.

Comments/suggestions: - (1) As a result of comments from both referees, we have adjusted the abstract and conclusions to clarify the main result of the paper. We think that the existing title accurately reflects the conclusions, so would prefer to keep it.   - (2) The differences are arising mostly by the use of different data sets. The more recent, the more data points were used in general. This is now clarified in the introduction. There was also a typo here for the lower number. Thanks for pointing this out!   - (3) Symbols were enhanced in the figure.   - (4) More information was added to the text and caption.   - (5) Our first model uses the same modelling as the previous studies and the result is in agreement with them. Our second, third and fourth models contain different corrections for the light-time effect (LTE) due to the uncertainty in the ephemeris of planet c. The results in Fig. 3 and 4 differ by the LTE correction having been applied to the data/model in Fig. 4. This is especially noticeable by comparing the lower panels of the figures. Clarifications were added in the captions.   - (6) Instead of different colors, we now use a dashed line for the apsidal precession model. This should clarify the situation. We think that it is beneficial to keep the figures separated from each other to avoid any confusion between the two cases that have been examined (no LTE correction and the nominal LTE correction).   - (7) Added a description of the figures and tables in appendix A and B.   Thank you again for your comments and suggestions!   Best regards, Jan-Vincent Harre