Searching for New Objects with the B[e] Phenomenon
, Nazgul Sh. Alimgazinova 1,*, Anatoly S. Miroshnichenko 2,3, Corinne Rossi 4, Inna V. Reva 3, Raushan I. Kokumbayeva 3, Chingis T. Omarov 3, Sergei V. Zharikov 5, Nadine Manset 6, Ashish Raj 7,8, Arti Joshi 9, Richard J. Rudy 10, Richard C. Puetter 11, Raleigh B. Perry 12 and Kunduz M. Turekhanova 1
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThis manuscript presents a good study with some new findings. However, there are several issues that need further clarification and improvement:
1. LINE 73: The quantitative criteria were as follows: V − K ≥ 2 mag, J − H ≥ 0.7 73 mag, and H − K ≥ 0.7 mag to select objects with IR excesses stronger than those typically 74 introduced by the interstellar reddening and free-free emission.
The paper mentions specific criteria for selecting objects with strong IR excess. Based on these criteria, a large number of targets should theoretically be identified. However, the study only focuses on 6 objects. Please clarify why only these 6 targets were selected?
2. LINE 78: These described criteria allow for selection of other kinds of object, such as binary 78 systems with components of very different temperatures and no real IR excess radiation 79 or extremely reddened hot stars and only gaseous CS environments.
The paper mentions that the selection criteria may include other kinds of objects. Please address the following: Were such objects indeed discovered during the selection process? If so, how many were identified, and were they analyzed further?
3. Section-2 Observations
The description of the observations is overly brief. For exclusive observational data, more detailed information should be provided.
The study has a clear direction, but it requires more detailed explanations regarding target selection and the observations. If additional scientific analysis of the results could be included, it would further enhance the manuscript.
Author Response
We thank the reviewer for a detailed analysis of our original manuscript and pointing out a need of explaining the methodology better. We have taken into account most of the comments and responded with our explanations to others.
This manuscript presents a good study with some new findings. However, there are several issues that need further clarification and improvement:
- LINE 73: The quantitative criteria were as follows: V − K ≥ 2 mag, J − H ≥ 0.7 mag, and H − K ≥ 0.7 mag to select objects with IR excesses stronger than those typically introduced by the interstellar reddening and free-free emission.
The paper mentions specific criteria for selecting objects with strong IR excess. Based on these criteria, a large number of targets should theoretically be identified. However, the study only focuses on 6 objects. Please clarify why only these 6 targets were selected?
Answer: We have selected and observed a few dozen more objects. All of them are being studied. We reported only those study was finished by the time of the conference “Hot Stars. Life with Circumstellar Matter.” (October 2024, Almaty, Kazakhstan). As we mentioned in the original version of the paper, studies of other objects will be reported later.
- LINE 78: These described criteria allow for selection of other kinds of object, such as binary systems with components of very different temperatures and no real IR excess radiation or extremely reddened hot stars and only gaseous CS environments.
The paper mentions that the selection criteria may include other kinds of objects. Please address the following: Were such objects indeed discovered during the selection process? If so, how many were identified, and were they analyzed further?
Answer: Yes, they were indeed discovered. One of them is AS 415 reported in the paper. We have not finished the analysis of all the selected objects but mentioned possible kinds of these other objects in line 78 of the original version. We added some information about the entire sample.
- Section-2 Observations
The description of the observations is overly brief. For exclusive observational data, more detailed information should be provided.
Answer: We added additional information about our observations.
The study has a clear direction, but it requires more detailed explanations regarding target selection and the observations. If additional scientific analysis of the results could be included, it would further enhance the manuscript.
Answer: We have analyzed the available data, which are limited mostly due to the objects’ faintness. Suggestions about their nature and evolutionary status were presented. Now it is up to other researchers to investigate these objects further.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsI have included my comments in the attached file.
Comments for author File: Comments.pdf
Author Response
We thank the reviewer for a detailed analysis of our original manuscript and pointing out a need of explaining the methodology better. We have taken into account most of the comments and responded with our explanations to others.
The authors present a study of already known emission-type B stars. The aim is to prove that those objects are B[e] and/or FS CMa stars. The analysis is quite thorough, but some points must be clarified before the paper can be published.
If I look into the referenced paper by Miroshnichenko (2007), two stars are less luminous than the log L/L(Sun) limit of 2.5.
Answer: The introductory paper for the FS CMa group was limited to previously studied objects with the B[e] phenomenon. Distances to a significant fraction of them were unknown at that time. Therefore, the luminosity limits were very preliminary. They should be improved with the currently available Gaia distances and an increased statistics of the group members.
It is also unclear which stars are part of stellar associations and why this fact is not counted as part of star-forming regions (Herbig Ae/Be stars).
Answer: The main observational difference between FS CMa group objects and Herbig Ae/Be stars is the slope of the IR spectral energy distribution. Our objects (except for AS 415) show a declining IR flux longward of ~10 microns that rules out the presence of large amounts of distant and cold dust in their circumstellar environments. Instead, younger Herbig Ae/Be stars exhibit a small or no decline of the IR flux in this wavelength region, while older ones (near the end of this evolutionary stage) show a weak or no near-IR excess compared to a far-IR one, an opposite situation compared to more evolved FS CMa objects.
Are the two luminous objects not supergiants?
Answer: We explained that AS 415 may or may not have such a large luminosity depending on the contribution of the putative secondary component. Also, a definition of a supergiant may have different meanings when applied to single stars and mass-transferring binaries. Some B[e] objects were classified as supergiants (e.g., 3 Pup studied by Miroshnichenko et al. 2020, ApJ, 897, id.48), but the revealed binarity suggest that the currently high-luminosity component started its evolution as a relatively low-mass (3 Msun) star. We anticipate that the definition of B[e] supergiant group and its relation to the FS CMa group will be reconsidered soon on the basis of a larger statistics, part of which is presented in this paper. The second high-luminosity object in our sample, IRAS 20402+4638, has most of the properties of FS CMa objects and is definitely not a conventional supergiant.
For how many stars was binarity detected? A table giving this information would help the reader very much.
Answer: Due to the limited data, we can only suspect binarity in one object, AS 415. We are not sure this information in a Table would help the reader. We keep it in the analysis subsections whenever we can comment on that.
What do you mean by the sentence “Such a small variability makes us confident in the existence of an IR excess (see Fig. 1).” on page 5?
Answer: A small variability at optical wavelengths suggests that the optical spectral energy distribution (SED) with respect to its infrared part is reliable. Therefore we can combine data taken at different times at different wavelengths for composing a SED.
You also state that “some pulsation-like activity with an amplitude of ≤ 0.1 mag” was found. Is this a common thing among FS CMa stars? If so, what kind of pulsation can this be for these spectral types?
Answer: This subject has not been investigated for FS CMa objects. Pulsations in the TESS data have been found in one object, CI Cam, whose classification is still uncertain (a B[e] supergiant or an FS CMa object). We cannot add anything here.
The SEDs presented in Figure 1 do not seem to include any observations in the Ultraviolet, which is most important for obtaining temperatures in the spectral region. Please comment on that.
Answer: All the objects discussed in our paper are relatively optically faint. As a result, no UV data are available for them. This explanation is added to the new text.
Table 2: List the distances in a more convenient format. Include coordinates (either equatorial or Galactic ones).
Answer: The format for distance is one of commonly used to show parameters with their uncertainties. The galactic coordinates were added.
Figure 4: Include the birth line so that the reader can judge if these stars might be Herbig Ae/Be stars.
Answer: A birth line was added to Figure 4, which became Fig.5 in the new version.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe reviewed paper is devoted to the search and study of new B[e]-objects and is the next paper in the cycle of similar publications of this team of authors.
The paper discusses six new B[e]-objects.
In particular, the authors draw attention to the importance of photometry, which is a much less expensive method for finding and studying B[e]-objects than spectroscopy.
The authors are recognised experts in this field.
The paper is certainly worthy of publication in the Galaxies journal.
I have a few minor comments.
In the caption to Fig.1, the authors state that "SEDs were corrected for total extinction".
It would be nice to clarify in the text: how exactly was this correction carried out?
The authors write "Gaia" and "GAIA" mixed up.
I recommend using the former version. "Gaia" is not an abbreviation.
In the caption to Fig.2 the authors mention blue symbols and red symbols, but in the figure I see only black symbols.
Author Response
We thank the reviewer for a detailed analysis of our original manuscript and suggestions for its improvements. We have taken into account all the comments. As a result, a new Figure and a new Section were added, and the methodology of searching for new objects and analysis of the collected data are explained in more detail.
The reviewed paper is devoted to the search and study of new B[e]-objects and is the next paper in the cycle of similar publications of this team of authors. The paper discusses six new B[e]-objects.
In particular, the authors draw attention to the importance of photometry, which is a much less expensive method for finding and studying B[e]-objects than spectroscopy.
The authors are recognised experts in this field.
The paper is certainly worthy of publication in the Galaxies journal.
I have a few minor comments.
In the caption to Fig.1, the authors state that "SEDs were corrected for total extinction".
It would be nice to clarify in the text: how exactly was this correction carried out?
Answer: A more detailed description of the dereddening procedure is added.
The authors write "Gaia" and "GAIA" mixed up.
I recommend using the former version. "Gaia" is not an abbreviation.
Answer: Corrected.
In the caption to Fig.2 the authors mention blue symbols and red symbols, but in the figure I see only black symbols.
Answer: We have corrected the colors on this Figure, which became Fig. 3 in the updated version.
Author Response File: Author Response.pdf
Reviewer 4 Report
Comments and Suggestions for Authors
Searching for New Objects with the B[e] Phenomenon
by Aisha Zh. Naurzbayeva et al.
B-type stars exhibiting the B[e] phenomenon are characterized by the presence of both permitted and forbidden emission lines, as well as a strong infrared (IR) excess caused by hot circumstellar dust. This is a highly heterogeneous group that includes pre-main sequence stars, symbiotic systems, B[e] supergiants, post-AGB stars, and an unclassified subgroup that shares properties of both young and evolved objects (Lamers et al 1998). Some of the latter become members of mass transfer binary systems, named FS CMa type objects. The study of all these groups are particularly compelling, as they offer valuable insights into the formation of circumstellar discs across different evolutionary stages, and provide clues about stellar evolution during a transition phase.
The present study is part of a long-term search for candidate objects with the B[e] phenomenon. Naurzbayeva et al. presented the results of low- and mid-resolution spectroscopic observations of six objects from a larger group selected on the basis of their photometric criteria. The spectra were complemented with BVR_c photometry of three objects taken at TShAO and photometric data from a range of optical and IR sky surveys. The effective temperature, luminosity and spectral type of the underlying stars were estimated from the SED fittings in the optical range, while the IR excess shapes were used to evaluate the evolutionary state. The authors concluded that forbidden lines were detected in only one object, and may be present in three more.
Although the spectroscopic survey of faint objects presented by the authors is interesting and has potential value, the study contains several significant weaknesses that need to be addressed. Therefore, I do not recommend publication in its current form, and I believe a major revision of the objetives and methodology is required. I justify my point of view below.
Finally, in my opinion, the corresponding author should use an institutional e-mail address or, at the very least, the e-mail name should clearly belong to one of the listed authors.
Major comments
1) The abstract does not provide a complete definition of the B[e] phenomenon, notably omitting the B[e] supergiants. While it appears that the authors intend to focus on a sample that excludes this subgroup, the definition as presented may be confusing for readers unfamiliar with the classification of the B[e] stars.
2) The spectroscopic analysis presented does not support the B[e] classification for five of the six objects studied, which contradicts the claim made in the abstract: “Spectroscopy of the candidates allows us making more confident conclusions on their classification. We present the results of our photometric and spectroscopic observations for a sample of recently found objects that satisfy our photometric selection criteria for candidate objects with the B[e] phenomenon.”
This study would be more suitable for a search of emission line stars, instead of B[e] stars. The stars could be interacting binaries with dust or cool companions (without forbidden lines or LBV). The results are not conclusive and do not justify the interpretations given.
3) It is not clear why these six stars were selected as fulfilling the criteria. The manuscript does not explain what disqualified the remaining stars in the larger sample, or why they were excluded (Do they show absorption lines?). This lack of clarity weakens the justification for focusing on the six objects presented. It also weakens the photometric criteria for searching B[e] stars.
If the other stars show absorption lines, an appendix with the list of objects will be useful, avoiding repeating the search.
4) At the beginning of the manuscript, the authors stated, “Symbiotic binaries and compact Planetary Nebulae can be identified relatively easily due to their distinct features, such as the dominance of a cool star or a special atmospheric chemical composition that reflects a very evolved evolutionary stage, respectively. It is more challenging to distinguish pre-main-sequence Herbig Ae/Be stars and dust-producing supposedly more evolved FS CMa objects.”
If the previous sentence is correct, a citation is needed. However, there are exceptions: the dominance of a cool star was also reported by Nodyarov et al (2024) in the B[e] binary system HD 327083. There, the authors concluded that both components of the system are supergiants.
In addition, I would like to comment that Herbig Ae/Be stars (including many FS CMa objects), B[e] supergiants, and cool stars cannot be reliably distinguished based on photometric criteria alone.
5) In the introduction, the authors said “uncertain contributions of the CS material to the systems’ brightness, and uncertain distances despite the recent Gaia measurements”.
Therefore, if the Gaia distances are considered unreliable, it is unclear why B[e] supergiants were excluded from the analysis. How was the luminosity of the stars derived?
6) Section 2: Observations. The near-IR spectra reduction procedure should be described. It would be helpful to specify the sky background correction - whether a nodding or dithering strategy was applied. As well as any additional steps (e.g., bad pixel masking, flat-fielding, or telluric correction).of
7) What is the criterion of the slope of the IR SED to classify the nature of an object?
7) 3.2. UCAC–4 729–007078 (IRAS 00411+5528) Why is a B[e] supergiant nature ruled out?
8) 3.3. UCAC–4 725–014138 (2MASS J01380790+5453463) Could the star be an LBV? LBVs and Herbig Ae/Be stars can show a PCygni profile in Hbeta.
9) UCAC4 657-086975 Here, the authors identified the He I line. However, the spectra of UCAC4 725-014138 and UCAC4 729-007078 look alike. A feature next to Na I line appears.
Minor comments
- Institutions
Mexico → México (many occurrences along the text)
astronom’a –> Astronomía
- Abstract
allow us making → allow us to make
- Observations
The footnote referencing Maxim-DL software does not explain the reduction procedure; it merely serves as a promotional notice to purchase the product.
- Include the effective temperatures in Table 2.
Author Response
We thank the reviewer for a detailed analysis of the original manuscript and suggestions for its improvements. We have taken into account most of the comments and responded with our explanations to others. As a result, a new Figure and a new Section were added, and the methodology of searching for new objects and analysis of the collected data are explained in more detail.
B-type stars exhibiting the B[e] phenomenon are characterized by the presence of both permitted and forbidden emission lines, as well as a strong infrared (IR) excess caused by hot circumstellar dust. This is a highly heterogeneous group that includes pre-main sequence stars, symbiotic systems, B[e] supergiants, post-AGB stars, and an unclassified subgroup that shares properties of both young and evolved objects (Lamers et al 1998). Some of the latter become members of mass transfer binary systems, named FS CMa type objects. The study of all these groups are particularly compelling, as they offer valuable insights into the formation of circumstellar discs across different evolutionary stages, and provide clues about stellar evolution during a transition phase.
The present study is part of a long-term search for candidate objects with the B[e] phenomenon. Naurzbayeva et al. presented the results of low- and mid-resolution spectroscopic observations of six objects from a larger group selected on the basis of their photometric criteria. The spectra were complemented with BVR_c photometry of three objects taken at TShAO and photometric data from a range of optical and IR sky surveys. The effective temperature, luminosity and spectral type of the underlying stars were estimated from the SED fittings in the optical range, while the IR excess shapes were used to evaluate the evolutionary state. The authors concluded that forbidden lines were detected in only one object, and may be present in three more.
Although the spectroscopic survey of faint objects presented by the authors is interesting and has potential value, the study contains several significant weaknesses that need to be addressed. Therefore, I do not recommend publication in its current form, and I believe a major revision of the objectives and methodology is required. I justify my point of view below.
Answer: A new Section on the used methodology was added to the corrected version.
Finally, in my opinion, the corresponding author should use an institutional e-mail address or, at the very least, the e-mail name should clearly belong to one of the listed authors.
Answer: Corrected.
Major comments
1) The abstract does not provide a complete definition of the B[e] phenomenon, notably omitting the B[e] supergiants. While it appears that the authors intend to focus on a sample that excludes this subgroup, the definition as presented may be confusing for readers unfamiliar with the classification of the B[e] stars.
Answer: A description of B[e] supergiant properties added.
2) The spectroscopic analysis presented does not support the B[e] classification for five of the six objects studied, which contradicts the claim made in the abstract: “Spectroscopy of the candidates allows us making more confident conclusions on their classification. We present the results of our photometric and spectroscopic observations for a sample of recently found objects that satisfy our photometric selection criteria for candidate objects with the B[e] phenomenon.”
This study would be more suitable for a search of emission line stars, instead of B[e] stars. The stars could be interacting binaries with dust or cool companions (without forbidden lines or LBV). The results are not conclusive and do not justify the interpretations given.
Answer: Although this sample contains just one object with obviously present B[e] phenomenon, this was our original intention to specifically search for such objects. We are not interested just in emission-line stars, especially because some of our selected targets have been recognized as such. The search criteria were based on the photometric properties of B[e] objects. Five of the six sample objects definitely possess IR excesses indicative of circumstellar dust and may well exhibit the B[e] phenomenon. It is simply a lack of relevant observations hampers a more definitive conclusion. Nevertheless, publication of our results may attract attention of other researchers before they discover these objects for themselves.
3) It is not clear why these six stars were selected as fulfilling the criteria. The manuscript does not explain what disqualified the remaining stars in the larger sample, or why they were excluded (Do they show absorption lines?). This lack of clarity weakens the justification for focusing on the six objects presented. It also weakens the photometric criteria for searching B[e] stars.
Answer: The criteria, although not very strict, are described. As we aimed at selecting candidates for objects with the B[e] phenomenon, obviously a disqualifying criterion is the absence of emission lines. There is no specific focus on these 6 objects. They are simply the first, whose analysis was presented at the conference “Hot Stars. Life with Circumstellar Matter” (October 2024, Almaty, Kazakhstan). This is a progress report on our larger project.
If the other stars show absorption lines, an appendix with the list of objects will be useful, avoiding repeating the search.
Answer: We are only going to present found emission-line stars.
4) At the beginning of the manuscript, the authors stated, “Symbiotic binaries and compact Planetary Nebulae can be identified relatively easily due to their distinct features, such as the dominance of a cool star or a special atmospheric chemical composition that reflects a very evolved evolutionary stage, respectively. It is more challenging to distinguish pre-main-sequence Herbig Ae/Be stars and dust-producing supposedly more evolved FS CMa objects.”
If the previous sentence is correct, a citation is needed. However, there are exceptions: the dominance of a cool star was also reported by Nodyarov et al (2024) in the B[e] binary system HD 327083. There, the authors concluded that both components of the system are supergiants.
Answer: We added a description of B[e] supergiants to Introduction. The dominance of the cool component in HD 327083 is different from that in symbiotic binaries, where the degenerate secondary does not directly contribute to the system brightness. The components of HD 327083 are just relatively luminous, but it is still a question of how to classify them. They should not be compared to single supergiants due a mass-exchange between the components that alters their initial evolution. This topic is beyond the scope of this paper.
In addition, I would like to comment that Herbig Ae/Be stars (including many FS CMa objects), B[e] supergiants, and cool stars cannot be reliably distinguished based on photometric criteria alone.
Answer: This is why we report our findings backed up with spectroscopy.
5) In the introduction, the authors said “uncertain contributions of the CS material to the systems’ brightness, and uncertain distances despite the recent Gaia measurements”.
Therefore, if the Gaia distances are considered unreliable, it is unclear why B[e] supergiants were excluded from the analysis. How was the luminosity of the stars derived?
Answer: We just warn that Gaia distances may be unreliable, but use the DR3 distances in the luminosity calculations. The luminosities were calculated in a usual way by taking into account the visual brightness, total extinction estimate, bolometric correction that corresponds to the assumed Teff, and the distance. We added a description of the luminosity calculations.
6) Section 2: Observations. The near-IR spectra reduction procedure should be described. It would be helpful to specify the sky background correction - whether a nodding or dithering strategy was applied. As well as any additional steps (e.g., bad pixel masking, flat-fielding, or telluric correction).
Answer: We added a description of the IR spectral data reduction.
7) What is the criterion of the slope of the IR SED to classify the nature of an object?
Answer: The slope has to be d(log λFλ)/dλ < −0.5, because Herbig Ae/Be stars typically have nearly a zero or even a positive slope. We added this criterion to the text.
7) 3.2. UCAC–4 729–007078 (IRAS 00411+5528) Why is a B[e] supergiant nature ruled out?
Answer: It is ruled out because of a low luminosity.
8) 3.3. UCAC–4 725–014138 (2MASS J01380790+5453463) Could the star be an LBV? LBVs and Herbig Ae/Be stars can show a PCygni profile in Hbeta.
Answer: The luminosity of this object is way too low for an LBV. It also shows very weak brightness variations according to ASAS SN data. Yes, Herbig Ae/Be stars can show P Cyg profiles in emission lines (not only in Hbeta), but our conclusion on the possible evolutionary status is based on the IR SED slope.
9) UCAC4 657-086975 Here, the authors identified the He I line. However, the spectra of UCAC4 725-014138 and UCAC4 729-007078 look alike. A feature next to Na I line appears.
Minor comments
- Institutions
Mexico → México (many occurrences along the text)
astronom’a –> Astronomía -- corrected
- Abstract
allow us making → allow us to make – corrected
- Observations
The footnote referencing Maxim-DL software does not explain the reduction procedure; it merely serves as a promotional notice to purchase the product.
Answer: more information about the photometric data reduction is added.
Include the effective temperatures in Table 2.
Answer: Teff were added to Table 2 (Table 3 in the new version) instead of spectral types.
Author Response File: Author Response.pdf
Reviewer 5 Report
Comments and Suggestions for AuthorsThis paper present and discuss six new objects presenting the B[e] phenomenon, in particular those following the properties of the subgroup FS CMA.
Major weaknesses: The most relevant contribution of this work will be the method and criteria for finding stars exhibiting the B[e] phenomenon, especially in a certain subgroup. However, the details of this method are not fully described, nor are the results of implementing it on the initial sample shown. Information is lacking to accompany the description of the results and their discussion.
In the following, general and specific comments are given in order to improve the work.
Introduction section:
From line 68 to the end of the paragraph, a brief explanation of the method used is included; this must be separated from the introduction section and should indicate more details, such as the number of objects studied (the authors mentioned that they discussed in detail six stars, but taken from a total of how many?). Also, a color-color diagram should be included, indicating the criteria mentioned for the selection sample.
Results section:
- subsection 3.1) Please be more precise in the selection criteria: what properties do you mean by absorption and emission lines? How many stars following the “mentioned criteria” were selected from the initial list?
- subsection 3.1) This object also appears in Fig.3 but is not mentioned.
- Figure 1: I recommend fixing the vertical axis of each column to visually compare the different spectra and SED. No information about what kind of stellar atmosphere model is used to obtain the best fit.
- subsection 3.6) Fig. 2 --> Fig. 1)
- Table 2. EW(Ha) units should follow the same format as the other columns.
- Table 2. Add the chi-square of the fits.
- General comments for this section: The text discusses other lines, but the spectra are not shown. Also, are changes observed between different observation epochs in these stars? If that is the case, Halpha should be overplotted, indicating the observation dates.
Conclusion section
line 265: "six objects from a ........ criteria" --> please again, specify from a larger group and the earlier developed photometric criteria.
line 268: "fundamental parameters ... from SED fitting" --> please provide information about the stellar atmosphere model used.
line 270: if forbidden lines are fundamental to characterize the B[e] phenomenon, why the spectral region of these lines is not included in the plots?
- Fig. 2 --> Fig.4 (Line 283)
- Line 291 a “)” is missing in the luminosity value.
- Fig. 3 -->Fig. 4 (Line 292)
- Table 3 is mentioned once in subsection 3.6 at line 248. The rest of the information in this table should be mentioned and explained in the text.
general comment of the conclusion section: How can we evaluate the proposed method for classifying or searching for B[e] stars? Especially FS CMa subgroup, how efficient is it? What other methods exist to characterize this phenomenon?
Author Response
We thank the reviewer for a detailed analysis of our original manuscript and pointing out a need of explaining the methodology better. We have taken into account most of the comments and responded with our explanations to others. As a result, a new Figure and a new Section were added, and the methodology of searching for new objects and analysis of the collected data are explained in more detail.
This paper present and discuss six new objects presenting the B[e] phenomenon, in particular those following the properties of the subgroup FS CMA.
Major weaknesses: The most relevant contribution of this work will be the method and criteria for finding stars exhibiting the B[e] phenomenon, especially in a certain subgroup. However, the details of this method are not fully described, nor are the results of implementing it on the initial sample shown. Information is lacking to accompany the description of the results and their discussion.
In the following, general and specific comments are given in order to improve the work.
Introduction section:
From line 68 to the end of the paragraph, a brief explanation of the method used is included; this must be separated from the introduction section and should indicate more details, such as the number of objects studied (the authors mentioned that they discussed in detail six stars, but taken from a total of how many?). Also, a color-color diagram should be included, indicating the criteria mentioned for the selection sample.
Answer: A description of the method used was added in the newly introduced Sect. 2. Color-color diagrams are shown in our previous publications, which we refer to.
Results section:
- subsection 3.1) Please be more precise in the selection criteria: what properties do you mean by absorption and emission lines? How many stars following the “mentioned criteria” were selected from the initial list?
Answer: This information was added to the newly introduced Sect. 2 on the method description.
- subsection 3.1) This object also appears in Fig.3 but is not mentioned.
- Figure 1: I recommend fixing the vertical axis of each column to visually compare the different spectra and SED. No information about what kind of stellar atmosphere model is used to obtain the best fit.
- subsection 3.6) Fig. 2 --> Fig. 1)
Answer: Corrected.
- Table 2. EW(Ha) units should follow the same format as the other columns.
Answer: This comment is unclear.
- Table 2. Add the chi-square of the fits.
Answer: We did not intend to find the best fit, because neither the spectral classification nor the extinction law is very precise. The chi-square values do not have much meaning in this situation. The plots show that the agreement between the dereddened observational data and the theoretical fits is reasonably good. Spectroscopic observations with a higher resolution and signal-to-noise are needed to further constrain the fits.
- General comments for this section: The text discusses other lines, but the spectra are not shown. Also, are changes observed between different observation epochs in these stars? If that is the case, Halpha should be overplotted, indicating the observation dates.
Answer: The brief format of the paper does not allow us to show all the mentioned spectral line. No significant changes were observed between the observations of all the objects. This information was added to the object’s properties description in Sect. 3.6.
Conclusion section
line 265: "six objects from a ........ criteria" --> please again, specify from a larger group and the earlier developed photometric criteria.
Answer: Corrected.
line 268: "fundamental parameters ... from SED fitting" --> please provide information about the stellar atmosphere model used.
Answer: Information added.
line 270: if forbidden lines are fundamental to characterize the B[e] phenomenon, why the spectral region of these lines is not included in the plots?
Answer: We discuss the presence of such lines in the text (Sect. 3 for each object and Sect. 4). We added a Figure with forbidden lines detected in the spectrum of VES 683.
- Fig. 2 --> Fig.4 (Line 283) --- Corrected
- Line 291 a “)” is missing in the luminosity value. --- Corrected
- Fig. 3 -->Fig. 4 (Line 292) --- Corrected
- Table 3 is mentioned once in subsection 3.6 at line 248. The rest of the information in this table should be mentioned and explained in the text.
Answer: This Table was also mentioned in Sect. 2 but misidentified with Table 2. Now this is corrected.
General comment of the conclusion section: How can we evaluate the proposed method for classifying or searching for B[e] stars? Especially FS CMa subgroup, how efficient is it? What other methods exist to characterize this phenomenon?
Answer: Our method is based on the current statistics of the observed color-indices of FS CMa type objects. It is an approximate and not a firmly established approach that would unambiguously identify only members of this group. This is now described in the new Section 2. There are no other methods to characterize this phenomenon photometrically. Photometric criteria are important because of the objects’ faintness that makes spectroscopic observations difficult. Although Gaia delivered spectrophotometry of millions of stars, these data are of an insufficent quality to make classificational conclusions beyond just the presence of line emission (only for objects with relatively strong Halpha lines).
Author Response File: Author Response.pdf
Round 2
Reviewer 4 Report
Comments and Suggestions for AuthorsI thank the authors for considering my comments and suggestions. The revised manuscript shows significant improvement and addresses most of my comments, resulting in a clearer research presentation.
I still have some minor suggestions that could help improve the revised version of the manuscript. Once these are addressed, the article will be ready for publication. I also recommend that the authors carefully check the manuscript for any grammatical or spelling errors.
Abstract:
As the authors intend to restrict the definition of stars with the B[e] phenomenon to those “from pre-main sequence to planetary nebulae”, in alignment with the scope of their target sample, I suggest rephrasing the first sentence of the abstract as:
“Low- and intermediate mass objects with the B[e] phenomenon …"
As the criteria are still not defined. It would be better to shorten the sentence “We developed photometric criteria to search for candidate objects with this phenomenon, based on a combination of optical and near-infrared color-indices and found nearly 40 objects”
I suggest also to rephrase the last phrase of the abstract “while IRAS 20402+4638 may be a luminous member of the FS CMa objects group with weak forbidden lines undetected due to its faintness (V ∼ 14.5 mag).”
saying
“while IRAS 20402+4638 may be a luminous candidate of the FS CMa objects group”. It provides, in my opinion, the same information in a shorter way.
Introduction
Page 1: last sentence
due their distinct features → due to their distinct features
The last paragraph is not clear enough.
“Here we describe the results of our study of six objects selected on the basis of these criteria as an example of a multi-method and multi-wavelength approach … “
Which criteria? The photometric criteria of Kuratova et al [7] or the large IR excess?
Or simply say “based on our criteria” or “based on the criteria outlined in Sect 2” and then delete the following sentence.
Methodology
First sentence: desfribed → described
Observations:
2nd paragraph: as those of objects images → as the object images.
3rd paragraph: objects’ images → object images
Tables 1, 2 and 3: Please remove line 2 of the Tables. The column numbers are not needed, as the columns are clearly defined.
Page 3: last sentence: objects’ SEDs → object SEDs or the SEDs of the objects
Section 4: delete (see Sect 4). It is the current section.
of from → from
1,000 - - 2,000 K → $1,000 – 2,000$~K
which is reasonable hot stars → which is reasonable for hot stars
interestelar part→ interestellar part
[3] , → [3],
Reword . The following sentence is incomplete “The IRAS mission measured IR fluxes at λ 12 and λ 25 µm [12]. Kerton and Brunt [26]”
Page 6 (Sect 4.3) Our medium-resolution spectrum taken at OAN SPM in October 2010 show → shows.
Sect 4.5: Our SED fitting a weak IR excess → Our SED fitting reveals/shows a weak IR excess
last sentence “shown in Fig. 5” → write this phrase between commas.
Page 8; Sect 4.6
“… Ca II K line at 3933 \AA several He I ...” → add a comma “Ca II K line at 3933 \AA, several He I ….”
IRAS 00205+7023 classified as → IRAS 00205+7023 is classified as
“The best fits are typically accurate to a few per cent, and the Teff derived this way …” →
“The best fits are typically accurate to a few per cent, and the Teff values derived this way …”
Conclusion
in one object UCAC–4 778–000339 → in one object, UCAC–4 778–000339
Fig. 1, add commas to separate atomic elements
Comments on the Quality of English Language
I recommend the authors carefully check the manuscript for grammatical or spelling errors.
Author Response
We are very grateful to the reviewer for such a careful reading our manuscript and useful suggestions. We have made corrections for most of the suggestions.
I thank the authors for considering my comments and suggestions. The revised manuscript shows significant improvement and addresses most of my comments, resulting in a clearer research presentation.
I still have some minor suggestions that could help improve the revised version of the manuscript. Once these are addressed, the article will be ready for publication. I also recommend that the authors carefully check the manuscript for any grammatical or spelling errors.
Abstract:
As the authors intend to restrict the definition of stars with the B[e] phenomenon to those “from pre-main sequence to planetary nebulae”, in alignment with the scope of their target sample, I suggest rephrasing the first sentence of the abstract as:
“Low- and intermediate mass objects with the B[e] phenomenon …"
Answer: This is just a general statement that shows what B[e] objects can be. Despite we are mostly interested in FS CMa objects, our criteria may catch B[e] supergiants as well. We would better not impose the proposed restriction.
As the criteria are still not defined. It would be better to shorten the sentence “We developed photometric criteria to search for candidate objects with this phenomenon, based on a combination of optical and near-infrared color-indices and found nearly 40 objects”
Answer: The criteria are defined and described in Section 2. They may not be strict enough for finding these kinds of object only, but they are based on properties of a large number of known B[e] objects and cut off certain unwanted objects, such as classical Be stars, Herbig Ae/Be stars, symbiotic binaries, and planetary nebulae. We do not see a need for changing this statement.
I suggest also to rephrase the last phrase of the abstract “while IRAS 20402+4638 may be a luminous member of the FS CMa objects group with weak forbidden lines undetected due to its faintness (V ∼ 14.5 mag).”
saying
“while IRAS 20402+4638 may be a luminous candidate of the FS CMa objects group”. It provides, in my opinion, the same information in a shorter way.
Answers: Corrected.
Introduction
Page 1: last sentence
due their distinct features → due to their distinct features -- corrected
The last paragraph is not clear enough.
“Here we describe the results of our study of six objects selected on the basis of these criteria as an example of a multi-method and multi-wavelength approach … “
Which criteria? The photometric criteria of Kuratova et al [7] or the large IR excess?
Or simply say “based on our criteria” or “based on the criteria outlined in Sect 2” and then delete the following sentence.
Answer: Corrected
Methodology
First sentence: desfribed → described – corrected
Observations:
2nd paragraph: as those of objects images → as the object images. – corrected
3rd paragraph: objects’ images → object images – corrected
Tables 1, 2 and 3: Please remove line 2 of the Tables. The column numbers are not needed, as the columns are clearly defined. – corrected
Page 3: last sentence: objects’ SEDs → object SEDs or the SEDs of the objects -- corrected
Section 4: delete (see Sect 4). It is the current section. -- corrected
of from → from -- corrected
1,000 - - 2,000 K → $1,000 – 2,000$~K -- corrected
which is reasonable hot stars → which is reasonable for hot stars
interestelar part→ interestellar part -- corrected
[3] , → [3], -- this is a compilation or viewing problem. We do not see this pattern. It is displayed correctly for us.
Reword . The following sentence is incomplete “The IRAS mission measured IR fluxes at λ 12 and λ 25 µm [12]. Kerton and Brunt [26]” – what is shown is one full sentence and the beginning of the second one. No incompleteness is detected. The micron symbol is added after 12 though.
Page 6 (Sect 4.3) Our medium-resolution spectrum taken at OAN SPM in October 2010 show → shows. -- corrected
Sect 4.5: Our SED fitting a weak IR excess → Our SED fitting reveals/shows a weak IR excess – “reveals” is added
last sentence “shown in Fig. 5” → write this phrase between commas. – changed to (see Fig. 5)
Page 8; Sect 4.6
“… Ca II K line at 3933 \AA several He I ...” → add a comma “Ca II K line at 3933 \AA, several He I ….” -- corrected
IRAS 00205+7023 classified as → IRAS 00205+7023 is classified as -- corrected
“The best fits are typically accurate to a few per cent, and the Teff derived this way …” →
“The best fits are typically accurate to a few per cent, and the Teff values derived this way …” -- corrected
Conclusion
in one object UCAC–4 778–000339 → in one object, UCAC–4 778–000339 – changed to in one object (UCAC–4 778–000339, see …)
Fig. 1, add commas to separate atomic elements
Comments on the Quality of English Language
I recommend the authors carefully check the manuscript for grammatical or spelling errors. -- done
Author Response File: Author Response.pdf
Reviewer 5 Report
Comments and Suggestions for AuthorsThe authors have improved their work presentation considerably in this new version of the manuscript. Also, almost all comments and recommendations given previously were incorporated. Only a few minor remarks about some typos are given below:
Minor comments
Section 2)
desfribed —> described
Last paragraph:
“Although the method is not perfect” —>
“Although the method has limitations”
Section 3)
“… The uncertainties of all the measurements range from 0.01 mag for the two brighter stars to 0.03 mag for the fainer one —> …”the two brightest stars to 0.03 mag for the faintest one.”
SED: is used for the first time in the methodology section but is defined in Observations.
Section 4)
dereddned —> dereddened
which is reasonable hot stars hotter than 10,000 K —> for stars hotter than 10,000 K
Subsection 4.6)
“The OAN SPM … (See Fig.3)” —> See Fig.4
I recommend putting the EW of Ha in Table 3 in the following way so that the units are below, unless the column width is affected.
EW(Ha) —> so below it could be the units.
Author Response
We appreciate a careful reading of the manuscript by the reviewer. All the corrections have been made.
The authors have improved their work presentation considerably in this new version of the manuscript. Also, almost all comments and recommendations given previously were incorporated. Only a few minor remarks about some typos are given below:
Minor comments
Section 2)
desfribed —> described -- corrected
Last paragraph:
“Although the method is not perfect” —>
“Although the method has limitations” -- corrected
Section 3)
“… The uncertainties of all the measurements range from 0.01 mag for the two brighter stars to 0.03 mag for the fainer one —> …”the two brightest stars to 0.03 mag for the faintest one.” -- corrected
SED: is used for the first time in the methodology section but is defined in Observations. -- corrected
Section 4)
dereddned —> dereddened -- corrected
which is reasonable hot stars hotter than 10,000 K —> for stars hotter than 10,000 K -- corrected
Subsection 4.6)
“The OAN SPM … (See Fig.3)” —> See Fig.4 -- corrected
I recommend putting the EW of Ha in Table 3 in the following way so that the units are below, unless the column width is affected.
EW(Ha) —> so below it could be the units. -- corrected
Author Response File: Author Response.pdf
