Change bibliography style in text within aastex

Question

I want to use the aastex style for an overleaf document, but I need to change the bibliography style, such that the references are indicated in the text as this is the references [1] and in the bibliography can mantain the standard \bibliographystyle{aasjournal}. I have read that I can get something similar by using \usepackage[square,numbers]{natbib}.

However, if I simply try to compile

\documentclass{aastex63}
\usepackage{comment}
\usepackage[square,numbers]{natbib}

it returns a conflict error:

 LaTeX Error: Option clash for package natbib.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...                                              

l.4 

The package natbib has already been loaded with options:
  [sort&compress]
There has now been an attempt to load it with options
  [square,numbers]
Adding the global options:
  sort&compress,square,numbers
to your \documentclass declaration may fix this.
Try typing  <return>  to proceed.

Now, if I go to the aastex63.cls document, I only find two entries related to natbib and this problem:

% Restore natbib package without sorting. 
\def\NAT@sort{0}
\def\NAT@cmprs{0}

% only redefine sort@cites for natbib versions < 2009
\@ifundefined{NAT@sort@cites@}{\def\NAT@sort@cites#1{\edef\NAT@cite@list{#1}}}%

I thought it was enough to comment out the first two of these lines, but this is evidently wrong. Any advice?

Answer 1

Try this:

\usepackage{natbib}

\setcitestyle{square}

\renewcommand\bibnumfmt[1]{[#1] }