Kibana console code 44 trying to get _souce timestamp

I am getting:
unexpected character (',' (code 44)): was expecting a colon to seperate field name and value\n at [Source: org.elasticsearch.transport. netty4.ByteBufStreamInput@249c1586; line: 3, column:28]"
I am using the input

GET logstash-*/_search
{
     "size" : 10,
     "_source": {"@timestamp"}
}

I am using kibana 6.5.4. Then I tried to change it to this:

GET logstash-*/_search
{
    "size" : 10,
    "_source": "{@timestamp}"
}

this gets no error but doesn't get the source.