The phrase "are closely observed" is correct and usable in written English.
It can be used when discussing subjects or phenomena that are monitored or watched carefully for details or changes.
Example: "The wildlife in the national park are closely observed by researchers to study their behavior and habitat."
Alternatives: "are carefully monitored" or "are attentively watched".
The 13 stories of "Billancourt Tales" are closely observed, potently phrased and dapperly shaped.
She told me later that job candidates taking the tour are closely observed; those who are brusque to the Help Desk personnel, for example, are weeded out immediately.
The fantasy worlds that Disney creates have a surprising amount in common with the ideal universe envisaged by the intelligence community, in which environments are carefully controlled and people are closely observed, and no one seems to mind.
Put a teenager who is desperate to escape the restrictions imposed by adults into a setting where they are closely observed and suddenly, it's more difficult for them to experiment with who they are or what they want.
Islamic dietary customs are closely observed; for instance, pork is not consumed, wine is eschewed, and even ritually licit animals such as lambs must be slaughtered in a prescribed fashion.
Conclusion: The preliminary data suggested that preoperative sedation might be safely administered to children with mild or moderate sleep-disordered breathing, and possibly to children with severe OSA, if children are closely observed prior to surgery.
Field workers are closely observing another 235 families.
Household appliance manufacturers are closely observing the early successes of industrial giants like Rolls-Royce and wondering if they, too, should offer IoT-powered data services and embrace the XaaS model.
Her writing about sex is closely observed.
Their routine must be closely observed.
As well as the state of his knee, Falcao's form will also be closely observed.
