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Standard Workflow for the Analysis of Stars in the Survey Field around Gaia DR3 2217998150488879232

Every star in the survey field around Gaia DR3 2217998150488879232 (the V582 Cep field) is analysed using the same fixed procedure, ensuring consistent and scientifically reliable treatment. The goal is to create a homogeneous, coordinate‑based dataset independent of legacy catalogues.

1. Source Identification

The process always begins with a precise identification of the source. Its position is retrieved from SIMBAD and compared directly with the observer’s own images in AstroImageJ. The object must appear at exactly the same location, typically within less than 0.5 arcseconds. When SIMBAD provides a Gaia identifier, this becomes the primary reference for all subsequent astrometric and photometric data. The **Gaia DR3 source ID** (if available) is the primary, permanent identifier for the object. Co‑ordinates (RA, Dec) are recorded as a secondary reference but may change over time due to proper motion; the Gaia ID does not. If no Gaia counterpart exists, the object is classified using its coordinates alone, and this is noted in the log. Traditional star names are not used in the survey; they are omitted from all formal records.

2. Catalogue Data Assembly

Once identity is verified, a complete set of catalogue data is assembled. This includes optical photometry from Gaia, near‑infrared measurements from 2MASS, and mid‑infrared data from WISE. All information is entered into a fixed template, ensuring that every star is documented in the same structured format and can be directly compared with others.

3. Incorporating Own Telescope Measurements

In addition to catalogue data, the analysis incorporates the observer’s own telescope measurements: filters used, exposure times, observing dates, instrumental settings, and signal‑to‑noise characteristics. The newly obtained photometry is systematically compared with catalogue values to identify variability and to assess observational reliability.

4. Variability Assessment

A preliminary assessment of variability is made using Tycho Tracker, which provides a quick overview of the light‑curve behaviour. A more detailed analysis is then carried out in AstroImageJ through differential photometry. This involves selecting suitable reference stars, determining optimal apertures, and correcting for trends such as airmass or background variations. The resulting light curve is included in the final description of the star.

5. Spectral Energy Distribution (SED)

All available photometry — both from catalogues and from the observer’s own measurements — is brought together in a spectral energy distribution (SED). The SED allows the detection of infrared excess, extinction effects, and circumstellar material, and it is a central component of the physical interpretation.

6. Data Compilation and Homogenisation

To ensure full consistency across the survey, all collected information for each star is ultimately compiled into a single uniform data sheet. This sheet follows a fixed structure that includes identification parameters, astrometric and photometric catalogue values, infrared measurements, and the observer’s own telescope data. By documenting every object in the same structured format, the survey builds a coherent and comparable set of stellar profiles.

Definitions and Interpretative Framework

In this work, two distinct but complementary frameworks are used: an observational framework and a physical interpretation framework. These are kept explicitly separate to avoid conflation between detection‑based catalogue data and astrophysical classification.

1. Observational Framework

All Gaia, IR, and WDS entries are treated as observational sources only. A source or point source refers strictly to an unresolved astrometric or photometric detection in a given survey. No assumptions are made about physical nature, evolutionary state, or multiplicity at this level of description.

Observational classifications used in this work are:

point source: unresolved detection in a given dataset
resolved source: spatially separated emission components in the same dataset
extended source: emission with measurable spatial structure beyond the point‑spread function (PSF)

These terms are instrument‑dependent and do not imply intrinsic physical singularity or multiplicity.

2. Physical Interpretation Framework

Physical classification is applied only after cross‑matching and multi‑wavelength comparison of observational sources.

A stellar object is defined as a self‑gravitating object that follows the stellar evolutionary track, including protostars, pre‑main‑sequence objects, and main‑sequence stars. Within this framework:

protostars are accretion‑dominated objects
pre‑main‑sequence objects are contraction‑dominated objects
main‑sequence stars are fusion‑dominated objects

This classification is continuous rather than discrete, and no sharp physical boundary is assumed between phases.

3. Mapping Principle

Observational sources and physical objects are not assumed to be equivalent on a one‑to‑one basis. A single physical object may correspond to multiple observational sources (e.g. in high‑resolution IR imaging), and multiple physical objects may appear as a single observational point source depending on instrumental resolution.

Therefore, physical interpretation is not derived from morphology alone but requires multi‑dataset consistency (Gaia astrometry, IR photometry, and literature cross‑identification).

Methodological Decision Flow for Source Classification

Young stellar objects do not evolve in discrete steps but across broad, overlapping physical bandwidths. Classical YSO classes impose hard observational boundaries on processes that are intrinsically continuous. To avoid the arbitrariness inherent in traditional schemes, this survey adopts a dual‑layer classification system that separates observational appearance from physical evolutionary state.

I. Observational Domain — Detection Level

Input: Any unresolved detection in Gaia, WISE, 2MASS, Pan‑STARRS, WDS, or survey imaging.

Criterion 1 – PSF Consistency

Is the source stable and consistent with the instrumental point‑spread function?

NO → Extended Source (nebulosity, cloud core, jet, reflection patch, or blended emission)

YES → Proceed to Point‑Source Analysis

II. Mapping Domain — Cross‑Identification & Consistency

Criterion 2 – Positional & Flux Agreement Across Wavelengths

Does the point source show consistent position and flux behaviour across optical and infrared datasets?

NO → Evaluate Extinction (AVAV)

If extinction insufficient to explain optical non‑detection → Catalogue Artefact / Misidentification

If extinction consistent with local cloud structure → Embedded Candidate

YES → Proceed to Physical Interpretation

III. Physical Domain — Astrophysical Nature

Criterion 3 – Combined Gaia Astrometry + SED Slope (αα)

Physical classification is based on the dominant energy source and evolutionary state.

Sub‑class A – Protostar

Steep IR slope (α>0α>0), no Gaia astrometric solution, high accretion signatures, envelope‑dominated SED.

Sub‑class B – Pre‑Main‑Sequence (PMS) Object

Moderate IR slope (−1.5<α<0−1.5<α<0), Gaia kinematic membership consistent with local cluster, contraction‑dominated luminosity, disk present or transitional.

Sub‑class C – Main‑Sequence (MS) Star

Negative IR slope (α<−1.5α<−1.5), full Gaia astrometry, hydrostatic equilibrium, no significant IR excess.

By naming this Flow, you capture the fluidity of nature:

The Source (Level I) may vary due to instrumental noise.

The Consistency (Level II) proves that there is something physical.

The Classification (Level III) acknowledges that the object exists on a continuum (accretion, contraction, fusion), so that a shift no longer overturns the entire definition.