From 50c058ec8542e98b8befe7bea630c48cecaf5a91 Mon Sep 17 00:00:00 2001
From: Abhimanyu Susobhanan <abhisrkckl@gmail.com>
Date: Fri, 7 Feb 2025 09:42:10 +0100
Subject: [PATCH 1/3] photon.jl

---
 src/toa/photon.jl | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)
 create mode 100644 src/toa/photon.jl

diff --git a/src/toa/photon.jl b/src/toa/photon.jl
new file mode 100644
index 00000000..7092e2f8
--- /dev/null
+++ b/src/toa/photon.jl
@@ -0,0 +1,27 @@
+export Photon
+
+struct Photon <: TOABase
+    arrival_time::TOA
+    weight::GQ{0,Float64}
+
+    function Photon(arrival_time, frequency, weight, ephem, index)
+        toa = TOA(arrival_time, time(0.0), frequency, dimensionless(0.0), ephem, index)
+        return new(toa, weight)
+    end
+end
+
+struct PhotonCorrection <: TOACorrectionBase
+    arrival_time_correction::TOACorrection
+end
+
+function PhotonCorrection(delay, phase, ssb_psr_pos)
+    @assert all(iszero.(ssb_psr_pos)) ||
+            dot(ssb_psr_pos, ssb_psr_pos) ≈ dimensionless(1.0) "ssb_psr_pos must be a zero vector (representing pending computation) or a unit vector."
+
+    return PhotonCorrection(TOACorrection(delay, phase, dimensionless(1.0), GQ{2}(0.0), frequency(0.0), dimensionless(1.1), ssb_psr_pos))
+end
+
+PhotonCorrection() = PhotonCorrection(time(0.0), dimensionless(0.0), dimensionless.((0.0, 0.0, 0.0)),)
+
+fractional_phase(photcorr::PhotonCorrection) = photcorr.arrival_time_correction.phase - round(photcorr.arrival_time_correction.phase)
+

From c30f554b2e679929763464aec755bfcb15cd6135 Mon Sep 17 00:00:00 2001
From: Abhimanyu Susobhanan <abhisrkckl@gmail.com>
Date: Fri, 7 Feb 2025 09:42:19 +0100
Subject: [PATCH 2/3] photon_model.jl

---
 src/Vela.jl               |  2 ++
 src/model/photon_model.jl | 14 ++++++++++++++
 2 files changed, 16 insertions(+)
 create mode 100644 src/model/photon_model.jl

diff --git a/src/Vela.jl b/src/Vela.jl
index 1dc7f596..da9e6b7f 100644
--- a/src/Vela.jl
+++ b/src/Vela.jl
@@ -16,6 +16,7 @@ export GQ
 include("toa/ephemeris.jl")
 include("toa/toa.jl")
 include("toa/wideband_toa.jl")
+include("toa/photon.jl")
 include("parameter/parameter.jl")
 include("model/component.jl")
 include("model/kernel.jl")
@@ -47,6 +48,7 @@ include("model/gp_noise.jl")
 include("model/dispersion_measurement_noise.jl")
 include("model/timing_model.jl")
 include("model/wideband_model.jl")
+include("model/photon_model.jl")
 include("prior/prior.jl")
 include("prior/prior_scaling.jl")
 include("prior/simple_prior.jl")
diff --git a/src/model/photon_model.jl b/src/model/photon_model.jl
new file mode 100644
index 00000000..9bbac7d2
--- /dev/null
+++ b/src/model/photon_model.jl
@@ -0,0 +1,14 @@
+"""Update a `CorrectedWidebandTOA` object. 
+Most components only affect the TOA part and not the DM part."""
+correct_toa(
+    component::Component,
+    photon::Photon,
+    photcorr::PhotonCorrection,
+    params::NamedTuple,
+) = PhotonCorrection(
+    correct_toa(component, photon.toa, photcorr.arrival_time_correction, params),
+)
+
+"""Update a `WidebandTOA` object using a timing model."""
+correct_toa(model::TimingModel, wtoa::Photon, params::NamedTuple) =
+    correct_toa(model, wtoa, PhotonCorrection(), params)

From 9eb36b4f3e275b4040287a88972cd6fe18531c9c Mon Sep 17 00:00:00 2001
From: Abhimanyu Susobhanan <abhisrkckl@gmail.com>
Date: Fri, 7 Feb 2025 09:42:55 +0100
Subject: [PATCH 3/3] photon.jl

---
 src/toa/photon.jl | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/src/toa/photon.jl b/src/toa/photon.jl
index 7092e2f8..74ea207f 100644
--- a/src/toa/photon.jl
+++ b/src/toa/photon.jl
@@ -15,13 +15,23 @@ struct PhotonCorrection <: TOACorrectionBase
 end
 
 function PhotonCorrection(delay, phase, ssb_psr_pos)
-    @assert all(iszero.(ssb_psr_pos)) ||
-            dot(ssb_psr_pos, ssb_psr_pos) ≈ dimensionless(1.0) "ssb_psr_pos must be a zero vector (representing pending computation) or a unit vector."
-
-    return PhotonCorrection(TOACorrection(delay, phase, dimensionless(1.0), GQ{2}(0.0), frequency(0.0), dimensionless(1.1), ssb_psr_pos))
+    @assert all(iszero.(ssb_psr_pos)) || dot(ssb_psr_pos, ssb_psr_pos) ≈ dimensionless(1.0) "ssb_psr_pos must be a zero vector (representing pending computation) or a unit vector."
+
+    return PhotonCorrection(
+        TOACorrection(
+            delay,
+            phase,
+            dimensionless(1.0),
+            GQ{2}(0.0),
+            frequency(0.0),
+            dimensionless(1.1),
+            ssb_psr_pos,
+        ),
+    )
 end
 
-PhotonCorrection() = PhotonCorrection(time(0.0), dimensionless(0.0), dimensionless.((0.0, 0.0, 0.0)),)
-
-fractional_phase(photcorr::PhotonCorrection) = photcorr.arrival_time_correction.phase - round(photcorr.arrival_time_correction.phase)
+PhotonCorrection() =
+    PhotonCorrection(time(0.0), dimensionless(0.0), dimensionless.((0.0, 0.0, 0.0)))
 
+fractional_phase(photcorr::PhotonCorrection) =
+    photcorr.arrival_time_correction.phase - round(photcorr.arrival_time_correction.phase)