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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

20542 results found.

  1. EP250911a: GTC/OSIRIS+ spectroscopic redshift z = 3.84
  2. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  3. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  4. GRB 250910B: SVOM/GRM observation
  5. EP250911a: SVOM/VT optical observation
  6. EP250911a: SAO RAS optical observations
  7. EP250911a: Optical detection with Kinder observations
  8. GRB 250911A: Swift/UVOT Detection
  9. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  10. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  11. LIGO/Virgo/KAGRA S250911ac: Updated Sky localization and Source Classification
  12. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  13. EP250911a: COLIBRÍ optical observations
  14. EP250911a: Einstein Probe detection of an X-ray transient
  15. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  16. GRB 250903A: SVOM/ECLAIRs refined analysis
  17. GRB 250911A: Enhanced Swift-XRT position
  18. GRB 250911A: Swift-XRT observations
  19. GRB 250911A: COLIBRÍ optical counterpart candidate
  20. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  21. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  22. GRB 250909B: AstroSat CZTI detection of a long burst
  23. GRB 250910A: SVOM/VT optical upper limit
  24. GRB 250910A: LCO optical upper limit
  25. GRB 250702B: Late time Chandra observations
  26. EP250908b/EP#01709240653: Swift/UVOT Detection
  27. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  28. EP250908c: SVOM/VT optical observation
  29. EP250908c: VLT/FORS2 optical counterpart identification
  30. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  31. EP250908b: SVOM/VT optical candidate
  32. EP250908c: Einstein Probe detection of an X-ray transient
  33. EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation
  34. Fermi-LAT Gamma-ray Observations of IceCube-250905A
  35. GRB 250903A: Swift-XRT afterglow detection
  36. LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
  37. IceCube-250905A: Upper limits from a search for additional neutrino events in IceCube
  38. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  39. EP250905a: Liverpool Telescope i-band upper limits
  40. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  41. EP250905a: Liverpool Telescope observations
  42. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  43. EP250905b: EP-WXT detection of a fast X-ray transient
  44. EP250905a: JinShan likely optical counterpart detection
  45. GRB 250905A: Swift/UVOT Upper Limits
  46. GRB 250901A - SVOM/ECLAIRs refined analysis
  47. EP250905a: Einstein Probe detection of an X-ray transient
  48. GRB250904A: Liverpool Telescope upper limits
  49. GRB 250905A: Enhanced Swift-XRT position
  50. GRB 250904A: Swift/UVOT Detection
  51. GRB 250903A: Swift/UVOT detection
  52. EP detected a brightening of LMXB 1ES 1735-26.9
  53. GRB 250905A: KAIT optical upper limit
  54. GRB 250905A: Swift detection of a burst
  55. GRB 250904A: Enhanced Swift-XRT position
  56. IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
  57. GRB 250904A: TRT optical counterpart detection
  58. GRB 250904A: Swift detection of a burst
  59. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  60. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  61. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  62. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  63. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  64. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  65. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  66. GRB 250903A: LCO optical observation
  67. GRB 250903A: LCO optical afterglow detection
  68. GRB 250903A: SVOM/VT optical confirmation with VHF data
  69. EP250901a: Mondy, Assy and SAO RAS optical limits
  70. GRB 250903A: TRT optical counterpart detection
  71. GRB 250903A: SVOM detection of a burst
  72. EP250903a: TRT optical observations
  73. EP250903a: Einstein Probe detection of an X-ray transient
  74. EP 250827B: Detection of supernova counterpart by LCO.
  75. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  76. GRB 250902B: SVOM/GRM observation
  77. EP250827b: SVOM/VT observation of AT 2025wkm
  78. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  79. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  80. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  81. GRB 250901A: Swift/UVOT Upper Limit
  82. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  83. GRB 250830B: Swift-XRT afterglow detection
  84. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  85. GRB 250902A: SVOM/GRM observation
  86. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  87. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  88. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  89. GRB 250901A: SVOM/VT optical afterglow with VHF data
  90. GRB 250901A: Swift-XRT afterglow detection
  91. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  92. GRB 250901A: LCO optical upper limit
  93. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  94. EP250831a: NOT optical observations and tentative afterglow candidate
  95. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  96. GRB 250901A: SVOM detection of a burst
  97. EP250901a: Mephisto optical upper limits
  98. GRB 250830C: AstroSat CZTI detection of a long burst
  99. EP250901a: Einstein Probe detection of an X-ray transient
  100. EP250831a: EP-WXT detection of a fast X-ray transient

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