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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. 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"

21803 results found.

  1. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  2. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  3. EP250911a: COLIBRÍ optical observations
  4. EP250911a: Einstein Probe detection of an X-ray transient
  5. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  6. GRB 250903A: SVOM/ECLAIRs refined analysis
  7. GRB 250911A: Enhanced Swift-XRT position
  8. GRB 250911A: Swift-XRT observations
  9. GRB 250911A: COLIBRÍ optical counterpart candidate
  10. GRB 250911A: Swift detection of a burst
  11. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  12. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  13. GRB 250910A: SVOM/VT optical upper limit
  14. GRB 250910A: LCO optical upper limit
  15. EP250908b/EP#01709240653: Swift/UVOT Detection
  16. EP#01709240653: Swift-XRT observations
  17. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  18. EP250908c: SVOM/VT optical observation
  19. EP250908c: VLT/FORS2 optical counterpart identification
  20. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  21. EP250908b: SVOM/VT optical candidate
  22. EP250908c: Einstein Probe detection of an X-ray transient
  23. EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation
  24. EP#01709240652 (possibly EP250908a): FTW optical and NIR observations
  25. LIGO/Virgo/KAGRA S250908y: Identification of a GW compact binary merger candidate
  26. GRB 250903A: Swift-XRT afterglow detection
  27. LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
  28. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  29. EP250905a: Liverpool Telescope i-band upper limits
  30. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  31. EP250905a: Liverpool Telescope observations
  32. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  33. EP250905b: EP-WXT detection of a fast X-ray transient
  34. EP250905a: JinShan likely optical counterpart detection
  35. GRB 250905A: Swift/UVOT Upper Limits
  36. GRB 250901A - SVOM/ECLAIRs refined analysis
  37. EP250905a: Einstein Probe detection of an X-ray transient
  38. GRB250904A: Liverpool Telescope upper limits
  39. GRB 250905A: Enhanced Swift-XRT position
  40. GRB 250904A: Swift/UVOT Detection
  41. GRB 250903A: Swift/UVOT detection
  42. GRB 250904A: Swift-XRT refined Analysis
  43. EP detected a brightening of LMXB 1ES 1735-26.9
  44. GRB 250905A: KAIT optical upper limit
  45. GRB 250905A: Swift detection of a burst
  46. GRB 250904A: Enhanced Swift-XRT position
  47. GRB 250904A: TRT optical counterpart detection
  48. GRB 250904A: Swift detection of a burst
  49. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  50. GRB 250903A: Swift-XRT observations
  51. EP250903a: Swift-XRT observations
  52. EP#01709201209: Swift-XRT observations
  53. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  54. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  55. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  56. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  57. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  58. GRB 250903A: LCO optical observation
  59. GRB 250903A: LCO optical afterglow detection
  60. GRB 250903A: SVOM/VT optical confirmation with VHF data
  61. EP250901a: Mondy, Assy and SAO RAS optical limits
  62. Subject GRB 250903A: SVOM/MXT afterglow detection
  63. EP250903a: LCO candidate counterpart discovery
  64. GRB 250903A: TRT optical counterpart detection
  65. EP250903a: TRT optical observations
  66. EP250903a: Einstein Probe detection of an X-ray transient
  67. EP 250827B: Detection of supernova counterpart by LCO.
  68. EP/WXT01709201159: GOTO optical follow-up
  69. GRB 250902B: SVOM/GRM observation
  70. EP250827b: SVOM/VT observation of AT 2025wkm
  71. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  72. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  73. GRB 250901A: Swift/UVOT Upper Limit
  74. GRB 250830B: Swift-XRT afterglow detection
  75. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  76. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  77. GRB 250902A: SVOM/GRM observation
  78. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  79. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  80. GRB 250901A: SVOM/VT optical afterglow with VHF data
  81. GRB 250901A: Swift-XRT afterglow detection
  82. EP250901a: Swift-XRT observations
  83. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  84. GRB 250901A: LCO optical upper limit
  85. EP250827b: Swift observations of AT 2025wkm
  86. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  87. EP250831a: NOT optical observations and tentative afterglow candidate
  88. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  89. GRB 250901A: SVOM detection of a burst
  90. EP250901a: Mephisto optical upper limits
  91. EP250901a: Einstein Probe detection of an X-ray transient
  92. EP250831a: Swift-XRT observations
  93. EP250831a: EP-WXT detection of a fast X-ray transient
  94. GRB 250831A: Swift-XRT counterpart detection
  95. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  96. GRB 250831A: SVOM/VT upper limit with VHF data
  97. GRB 250831A: SVOM detection of a soft burst
  98. GRB 250830B: Swift-XRT observations
  99. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  100. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations

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