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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').
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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.

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

19551 results found.

  1. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  2. EP250821a: MeerKAT radio counterpart
  3. GRB 250823A: COLIBRÍ optical observations
  4. GRB 250823A: SVOM/VT optical observation
  5. GRB 250823A: Swift/UVOT Detection
  6. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  7. GRB 250823A: Enhanced Swift-XRT position
  8. GRB 250823A: LCOGT Optical Detection
  9. GRB 250823A: Swift detection of a burst
  10. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  11. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  12. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  13. GRB 250821A: Kilonova-Catcher optical upper limits
  14. GRB 250821A: VLT/FORS2 Optical Observation
  15. GRB 250821B: SVOM/GRM observation
  16. EP250821a: SVOM/VT optical observation
  17. GRB 250821A: NOT z-band upper limit
  18. GRB 250821A: KAIT optical upper limit
  19. GRB 250821A: Enhanced Swift-XRT position
  20. GRB 250821A: Swift/UVOT Upper Limits
  21. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  22. GRB 250821A: LCOGT Optical Upper Limits
  23. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  24. GRB 250821A: Swift detection of a burst
  25. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  26. EP250821a: Einstein Probe detection of an X-ray transient
  27. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  28. LIGO/Virgo/KAGRA S250818k: WINTER J-band observations of AT 2025ulz
  29. LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz
  30. GRB 250814A: Swift/UVOT Upper Limits
  31. GRB 250813B: Swift/UVOT Upper Limit
  32. IPN triangulation of GRB 250816A (short)
  33. IPN triangulation of GRB 250814C (short)
  34. IPN triangulation of GRB 250804B (short)
  35. GRB 250818B: Kilonova-Catcher optical afterglow detection
  36. GRB 250818B: Swift/UVOT Detection
  37. GRB 250818B: SAO RAS optical observations
  38. GRB 250818B: KAIT optical observations
  39. GRB 250818A: Swift/UVOT Upper Limits
  40. GRB 250818A: Enhanced Swift-XRT position
  41. LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations
  42. GRB 250814A: Further GRAWITA TNG NIR observations
  43. GRB 250818B: SVOM detection of a short burst
  44. GRB 250818A: Swift detection of a burst
  45. GRB 250816A: SVOM/GRM observation of a short burst
  46. GRB 250813B: Liverpool Telescope optical upper limits
  47. GRB 250814A: Further COLIBRÍ optical upper limit
  48. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  49. GRB 250814A: GRAWITA TNG NIR observations
  50. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  51. GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  52. GRB250814A: TRT optical upper limits
  53. GRB 250814B: SVOM/GRM observation
  54. GRB 250814A: P200/WIRC observations of the afterglow candidate
  55. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  56. GRB 250814A: KAIT optical upper limit
  57. GRB 250814A: Swift-XRT refined Analysis
  58. GRB 250814A: Possible afterglow candidate from P200/WIRC
  59. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  60. GRB 250814A: J-band upper limit from WINTER
  61. GRB 250813B: NOT observations of the optical afterglow
  62. GRB 250814A: COLIBRÍ optical upper limit
  63. GRB 250813A: AstroSat CZTI detection
  64. GRB 250814A: DDOTI Optical Upper Limit
  65. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  66. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  67. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  68. GRB 250813B: SVOM detection of a bright long burst
  69. EP250812a: Nickel optical upper limit
  70. EP250812a: NOT, NTT, and GS observations
  71. GRB 250812A: Swift/UVOT Detection
  72. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  73. EP250812a: Liverpool Telescope upper limits
  74. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  75. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  76. GRB 250812A: Swift ToO observations
  77. EP 250812a: GOTO optical upper limit
  78. GRB 250812A: Kilonova-Catcher optical afterglow detection
  79. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  80. EP250812a: Einstein Probe detection of an X-ray transient
  81. GRB 250812A: Swift-XRT afterglow detection
  82. GRB 250812A: TRT likely optical counterpart detection
  83. GRB 250812A: SVOM detection of a faint long burst
  84. GRB 250809A: Swift/UVOT Detection
  85. Corrected Swift-XRT Refined Analysis of GRB 250809A
  86. GRB 250809A: Swift-XRT refined Analysis
  87. GRB 250809A: LCOGT Optical Upper Limits
  88. GRB 250808A: VLT X-shooter candidate counterpart
  89. GRB 250809A: Swift detection of a gamma ray burst
  90. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  91. GRB 250808A: Fermi GBM Final Real-time Localization
  92. GRB 250807B: Swift/UVOT Detection
  93. GRB 250807B: Kilonova-Catcher optical afterglow detection
  94. GRB 250807A: Swift/UVOT Detection
  95. GRB 250806A: SVOM/ECLAIRs refined analysis
  96. EP250807a: NTT z-band optical upper limit
  97. GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
  98. GRB 250807A: SVOM/GRM observation
  99. EP250807a: EP-WXT detection of a fast X-ray transient
  100. EP 250807.979: GOTO optical upper limit

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