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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.

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

21769 results found.

  1. IPN triangulation of GRB 250816A (short)
  2. IPN triangulation of GRB 250814C (short)
  3. IPN triangulation of GRB 250804B (short)
  4. GRB 250818B: Kilonova-Catcher optical afterglow detection
  5. LIGO/Virgo/KAGRA S250818k: AstroSat CZTI non-detection and upper limits
  6. GRB 250818B: Liverpool Telescope optical detections
  7. LIGO/Virgo/KAGRA S250818k: Updated Sky localization and EM Bright Classification
  8. GRB 250818A: AstroSat CZTI detection
  9. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  10. GRB 250818B: Swift/UVOT Detection
  11. GRB 250818B: SAO RAS optical observations
  12. GRB 250818B: KAIT optical observations
  13. GRB 250818A: Swift/UVOT Upper Limits
  14. GRB 250818A: Enhanced Swift-XRT position
  15. GRB 250813B: SVOM/ECLAIRs refined analysis
  16. GRB 250818A: Fermi GBM Observation
  17. LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations
  18. GRB 250814A: Further GRAWITA TNG NIR observations
  19. GRB 250818B: SVOM detection of a short burst
  20. LIGO/Virgo/KAGRA S250818t: Identification of a GW compact binary merger candidate
  21. GRB 250818A: Swift detection of a burst
  22. GRB 250816A: SVOM/GRM observation of a short burst
  23. SVOM/sb25081602: detection of a likely X-ray transient
  24. GRB 250813B: Liverpool Telescope optical upper limits
  25. GRB 250814A: Further COLIBRÍ optical upper limit
  26. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  27. GRB 250814A: GRAWITA TNG NIR observations
  28. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  29. GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  30. GRB250814A: TRT optical upper limits
  31. GRB 250814B: SVOM/GRM observation
  32. GRB 250813B: SVOM/GRM observation
  33. GRB 250814A: P200/WIRC observations of the afterglow candidate
  34. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  35. GRB 250814A: KAIT optical upper limit
  36. GRB 250814A: Swift-XRT refined Analysis
  37. GRB 250814A: Possible afterglow candidate from P200/WIRC
  38. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  39. GRB 250814A: J-band upper limit from WINTER
  40. GRB 250813B: NOT observations of the optical afterglow
  41. GRB 250814A: COLIBRÍ optical upper limit
  42. GRB 250813A: AstroSat CZTI detection
  43. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  44. GRB 250814A: DDOTI Optical Upper Limit
  45. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  46. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  47. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  48. GRB 250813B: SVOM detection of a bright long burst
  49. EP250812a: Nickel optical upper limit
  50. EP250812a: NOT, NTT, and GS observations
  51. GRB 250812A: Swift/UVOT Detection
  52. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  53. EP250812a: Liverpool Telescope upper limits
  54. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  55. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  56. EP 250812a: GOTO optical upper limit
  57. GRB 250812A: Kilonova-Catcher optical afterglow detection
  58. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  59. EP250812a: Einstein Probe detection of an X-ray transient
  60. GRB 250812A: Swift-XRT afterglow detection
  61. GRB 250812A: TRT likely optical counterpart detection
  62. LIGO/Virgo/KAGRA S250810ck: Updated Sky localization and EM Bright Classification
  63. GRB 250809A: Swift/UVOT Detection
  64. LIGO/Virgo/KAGRA S250810ck: Identification of a GW compact binary merger candidate
  65. GRB 250809A: Swift-XRT refined Analysis
  66. GRB 250809A: LCOGT Optical Upper Limits
  67. GRB 250808A: VLT X-shooter candidate counterpart
  68. GRB 250809A: Swift detection of a gamma ray burst
  69. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  70. GRB 250808A: SVOM detection of a long burst
  71. Konus-Wind detection of GRB 250807A
  72. GRB 250807B: Swift/UVOT Detection
  73. GRB 250807B: Kilonova-Catcher optical afterglow detection
  74. GRB 250807A: Swift/UVOT Detection
  75. GRB 250807A: Swift-XRT refined Analysis
  76. GRB 250806A: SVOM/MXT refined analysis
  77. EP250807a: NTT z-band optical upper limit
  78. GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
  79. GRB 250807A: SVOM/GRM observation
  80. GRB 250807A: AstroSat CZTI detection of bright long burst
  81. EP250807a: EP-WXT detection of a fast X-ray transient
  82. EP 250807.979: GOTO optical upper limit
  83. EP250807a: COLIBRÍ optical upper limit
  84. GRB 250807B: Enhanced Swift-XRT position
  85. GRB 250807A: Enhanced Swift-XRT position
  86. GRB 250807B: Swift detection of a burst with an optical counterpart.
  87. GRB 250805A: Kilonova-Catcher optical upper limits
  88. GRB 250805A: Swift/UVOT Upper Limits
  89. GRB 250806A: Swift/UVOT U-band detection
  90. EP250806a: Liverpool telescope optical upper limit
  91. GRB 250807A: Swift detection of a burst with an optical counterpart
  92. EP250806a: refined analysis of the EP-WXT and EP-FXT observations
  93. EP250806a: SVOM /VT optical candidate
  94. GRB 250806A: J-band upper limit from WINTER
  95. GRB 250806A: KAIT optical upper limit
  96. GRB 250806A: Swift-XRT counterpart detection
  97. EP250806a: COLIBRÍ optical upper limit
  98. GRB 250806A: Kilonova-Catcher optical upper limits
  99. EP250806a: Einstein Probe detection of an X-ray transient
  100. GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit

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