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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"

21772 results found.

  1. LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz
  2. GRB 250814A: Swift/UVOT Upper Limits
  3. GRB 250813B: Swift/UVOT Upper Limit
  4. IPN triangulation of GRB 250816A (short)
  5. IPN triangulation of GRB 250814C (short)
  6. IPN triangulation of GRB 250804B (short)
  7. GRB 250818B: Kilonova-Catcher optical afterglow detection
  8. LIGO/Virgo/KAGRA S250818k: AstroSat CZTI non-detection and upper limits
  9. GRB 250818B: Liverpool Telescope optical detections
  10. LIGO/Virgo/KAGRA S250818k: Updated Sky localization and EM Bright Classification
  11. GRB 250818A: AstroSat CZTI detection
  12. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  13. GRB 250818B: Swift/UVOT Detection
  14. GRB 250818B: SAO RAS optical observations
  15. GRB 250818B: KAIT optical observations
  16. GRB 250818A: Swift/UVOT Upper Limits
  17. GRB 250818A: Enhanced Swift-XRT position
  18. GRB 250813B: SVOM/ECLAIRs refined analysis
  19. GRB 250818A: Fermi GBM Observation
  20. LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations
  21. GRB 250814A: Further GRAWITA TNG NIR observations
  22. GRB 250818B: SVOM detection of a short burst
  23. LIGO/Virgo/KAGRA S250818t: Identification of a GW compact binary merger candidate
  24. GRB 250818A: Swift detection of a burst
  25. GRB 250816A: SVOM/GRM observation of a short burst
  26. SVOM/sb25081602: detection of a likely X-ray transient
  27. GRB 250813B: Liverpool Telescope optical upper limits
  28. GRB 250814A: Further COLIBRÍ optical upper limit
  29. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  30. GRB 250814A: GRAWITA TNG NIR observations
  31. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  32. GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  33. GRB250814A: TRT optical upper limits
  34. GRB 250814B: SVOM/GRM observation
  35. GRB 250813B: SVOM/GRM observation
  36. GRB 250814A: P200/WIRC observations of the afterglow candidate
  37. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  38. GRB 250814A: KAIT optical upper limit
  39. GRB 250814A: Swift-XRT refined Analysis
  40. GRB 250814A: Possible afterglow candidate from P200/WIRC
  41. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  42. GRB 250814A: J-band upper limit from WINTER
  43. GRB 250813B: NOT observations of the optical afterglow
  44. GRB 250814A: COLIBRÍ optical upper limit
  45. GRB 250813A: AstroSat CZTI detection
  46. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  47. GRB 250814A: DDOTI Optical Upper Limit
  48. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  49. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  50. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  51. GRB 250813B: SVOM detection of a bright long burst
  52. EP250812a: Nickel optical upper limit
  53. EP250812a: NOT, NTT, and GS observations
  54. GRB 250812A: Swift/UVOT Detection
  55. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  56. EP250812a: Liverpool Telescope upper limits
  57. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  58. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  59. EP 250812a: GOTO optical upper limit
  60. GRB 250812A: Kilonova-Catcher optical afterglow detection
  61. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  62. EP250812a: Einstein Probe detection of an X-ray transient
  63. GRB 250812A: Swift-XRT afterglow detection
  64. GRB 250812A: TRT likely optical counterpart detection
  65. LIGO/Virgo/KAGRA S250810ck: Updated Sky localization and EM Bright Classification
  66. GRB 250809A: Swift/UVOT Detection
  67. LIGO/Virgo/KAGRA S250810ck: Identification of a GW compact binary merger candidate
  68. GRB 250809A: Swift-XRT refined Analysis
  69. GRB 250809A: LCOGT Optical Upper Limits
  70. GRB 250808A: VLT X-shooter candidate counterpart
  71. GRB 250809A: Swift detection of a gamma ray burst
  72. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  73. GRB 250808A: SVOM detection of a long burst
  74. Konus-Wind detection of GRB 250807A
  75. GRB 250807B: Swift/UVOT Detection
  76. GRB 250807B: Kilonova-Catcher optical afterglow detection
  77. GRB 250807A: Swift/UVOT Detection
  78. GRB 250807A: Swift-XRT refined Analysis
  79. GRB 250806A: SVOM/MXT refined analysis
  80. EP250807a: NTT z-band optical upper limit
  81. GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
  82. GRB 250807A: SVOM/GRM observation
  83. GRB 250807A: AstroSat CZTI detection of bright long burst
  84. EP250807a: EP-WXT detection of a fast X-ray transient
  85. EP 250807.979: GOTO optical upper limit
  86. EP250807a: COLIBRÍ optical upper limit
  87. GRB 250807B: Enhanced Swift-XRT position
  88. GRB 250807A: Enhanced Swift-XRT position
  89. GRB 250807B: Swift detection of a burst with an optical counterpart.
  90. GRB 250805A: Kilonova-Catcher optical upper limits
  91. GRB 250805A: Swift/UVOT Upper Limits
  92. GRB 250806A: Swift/UVOT U-band detection
  93. EP250806a: Liverpool telescope optical upper limit
  94. GRB 250807A: Swift detection of a burst with an optical counterpart
  95. EP250806a: refined analysis of the EP-WXT and EP-FXT observations
  96. EP250806a: SVOM /VT optical candidate
  97. GRB 250806A: J-band upper limit from WINTER
  98. GRB 250806A: KAIT optical upper limit
  99. GRB 250806A: Swift-XRT counterpart detection
  100. EP250806a: COLIBRÍ optical upper limit

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