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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').
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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"

18496 results found.

  1. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  2. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  3. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  4. GRB 250821B: AstroSat CZTI detection
  5. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  6. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  7. EP250821a: MeerKAT radio counterpart
  8. The EP-WXT trigger 01709200707 is likely a flaring star
  9. GRB 250823A: COLIBRÍ optical observations
  10. The EP-WXT trigger 01709200706 is likely a flaring star
  11. GRB 250823A: SVOM/VT optical observation
  12. GRB 250823A: Swift/UVOT Detection
  13. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  14. GRB 250823A: Enhanced Swift-XRT position
  15. GRB 250823A: LCOGT Optical Detection
  16. GRB 250823A: Swift detection of a burst
  17. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  18. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  19. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  20. GRB 250821A: Kilonova-Catcher optical upper limits
  21. GRB 250821A: VLT/FORS2 Optical Observation
  22. GRB 250821B: SVOM/GRM observation
  23. EP250821a: SVOM/VT optical observation
  24. GRB 250821A: NOT z-band upper limit
  25. GRB 250821A: KAIT optical upper limit
  26. GRB 250821A: Enhanced Swift-XRT position
  27. GRB 250821A: Swift/UVOT Upper Limits
  28. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  29. GRB 250821A: LCOGT Optical Upper Limits
  30. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  31. GRB 250821A: Swift detection of a burst
  32. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  33. LIGO/Virgo/KAGRA S250818k: EP/FXT observation of AT 2025ulz
  34. EP250821a: Einstein Probe detection of an X-ray transient
  35. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  36. LIGO/Virgo/KAGRA S250818k: WINTER J-band observations of AT 2025ulz
  37. LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz
  38. GRB 250814A: Swift/UVOT Upper Limits
  39. GRB 250813B: Swift/UVOT Upper Limit
  40. IPN triangulation of GRB 250816A (short)
  41. IPN triangulation of GRB 250814C (short)
  42. IPN triangulation of GRB 250804B (short)
  43. GRB 250818B: Kilonova-Catcher optical afterglow detection
  44. GRB 250818B: Swift/UVOT Detection
  45. GRB 250818B: SAO RAS optical observations
  46. GRB 250818B: EP-FXT counterpart detection
  47. GRB 250818B: KAIT optical observations
  48. GRB 250818A: Swift/UVOT Upper Limits
  49. GRB 250818A: Enhanced Swift-XRT position
  50. LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations
  51. GRB 250814A: Further GRAWITA TNG NIR observations
  52. GRB 250818A: Swift detection of a burst
  53. GRB 250816A: SVOM/GRM observation of a short burst
  54. GRB 250813B: Liverpool Telescope optical upper limits
  55. GRB 250814A: Further COLIBRÍ optical upper limit
  56. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  57. GRB 250814A: GRAWITA TNG NIR observations
  58. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  59. GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  60. GRB250814A: TRT optical upper limits
  61. GRB 250814B: SVOM/GRM observation
  62. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  63. GRB 250814A: P200/WIRC observations of the afterglow candidate
  64. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  65. GRB 250814A: KAIT optical upper limit
  66. GRB 250814A: Swift-XRT refined Analysis
  67. GRB 250814A: Possible afterglow candidate from P200/WIRC
  68. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  69. GRB 250814A: J-band upper limit from WINTER
  70. GRB 250813B: NOT observations of the optical afterglow
  71. GRB 250814A: COLIBRÍ optical upper limit
  72. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  73. GRB 250814A: DDOTI Optical Upper Limit
  74. GRB 250813B: EP-FXT counterpart detection
  75. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  76. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  77. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  78. GRB 250813B: SVOM detection of a bright long burst
  79. EP250812a: Nickel optical upper limit
  80. EP250812a: NOT, NTT, and GS observations
  81. GRB 250812A: Swift/UVOT Detection
  82. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  83. EP250812a: Liverpool Telescope upper limits
  84. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  85. GRB 250812A: EP-FXT counterpart detection
  86. EP 250812a: GOTO optical upper limit
  87. GRB 250812A: Kilonova-Catcher optical afterglow detection
  88. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  89. EP250812a: Einstein Probe detection of an X-ray transient
  90. GRB 250812A: Swift-XRT afterglow detection
  91. GRB 250812A: TRT likely optical counterpart detection
  92. GRB 250809A: Swift/UVOT Detection
  93. LIGO/Virgo/KAGRA S250810ck: Identification of a GW compact binary merger candidate
  94. GRB 250809A: Swift-XRT refined Analysis
  95. EP250807a: EP-FXT follow-up observation upper limit
  96. GRB 250809A: LCOGT Optical Upper Limits
  97. GRB 250808A: VLT X-shooter candidate counterpart
  98. GRB 250809A: Swift detection of a gamma ray burst
  99. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  100. GRB 250808A: Fermi GBM Observation

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