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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"

21206 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 250818B: MeerKAT Detection
  8. GRB 250823A: Enhanced Swift-XRT position
  9. GRB 250823A: LCOGT Optical Detection
  10. GRB 250823A: Liverpool Telescope optical detection
  11. GRB 250823A: Swift detection of a burst
  12. Konus-Wind detection of GRB 250821B
  13. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  14. LIGO/Virgo/KAGRA S250818k: J-GEM follow-up observation for AT2025ulz
  15. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  16. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  17. GRB 250821A: Kilonova-Catcher optical upper limits
  18. GRB 250821A: VLT/FORS2 Optical Observation
  19. GRB 250821B: SVOM/GRM observation
  20. EP250821a: SVOM/VT optical observation
  21. GRB 250821A: NOT z-band upper limit
  22. GRB 250821A: KAIT optical upper limit
  23. LIGO/Virgo/KAGRA S250818k: Continued fading and reddening of AT2025ulz from Keck/LRIS imaging observations
  24. GRB 250821A: Enhanced Swift-XRT position
  25. GRB 250821A: Swift/UVOT Upper Limits
  26. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  27. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  28. GRB 250821A: LCOGT Optical Upper Limits
  29. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  30. GRB 250821A: Swift detection of a burst
  31. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  32. EP250821a: Einstein Probe detection of an X-ray transient
  33. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  34. LIGO/Virgo/KAGRA S250818k: WINTER J-band observations of AT 2025ulz
  35. LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz
  36. GRB 250814A: Swift/UVOT Upper Limits
  37. GRB 250813B: Swift/UVOT Upper Limit
  38. IPN triangulation of GRB 250816A (short)
  39. IPN triangulation of GRB 250814C (short)
  40. IPN triangulation of GRB 250804B (short)
  41. GRB 250818B: Kilonova-Catcher optical afterglow detection
  42. LIGO/Virgo/KAGRA S250818k: AstroSat CZTI non-detection and upper limits
  43. GRB 250818B: Liverpool Telescope optical detections
  44. LIGO/Virgo/KAGRA S250818k: Updated Sky localization and EM Bright Classification
  45. GRB 250818A: AstroSat CZTI detection
  46. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  47. GRB 250818B: Swift/UVOT Detection
  48. GRB 250818B: SAO RAS optical observations
  49. GRB 250818B: KAIT optical observations
  50. GRB 250818A: Swift/UVOT Upper Limits
  51. GRB 250818A: Enhanced Swift-XRT position
  52. GRB 250813B: SVOM/ECLAIRs refined analysis
  53. GRB 250818A: Fermi GBM Observation
  54. LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations
  55. GRB 250814A: Further GRAWITA TNG NIR observations
  56. GRB 250818B: SVOM detection of a short burst
  57. LIGO/Virgo/KAGRA S250818t: Identification of a GW compact binary merger candidate
  58. GRB 250818A: Swift detection of a burst
  59. GRB 250816A: SVOM/GRM observation of a short burst
  60. SVOM/sb25081602: detection of a likely X-ray transient
  61. GRB 250813B: Liverpool Telescope optical upper limits
  62. GRB 250814A: Further COLIBRÍ optical upper limit
  63. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  64. GRB 250814A: GRAWITA TNG NIR observations
  65. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  66. GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  67. GRB250814A: TRT optical upper limits
  68. GRB 250814B: SVOM/GRM observation
  69. GRB 250813B: SVOM/GRM observation
  70. GRB 250814A: P200/WIRC observations of the afterglow candidate
  71. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  72. GRB 250814A: KAIT optical upper limit
  73. GRB 250814A: Swift-XRT refined Analysis
  74. GRB 250814A: Possible afterglow candidate from P200/WIRC
  75. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  76. GRB 250814A: J-band upper limit from WINTER
  77. GRB 250813B: NOT observations of the optical afterglow
  78. GRB 250814A: COLIBRÍ optical upper limit
  79. GRB 250813A: AstroSat CZTI detection
  80. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  81. GRB 250814A: DDOTI Optical Upper Limit
  82. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  83. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  84. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  85. GRB 250813B: SVOM detection of a bright long burst
  86. EP250812a: Nickel optical upper limit
  87. EP250812a: NOT, NTT, and GS observations
  88. GRB 250812A: Swift/UVOT Detection
  89. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  90. EP250812a: Liverpool Telescope upper limits
  91. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  92. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  93. EP 250812a: GOTO optical upper limit
  94. GRB 250812A: Kilonova-Catcher optical afterglow detection
  95. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  96. EP250812a: Einstein Probe detection of an X-ray transient
  97. GRB 250812A: Swift-XRT afterglow detection
  98. GRB 250812A: TRT likely optical counterpart detection
  99. LIGO/Virgo/KAGRA S250810ck: Updated Sky localization and EM Bright Classification
  100. GRB 250809A: Swift/UVOT Detection

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