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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').
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"

28286 results found.

  1. GRB 250823A: Fermi GBM Observation
  2. GRB 250823A: Enhanced Swift-XRT position
  3. GRB 250823A: LCOGT Optical Detection
  4. GRB 250823A: Swift detection of a burst
  5. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  6. LIGO/Virgo/KAGRA S250818k: JinShan optical observations of AT2025ulz
  7. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  8. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  9. GRB 250806A: Gemini observations of host galaxy candidate
  10. GRB 250821A: Kilonova-Catcher optical upper limits
  11. EP250821a: Swift/XRT counterpart fading
  12. GRB 250821A: Swift-BAT refined analysis
  13. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
  14. LIGO/Virgo/KAGRA S250818k: NOT optical observations of AT2025ulz
  15. GRB 250821A: VLT/FORS2 Optical Observation
  16. GRB 250821B: SVOM/GRM observation
  17. EP250821a: SVOM/VT optical observation
  18. GRB 250821A: NOT z-band upper limit
  19. GRB 250821A: KAIT optical upper limit
  20. GRB 250821A: Swift-XRT refined Analysis
  21. GRB 250821B: Fermi GBM Detection
  22. GRB 250821B: BALROG localization (Fermi Trigger / GRB 250821672)
  23. GRB 250821A: Enhanced Swift-XRT position
  24. GRB 250821A: Swift/UVOT Upper Limits
  25. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  26. EP250821a: Swift XRT and UVOT counterpart detection
  27. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and 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. EP250821a: Einstein Probe detection of an X-ray transient
  34. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  35. LIGO/Virgo/KAGRA S250818k: WINTER J-band observations of AT 2025ulz
  36. LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz
  37. GRB 250814A: Swift/UVOT Upper Limits
  38. GRB 250813B: Swift/UVOT Upper Limit
  39. IPN triangulation of GRB 250816A (short)
  40. IPN triangulation of GRB 250814C (short)
  41. IPN triangulation of GRB 250804B (short)
  42. GRB 250818B: Kilonova-Catcher optical afterglow detection
  43. LIGO/Virgo/KAGRA S250818k: AstroSat CZTI non-detection and upper limits
  44. LIGO/Virgo/KAGRA S250818k: Upper limits from Fermi-GBM Observations
  45. LIGO/Virgo/KAGRA S250818k: Updated Sky localization and EM Bright Classification
  46. LIGO/Virgo/KAGRA S250818k: Pan-STARRS pre-detection limits for AT2025ulz
  47. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  48. GRB 250818B: Swift/UVOT Detection
  49. GRB 250818B: optical afterglow detection with Lesedi (GOTO25fzq)
  50. GRB 250818B: SAO RAS optical observations
  51. GRB 250818A: Swift-XRT refined Analysis
  52. GRB 250818B: EP-FXT counterpart detection
  53. GRB 250818A: Swift-BAT refined analysis
  54. GRB 250818B: KAIT optical observations
  55. GRB 250818A: Swift/UVOT Upper Limits
  56. LIGO/Virgo/KAGRA S250818t: Updated Sky localization
  57. GRB 250818A: Enhanced Swift-XRT position
  58. GRB 250813B: SVOM/ECLAIRs refined analysis
  59. GRB 250818A: Fermi GBM Observation
  60. LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations
  61. GRB 250814A: Further GRAWITA TNG NIR observations
  62. GRB 250818B: Swift-XRT afterglow detection
  63. GRB 250818B: SVOM detection of a short burst
  64. LIGO/Virgo/KAGRA S250818t: Identification of a GW compact binary merger candidate
  65. GRB 250818A: Swift detection of a burst
  66. sb25081602: Swift-XRT observations
  67. GRB 250816A: SVOM/GRM observation of a short burst
  68. GRB 250814A: Swift-BAT refined analysis
  69. GRB 250813B: Liverpool Telescope optical upper limits
  70. GRB 250814A: Further COLIBRÍ optical upper limit
  71. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  72. GRB 250814A: GRAWITA TNG NIR observations
  73. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  74. GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  75. GRB250814A: TRT optical upper limits
  76. GRB 250814B: SVOM/GRM observation
  77. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  78. GRB 250813B: SVOM/GRM observation
  79. GRB 250814A: P200/WIRC observations of the afterglow candidate
  80. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  81. GRB 250814A: KAIT optical upper limit
  82. GRB 250814A: Swift-XRT refined Analysis
  83. GRB 240814A: Fermi GBM Observation
  84. GRB 250814A: Possible afterglow candidate from P200/WIRC
  85. GRB 250813B: Fermi GBM Observation
  86. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  87. GRB 250814A: J-band upper limit from WINTER
  88. IceCube-250813A: Upper limits from a search for additional neutrino events in IceCube
  89. GRB 250813B: NOT observations of the optical afterglow
  90. GRB 250814A: COLIBRÍ optical upper limit
  91. GRB 250813A: AstroSat CZTI detection
  92. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  93. GRB 250814A: DDOTI Optical Upper Limit
  94. GRB 250813B: EP-FXT counterpart detection
  95. Fermi-LAT Gamma-ray Observations of IceCube-250813A
  96. GRB 250813B: Swift-XRT afterglow detection
  97. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  98. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  99. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  100. GRB 250813B: SVOM detection of a bright long burst

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