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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"

28049 results found.

  1. GRB 250830C: GECAM-B detection
  2. EP250901a: Einstein Probe detection of an X-ray transient
  3. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  4. EP250831a: Swift-XRT observations
  5. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  6. EP250831a: EP-WXT detection of a fast X-ray transient
  7. GRB 250831A: Swift-XRT counterpart detection
  8. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  9. GRB 250831A: SVOM/VT upper limit with VHF data
  10. GRB 250831A: SVOM detection of a soft burst
  11. GRB 250830B: Swift-XRT observations
  12. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  13. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  14. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  15. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  16. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  17. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  18. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  19. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  20. GRB 250830B: MAXI/GSC detection
  21. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  22. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  23. GRB 250828B: Swift-BAT refined analysis
  24. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  25. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  26. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  27. EP250828a: Optical counterpart detection with Kinder observations
  28. EP250828a: Liverpool Telescope upper limits
  29. EP250828a: Global MASTER-Net observations report
  30. EP-WXT trigger 01709200800 : KAIT optical observations
  31. EP250828a: KAIT optical upper limit
  32. EP250827a: Swift/UVOT Detection
  33. EP250828a: NOT optical counterpart confirmation
  34. EP250828a: SVOM/VT optical candidate
  35. EP250828a: Seimei/TriCCS optical counterpart detection
  36. EP250828a: Optical upper limit with Kinder observations
  37. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  38. EP250827a: LCO observations show fading optical counterpart
  39. EP250828a: Einstein Probe detection of an X-ray transient
  40. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  41. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  42. EP250827a: confirmation of optical rebrightening with LCO
  43. GRB 250826A: SVOM/GRM observation
  44. EP250827A: An optical rebrightening was detected by LCO.
  45. EP250827a: Swift-XRT counterpart detection
  46. LIGO/Virgo/KAGRA S250827l: Updated Sky localization
  47. EP250827a: TRT optical observations
  48. EP250827a: Gemini-South redshift z = 1.613
  49. EP250827a: Einstein Probe detection of an X-ray transient
  50. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  51. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  52. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  53. Fermi GRB 250824B: Global MASTER-Net observations report
  54. LIGO/Virgo/KAGRA S250818k: nature of the AT2025ulz/ZTF25abjmnnps OT
  55. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  56. GRB 250823A: Swift-BAT refined analysis
  57. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  58. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  59. GRB 250823A: Swift-XRT refined Analysis
  60. EP250821a: MeerKAT radio counterpart
  61. GRB 250823A: COLIBRÍ optical observations
  62. GRB 250823A: SVOM/VT optical observation
  63. GRB 250823A: Swift/UVOT Detection
  64. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  65. GRB 250823A: Fermi GBM Observation
  66. GRB 250823A: Enhanced Swift-XRT position
  67. GRB 250823A: LCOGT Optical Detection
  68. GRB 250823A: Swift detection of a burst
  69. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  70. LIGO/Virgo/KAGRA S250818k: JinShan optical observations of AT2025ulz
  71. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  72. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  73. GRB 250806A: Gemini observations of host galaxy candidate
  74. GRB 250821A: Kilonova-Catcher optical upper limits
  75. EP250821a: Swift/XRT counterpart fading
  76. GRB 250821A: Swift-BAT refined analysis
  77. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
  78. LIGO/Virgo/KAGRA S250818k: NOT optical observations of AT2025ulz
  79. GRB 250821A: VLT/FORS2 Optical Observation
  80. GRB 250821B: SVOM/GRM observation
  81. EP250821a: SVOM/VT optical observation
  82. GRB 250821A: NOT z-band upper limit
  83. GRB 250821A: KAIT optical upper limit
  84. GRB 250821A: Swift-XRT refined Analysis
  85. GRB 250821B: Fermi GBM Detection
  86. GRB 250821B: BALROG localization (Fermi Trigger / GRB 250821672)
  87. GRB 250821A: Enhanced Swift-XRT position
  88. GRB 250821A: Swift/UVOT Upper Limits
  89. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  90. EP250821a: Swift XRT and UVOT counterpart detection
  91. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  92. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  93. GRB 250821A: LCOGT Optical Upper Limits
  94. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  95. GRB 250821A: Swift detection of a burst
  96. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  97. EP250821a: Einstein Probe detection of an X-ray transient
  98. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  99. LIGO/Virgo/KAGRA S250818k: WINTER J-band observations of AT 2025ulz
  100. LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz

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