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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"

28047 results found.

  1. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  2. EP250831a: EP-WXT detection of a fast X-ray transient
  3. GRB 250831A: Swift-XRT counterpart detection
  4. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  5. GRB 250831A: SVOM/VT upper limit with VHF data
  6. GRB 250831A: SVOM detection of a soft burst
  7. GRB 250830B: Swift-XRT observations
  8. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  9. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  10. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  11. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  12. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  13. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  14. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  15. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  16. GRB 250830B: MAXI/GSC detection
  17. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  18. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  19. GRB 250828B: Swift-BAT refined analysis
  20. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  21. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  22. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  23. EP250828a: Optical counterpart detection with Kinder observations
  24. EP250828a: Liverpool Telescope upper limits
  25. EP250828a: Global MASTER-Net observations report
  26. EP-WXT trigger 01709200800 : KAIT optical observations
  27. EP250828a: KAIT optical upper limit
  28. EP250827a: Swift/UVOT Detection
  29. EP250828a: NOT optical counterpart confirmation
  30. EP250828a: SVOM/VT optical candidate
  31. EP250828a: Seimei/TriCCS optical counterpart detection
  32. EP250828a: Optical upper limit with Kinder observations
  33. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  34. EP250827a: LCO observations show fading optical counterpart
  35. EP250828a: Einstein Probe detection of an X-ray transient
  36. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  37. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  38. EP250827a: confirmation of optical rebrightening with LCO
  39. GRB 250826A: SVOM/GRM observation
  40. EP250827A: An optical rebrightening was detected by LCO.
  41. EP250827a: Swift-XRT counterpart detection
  42. LIGO/Virgo/KAGRA S250827l: Updated Sky localization
  43. EP250827a: TRT optical observations
  44. EP250827a: Gemini-South redshift z = 1.613
  45. EP250827a: Einstein Probe detection of an X-ray transient
  46. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  47. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  48. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  49. Fermi GRB 250824B: Global MASTER-Net observations report
  50. LIGO/Virgo/KAGRA S250818k: nature of the AT2025ulz/ZTF25abjmnnps OT
  51. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  52. GRB 250823A: Swift-BAT refined analysis
  53. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  54. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  55. GRB 250823A: Swift-XRT refined Analysis
  56. EP250821a: MeerKAT radio counterpart
  57. GRB 250823A: COLIBRÍ optical observations
  58. GRB 250823A: SVOM/VT optical observation
  59. GRB 250823A: Swift/UVOT Detection
  60. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  61. GRB 250823A: Fermi GBM Observation
  62. GRB 250823A: Enhanced Swift-XRT position
  63. GRB 250823A: LCOGT Optical Detection
  64. GRB 250823A: Swift detection of a burst
  65. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  66. LIGO/Virgo/KAGRA S250818k: JinShan optical observations of AT2025ulz
  67. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  68. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  69. GRB 250806A: Gemini observations of host galaxy candidate
  70. GRB 250821A: Kilonova-Catcher optical upper limits
  71. EP250821a: Swift/XRT counterpart fading
  72. GRB 250821A: Swift-BAT refined analysis
  73. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
  74. LIGO/Virgo/KAGRA S250818k: NOT optical observations of AT2025ulz
  75. GRB 250821A: VLT/FORS2 Optical Observation
  76. GRB 250821B: SVOM/GRM observation
  77. EP250821a: SVOM/VT optical observation
  78. GRB 250821A: NOT z-band upper limit
  79. GRB 250821A: KAIT optical upper limit
  80. GRB 250821A: Swift-XRT refined Analysis
  81. GRB 250821B: Fermi GBM Detection
  82. GRB 250821B: BALROG localization (Fermi Trigger / GRB 250821672)
  83. GRB 250821A: Enhanced Swift-XRT position
  84. GRB 250821A: Swift/UVOT Upper Limits
  85. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  86. EP250821a: Swift XRT and UVOT counterpart detection
  87. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  88. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  89. GRB 250821A: LCOGT Optical Upper Limits
  90. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  91. GRB 250821A: Swift detection of a burst
  92. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  93. EP250821a: Einstein Probe detection of an X-ray transient
  94. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  95. LIGO/Virgo/KAGRA S250818k: WINTER J-band observations of AT 2025ulz
  96. LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz
  97. GRB 250814A: Swift/UVOT Upper Limits
  98. GRB 250813B: Swift/UVOT Upper Limit
  99. IPN triangulation of GRB 250816A (short)
  100. IPN triangulation of GRB 250814C (short)

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