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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"

28044 results found.

  1. EP250831a: EP-WXT detection of a fast X-ray transient
  2. GRB 250831A: Swift-XRT counterpart detection
  3. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  4. GRB 250831A: SVOM/VT upper limit with VHF data
  5. GRB 250831A: SVOM detection of a soft burst
  6. GRB 250830B: Swift-XRT observations
  7. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  8. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  9. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  10. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  11. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  12. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  13. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  14. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  15. GRB 250830B: MAXI/GSC detection
  16. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  17. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  18. GRB 250828B: Swift-BAT refined analysis
  19. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  20. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  21. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  22. EP250828a: Optical counterpart detection with Kinder observations
  23. EP250828a: Liverpool Telescope upper limits
  24. EP250828a: Global MASTER-Net observations report
  25. EP-WXT trigger 01709200800 : KAIT optical observations
  26. EP250828a: KAIT optical upper limit
  27. EP250827a: Swift/UVOT Detection
  28. EP250828a: NOT optical counterpart confirmation
  29. EP250828a: SVOM/VT optical candidate
  30. EP250828a: Seimei/TriCCS optical counterpart detection
  31. EP250828a: Optical upper limit with Kinder observations
  32. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  33. EP250827a: LCO observations show fading optical counterpart
  34. EP250828a: Einstein Probe detection of an X-ray transient
  35. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  36. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  37. EP250827a: confirmation of optical rebrightening with LCO
  38. GRB 250826A: SVOM/GRM observation
  39. EP250827A: An optical rebrightening was detected by LCO.
  40. EP250827a: Swift-XRT counterpart detection
  41. LIGO/Virgo/KAGRA S250827l: Updated Sky localization
  42. EP250827a: TRT optical observations
  43. EP250827a: Gemini-South redshift z = 1.613
  44. EP250827a: Einstein Probe detection of an X-ray transient
  45. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  46. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  47. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  48. Fermi GRB 250824B: Global MASTER-Net observations report
  49. LIGO/Virgo/KAGRA S250818k: nature of the AT2025ulz/ZTF25abjmnnps OT
  50. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  51. GRB 250823A: Swift-BAT refined analysis
  52. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  53. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  54. GRB 250823A: Swift-XRT refined Analysis
  55. EP250821a: MeerKAT radio counterpart
  56. GRB 250823A: COLIBRÍ optical observations
  57. GRB 250823A: SVOM/VT optical observation
  58. GRB 250823A: Swift/UVOT Detection
  59. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  60. GRB 250823A: Fermi GBM Observation
  61. GRB 250823A: Enhanced Swift-XRT position
  62. GRB 250823A: LCOGT Optical Detection
  63. GRB 250823A: Swift detection of a burst
  64. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  65. LIGO/Virgo/KAGRA S250818k: JinShan optical observations of AT2025ulz
  66. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  67. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  68. GRB 250806A: Gemini observations of host galaxy candidate
  69. GRB 250821A: Kilonova-Catcher optical upper limits
  70. EP250821a: Swift/XRT counterpart fading
  71. GRB 250821A: Swift-BAT refined analysis
  72. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
  73. LIGO/Virgo/KAGRA S250818k: NOT optical observations of AT2025ulz
  74. GRB 250821A: VLT/FORS2 Optical Observation
  75. GRB 250821B: SVOM/GRM observation
  76. EP250821a: SVOM/VT optical observation
  77. GRB 250821A: NOT z-band upper limit
  78. GRB 250821A: KAIT optical upper limit
  79. GRB 250821A: Swift-XRT refined Analysis
  80. GRB 250821B: Fermi GBM Detection
  81. GRB 250821B: BALROG localization (Fermi Trigger / GRB 250821672)
  82. GRB 250821A: Enhanced Swift-XRT position
  83. GRB 250821A: Swift/UVOT Upper Limits
  84. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  85. EP250821a: Swift XRT and UVOT counterpart detection
  86. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  87. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  88. GRB 250821A: LCOGT Optical Upper Limits
  89. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  90. GRB 250821A: Swift detection of a burst
  91. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  92. EP250821a: Einstein Probe detection of an X-ray transient
  93. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  94. LIGO/Virgo/KAGRA S250818k: WINTER J-band observations of AT 2025ulz
  95. LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz
  96. GRB 250814A: Swift/UVOT Upper Limits
  97. GRB 250813B: Swift/UVOT Upper Limit
  98. IPN triangulation of GRB 250816A (short)
  99. IPN triangulation of GRB 250814C (short)
  100. IPN triangulation of GRB 250804B (short)

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