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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"

28050 results found.

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

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