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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"

23603 results found.

  1. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  2. EP250831a: NOT optical observations and tentative afterglow candidate
  3. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  4. GRB 250901A: SVOM detection of a burst
  5. EP250901a: Mephisto optical upper limits
  6. GRB 250830C: AstroSat CZTI detection of a long burst
  7. EP250831a: EP-FXT follow-up observation
  8. EP250831a: Swift-XRT observations
  9. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  10. GRB 250831A: Swift-XRT counterpart detection
  11. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  12. GRB 250831A: SVOM/VT upper limit with VHF data
  13. GRB 250831A: SVOM detection of a soft burst
  14. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  15. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  16. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  17. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  18. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  19. GRB 250830B: MAXI/GSC detection
  20. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  21. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  22. GRB 250828B: Swift-BAT refined analysis
  23. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  24. GRB 250808B: SVOM detection of a burst through offline search
  25. EP250828a: Optical counterpart detection with Kinder observations
  26. EP-WXT trigger 01709200800 : KAIT optical observations
  27. EP250828a: KAIT optical upper limit
  28. EP250827a: Swift/UVOT Detection
  29. EP250828a: Seimei/TriCCS optical counterpart detection
  30. GRB 250828B: Swift detection of a burst
  31. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  32. EP250828a: Optical upper limit with Kinder observations
  33. EP250827a: LCO observations show fading optical counterpart
  34. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  35. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  36. EP250827a: confirmation of optical rebrightening with LCO
  37. EP250827a: GOTO observation of the optical afterglow
  38. EP250827A: An optical rebrightening was detected by LCO.
  39. EP250827a: Swift-XRT counterpart detection
  40. The EP-WXT trigger 01709200800 is likely a flaring star
  41. EP250827a: TRT optical observations
  42. EP250827a: BOOTES-7 early optical dectection
  43. EP250827a / GRB 250827A: MASTER-OAFA OT observation
  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. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Confirmation of Rebrightening of AT2025ulz
  49. LIGO/Virgo/KAGRA S250818k: VLA upper limits on AT2025ulz
  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: Continued Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
  53. GRB 250821B: AstroSat CZTI detection
  54. GRB 250819A: AstroSat CZTI detection
  55. EP250821a: MeerKAT radio counterpart
  56. EP triggers 01709200706 and 01709200707: GOTO confirmation of flaring stars
  57. GRB 250823A: COLIBRÍ optical observations
  58. The EP-WXT trigger 01709200706 is likely a flaring star
  59. GRB 250823A: Swift/UVOT Detection
  60. LIGO/Virgo/KAGRA S250818k: CFH/MegaCam follow-up observation for AT2025ulz
  61. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  62. GRB 250823A: Fermi GBM Observation
  63. GRB 250823A: BOOTES6/DPRT early optical detection
  64. GRB 250823A: Swift detection of a burst
  65. Konus-Wind detection of GRB 250821B
  66. LIGO/Virgo/KAGRA S250818k: Rebrightening detected with Gemini/GMOS
  67. LIGO/Virgo/KAGRA S250818k: J-GEM follow-up observation for AT2025ulz
  68. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  69. LIGO/Virgo/Kagra S250818k: STEP/T80N upper limits on 2025ulz
  70. IPN triangulation of GRB 250821B (long/bright)
  71. GRB 250821A: Kilonova-Catcher optical upper limits
  72. GRB 250812A: SVOM/ECLAIRs refined analysis
  73. GRB 250821A: Swift-BAT refined analysis
  74. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
  75. LIGO/Virgo/KAGRA S250818k: NOT optical observations of AT2025ulz
  76. LIGO/Virgo/KAGRA S250818k: GRAWITA TNG NIR observations of AT2025ulz
  77. GRB 250821A: NOT z-band upper limit
  78. GRB 250821A: KAIT optical upper limit
  79. LIGO/Virgo/KAGRA S250818k: Continued fading and reddening of AT2025ulz from Keck/LRIS imaging observations
  80. LIGO/Virgo/KAGRA S250818k : Tautenburg observations, upper limits
  81. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  82. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  83. LIGO/Virgo/KAGRA S250818k: 10 GHz VLA observations of AT2025ulz
  84. GRB 250821A: Swift detection of a burst
  85. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  86. LIGO/Virgo/KAGRA S250818k: WINTER J-band observations of AT 2025ulz
  87. GRB 250818B: 10 GHz VLA detection
  88. LIGO/Virgo/KAGRA S250818k: Pan-STARRS grizy-band imaging and photometry of AT2025ulz
  89. LIGO/Virgo/KAGRA S250818k: Swift observations of AT 2025ulz
  90. LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz
  91. GRB 250814A: Swift/UVOT Upper Limits
  92. GRB 250813B: Swift/UVOT Upper Limit
  93. IPN triangulation of GRB 250816A (short)
  94. GRB 250818B: Kilonova-Catcher optical afterglow detection
  95. LIGO/Virgo/KAGRA S250818k: Pan-STARRS pre-detection limits for AT2025ulz
  96. LIGO/Virgo/KAGRA S250818k: Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
  97. GRB 250818B: Swift/UVOT Detection
  98. GRB 250818B: optical afterglow detection with Lesedi (GOTO25fzq)
  99. GRB 250818B: TRT Optical Observation
  100. GRB 250818B: SAO RAS optical observations

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