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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').
Advanced Search

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"

32509 results found.

  1. GRB 250902B: AstroSat CZTI detection
  2. EP250903a: Global MASTER-Net observations report
  3. EP250903a: TRT optical observations
  4. EP250903a: Einstein Probe detection of an X-ray transient
  5. EP 250827B: Detection of supernova counterpart by LCO.
  6. EP250827b / AT 2025wkm: TRT optical observations
  7. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  8. EP250827b: continued Liverpool Telescope observations
  9. GRB 250902B: SVOM/GRM observation
  10. EP250827b: SVOM/VT observation of AT 2025wkm
  11. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  12. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  13. Fermi GRB 250902B: Global MASTER-Net observations report
  14. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  15. GRB 250902A: Fermi GBM Detection
  16. GRB 250901A: Swift/UVOT Upper Limit
  17. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  18. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  19. EP250827b: Liverpool Telescope observations
  20. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  21. GRB 250902A: SVOM/GRM observation
  22. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  23. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  24. GRB 250901A: EP-FXT follow-up observation
  25. GRB 250901A: NOT optical observations
  26. GRB 250901A: SVOM/VT optical afterglow with VHF data
  27. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  28. GRB 250901A: LCO optical upper limit
  29. EP250827b: Swift observations of AT 2025wkm
  30. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  31. EP250827b: Gemini Spectroscopy of AT 2025wkm
  32. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  33. EP250831a: NOT optical observations and tentative afterglow candidate
  34. EP250827b: FTW Observations of AT 2025wkm
  35. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  36. GRB 250830C: Insight-HXMT detection
  37. EP250901a: Mephisto optical upper limits
  38. EP250901a: Global MASTER-Net observations report
  39. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  40. EP250831a: EP-FXT follow-up observation
  41. EP250831a: Swift-XRT observations
  42. EP250831a: Global MASTER-Net observations report
  43. GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
  44. GRB 250831A: Swift-XRT counterpart detection
  45. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  46. GRB 250831A: SVOM/VT upper limit with VHF data
  47. EP250830a: Global MASTER-Net observations report
  48. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  49. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  50. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  51. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  52. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  53. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  54. GRB 250830B: Swift ToO observations
  55. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  56. GRB 250828B: Swift-BAT refined analysis
  57. EP250821a: SOAR observations
  58. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  59. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  60. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  61. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  62. EP250828a: Optical counterpart detection with Kinder observations
  63. EP250828a: Liverpool Telescope upper limits
  64. Swift GRB 250828B: Global MASTER-Net observations report
  65. EP250828a: Global MASTER-Net observations report
  66. EP-WXT trigger 01709200800 : KAIT optical observations
  67. EP250828a: KAIT optical upper limit
  68. EP250827a: Swift/UVOT Detection
  69. EP250828a: NOT optical counterpart confirmation
  70. EP250828a: SVOM/VT optical candidate
  71. EP250828a: Seimei/TriCCS optical counterpart detection
  72. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  73. EP250828a: Optical upper limit with Kinder observations
  74. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  75. LIGO/Virgo/KAGRA S250818k: uGMRT 1.3 GHz observations of AT2025ulz
  76. EP250827a: LCO observations show fading optical counterpart
  77. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  78. GRID detection of GRB 250824A
  79. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  80. EP250827A: VLT/X-shooter redshift confirmation
  81. Fermi GRB 250827A: Global MASTER-Net observations report
  82. EP250827a: confirmation of optical rebrightening with LCO
  83. EP250827a: GOTO observation of the optical afterglow
  84. GRB 250826A: SVOM/GRM observation
  85. EP250827A: An optical rebrightening was detected by LCO.
  86. EP250827a: Swift-XRT counterpart detection
  87. LIGO/Virgo/KAGRA S250827l: Updated Sky localization
  88. EP250827a: TRT optical observations
  89. EP250827a / GRB 250827A: MASTER-OAFA OT observation
  90. EP250827a: Gemini-South redshift z = 1.613
  91. EP250827a: Global MASTER-Net observations report
  92. EP250827a: Las Cumbres independent detection of the optical counterpart
  93. EP250827a: Gemini-South optical counterpart detection
  94. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  95. Fermi GRB 250826A: Global MASTER-Net observations report
  96. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  97. EP250821a: Gemini GMOS Redshift Confirmation
  98. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  99. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Confirmation of Rebrightening of AT2025ulz
  100. Fermi GRB 250824B: Global MASTER-Net observations report

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