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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"

28084 results found.

  1. GRB 250903A: TRT optical counterpart detection
  2. EP250903a: TRT optical observations
  3. EP250903a: Einstein Probe detection of an X-ray transient
  4. EP 250827B: Detection of supernova counterpart by LCO.
  5. GRB 250902B: SVOM/GRM observation
  6. EP250827b: SVOM/VT observation of AT 2025wkm
  7. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  8. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  9. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  10. GRB 250902A: Fermi GBM Detection
  11. GRB 250901A: Swift/UVOT Upper Limit
  12. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  13. GRB 250830B: Swift-XRT afterglow detection
  14. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  15. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  16. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  17. GRB 250902A: SVOM/GRM observation
  18. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  19. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  20. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  21. GRB 250901A: SVOM/VT optical afterglow with VHF data
  22. GRB 250901A: Swift-XRT afterglow detection
  23. EP250901a: Swift-XRT observations
  24. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  25. GRB 250901A: LCO optical upper limit
  26. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  27. EP250827b: Gemini Spectroscopy of AT 2025wkm
  28. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  29. EP250831a: NOT optical observations and tentative afterglow candidate
  30. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  31. GRB 250901A: SVOM detection of a burst
  32. EP250901a: Mephisto optical upper limits
  33. GRB 250830C: GECAM-B detection
  34. EP250901a: Einstein Probe detection of an X-ray transient
  35. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  36. EP250831a: Swift-XRT observations
  37. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  38. EP250831a: EP-WXT detection of a fast X-ray transient
  39. GRB 250831A: Swift-XRT counterpart detection
  40. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  41. GRB 250831A: SVOM/VT upper limit with VHF data
  42. GRB 250831A: SVOM detection of a soft burst
  43. GRB 250830B: Swift-XRT observations
  44. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  45. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  46. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  47. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  48. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  49. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  50. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  51. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  52. GRB 250830B: MAXI/GSC detection
  53. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  54. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  55. GRB 250828B: Swift-BAT refined analysis
  56. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  57. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  58. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  59. EP250828a: Optical counterpart detection with Kinder observations
  60. EP250828a: Liverpool Telescope upper limits
  61. EP250828a: Global MASTER-Net observations report
  62. EP-WXT trigger 01709200800 : KAIT optical observations
  63. EP250828a: KAIT optical upper limit
  64. EP250827a: Swift/UVOT Detection
  65. EP250828a: NOT optical counterpart confirmation
  66. EP250828a: SVOM/VT optical candidate
  67. EP250828a: Seimei/TriCCS optical counterpart detection
  68. EP250828a: Optical upper limit with Kinder observations
  69. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  70. EP250827a: LCO observations show fading optical counterpart
  71. EP250828a: Einstein Probe detection of an X-ray transient
  72. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  73. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  74. EP250827a: confirmation of optical rebrightening with LCO
  75. GRB 250826A: SVOM/GRM observation
  76. EP250827A: An optical rebrightening was detected by LCO.
  77. EP250827a: Swift-XRT counterpart detection
  78. LIGO/Virgo/KAGRA S250827l: Updated Sky localization
  79. EP250827a: TRT optical observations
  80. EP250827a: Gemini-South redshift z = 1.613
  81. EP250827a: Einstein Probe detection of an X-ray transient
  82. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  83. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  84. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  85. Fermi GRB 250824B: Global MASTER-Net observations report
  86. LIGO/Virgo/KAGRA S250818k: nature of the AT2025ulz/ZTF25abjmnnps OT
  87. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  88. GRB 250823A: Swift-BAT refined analysis
  89. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  90. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  91. GRB 250823A: Swift-XRT refined Analysis
  92. EP250821a: MeerKAT radio counterpart
  93. GRB 250823A: COLIBRÍ optical observations
  94. GRB 250823A: SVOM/VT optical observation
  95. GRB 250823A: Swift/UVOT Detection
  96. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  97. GRB 250823A: Fermi GBM Observation
  98. GRB 250823A: Enhanced Swift-XRT position
  99. GRB 250823A: LCOGT Optical Detection
  100. GRB 250823A: Swift detection of a burst

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