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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

28111 results found.

  1. LIGO/Virgo/KAGRA S250904cv: Updated Sky localization
  2. LIGO/Virgo/KAGRA S250904br: Updated Sky localization
  3. EP detected a brightening of LMXB 1ES 1735-26.9
  4. GRB 250905A: KAIT optical upper limit
  5. GRB 250905A: Swift detection of a burst
  6. GRB 250904A: Enhanced Swift-XRT position
  7. IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
  8. GRB 250904A: TRT optical counterpart detection
  9. EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
  10. GRB 250904A: Swift detection of a burst
  11. LIGO/Virgo/KAGRA S250904ae: Updated Sky localization
  12. GRB 250902A: VZLUSAT-2 detection
  13. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  14. GRB 250903A: Swift-XRT observations
  15. EP250903a: Swift-XRT observations
  16. EP#01709201209: Swift-XRT observations
  17. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  18. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  19. GRB 250830C: VZLUSAT-2 detection
  20. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  21. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  22. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  23. GRB 250903A: EP-FXT counterpart detection
  24. GRB 250902A: GECAM-B detection
  25. GRB 250903A: LCO optical observation
  26. GRB 250903A: LCO optical afterglow detection
  27. GRB 250903A: SVOM/VT optical confirmation with VHF data
  28. EP250901a: Mondy, Assy and SAO RAS optical limits
  29. EP250903a: LCO candidate counterpart discovery
  30. GRB 250903A: TRT optical counterpart detection
  31. EP250903a: TRT optical observations
  32. EP250903a: Einstein Probe detection of an X-ray transient
  33. EP 250827B: Detection of supernova counterpart by LCO.
  34. GRB 250902B: SVOM/GRM observation
  35. EP250827b: SVOM/VT observation of AT 2025wkm
  36. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  37. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  38. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  39. GRB 250902A: Fermi GBM Detection
  40. GRB 250901A: Swift/UVOT Upper Limit
  41. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  42. GRB 250830B: Swift-XRT afterglow detection
  43. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  44. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  45. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  46. GRB 250902A: SVOM/GRM observation
  47. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  48. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  49. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  50. GRB 250901A: SVOM/VT optical afterglow with VHF data
  51. GRB 250901A: Swift-XRT afterglow detection
  52. EP250901a: Swift-XRT observations
  53. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  54. GRB 250901A: LCO optical upper limit
  55. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  56. EP250827b: Gemini Spectroscopy of AT 2025wkm
  57. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  58. EP250831a: NOT optical observations and tentative afterglow candidate
  59. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  60. GRB 250901A: SVOM detection of a burst
  61. EP250901a: Mephisto optical upper limits
  62. GRB 250830C: GECAM-B detection
  63. EP250901a: Einstein Probe detection of an X-ray transient
  64. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  65. EP250831a: Swift-XRT observations
  66. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  67. EP250831a: EP-WXT detection of a fast X-ray transient
  68. GRB 250831A: Swift-XRT counterpart detection
  69. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  70. GRB 250831A: SVOM/VT upper limit with VHF data
  71. GRB 250831A: SVOM detection of a soft burst
  72. GRB 250830B: Swift-XRT observations
  73. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  74. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  75. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  76. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  77. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  78. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  79. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  80. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  81. GRB 250830B: MAXI/GSC detection
  82. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  83. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  84. GRB 250828B: Swift-BAT refined analysis
  85. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  86. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  87. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  88. EP250828a: Optical counterpart detection with Kinder observations
  89. EP250828a: Liverpool Telescope upper limits
  90. EP250828a: Global MASTER-Net observations report
  91. EP-WXT trigger 01709200800 : KAIT optical observations
  92. EP250828a: KAIT optical upper limit
  93. EP250827a: Swift/UVOT Detection
  94. EP250828a: NOT optical counterpart confirmation
  95. EP250828a: SVOM/VT optical candidate
  96. EP250828a: Seimei/TriCCS optical counterpart detection
  97. EP250828a: Optical upper limit with Kinder observations
  98. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  99. EP250827a: LCO observations show fading optical counterpart
  100. EP250828a: Einstein Probe detection of an X-ray transient

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