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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"

28094 results found.

  1. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  2. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  3. GRB 250830C: VZLUSAT-2 detection
  4. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  5. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  6. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  7. GRB 250903A: EP-FXT counterpart detection
  8. GRB 250902A: GECAM-B detection
  9. GRB 250903A: LCO optical observation
  10. GRB 250903A: LCO optical afterglow detection
  11. GRB 250903A: SVOM/VT optical confirmation with VHF data
  12. EP250901a: Mondy, Assy and SAO RAS optical limits
  13. EP250903a: LCO candidate counterpart discovery
  14. GRB 250903A: TRT optical counterpart detection
  15. EP250903a: TRT optical observations
  16. EP250903a: Einstein Probe detection of an X-ray transient
  17. EP 250827B: Detection of supernova counterpart by LCO.
  18. GRB 250902B: SVOM/GRM observation
  19. EP250827b: SVOM/VT observation of AT 2025wkm
  20. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  21. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  22. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  23. GRB 250902A: Fermi GBM Detection
  24. GRB 250901A: Swift/UVOT Upper Limit
  25. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  26. GRB 250830B: Swift-XRT afterglow detection
  27. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  28. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  29. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  30. GRB 250902A: SVOM/GRM observation
  31. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  32. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  33. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  34. GRB 250901A: SVOM/VT optical afterglow with VHF data
  35. GRB 250901A: Swift-XRT afterglow detection
  36. EP250901a: Swift-XRT observations
  37. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  38. GRB 250901A: LCO optical upper limit
  39. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  40. EP250827b: Gemini Spectroscopy of AT 2025wkm
  41. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  42. EP250831a: NOT optical observations and tentative afterglow candidate
  43. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  44. GRB 250901A: SVOM detection of a burst
  45. EP250901a: Mephisto optical upper limits
  46. GRB 250830C: GECAM-B detection
  47. EP250901a: Einstein Probe detection of an X-ray transient
  48. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  49. EP250831a: Swift-XRT observations
  50. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  51. EP250831a: EP-WXT detection of a fast X-ray transient
  52. GRB 250831A: Swift-XRT counterpart detection
  53. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  54. GRB 250831A: SVOM/VT upper limit with VHF data
  55. GRB 250831A: SVOM detection of a soft burst
  56. GRB 250830B: Swift-XRT observations
  57. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  58. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  59. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  60. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  61. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  62. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  63. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  64. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  65. GRB 250830B: MAXI/GSC detection
  66. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  67. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  68. GRB 250828B: Swift-BAT refined analysis
  69. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  70. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  71. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  72. EP250828a: Optical counterpart detection with Kinder observations
  73. EP250828a: Liverpool Telescope upper limits
  74. EP250828a: Global MASTER-Net observations report
  75. EP-WXT trigger 01709200800 : KAIT optical observations
  76. EP250828a: KAIT optical upper limit
  77. EP250827a: Swift/UVOT Detection
  78. EP250828a: NOT optical counterpart confirmation
  79. EP250828a: SVOM/VT optical candidate
  80. EP250828a: Seimei/TriCCS optical counterpart detection
  81. EP250828a: Optical upper limit with Kinder observations
  82. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  83. EP250827a: LCO observations show fading optical counterpart
  84. EP250828a: Einstein Probe detection of an X-ray transient
  85. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  86. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  87. EP250827a: confirmation of optical rebrightening with LCO
  88. GRB 250826A: SVOM/GRM observation
  89. EP250827A: An optical rebrightening was detected by LCO.
  90. EP250827a: Swift-XRT counterpart detection
  91. LIGO/Virgo/KAGRA S250827l: Updated Sky localization
  92. EP250827a: TRT optical observations
  93. EP250827a: Gemini-South redshift z = 1.613
  94. EP250827a: Einstein Probe detection of an X-ray transient
  95. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  96. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  97. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  98. Fermi GRB 250824B: Global MASTER-Net observations report
  99. LIGO/Virgo/KAGRA S250818k: nature of the AT2025ulz/ZTF25abjmnnps OT
  100. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz

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