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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"

4055 results found.

  1. LIGO/Virgo/KAGRA S250701bq: Identification of a GW compact binary merger candidate
  2. LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
  3. LIGO/Virgo/KAGRA S250629bs: Updated Sky localization
  4. LIGO/Virgo/KAGRA S250629ae: Updated Sky localization
  5. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  6. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate (duplicate submission)
  7. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  8. LIGO/Virgo/KAGRA S250628am: Updated Sky localization
  9. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  10. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  11. GRB 250530C: BOOTES-7 optical upper limit
  12. EP-WXT trigger 01709177124: confirmation of a stellar flare by BOOTES-6
  13. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  14. EP J1350.0-8622: BOOTES-6/DPRT optical upper limit
  15. GRB 250424A: COLIBRÍ detection of the associated supernova
  16. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)
  17. EP250511a: BOOTES-5 optical upper limit
  18. IceCube-250506A: Upper limits from a search for additional neutrino events in IceCube
  19. GRB 250504A: EIRSAT-1 GMOD Detection
  20. IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
  21. IceCube-250426A: Upper limits from a search for additional neutrino events in IceCube
  22. GRB 250424A: EIRSAT-1 GMOD Detection
  23. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  24. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  25. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  26. SVOM/sb25042207: BOOTES-2 early optical upper limit
  27. IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
  28. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  29. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  30. EP250404a: BOOTES-4/JGT optical afterglow detection
  31. GRB 250403A: 1.6m Mephisto multi-band optical detection
  32. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  33. GRB 250330B: EIRSAT-1 GMOD Detection
  34. LIGO/Virgo/KAGRA S250331o: Updated Sky localization
  35. GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
  36. IceCube-250330A: Upper limits from a search for additional neutrino events in IceCube
  37. LIGO/Virgo/KAGRA S250331o: NED Galaxies in the 3-Initial Localization Volume
  38. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  39. LIGO/Virgo/KAGRA S250331o: Identification of a GW compact binary merger candidate
  40. GRB 250330A: BOOTES-7 early optical upper limit
  41. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  42. LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
  43. LIGO/Virgo/KAGRA S250328ae: NED Galaxies in the 4-Update Localization Volume
  44. LIGO/Virgo/KAGRA S250328ae: Updated Sky localization
  45. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  46. GRB 250327B: Las Cumbres optical counterpart detection
  47. LIGO/Virgo/KAGRA S250326y: Updated Sky localization
  48. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  49. GRB250322A: STEP/T80S optical limits
  50. LIGO/Virgo/KAGRA S250206dm: LIGHETR followup observations of AT2025azn
  51. LIGO/Virgo/KAGRA S250319bu: Updated Sky localization
  52. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  53. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  54. FRB 20250206A: Nondetection of Repeating Bursts from FRB 20250206A with FAST
  55. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  56. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  57. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  58. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  59. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  60. LIGO/Virgo/KAGRA S250306ej: Retraction of GW compact binary merger candidate
  61. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  62. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  63. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  64. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  65. EP250302a: NUTTelA-TAO Early Measurments
  66. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  67. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  68. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  69. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  70. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  71. LIGO/Virgo/KAGRA S250227y: Retraction of GW compact binary merger candidate
  72. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  73. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  74. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  75. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  76. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  77. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  78. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  79. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  80. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  81. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  82. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  83. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  84. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO trigger with ID 762004910: Identification of a GW compact binary merger candidate possibly associated with a sub-threshold Swift/BAT-GUANO trigger
  85. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  86. LIGO/Virgo/KAGRA S250221gb: Retraction of GW compact binary merger candidate
  87. LIGO/Virgo/KAGRA S250221eb: Retraction of GW compact binary merger candidate
  88. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  89. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  90. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  91. LIGO/Virgo/KAGRA S250206dm: MASTER LC AT2025bbo
  92. LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
  93. LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
  94. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  95. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  96. LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
  97. LIGO/Virgo/KAGRA S250211be: Updated Sky localization
  98. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  99. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  100. LIGO/Virgo/KAGRA S250211be: Identification of a GW compact binary merger candidate

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