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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 S251108dn: Updated Sky localization
  2. LIGO/Virgo/KAGRA S251108fi: Identification of a GW compact binary merger candidate
  3. LIGO/Virgo/KAGRA S251108dn: Identification of a GW compact binary merger candidate
  4. LIGO/Virgo/KAGRA S251105aj: Updated Sky localization
  5. LIGO/Virgo/KAGRA S251103f: Updated Sky localization
  6. LIGO/Virgo/KAGRA S251031dw: Candidates from the Zwicky Transient Facility
  7. LIGO/Virgo/KAGRA S251105aj: Identification of a GW compact binary merger candidate
  8. LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate
  9. LIGO/Virgo/KAGRA S251031cq: Updated Sky localization
  10. GRB 251103A: NOT optical afterglow candidate (duplicate submission)
  11. LIGO/Virgo/KAGRA S251031cq: Identification of a GW compact binary merger candidate
  12. IceCube-251025A: Upper limits from a search for additional neutrino events in IceCube
  13. GRB 251013C : 3.4-m telescope of Iranian National Observatory (INO340) optical observations
  14. LIGO/Virgo/KAGRA S251026bn: Updated Sky localization
  15. LIGO/Virgo/KAGRA S251026bn: Identification of a GW compact binary merger candidate
  16. LIGO/Virgo/KAGRA S251021u: Updated Sky localization
  17. LIGO/Virgo/KAGRA S251021u: Identification of a GW compact binary merger candidate
  18. LIGO/Virgo/KAGRA S251018bi: Updated Sky localization
  19. IceCube-251018A: Upper limits from a search for additional neutrino events in IceCube
  20. LIGO/Virgo/KAGRA S251018bi: Identification of a GW compact binary merger candidate
  21. LIGO/Virgo/KAGRA S251017di: Retraction of GW compact binary merger candidate
  22. GRB 251013C: Leavitt Observatory optical photometry
  23. LIGO/Virgo/KAGRA S251014cn: Updated Sky localization
  24. Upper limits from a search for additional neutrino events in IceCube
  25. GRB 251014B: Swift/BAT-GUANO arcminute localization of a short burst
  26. LIGO/Virgo/KAGRA S251014cn: NED Galaxies in the 3-Initial Localization Volume
  27. LIGO/Virgo/KAGRA S251014cn: Identification of a GW compact binary merger candidate
  28. GRB 251013D: Swift/BAT-GUANO arcminute localization of a burst
  29. LIGO/Virgo/KAGRA S251013x: Updated Sky localization and Source Classification
  30. LIGO/Virgo/KAGRA S251013x: Identification of a GW compact binary merger candidate
  31. LIGO/Virgo/KAGRA S251006dd: Identification of a GW compact binary merger candidate
  32. LIGO/Virgo/KAGRA S251003at: Retraction of GW compact binary merger candidate
  33. LIGO/Virgo/KAGRA S250830bp: SOAR spectroscopy of two DESGW candidates
  34. LIGO/Virgo/KAGRA S250818k: further MeerKAT monitoring
  35. LIGO/Virgo/KAGRA S250929c: Updated Sky localization
  36. LIGO/Virgo/KAGRA S250929c: Identification of a GW compact binary merger candidate
  37. LIGO/Virgo/KAGRA S250927cy: Updated Sky localization
  38. LIGO/Virgo/KAGRA S250927ck: Updated Sky localization
  39. LIGO/Virgo/KAGRA S250927cy: Identification of a GW compact binary merger candidate
  40. LIGO/Virgo/KAGRA S250927ck: Identification of a GW compact binary merger candidate
  41. IceCube-250926A: Upper limits from a search for additional neutrino events in IceCube
  42. LIGO/Virgo/KAGRA S250920bq: Coverage and upper limits from MAXI/GSC observations
  43. LIGO/Virgo/KAGRA S250918aw: 1 counterpart neutrino candidate event from an IceCube neutrino search
  44. LIGO/Virgo/KAGRA S250917aq: Three counterpart neutrino candidates from IceCube neutrino searches
  45. LIGO/Virgo/KAGRA S250917aq: Updated Sky localization
  46. LIGO/Virgo/KAGRA S250917aq: Identification of a GW compact binary merger candidate
  47. LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
  48. LIGO/Virgo/KAGRA S250912s: 2 counterpart neutrino candidate events from an IceCube neutrino search
  49. LIGO/Virgo/KAGRA S250912f: Updated Sky localization
  50. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  51. LIGO/Virgo/KAGRA S250911ac: Updated Sky localization and Source Classification
  52. LIGO/Virgo/KAGRA S250908y: Updated Sky localization
  53. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  54. LIGO/Virgo/KAGRA S250906ca: Updated Sky localization
  55. LIGO/Virgo/KAGRA S250910b: Retraction of GW compact binary merger candidate
  56. LIGO/Virgo/KAGRA S250908y: Identification of a GW compact binary merger candidate
  57. LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
  58. IceCube-250905A: Upper limits from a search for additional neutrino events in IceCube
  59. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  60. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
  61. LIGO/Virgo/KAGRA S250904cv: Updated Sky localization
  62. LIGO/Virgo/KAGRA S250904br: Updated Sky localization
  63. LIGO/Virgo/KAGRA S250904ae: Updated Sky localization
  64. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  65. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  66. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  67. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  68. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  69. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  70. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  71. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  72. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  73. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  74. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  75. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  76. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  77. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  78. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  79. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  80. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  81. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  82. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  83. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  84. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  85. LIGO/Virgo/KAGRA S250818k: uGMRT 1.3 GHz observations of AT2025ulz
  86. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  87. LIGO/Virgo/KAGRA S250827l: Updated Sky localization
  88. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  89. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  90. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Confirmation of Rebrightening of AT2025ulz
  91. LIGO/Virgo/KAGRA S250818k: VLA upper limits on AT2025ulz
  92. LIGO/Virgo/KAGRA S250818k: nature of the AT2025ulz/ZTF25abjmnnps OT
  93. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  94. LIGO/Virgo/KAGRA S250818k: Continued Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
  95. LIGO/Virgo/KAGRA S250818k: FTW Observations Show Continued Reddening of AT 2025ulz
  96. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  97. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  98. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  99. LIGO/Virgo/KAGRA S250818k: CFH/MegaCam follow-up observation for AT2025ulz
  100. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz

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