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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"

32531 results found.

  1. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  2. EP250827A: VLT/X-shooter redshift confirmation
  3. Fermi GRB 250827A: Global MASTER-Net observations report
  4. EP250827a: confirmation of optical rebrightening with LCO
  5. EP250827a: GOTO observation of the optical afterglow
  6. GRB 250826A: SVOM/GRM observation
  7. EP250827A: An optical rebrightening was detected by LCO.
  8. EP250827a: Swift-XRT counterpart detection
  9. LIGO/Virgo/KAGRA S250827l: Updated Sky localization
  10. EP250827a: TRT optical observations
  11. EP250827a / GRB 250827A: MASTER-OAFA OT observation
  12. EP250827a: Gemini-South redshift z = 1.613
  13. EP250827a: Global MASTER-Net observations report
  14. EP250827a: Las Cumbres independent detection of the optical counterpart
  15. EP250827a: Gemini-South optical counterpart detection
  16. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  17. Fermi GRB 250826A: Global MASTER-Net observations report
  18. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  19. EP250821a: Gemini GMOS Redshift Confirmation
  20. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  21. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Confirmation of Rebrightening of AT2025ulz
  22. Fermi GRB 250824B: Global MASTER-Net observations report
  23. LIGO/Virgo/KAGRA S250818k: VLA upper limits on AT2025ulz
  24. LIGO/Virgo/KAGRA S250818k: nature of the AT2025ulz/ZTF25abjmnnps OT
  25. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  26. GRB 250823A: Swift-BAT refined analysis
  27. LIGO/Virgo/KAGRA S250818k: Continued Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
  28. GRB 250821B: AstroSat CZTI detection
  29. GRB 250819A: AstroSat CZTI detection
  30. LIGO/Virgo/KAGRA S250818k: FTW Observations Show Continued Reddening of AT 2025ulz
  31. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  32. GRB 250821B: Insight-HXMT detection
  33. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  34. EP250821a: MeerKAT radio counterpart
  35. EP triggers 01709200706 and 01709200707: GOTO confirmation of flaring stars
  36. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  37. GRB 250823A: COLIBRÍ optical observations
  38. GRB 250823A: SVOM/VT optical observation
  39. GRB 250823A: Swift/UVOT Detection
  40. GRB 250823A: NOT optical observations
  41. LIGO/Virgo/KAGRA S250818k: CFH/MegaCam follow-up observation for AT2025ulz
  42. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  43. GRB 250823A: Fermi GBM Observation
  44. GRB 250818B: MeerKAT Detection
  45. GRB 250823A: LCOGT Optical Detection
  46. GRB 250823A: BOOTES6/DPRT early optical detection
  47. GRB 250823A: Liverpool Telescope optical detection
  48. Konus-Wind detection of GRB 250821B
  49. LIGO/Virgo/KAGRA S250818k: Rebrightening detected with Gemini/GMOS
  50. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  51. LIGO/Virgo/KAGRA S250818k: J-GEM follow-up observation for AT2025ulz
  52. LIGO/Virgo/KAGRA S250818k: PRIME nIR observations of AT2025ulz
  53. LIGO/Virgo/KAGRA S250818k: JinShan optical observations of AT2025ulz
  54. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  55. LIGO/Virgo/Kagra S250818k: STEP/T80N upper limits on 2025ulz
  56. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  57. GRB 250806A: Gemini observations of host galaxy candidate
  58. IPN triangulation of GRB 250821B (long/bright)
  59. GRB 250821A: Kilonova-Catcher optical upper limits
  60. EP250821a: Swift/XRT counterpart fading
  61. GRB 250812A: SVOM/ECLAIRs refined analysis
  62. GRB 250821A: Swift-BAT refined analysis
  63. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
  64. LIGO/Virgo/KAGRA S250818k: NOT optical observations of AT2025ulz
  65. EP250821a: Swift/UVOT further observations.
  66. EP250821a: VLT X-shooter spectroscopic redshift z = 0.577
  67. LIGO/Virgo/KAGRA S250818k: GRAWITA TNG NIR observations of AT2025ulz
  68. GRB 250821A: VLT/FORS2 Optical Observation
  69. GRB 250821A: GECAM-B detection
  70. GRB 250821B: SVOM/GRM observation
  71. EP250821a: SVOM/VT optical observation
  72. Fermi GRB 250821B: Global MASTER-Net observations report
  73. GRB 250821A: NOT z-band upper limit
  74. GRB 250821A: KAIT optical upper limit
  75. LIGO/Virgo/KAGRA S250818k: Continued fading and reddening of AT2025ulz from Keck/LRIS imaging observations
  76. Swift GRB 250821A: Global MASTER-Net observations report
  77. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of AT 2025ulz
  78. LIGO/Virgo/KAGRA S250818k : Tautenburg observations, upper limits
  79. GRB 250821A: Swift/UVOT Upper Limits
  80. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  81. EP250821a: Swift XRT and UVOT counterpart detection
  82. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  83. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  84. GRB 250821A: LCOGT Optical Upper Limits
  85. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  86. LIGO/Virgo/KAGRA S250818k: 10 GHz VLA observations of AT2025ulz
  87. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  88. LIGO/Virgo/KAGRA S250818k: EP/FXT observation of AT 2025ulz
  89. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  90. LIGO/Virgo/KAGRA S250818k: WINTER J-band observations of AT 2025ulz
  91. GRB 250818B: 10 GHz VLA detection
  92. LIGO/Virgo/KAGRA S250818k: Pan-STARRS grizy-band imaging and photometry of AT2025ulz
  93. LIGO/Virgo/KAGRA S250818k: Swift observations of AT 2025ulz
  94. LIGO/Virgo/KAGRA S250818k: Multi-band Gemini GMOS Detections
  95. LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz
  96. GRB 250814A: Swift/UVOT Upper Limits
  97. GRB 250813B: Swift/UVOT Upper Limit
  98. IPN triangulation of GRB 250816A (short)
  99. IPN triangulation of GRB 250814C (short)
  100. IPN triangulation of GRB 250804B (short)

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