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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"

43045 results found.

  1. EP250827a: BOOTES-7 early optical dectection
  2. EP250827a / GRB 250827A: MASTER-OAFA OT observation
  3. EP250827a: Gemini-South redshift z = 1.613
  4. EP250827a: Global MASTER-Net observations report
  5. EP250827a: Las Cumbres independent detection of the optical counterpart
  6. EP250827a: Gemini-South optical counterpart detection
  7. EP250827a: Einstein Probe detection of an X-ray transient
  8. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  9. Fermi GRB 250826A: Global MASTER-Net observations report
  10. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  11. EP250821a: Gemini GMOS Redshift Confirmation
  12. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  13. Fermi trigger No 777883624: Global MASTER-Net observations report
  14. GRB 250826A: Fermi GBM Final Real-time Localization
  15. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Confirmation of Rebrightening of AT2025ulz
  16. Fermi GRB 250824B: Global MASTER-Net observations report
  17. LIGO/Virgo/KAGRA S250818k: VLA upper limits on AT2025ulz
  18. LIGO/Virgo/KAGRA S250818k: nature of the AT2025ulz/ZTF25abjmnnps OT
  19. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  20. LIGO/Virgo/KAGRA S250818k: Continued Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
  21. GRB 250821B: AstroSat CZTI detection
  22. GRB 250819A: AstroSat CZTI detection
  23. LIGO/Virgo/KAGRA S250818k: FTW Observations Show Continued Reddening of AT 2025ulz
  24. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  25. GRB 250821B: Insight-HXMT detection
  26. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  27. GRB 250823A: Swift-XRT refined Analysis
  28. EP250821a: MeerKAT radio counterpart
  29. EP triggers 01709200706 and 01709200707: GOTO confirmation of flaring stars
  30. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  31. GRB 250824B: Fermi GBM Final Real-time Localization
  32. The EP-WXT trigger 01709200707 is likely a flaring star
  33. GRB 250823A: COLIBRÍ optical observations
  34. The EP-WXT trigger 01709200706 is likely a flaring star
  35. GRB 250823A: SVOM/VT optical observation
  36. GRB 250824A: Fermi GBM Final Real-time Localization
  37. GRB 250823A: Swift/UVOT Detection
  38. GRB 250823A: NOT optical observations
  39. LIGO/Virgo/KAGRA S250818k: CFH/MegaCam follow-up observation for AT2025ulz
  40. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  41. GRB 250823A: Fermi GBM Observation
  42. GRB 250818B: MeerKAT Detection
  43. GRB 250823A: Enhanced Swift-XRT position
  44. GRB 250823A: LCOGT Optical Detection
  45. GRB 250823A: BOOTES6/DPRT early optical detection
  46. GRB 250823A: Liverpool Telescope optical detection
  47. GRB 250823A: Swift detection of a burst
  48. GRB 250823A: Fermi GBM Final Real-time Localization
  49. Swift GRB250823.84: Global MASTER-Net observations report
  50. Konus-Wind detection of GRB 250821B
  51. LIGO/Virgo/KAGRA S250818k: Rebrightening detected with Gemini/GMOS
  52. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  53. LIGO/Virgo/KAGRA S250818k: J-GEM follow-up observation for AT2025ulz
  54. LIGO/Virgo/KAGRA S250818k: PRIME nIR observations of AT2025ulz
  55. LIGO/Virgo/KAGRA S250818k: JinShan optical observations of AT2025ulz
  56. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  57. LIGO/Virgo/Kagra S250818k: STEP/T80N upper limits on 2025ulz
  58. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  59. GRB 250806A: Gemini observations of host galaxy candidate
  60. IPN triangulation of GRB 250821B (long/bright)
  61. GRB 250821A: Kilonova-Catcher optical upper limits
  62. EP250821a: Swift/XRT counterpart fading
  63. GRB 250812A: SVOM/ECLAIRs refined analysis
  64. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
  65. LIGO/Virgo/KAGRA S250818k: NOT optical observations of AT2025ulz
  66. EP250821a: Swift/UVOT further observations.
  67. EP250821a: VLT X-shooter spectroscopic redshift z = 0.577
  68. LIGO/Virgo/KAGRA S250818k: GRAWITA TNG NIR observations of AT2025ulz
  69. GRB 250821A: VLT/FORS2 Optical Observation
  70. GRB 250821A: GECAM-B detection
  71. GRB 250821B: SVOM/GRM observation
  72. EP250821a: SVOM/VT optical observation
  73. Fermi GRB 250821B: Global MASTER-Net observations report
  74. GRB 250821A: NOT z-band upper limit
  75. GRB 250821C: Fermi GBM Final Real-time Localization
  76. GRB 250821A: KAIT optical upper limit
  77. LIGO/Virgo/KAGRA S250818k: Continued fading and reddening of AT2025ulz from Keck/LRIS imaging observations
  78. GRB 250821A: Swift-XRT refined Analysis
  79. Swift GRB 250821A: Global MASTER-Net observations report
  80. GRB 250821B: Fermi GBM Detection
  81. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of AT 2025ulz
  82. GRB 250821B: BALROG localization (Fermi Trigger / GRB 250821672)
  83. LIGO/Virgo/KAGRA S250818k : Tautenburg observations, upper limits
  84. GRB 250821B: Fermi GBM Final Localization of a Bright Burst
  85. GRB 250821A: Enhanced Swift-XRT position
  86. GRB 250821A: Swift/UVOT Upper Limits
  87. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  88. EP250821a: Swift XRT and UVOT counterpart detection
  89. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  90. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  91. GRB 250821A: LCOGT Optical Upper Limits
  92. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  93. LIGO/Virgo/KAGRA S250818k: 10 GHz VLA observations of AT2025ulz
  94. GRB 250821A: Prompt enhanced Swift-XRT position
  95. GRB 250821A: Swift detection of a burst
  96. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  97. LIGO/Virgo/KAGRA S250818k: EP/FXT observation of AT 2025ulz
  98. EP250821a: Einstein Probe detection of an X-ray transient
  99. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  100. GRB 250819A: Insight-HXMT detection

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