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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.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

24368 results found.

  1. GRB 250831A: SVOM detection of a soft burst
  2. GRB 250830B: Swift-XRT observations
  3. EP250830a: Global MASTER-Net observations report
  4. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  5. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  6. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  7. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  8. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  9. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  10. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  11. The EP-WXT trigger 01709200994 is likely a flaring star
  12. GRB 250828B: Swift-BAT refined analysis
  13. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  14. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  15. GRB 250808B: SVOM detection of a burst through offline search
  16. Swift GRB 250828B: Global MASTER-Net observations report
  17. EP250828a: Global MASTER-Net observations report
  18. EP250828a: KAIT optical upper limit
  19. EP250828a: NOT optical counterpart confirmation
  20. EP250828a: SVOM/VT optical candidate
  21. EP250828a: Seimei/TriCCS optical counterpart detection
  22. GRB 250828B: Swift detection of a burst
  23. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  24. EP250828a: Optical upper limit with Kinder observations
  25. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  26. GRB 250828A: Fermi GBM Final Localization
  27. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  28. Fermi GRB 250827A: Global MASTER-Net observations report
  29. EP250827a: GOTO observation of the optical afterglow
  30. GRB 250827A: Fermi GBM Final Real-time Localization
  31. LIGO/Virgo/KAGRA S250827l: Updated Sky localization
  32. The EP-WXT trigger 01709200800 is likely a flaring star
  33. EP250827a: BOOTES-7 early optical dectection
  34. EP250827a: Gemini-South redshift z = 1.613
  35. EP250827a: Global MASTER-Net observations report
  36. EP250827a: Gemini-South optical counterpart detection
  37. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  38. Fermi GRB 250826A: Global MASTER-Net observations report
  39. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  40. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  41. Fermi trigger No 777883624: Global MASTER-Net observations report
  42. GRB 250826A: Fermi GBM Final Real-time Localization
  43. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Confirmation of Rebrightening of AT2025ulz
  44. Fermi GRB 250824B: Global MASTER-Net observations report
  45. LIGO/Virgo/KAGRA S250818k: VLA upper limits on AT2025ulz
  46. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  47. GRB 250823A: Swift-BAT refined analysis
  48. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  49. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  50. EP250821a: MeerKAT radio counterpart
  51. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  52. GRB 250824B: Fermi GBM Final Real-time Localization
  53. The EP-WXT trigger 01709200707 is likely a flaring star
  54. The EP-WXT trigger 01709200706 is likely a flaring star
  55. GRB 250823A: SVOM/VT optical observation
  56. GRB 250824A: Fermi GBM Final Real-time Localization
  57. GRB 250823A: NOT optical observations
  58. GRB 250823A: Fermi GBM Observation
  59. GRB 250823A: LCOGT Optical Detection
  60. GRB 250823A: BOOTES6/DPRT early optical detection
  61. GRB 250823A: Liverpool Telescope optical detection
  62. GRB 250823A: Fermi GBM Final Real-time Localization
  63. Swift GRB250823.84: Global MASTER-Net observations report
  64. Konus-Wind detection of GRB 250821B
  65. LIGO/Virgo/KAGRA S250818k: JinShan optical observations of AT2025ulz
  66. GRB 250806A: Gemini observations of host galaxy candidate
  67. IPN triangulation of GRB 250821B (long/bright)
  68. GRB 250812A: SVOM/ECLAIRs refined analysis
  69. GRB 250821A: Swift-BAT refined analysis
  70. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
  71. LIGO/Virgo/KAGRA S250818k: NOT optical observations of AT2025ulz
  72. LIGO/Virgo/KAGRA S250818k: GRAWITA TNG NIR observations of AT2025ulz
  73. GRB 250821B: SVOM/GRM observation
  74. EP250821a: SVOM/VT optical observation
  75. Fermi GRB 250821B: Global MASTER-Net observations report
  76. GRB 250821C: Fermi GBM Final Real-time Localization
  77. GRB 250821A: KAIT optical upper limit
  78. Swift GRB 250821A: Global MASTER-Net observations report
  79. GRB 250821B: Fermi GBM Detection
  80. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of AT 2025ulz
  81. GRB 250821B: BALROG localization (Fermi Trigger / GRB 250821672)
  82. GRB 250821B: Fermi GBM Final Localization of a Bright Burst
  83. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  84. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  85. GRB 250821A: LCOGT Optical Upper Limits
  86. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  87. GRB 250821A: Swift detection of a burst
  88. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  89. LIGO/Virgo/KAGRA S250818k: EP/FXT observation of AT 2025ulz
  90. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  91. LIGO/Virgo/KAGRA S250818k: Pan-STARRS grizy-band imaging and photometry of AT2025ulz
  92. LIGO/Virgo/KAGRA S250818k: Swift observations of AT 2025ulz
  93. IPN triangulation of GRB 250816A (short)
  94. IPN triangulation of GRB 250814C (short)
  95. IPN triangulation of GRB 250804B (short)
  96. LIGO/Virgo/KAGRA S250818k: AstroSat CZTI non-detection and upper limits
  97. GRB 250818B: Liverpool Telescope optical detections
  98. LIGO/Virgo/KAGRA S250818k: Upper limits from Fermi-GBM Observations
  99. LIGO/Virgo/KAGRA S250818k: Updated Sky localization and EM Bright Classification
  100. LIGO/Virgo/KAGRA S250818k: Pan-STARRS pre-detection limits for AT2025ulz

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