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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').
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.

Advanced Search Examples (click to copy):

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

32495 results found.

  1. GRB 250901A: Swift/UVOT Upper Limit
  2. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  3. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  4. EP250827b: Liverpool Telescope observations
  5. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  6. GRB 250902A: SVOM/GRM observation
  7. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  8. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  9. GRB 250901A: EP-FXT follow-up observation
  10. GRB 250901A: NOT optical observations
  11. GRB 250901A: SVOM/VT optical afterglow with VHF data
  12. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  13. GRB 250901A: LCO optical upper limit
  14. EP250827b: Swift observations of AT 2025wkm
  15. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  16. EP250827b: Gemini Spectroscopy of AT 2025wkm
  17. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  18. EP250831a: NOT optical observations and tentative afterglow candidate
  19. EP250827b: FTW Observations of AT 2025wkm
  20. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  21. GRB 250830C: Insight-HXMT detection
  22. EP250901a: Mephisto optical upper limits
  23. EP250901a: Global MASTER-Net observations report
  24. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  25. EP250831a: EP-FXT follow-up observation
  26. EP250831a: Swift-XRT observations
  27. EP250831a: Global MASTER-Net observations report
  28. GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
  29. GRB 250831A: Swift-XRT counterpart detection
  30. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  31. GRB 250831A: SVOM/VT upper limit with VHF data
  32. EP250830a: Global MASTER-Net observations report
  33. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  34. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  35. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  36. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  37. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  38. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  39. GRB 250830B: Swift ToO observations
  40. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  41. GRB 250828B: Swift-BAT refined analysis
  42. EP250821a: SOAR observations
  43. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  44. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  45. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  46. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  47. EP250828a: Optical counterpart detection with Kinder observations
  48. EP250828a: Liverpool Telescope upper limits
  49. Swift GRB 250828B: Global MASTER-Net observations report
  50. EP250828a: Global MASTER-Net observations report
  51. EP-WXT trigger 01709200800 : KAIT optical observations
  52. EP250828a: KAIT optical upper limit
  53. EP250827a: Swift/UVOT Detection
  54. EP250828a: NOT optical counterpart confirmation
  55. EP250828a: SVOM/VT optical candidate
  56. EP250828a: Seimei/TriCCS optical counterpart detection
  57. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  58. EP250828a: Optical upper limit with Kinder observations
  59. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  60. LIGO/Virgo/KAGRA S250818k: uGMRT 1.3 GHz observations of AT2025ulz
  61. EP250827a: LCO observations show fading optical counterpart
  62. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  63. GRID detection of GRB 250824A
  64. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  65. EP250827A: VLT/X-shooter redshift confirmation
  66. Fermi GRB 250827A: Global MASTER-Net observations report
  67. EP250827a: confirmation of optical rebrightening with LCO
  68. EP250827a: GOTO observation of the optical afterglow
  69. GRB 250826A: SVOM/GRM observation
  70. EP250827A: An optical rebrightening was detected by LCO.
  71. EP250827a: Swift-XRT counterpart detection
  72. LIGO/Virgo/KAGRA S250827l: Updated Sky localization
  73. EP250827a: TRT optical observations
  74. EP250827a / GRB 250827A: MASTER-OAFA OT observation
  75. EP250827a: Gemini-South redshift z = 1.613
  76. EP250827a: Global MASTER-Net observations report
  77. EP250827a: Las Cumbres independent detection of the optical counterpart
  78. EP250827a: Gemini-South optical counterpart detection
  79. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  80. Fermi GRB 250826A: Global MASTER-Net observations report
  81. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  82. EP250821a: Gemini GMOS Redshift Confirmation
  83. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  84. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Confirmation of Rebrightening of AT2025ulz
  85. Fermi GRB 250824B: Global MASTER-Net observations report
  86. LIGO/Virgo/KAGRA S250818k: VLA upper limits on AT2025ulz
  87. LIGO/Virgo/KAGRA S250818k: nature of the AT2025ulz/ZTF25abjmnnps OT
  88. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  89. GRB 250823A: Swift-BAT refined analysis
  90. LIGO/Virgo/KAGRA S250818k: Continued Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
  91. GRB 250821B: AstroSat CZTI detection
  92. GRB 250819A: AstroSat CZTI detection
  93. LIGO/Virgo/KAGRA S250818k: FTW Observations Show Continued Reddening of AT 2025ulz
  94. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  95. GRB 250821B: Insight-HXMT detection
  96. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  97. EP250821a: MeerKAT radio counterpart
  98. EP triggers 01709200706 and 01709200707: GOTO confirmation of flaring stars
  99. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  100. GRB 250823A: COLIBRÍ optical observations

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