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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"

16161 results found.

  1. EP250223a: refined analysis of the EP-WXT and FXT observations
  2. EP250223a: 1.6m Mephisto and 50cm array observations
  3. GRB 250221A: TNOT detection of the optical counterpart
  4. EP250223a: SVOM/VT optical observation
  5. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  6. EP250223a: OASDG optical observations
  7. EP250223a: LCO detection of the afterglow
  8. EP250223a: early optical detection by BOOTES-4
  9. EP250223a: NOT redshift z = 2.756
  10. EP250223a: NOT optical afterglow candidate
  11. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  12. GRB 250221A: continued Mondy optical observations, brightening afterglow
  13. GRB 250221A: Optical counterpart detection by LCO.
  14. GRB 250221A: Mondy optical observations
  15. GRB 250221A: Assy optical observations
  16. EP250220a: FTW optical and NIR observations and upper limits
  17. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  18. GRB 250221A: VLT/X-shooter redshift z = 0.768
  19. GRB 250221A: GRANDMA/TAROT Detection
  20. GRB 250221A: NOT optical observations
  21. GRB 250221A: 1.6m Mephisto optical detection
  22. GRB 250221A: AKO Optical Upper Limit
  23. GRB 250221A: Swift/UVOT Detection
  24. EP250220a: Liverpool Telescope upper limits
  25. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  26. GRB 250221A: REM optical/NIR afterglow detection
  27. EP250220a: 1.6m Mephisto observations
  28. EP250220a: Liverpool Telescope optical upper limits
  29. EP250220a: Optical upper limit with Kinder observations
  30. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  31. GRB 250221A: Swift detection of a burst with an optical counterpart
  32. Swift GRB250221.15: Global MASTER-Net OT detection
  33. EP250220a: Xinglong optical upper limit
  34. GRB 250219A: OHP/T193 optical upper limit
  35. GRB 250219A: NOT optical observations
  36. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  37. GRB 250219A: 1.6m Mephisto optical upper limits
  38. GRB 250219A: SVOM/VT optical counterpart
  39. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  40. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  41. GRB 250217C: SVOM/GRM observation
  42. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  43. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  44. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  45. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  46. GRB 250215A / EP250215a: LCO detection of the afterglow
  47. EP250212a: FTW optical and NIR upper limits
  48. GRB 250215A: Swift/UVOT Upper Limits
  49. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  50. EP250215a / GRB 250215A : GTC redshift z = 4.61
  51. GRB 250215A: Fermi GBM Observation
  52. EP250215a / GRB 250215A : NOT optical observations
  53. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  54. GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
  55. LIGO/Virgo/KAGRA S250206dm: MASTER LC AT2025bbo
  56. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  57. GRB 250215A: Swift-XRT refined Analysis
  58. GRB 250215A: SVOM/GRM observation
  59. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  60. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  61. GRB 250213A:SVOM/VT optical candidate
  62. EP250207b: Xinglong optical upper limit
  63. EP250212a: Xinglong optical upper limit
  64. GRB 250205A: VIRT Optical Upper Limit
  65. GRB 250205A: Leavitt Observatory optical upper limit
  66. EP250207B: Chandra localization of the X-ray counterpart
  67. EP250212a: Liverpool Telescope optical upper limits
  68. GRB250101A: Radio upper limits from GMRT observations
  69. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  70. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  71. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  72. EP250207b: NOT optical counterpart candidate
  73. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  74. GRB 250205A / EP250205A: radio detection with the VLA
  75. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  76. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  77. GRB 250210A: SVOM/GRM observation of a long burst
  78. EP250207b: Liverpool Telescope possible optical counterpart
  79. Gemini-South spectroscopic redshift of EP250207b host galaxy candidate (z=0.082)
  80. GRB 250207A: Skynet optical afterglow observations
  81. GRB 241128A: VIRT Optical Upper Limit
  82. EP250207b: Gemini GMOS-N z-band observations
  83. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  84. LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
  85. GRB 250207A: 1.3m DFOT Optical observations
  86. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A BOOTES-5 and 2.2m CAHA optical upper limits
  87. GRB 250129A: GRANDMA Continued Afterglow Detection
  88. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  89. GRB 250205A: 1.3m DFOT optical upper limit
  90. LIGO/Virgo/KAGRA S250206dm: Spectroscopic Classification of AT2025bay and AT2025baz with Keck I/LRIS
  91. LIGO/Virgo/KAGRA S250206dm: Candidates from the Zwicky Transient Facility
  92. LIGO/Virgo/KAGRA S250206dm: ePESSTO+ classification of AT2025bar
  93. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates
  94. LIGO/Virgo/KAGRA S250206dm: MMT galaxy targeted observations
  95. EP-WXT trigger 01709131361: correction to GCN 39214
  96. EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
  97. LIGO/Virgo/KAGRA S250206dm: GOTO counterpart search update - AT2025bar
  98. EP-WXT trigger 01709131361 / LIGO/Virgo/KAGRA S250206dm: FTW optical and NIR observations
  99. GRB 250129A: ABObservatory SLOAN r’ afterglow detection
  100. GRB 250207A: REM IR afterglow detection

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