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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"

15721 results found.

  1. GRB 250217C: SVOM/GRM observation
  2. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  3. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  4. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  5. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  6. GRB 250215A / EP250215a: LCO detection of the afterglow
  7. EP250212a: FTW optical and NIR upper limits
  8. GRB 250215A: Swift/UVOT Upper Limits
  9. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  10. EP250215a / GRB 250215A : GTC redshift z = 4.61
  11. GRB 250215A: Fermi GBM Observation
  12. EP250215a / GRB 250215A : NOT optical observations
  13. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  14. GRB 250215A / EP250215a: Gemini-South optical observation of a likely rebrightening
  15. LIGO/Virgo/KAGRA S250206dm: MASTER LC AT2025bbo
  16. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  17. GRB 250215A: Swift-XRT refined Analysis
  18. GRB 250215A: SVOM/GRM observation
  19. GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
  20. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  21. GRB 250213A：SVOM/VT optical candidate
  22. EP250207b: Xinglong optical upper limit
  23. EP250212a: Xinglong optical upper limit
  24. GRB 250205A: VIRT Optical Upper Limit
  25. GRB 250205A: Leavitt Observatory optical upper limit
  26. EP250207B: Chandra localization of the X-ray counterpart
  27. EP250212a: Liverpool Telescope optical upper limits
  28. GRB250101A: Radio upper limits from GMRT observations
  29. EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
  30. LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
  31. GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  32. EP250207b: NOT optical counterpart candidate
  33. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  34. GRB 250205A / EP250205A: radio detection with the VLA
  35. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  36. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  37. GRB 250210A: SVOM/GRM observation of a long burst
  38. EP250207b: Liverpool Telescope possible optical counterpart
  39. Gemini-South spectroscopic redshift of EP250207b host galaxy candidate (z=0.082)
  40. GRB 250207A: Skynet optical afterglow observations
  41. GRB 241128A: VIRT Optical Upper Limit
  42. EP250207b: Gemini GMOS-N z-band observations
  43. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  44. LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
  45. GRB 250207A: 1.3m DFOT Optical observations
  46. LIGO/Virgo/KAGRA S250206dm: FRB 20250206A BOOTES-5 and 2.2m CAHA optical upper limits
  47. GRB 250129A: GRANDMA Continued Afterglow Detection
  48. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  49. GRB 250205A: 1.3m DFOT optical upper limit
  50. LIGO/Virgo/KAGRA S250206dm: Spectroscopic Classification of AT2025bay and AT2025baz with Keck I/LRIS
  51. LIGO/Virgo/KAGRA S250206dm: Candidates from the Zwicky Transient Facility
  52. LIGO/Virgo/KAGRA S250206dm: ePESSTO+ classification of AT2025bar
  53. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates
  54. LIGO/Virgo/KAGRA S250206dm: MMT galaxy targeted observations
  55. EP-WXT trigger 01709131361: correction to GCN 39214
  56. EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
  57. LIGO/Virgo/KAGRA S250206dm: GOTO counterpart search update - AT2025bar
  58. EP-WXT trigger 01709131361 / LIGO/Virgo/KAGRA S250206dm: FTW optical and NIR observations
  59. GRB 250129A: ABObservatory SLOAN r’ afterglow detection
  60. GRB 250207A: REM IR afterglow detection
  61. LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap
  62. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS survey of the skymap for optical transients
  63. GRB 250207A: FRAM-Auger optical detection
  64. IGO/Virgo/KAGRA S250206dm: Virtual Telescope Project upper limit for the Neutrino IceCube Candidate
  65. GRB 250207A: REM optical afterglow detection
  66. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limit for the Neutrino IceCube Candidate
  67. LIGO/Virgo/KAGRA S250206dm: GOTO observations of optical candidates AT 2025azn and AT 2025azm
  68. LIGO/Virgo/KAGRA S250206dm: Pan-STARRS observations of AT2025azm and AT2025azn
  69. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the AT 2025azn Optical Candidate
  70. GRB 250129A: Continued AbAO and Mondy optical observations
  71. LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
  72. GRB 250207A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  73. GRB 250207A: Swift detection of a burst with optical counterpart
  74. GRB 250205A: REM NIR upper limit
  75. EP250205a/GRB 250205A: FTW optical and NIR observations of the counterpart
  76. GRB 250127C: SVOM/GRM observation of a burst
  77. GRB 250204B: SVOM/GRM observation of a likely short burst
  78. GRB 250205A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  79. GRB 250205A: Swift/XRT detection
  80. GRB 250205A: Redshift from OSIRIS+/GTC z = 3.55
  81. GRB250205A: SVOM/VT optical afterglow detection
  82. GRB 250205A: GOTO optical upper limits
  83. GRB 250205A: OHP/T193 optical counterpart candidate
  84. GRB 250205A: Liverpool Telescope optical counterpart candidate detection
  85. GRB 250205A: SVOM detection of a burst
  86. GRB 250129A: LCO late afterglow detection
  87. GRB 250129A: AbAO AS-32 and Mondy AZT-33IK optical observations
  88. GRB 250129a: Liverpool Telescope optical follow-up
  89. GRB 240129A: further SAO RAS optical observations
  90. GRB 250129A: 7DT Detection and Medium-band SED of Afterglow
  91. GRB 250129A: SVOM/C-GFT optical observations
  92. Swift GRB250129A: MASTER 4 days observations report
  93. GRB 250129A: 1.3m DFOT Optical observations
  94. GRB 250129A: Liverpool Telescope observations suggest continued engine activity
  95. GRB 250129A: Skynet Continued Optical Observations
  96. GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
  97. GRB 250129A: SAO RAS optical observations
  98. GRB 250129A: COLIBRÍ Continuing Detection of the Afterglow
  99. GRB 250129A: optical photometry from Konkoly
  100. GRB 250129A: COLIBRÍ Optical Observations

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