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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').

2439 results found.

  1. LIGO/Virgo/KAGRA S240422ed: DDOTI Optical Upper Limit for J-GEM24a
  2. LIGO/Virgo/KAGRA S240422ed: Swope Follow-up of AT2024hfq, AT2024hfr, AT2024hfs, and AT2024hfx
  3. LIGO/Virgo/KAGRA S240422ed: BOOTES-6/DPRT optical upper limits for EP240426a
  4. LIGO/Virgo/KAGRA S240422ed: GRANDMA Optical Upper Limits for EP240426a
  5. LIGO/VIRGO/KAGRA S240422ed: Historical variability for EP240426a
  6. EP240426a: YAHPT optical upper limit
  7. LIGO/Virgo/KAGRA S240422ed: BOOTES-4/MET Optical Upper Limits for EP240426a
  8. LIGO/Virgo/KAGRA S240422ed: EP240426a possible optical detection
  9. LIGO/Virgo/KAGRA S240422ed: Continued Magellan Observations
  10. LIGO/Virgo/KAGRA S240422ed: EP-FXT detection of a candidate counterpart EP240426a
  11. LIGO/Virgo/KAGRA S240422ed: Magellan Follow-up Observations of Swift/XRT candidates
  12. S240422ed: BlackGEM/MeerLICHT transient detection AT2024hgl/MLTJ080628.10-250116.4
  13. S240422ed: MeerLICHT/BlackGEM photometry on AT2024hfx and archival ZTF detection
  14. LIGO/Virgo/KAGRA S240422ed: Magellan Spectrum of GW-MMADS Candidate AT2024hdo Indicates a Type II SN
  15. LIGO/Virgo/KAGRA S240422ed: Archival BlackGEM/MeerLICHT detections of AT 2024hdr & AT 2024hdq
  16. LIGO/Virgo/KAGRA S240422ed: Vetting of DECam Candidates Using Real-Time Resources and SAGUARO Infrastructure
  17. IceCube-240424A - IceCube observation of a high-energy neutrino candidate track-like event
  18. LIGO/Virgo/KAGRA S240422ed: MOSFIRE spectroscopy of the DECam GW-MMADS candidate AT 2024hdn
  19. LIGO/Virgo S240422ed: Swift-XRT detection of 3 possible counterparts
  20. LIGO/Virgo/KAGRA S240422ed: Continued Imaging of Mag24a
  21. LIGO/Virgo/KAGRA S240422ed: Magellan Detection of a Potential Electromagnetic Counterpart
  22. LIGO/Virgo/KAGRA S240422ed: no candidate counterparts from ATLAS observations
  23. GRB 240419A: Possible ATCA radio detection
  24. LIGO/Virgo/KAGRA S240422ed: Magellan Observations
  25. LIGO/Virgo/KAGRA S240422ed: Identification of a GW compact binary merger candidate
  26. GRB240418A - Candidate afterglow from NIRES
  27. IceCube-240419A - IceCube observation of a high-energy neutrino candidate track-like event
  28. IceCube-240419A - IceCube observation of a high-energy neutrino candidate track-like event
  29. EP240417a: YAHPT Optical Upper Limits
  30. LIGO/Virgo/KAGRA S240413p: STEP - T80S Search and Candidate Counterpart Identification
  31. EP240416a: Kinder optical counterpart candidate
  32. GRB 240415A: Mondy optical transient detection
  33. LXT 240402A/GRB 240402B: Swift follow-up observations
  34. EP240414a: Kinder optical counterpart candidate possibly associated with the galaxy SDSS J124601.99-094309.3
  35. EP240413a: possible detection of the X-ray emission with EP-FXT after 14 hours
  36. GRB 240414A: Swift detection of a burst
  37. IceCube-240412A - IceCube observation of a high-energy neutrino candidate track-like event
  38. EP240408a: Swift follow-up observation
  39. X-ray transient EP240331a: Kinder optical upper limits
  40. IceCube-240327B - IceCube observation of a high-energy neutrino candidate track-like event
  41. IceCube-240327A - IceCube observation of a high-energy neutrino candidate track-like event
  42. X-ray transient EP240315a: e-MERLIN radio observations
  43. Transient EPW20240219aa: REM optical/NIR further observations
  44. Konus-Wind detection of GRB 240315C (possible counterpart of EP240315a)
  45. GRB 240315C / X-ray transient EP240315a: Swift/BAT detection
  46. Swift satellite in safe mode
  47. X-ray transient EP240315a: Montarrenti Observatory optical upper limit
  48. X-ray transient EP240315a: orphan FXT?
  49. X-ray transient EP240315a: Kinder follow-up observations for AT 2024eju with Lulin observatory
  50. AT2024eju: followup observations with Liverpool Telescope suggest a fading transient
  51. X-ray transient EP240315a: ATLAS detection of a possible optical counterpart AT2024eju
  52. IceCube-240307A - IceCube observation of a high-energy neutrino candidate track-like event
  53. IceCube-240229A - IceCube observation of a high-energy neutrino candidate track-like event
  54. Transient EPW20240219aa: upper limit in gamma-ray range from SPI-ACS/INTEGRAL observations
  55. Transient EPW20240219aa: Liverpool Telescope non-detection and limiting magnitude
  56. Fermi GBM Sub-Threshold Detection of EPW20240219aa as a likely GRB
  57. GRB 240209A: Classification of AT2024cew/GOTO24pw as Type Ia-pec supernova
  58. GRB 240214A/1H 0451-560: MAXI/GSC detection
  59. IceCube-240204A - IceCube observation of a high-energy neutrino candidate track-like event
  60. IceCube-240123A - IceCube observation of a high-energy neutrino candidate track-like event
  61. GRB 240123A: Swift detection of a burst with a possible optical counterpart
  62. IceCube-240105A: Detection of NIR flare of PKS 0446+11 with WINTER
  63. IceCube-240105A - IceCube observation of a high-energy neutrino candidate track-like event
  64. GRB 240101B: Swift-BAT refined analysis
  65. IceCube-231211A - IceCube observation of a high-energy neutrino candidate track-like event
  66. IceCube-231202A - IceCube observation of a high-energy neutrino candidate track-like event
  67. IceCube-231125A - IceCube observation of a high-energy neutrino candidate track-like event
  68. GRB 231117A: Keck spectroscopy of afterglow candidate
  69. MAGIC observation of GRB 231115A, a possible magnetar giant flare
  70. GRB231115A: Liverpool Telescope imaging
  71. GRB 231115A: AGILE/MCAL upper limits
  72. GRB 231115A: significance of INTEGRAL localization alignment with M82
  73. GRB 231111A: TNG tentative redshift
  74. GRB231110A: WFST Observation and upper limits
  75. IceCube-231103A - IceCube observation of a high-energy neutrino candidate track-like event
  76. IceCube-231027A - IceCube observation of a high-energy neutrino candidate track-like event
  77. IC231004A: GRANDMA observations of AT2023uqf/ZTF23abidzvf candidate
  78. GRB 231017A: Mondy optical observations. A possible candidate for an afterglow or host galaxy.
  79. GRB 230911C: ATCA detection of possible radio counterpart
  80. IC231004A: Classification of AT2023uqf/ZTF23abidzvf as a rapidly-evolving supernova with CSM interaction
  81. IceCube-231014A - IceCube observation of a high-energy neutrino candidate track-like event
  82. IceCube-231004A - IceCube observation of a high-energy neutrino candidate track-like event
  83. transient AT2023sva: A Binary Driven Hypernova with a possible associated supernova
  84. LIGO/Virgo/KAGRA S230904n: Classification of the candidate AT2023rkw with DBSP
  85. Correction to Fermi GBM Statement for Trigger 716527670/230916144
  86. LIGO/Virgo S230917af: Swift XRT observations, 6 X-ray sources
  87. IceCube-230914A - IceCube observation of a high-energy neutrino candidate track-like event
  88. GRB 230911D: NuSTAR Detection of Prompt Emission
  89. IceCube-230823A - IceCube observation of a high-energy neutrino candidate track-like event
  90. GRB 230812B: Assy optical observations, possible SN rise
  91. GRB 230812B: SAO RAS observations, possible re-brightening
  92. GRB 230812B: SAO RAS optical observations
  93. GRB230816A: Possible host and GIT detection of optical counterpart
  94. GOTO confirmation and possible host galaxy of GRB230812B optical afterglow
  95. GRB 230805B: SAO RAS optical observations
  96. GRB 230728A: NOT optical observations and possible host galaxy
  97. IceCube-230727A - IceCube observation of a high-energy neutrino candidate track-like event
  98. IceCube-230724A - IceCube observation of a high-energy neutrino candidate track-like event
  99. IceCube-230725A - IceCube observation of a high-energy neutrino candidate track-like event
  100. GRB 230723B: Optical afterglow candidate from CAHA

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