SDSS-V DR20 added a new mode of operation for the observation of a Target of Opportunity (ToO). In its current implementation, ToOs do not drive the observation plan for a given night, but rather tag along and only observe when the main survey plan goes to a pre-designed field, at which individual targets from a list of potential ToO targets replace targets in the predefined designs. The available ToO targets are currently from one of two predefined programs, though more programs might be added in the future.
Releasing ToO Spectra
The SDSS-V observed ToO spectra will be included with all other released spectra in the standard data releases. In the DR20 release, we are releasing a single targeted ToO spectra (taken on MJD 60706; https://dr20.sdss.org/zora/target/137729429) as part of the standard BOSS pipeline products. This spectrum is likely a Type Ia supernova. Another spectrum was taken on MJD 60454 as a test of the ToO targeting pipeline, but it was not actually a targeted ToO.
However, to support the needs of the time domain community, a new (for SDSS) mode of releasing spectra has been added. In this mode, the proposers and science teams have the option for accelerated release through alternative methods (such as TNS Astronotes) preferred by the time domain community. As of DR20, SDSS-V has released a single such target to the community: Classification of AT 2025alls as a Flaring AGN (https://www.wis-tns.org/astronotes/astronote/2026-139).
SDSS-V ToO Programs
As of the release of DR20, two programs have been observed as part of the ToO targeting mode: BHM TNS Transient program and The population of Galactic outbursting accreting white dwarfs.
BHM TNS Transient program
BHM TNS Transient program ToO project aims to obtain SDSS BHM spectra for mostly extragalactic transient sources discovered by ongoing time-domain surveys (e.g., ZTF, BlackGEM, Gaia, ATLAS, and ASAS-SN) and reported to TNS (Transient Name Server). Based on rough numbers, we expect ~1 spectral classification per night, which could augment by up to ~20% the total number of currently reported spectroscopic classifications of transients per year, and increase by potentially 50-100% the number with R > 1000 spectral resolution, ~3650-9500Å coverage, and S/N > 0.5/Å. Such classifications should be of broad interest to the transient community.
The population of Galactic outbursting accreting white dwarfs
AM CVn type binaries are helium rich ultra-compact accreting binaries with a white dwarf primary and a (semi-)degenerate secondary. They are important as supernova Ia progenitors and LISA gravitational wave sources, and without spectroscopic classification, are often misclassified as regular dwarf novae. Their spectra are dominated by helium lines as compared to regular dwarf novae, which are dominated by hydrogen lines. Therefore, we run a ToO program in order to classify them correctly with spectroscopic confirmation when a system is in outburst.
In order to do this, we look at a sample of ~9000 candidate accreting white dwarf candidates with previously reported outbursts and submit those systems that show an outburst > 1mag to obtain a classification spectrum when they are sufficiently bright for classification. The current known population of AM CVns is still small, with only a hundred confirmed. This method helps build up the sample of known AM CVns, and hence any new identification is an interesting discovery.